Nephrology

Chronic kidney disease (CKD) is estimated to affect 14% of Americans, but it is likely underdiagnosed because it is often asymptomatic.^1,2 Its prevalence is even higher in patients who undergo surgery—up to 30% in cardiac surgery.³ Its impact on surgical outcomes is substantial.⁴ Importantly, patients with CKD are at higher risk of postoperative acute kidney injury (AKI), which is also associated with adverse outcomes. Thus, it is important to recognize, assess, and manage abnormal renal function in surgical patients.

WHAT IS THE IMPACT ON POSTOPERATIVE OUTCOMES?

Cardiac surgery outcomes

Moreover, in patients undergoing coronary artery bypass grafting (CABG), the worse the renal dysfunction, the higher the long-term mortality rate. Patients with moderate (stage 3) CKD had a 3.5 times higher odds of in-hospital mortality compared with patients with normal renal function, rising to 8.8 with severe (stage 4) and to 9.6 with dialysis-dependent (stage 5) CKD.¹¹

The mechanisms linking CKD with negative cardiac outcomes are unclear, but many possibilities exist. CKD is an independent risk factor for coronary artery disease and shares underlying risk factors such as hypertension and diabetes. Cardiac surgery patients with CKD are also more likely to have diabetes, left ventricular dysfunction, and peripheral vascular disease.

Noncardiac surgery outcomes

CKD is also associated with adverse outcomes in noncardiac surgery patients, especially at higher levels of renal dysfunction.^12–14 For example, in patients who underwent major noncardiac surgery, compared with patients in stage 1 (estimated GFR > 90 mL/min/1.73 m²), the odds ratios for all-cause mortality were as follows:

• 0.8 for patients with stage 2 CKD
• 2.2 in stage 3a
• 2.8 in stage 3b
• 11.3 in stage 4
• 5.8 in stage 5.¹⁴

The association between estimated GFR and all-cause mortality was not statistically significant (P = .071), but statistically significant associations were observed between estimated GFR and major adverse cardiovascular events (P < .001) and hospital length of stay (P < .001).

The association of CKD with major adverse outcomes and death in both cardiac and noncardiac surgical patients demonstrates the importance of understanding this risk, identifying patients with CKD preoperatively, and taking steps to lower the risk.

WHAT IS THE IMPACT OF ACUTE KIDNEY INJURY?

AKI is a common and serious complication of surgery, especially cardiac surgery. It has been associated with higher rates of morbidity, mortality, and cardiovascular events, longer hospital length of stay, and higher cost.

Several groups have proposed criteria for defining AKI and its severity; the KDIGO criteria are the most widely accepted.¹⁵ These define AKI as an increase in serum creatinine concentration of 0.3 mg/dL or more within 48 hours or at least 1.5 times the baseline value within 7 days, or urine volume less than 0.5 mL/kg/hour for more than 6 hours. There are 3 stages of severity:

• Stage 1—an increase in serum creatinine of 1.5 to 1.9 times baseline, an absolute increase of at least 0.3 mg/dL, or urine output less than 0.5 mL/kg/hour for 6 to 12 hours
• Stage 2—an increase in serum creatinine of 2.0 to 2.9 times baseline or urine output less than 0.5 mmL/kg/hour for 12 or more hours
• Stage 3—an increase in serum creatinine of 3 times baseline, an absolute increase of at least 4 mg/dL, initiation of renal replacement therapy, urine output less than 0.3 mL/kg/hour for 24 or more hours, or anuria for 12 or more hours.¹⁵

Multiple factors associated with surgery may contribute to AKI, including hemodynamic instability, volume shifts, blood loss, use of heart-lung bypass, new medications, activation of the inflammatory cascade, oxidative stress, and anemia.

AKI in cardiac surgery

The incidence of AKI is high in cardiac surgery. In a meta-analysis of 46 studies (N = 242,000), its incidence in cardiopulmonary bypass surgery was about 18%, with 2.1% of patients needing renal replacement therapy.¹⁶ However, the incidence varied considerably from study to study, ranging from 1% to 53%, and was influenced by the definition of AKI, the type of cardiac surgery, and the patient population.¹⁶

Cardiac surgery-associated AKI adversely affects outcomes. Several studies have shown that cardiac surgery patients who develop AKI have higher rates of death and stroke.^16–21 More severe AKI confers higher mortality rates, with the highest mortality rate in patients who need renal replacement therapy, approximately 37%.¹⁷ Patients with cardiac surgery-associated AKI also have a longer hospital length of stay and significantly higher costs of care.^17,18

Long-term outcomes are also negatively affected by AKI. In cardiac surgery patients with AKI who had completely recovered renal function by the time they left the hospital, the 2-year incidence rate of CKD was 6.8%, significantly higher than the 0.2% rate in patients who did not develop AKI.¹⁹ The 2-year survival rates also were significantly worse for patients who developed postoperative AKI (82.3% vs 93.7%). Similarly, in patients undergoing CABG who had normal renal function before surgery, those who developed AKI postoperatively had significantly shorter long-term survival rates.²⁰ The effect does not require a large change in renal function. An increase in creatinine as small as 0.3 mg/dL has been associated with a higher rate of death and a long-term risk of end-stage renal disease that is 3 times higher.²¹

Cardiac surgery

CKD is a risk factor not only after cardiac surgery but also after percutaneous procedures. In a meta-analysis of 4,992 patients with CKD who underwent transcatheter aortic valve replacement, both moderate and severe CKD increased the odds of AKI, early stroke, the need for dialysis, and all-cause and cardiovascular mortality at 1 year.^22,23 Increased rates of AKI also have been found in patients with CKD undergoing CABG surgery.²⁴ These results point to a synergistic effect between AKI and CKD, with outcomes much worse in combination than alone.

In cardiac surgery, the most important patient risk factors associated with a higher incidence of postoperative AKI are age older than 75, CKD, preoperative heart failure, and prior myocardial infarction.^19,25 Diabetes is an additional independent risk factor, with type 1 conferring higher risk than type 2.²⁶ Preoperative use of angiotensin-converting enzyme (ACE) inhibitors may or may not be a risk factor for cardiac surgery-associated AKI, with some studies finding increased risk and others finding reduced rates.^27,28

Anemia, which may be related to either patient or surgical risk factors (eg, intraoperative blood loss), also increases the risk of AKI in cardiac surgery.^29,30 A retrospective study of CABG surgery patients found that intraoperative hemoglobin levels below 8 g/dL were associated with a 25% to 30% incidence of AKI, compared with 15% to 20% with hemoglobin levels above 9 g/dL.²⁹ Additionally, having severe hypotension (mean arterial pressure < 50 mm Hg) significantly increased the AKI rates in the low-hemoglobin group.²⁹ Similar results were reported in a later study.³⁰

Among surgical factors, several randomized controlled trials have shown that off-pump CABG is associated with a significantly lower risk of postoperative AKI than on-pump CABG; however, this difference did not translate into any long-term difference in mortality rates.^31,32 Longer cardiopulmonary bypass time is strongly associated with a higher incidence of AKI and postoperative death.³³

Noncardiac surgery

AKI is less common after noncardiac surgery; however, outcomes are severe in patients in whom it occurs. In a study of 15,102 noncardiac surgery patients, only 0.8% developed AKI and 0.1% required renal replacement therapy.³⁴

Risk factors after noncardiac surgery are similar to those after cardiac surgery (Table 3).^34–36 Factors with the greatest impact are older age, peripheral vascular occlusive disease, chronic obstructive pulmonary disease necessitating chronic bronchodilator therapy, high-risk surgery, hepatic disease, emergent or urgent surgery, and high body mass index.

Surgical risk factors include total vasopressor dose administered, use of a vasopressor infusion, and diuretic administration.³⁴ In addition, intraoperative hypotension is associated with a higher risk of AKI, major adverse cardiac events, and 30-day mortality.³⁷

Noncardiac surgery patients with postoperative AKI have significantly higher rates of 30-day readmissions, 1-year progression to end-stage renal disease, and mortality than patients who do not develop AKI.³⁵ Additionally, patients with AKI have significantly higher rates of cardiovascular complications (33.3% vs 11.3%) and death (6.1% vs 0.9%), as well as a significantly longer length of hospital stay.^34,36

CAN WE DECREASE THE IMPACT OF RENAL DISEASE IN SURGERY?

Before surgery, practitioners need to identify patients at risk of AKI, implement possible risk-reduction measures, and, afterward, treat it early in its course if it occurs.

The preoperative visit is the ideal time to assess a patient’s risk of postoperative renal dysfunction. Laboratory tests can identify risks based on surgery type, age, hypertension, the presence of CKD, and medications that affect renal function. However, the basic chemistry panel is abnormal in only 8.2% of patients and affects management in just 2.6%, requiring the clinician to target testing to patients at high risk.³⁸

Patients with a significant degree of renal dysfunction, particularly those previously undiagnosed, may benefit from additional preoperative testing and medication management. Perioperative management of medications that could adversely affect renal function should be carefully considered during the preoperative visit. In addition, the postoperative inpatient team needs to be informed about potentially nephrotoxic medications and medications that are renally cleared. Attention needs to be given to the renal impact of common perioperative medications such as nonsteroidal anti-inflammatory drugs, antibiotics, intravenous contrast, low-molecular-weight heparins, diuretics, ACE inhibitors, and angiotensin II receptor blockers. With the emphasis on opioid-sparing analgesics, it is particularly important to assess the risk of AKI if nonsteroidal anti-inflammatory drugs are part of the pain control plan.

Nephrology referral may help, especially for patients with a GFR less than 45 mL/min. This information enables more informed decision-making regarding the risks of adverse outcomes related to kidney disease.

WHAT TOOLS DO WE HAVE TO DIAGNOSE RENAL INJURY?

Several risk-prediction models have been developed to assess the postoperative risk of AKI in both cardiac and major noncardiac surgery patients. Although these models can identify risk factors, their clinical accuracy and utility have been questioned.

Biomarkers

Early diagnosis is the first step in managing AKI, allowing time to implement measures to minimize its impact.

Serum creatinine testing is widely used to measure renal function and diagnose AKI; however, it does not detect small reductions in renal function, and there is a time lag between renal insult and a rise in creatinine. The result is a delay to diagnosis of AKI.

Biomarkers other than creatinine have been studied for early detection of intraoperative and postoperative renal insult. These novel renal injury markers include the following:

Neutrophil gelatinase-associated lipocalin (NGAL). Two studies looked at plasma NGAL as an early marker of AKI in patients with CKD who were undergoing cardiac surgery.^39,40 One study found that by using NGAL instead of creatinine, postoperative AKI could be diagnosed an average of 20 hours earlier.³⁹ In addition, NGAL helped detect renal recovery earlier than creatinine.⁴⁰ The diagnostic cut-off values of NGAL were different for patients with CKD than for those without CKD.^39,40

Other novel markers include:

• Kidney injury marker 1
• N-acetyl-beta-D-glucosaminidase
• Cysteine C.

Although these biomarkers show some ability to detect renal injury, they provide only modest discrimination and are not widely available for clinical use.⁴¹ Current evidence does not support routine use of these markers in clinical settings.

Interventions to prevent or ameliorate the impact of CKD and AKI on surgical outcomes have been studied most extensively in cardiac surgery patients.

Aspirin. A retrospective study of 3,585 cardiac surgery patients with CKD found that preoperative aspirin use significantly lowered the incidence of postoperative AKI and 30-day mortality compared with patients not using aspirin.⁴² Aspirin use reduced 30-day mortality in CKD stages 1, 2, and 3 by 23.3%, 58%, and 70%, respectively. On the other hand, in the Perioperative Ischemic Evaluation (POISE) trial, in noncardiac surgery patients, neither aspirin nor clonidine started 2 to 4 hours preoperatively and continued up to 30 days after surgery altered the risk of AKI significantly more than placebo.⁴³

Statins have been ineffective in reducing the incidence of AKI in cardiac surgery patients. In fact, a meta-analysis of 8 interventional trials found an increased incidence of AKI in patients in whom statins were started perioperatively.⁴⁴ Erythropoietin was also found to be ineffective in the prevention of perioperative AKI in cardiac surgery patients in a separate study.⁴⁵

The evidence regarding other therapies has also varied.

N-acetylcysteine in high doses reduced the incidence of AKI in patients with CKD stage 3 and 4 undergoing CABG.⁴⁶ Another meta-analysis of 10 studies in cardiac surgery patients published recently did not show any benefit of N-acetylcysteine in reducing AKI.⁴⁷

Human atrial natriuretic peptide, given preoperatively to patients with CKD, reduced the acute and long-term creatinine rise as well as the number of cardiac events after CABG; however, it did not reduce mortality rates.⁴⁸

Renin-angiotensin system inhibitors, given preoperatively to patients with heart failure was associated with a decrease in the incidence of AKI in 1 study.⁴⁹

Dexmedetomidine is a highly selective alpha 2 adrenoreceptor agonist. A recent meta-analysis of 10 clinical trials found it beneficial in reducing the risk of perioperative AKI in cardiac surgery patients.⁵⁰ An earlier meta-analysis had similar results.⁵¹

Levosimendan is an inotropic vasodilator that improves cardiac output and renal perfusion in patients with systolic heart failure, and it has been hypothesized to decrease the risk of AKI after cardiac surgery. Previous data demonstrated that this drug reduced AKI and mortality; however, analysis was limited by small sample size and varying definitions of AKI.⁵² A recent meta-analysis showed that levosimendan was associated with a lower incidence of AKI but was also associated with an increased incidence of atrial fibrillation and no reduction in 30-day mortality.⁵³

Remote ischemic preconditioning is a procedure that subjects the kidneys to brief episodes of ischemia before surgery, protecting them when they are later subjected to prolonged ischemia or reperfusion injury. It has shown initial promising results in preventing AKI. In a randomized controlled trial in 240 patients at high risk of AKI, those who received remote ischemic preconditioning had an AKI incidence of 37.5% compared with 52.5% for controls (P = .02); however, the mortality rate was the same.⁵⁴ Similarly, remote ischemic preconditioning significantly lowered the incidence of AKI in nondiabetic patients undergoing CABG surgery compared with controls.⁵⁵

Fluid management. Renal perfusion is intimately related to the development of AKI, and there is evidence that both hypovolemia and excessive fluid resuscitation can increase the risk of AKI in noncardiac surgery patients.⁵⁶ Because of this, fluid management has also received attention in perioperative AKI. Goal-directed fluid management has been evaluated in noncardiac surgery patients, and it did not show any benefit in preventing AKI.⁵⁷ However, in a more recent retrospective study, postoperative positive fluid balance was associated with increased incidence of AKI compared with zero fluid balance. Negative fluid balance did not appear to have a detrimental effect.⁵⁸

RECOMMENDATIONS

No prophylactic therapy has yet been shown to definitively decrease the risk of postoperative AKI in all patients. Nevertheless, it is important to identify patients at risk during the preoperative visit, especially those with CKD. Many patients undergoing surgery have CKD, placing them at high risk of developing AKI in the perioperative period. The risk is particularly high with cardiac surgery.

Serum creatinine and urine output should be closely monitored perioperatively in at-risk patients. If AKI is diagnosed, practitioners need to identify and ameliorate the cause as early as possible.

Recommendations from KDIGO for perioperative prevention and management of AKI are listed in Table 4.¹⁵ These include avoiding additional nephrotoxic medications and adjusting the doses of renally cleared medications. Also, some patients may benefit from preoperative counseling and specialist referral.

Chronic kidney disease (CKD) is estimated to affect 14% of Americans, but it is likely underdiagnosed because it is often asymptomatic.^1,2 Its prevalence is even higher in patients who undergo surgery—up to 30% in cardiac surgery.³ Its impact on surgical outcomes is substantial.⁴ Importantly, patients with CKD are at higher risk of postoperative acute kidney injury (AKI), which is also associated with adverse outcomes. Thus, it is important to recognize, assess, and manage abnormal renal function in surgical patients.

WHAT IS THE IMPACT ON POSTOPERATIVE OUTCOMES?

Cardiac surgery outcomes

Moreover, in patients undergoing coronary artery bypass grafting (CABG), the worse the renal dysfunction, the higher the long-term mortality rate. Patients with moderate (stage 3) CKD had a 3.5 times higher odds of in-hospital mortality compared with patients with normal renal function, rising to 8.8 with severe (stage 4) and to 9.6 with dialysis-dependent (stage 5) CKD.¹¹

The mechanisms linking CKD with negative cardiac outcomes are unclear, but many possibilities exist. CKD is an independent risk factor for coronary artery disease and shares underlying risk factors such as hypertension and diabetes. Cardiac surgery patients with CKD are also more likely to have diabetes, left ventricular dysfunction, and peripheral vascular disease.

Noncardiac surgery outcomes

CKD is also associated with adverse outcomes in noncardiac surgery patients, especially at higher levels of renal dysfunction.^12–14 For example, in patients who underwent major noncardiac surgery, compared with patients in stage 1 (estimated GFR > 90 mL/min/1.73 m²), the odds ratios for all-cause mortality were as follows:

• 0.8 for patients with stage 2 CKD
• 2.2 in stage 3a
• 2.8 in stage 3b
• 11.3 in stage 4
• 5.8 in stage 5.¹⁴

The association between estimated GFR and all-cause mortality was not statistically significant (P = .071), but statistically significant associations were observed between estimated GFR and major adverse cardiovascular events (P < .001) and hospital length of stay (P < .001).

The association of CKD with major adverse outcomes and death in both cardiac and noncardiac surgical patients demonstrates the importance of understanding this risk, identifying patients with CKD preoperatively, and taking steps to lower the risk.

WHAT IS THE IMPACT OF ACUTE KIDNEY INJURY?

AKI is a common and serious complication of surgery, especially cardiac surgery. It has been associated with higher rates of morbidity, mortality, and cardiovascular events, longer hospital length of stay, and higher cost.

Several groups have proposed criteria for defining AKI and its severity; the KDIGO criteria are the most widely accepted.¹⁵ These define AKI as an increase in serum creatinine concentration of 0.3 mg/dL or more within 48 hours or at least 1.5 times the baseline value within 7 days, or urine volume less than 0.5 mL/kg/hour for more than 6 hours. There are 3 stages of severity:

• Stage 1—an increase in serum creatinine of 1.5 to 1.9 times baseline, an absolute increase of at least 0.3 mg/dL, or urine output less than 0.5 mL/kg/hour for 6 to 12 hours
• Stage 2—an increase in serum creatinine of 2.0 to 2.9 times baseline or urine output less than 0.5 mmL/kg/hour for 12 or more hours
• Stage 3—an increase in serum creatinine of 3 times baseline, an absolute increase of at least 4 mg/dL, initiation of renal replacement therapy, urine output less than 0.3 mL/kg/hour for 24 or more hours, or anuria for 12 or more hours.¹⁵

Multiple factors associated with surgery may contribute to AKI, including hemodynamic instability, volume shifts, blood loss, use of heart-lung bypass, new medications, activation of the inflammatory cascade, oxidative stress, and anemia.

AKI in cardiac surgery

The incidence of AKI is high in cardiac surgery. In a meta-analysis of 46 studies (N = 242,000), its incidence in cardiopulmonary bypass surgery was about 18%, with 2.1% of patients needing renal replacement therapy.¹⁶ However, the incidence varied considerably from study to study, ranging from 1% to 53%, and was influenced by the definition of AKI, the type of cardiac surgery, and the patient population.¹⁶

Cardiac surgery-associated AKI adversely affects outcomes. Several studies have shown that cardiac surgery patients who develop AKI have higher rates of death and stroke.^16–21 More severe AKI confers higher mortality rates, with the highest mortality rate in patients who need renal replacement therapy, approximately 37%.¹⁷ Patients with cardiac surgery-associated AKI also have a longer hospital length of stay and significantly higher costs of care.^17,18

Long-term outcomes are also negatively affected by AKI. In cardiac surgery patients with AKI who had completely recovered renal function by the time they left the hospital, the 2-year incidence rate of CKD was 6.8%, significantly higher than the 0.2% rate in patients who did not develop AKI.¹⁹ The 2-year survival rates also were significantly worse for patients who developed postoperative AKI (82.3% vs 93.7%). Similarly, in patients undergoing CABG who had normal renal function before surgery, those who developed AKI postoperatively had significantly shorter long-term survival rates.²⁰ The effect does not require a large change in renal function. An increase in creatinine as small as 0.3 mg/dL has been associated with a higher rate of death and a long-term risk of end-stage renal disease that is 3 times higher.²¹

Cardiac surgery

CKD is a risk factor not only after cardiac surgery but also after percutaneous procedures. In a meta-analysis of 4,992 patients with CKD who underwent transcatheter aortic valve replacement, both moderate and severe CKD increased the odds of AKI, early stroke, the need for dialysis, and all-cause and cardiovascular mortality at 1 year.^22,23 Increased rates of AKI also have been found in patients with CKD undergoing CABG surgery.²⁴ These results point to a synergistic effect between AKI and CKD, with outcomes much worse in combination than alone.

In cardiac surgery, the most important patient risk factors associated with a higher incidence of postoperative AKI are age older than 75, CKD, preoperative heart failure, and prior myocardial infarction.^19,25 Diabetes is an additional independent risk factor, with type 1 conferring higher risk than type 2.²⁶ Preoperative use of angiotensin-converting enzyme (ACE) inhibitors may or may not be a risk factor for cardiac surgery-associated AKI, with some studies finding increased risk and others finding reduced rates.^27,28

Anemia, which may be related to either patient or surgical risk factors (eg, intraoperative blood loss), also increases the risk of AKI in cardiac surgery.^29,30 A retrospective study of CABG surgery patients found that intraoperative hemoglobin levels below 8 g/dL were associated with a 25% to 30% incidence of AKI, compared with 15% to 20% with hemoglobin levels above 9 g/dL.²⁹ Additionally, having severe hypotension (mean arterial pressure < 50 mm Hg) significantly increased the AKI rates in the low-hemoglobin group.²⁹ Similar results were reported in a later study.³⁰

Among surgical factors, several randomized controlled trials have shown that off-pump CABG is associated with a significantly lower risk of postoperative AKI than on-pump CABG; however, this difference did not translate into any long-term difference in mortality rates.^31,32 Longer cardiopulmonary bypass time is strongly associated with a higher incidence of AKI and postoperative death.³³

Noncardiac surgery

AKI is less common after noncardiac surgery; however, outcomes are severe in patients in whom it occurs. In a study of 15,102 noncardiac surgery patients, only 0.8% developed AKI and 0.1% required renal replacement therapy.³⁴

Risk factors after noncardiac surgery are similar to those after cardiac surgery (Table 3).^34–36 Factors with the greatest impact are older age, peripheral vascular occlusive disease, chronic obstructive pulmonary disease necessitating chronic bronchodilator therapy, high-risk surgery, hepatic disease, emergent or urgent surgery, and high body mass index.

Surgical risk factors include total vasopressor dose administered, use of a vasopressor infusion, and diuretic administration.³⁴ In addition, intraoperative hypotension is associated with a higher risk of AKI, major adverse cardiac events, and 30-day mortality.³⁷

Noncardiac surgery patients with postoperative AKI have significantly higher rates of 30-day readmissions, 1-year progression to end-stage renal disease, and mortality than patients who do not develop AKI.³⁵ Additionally, patients with AKI have significantly higher rates of cardiovascular complications (33.3% vs 11.3%) and death (6.1% vs 0.9%), as well as a significantly longer length of hospital stay.^34,36

CAN WE DECREASE THE IMPACT OF RENAL DISEASE IN SURGERY?

Before surgery, practitioners need to identify patients at risk of AKI, implement possible risk-reduction measures, and, afterward, treat it early in its course if it occurs.

The preoperative visit is the ideal time to assess a patient’s risk of postoperative renal dysfunction. Laboratory tests can identify risks based on surgery type, age, hypertension, the presence of CKD, and medications that affect renal function. However, the basic chemistry panel is abnormal in only 8.2% of patients and affects management in just 2.6%, requiring the clinician to target testing to patients at high risk.³⁸

Patients with a significant degree of renal dysfunction, particularly those previously undiagnosed, may benefit from additional preoperative testing and medication management. Perioperative management of medications that could adversely affect renal function should be carefully considered during the preoperative visit. In addition, the postoperative inpatient team needs to be informed about potentially nephrotoxic medications and medications that are renally cleared. Attention needs to be given to the renal impact of common perioperative medications such as nonsteroidal anti-inflammatory drugs, antibiotics, intravenous contrast, low-molecular-weight heparins, diuretics, ACE inhibitors, and angiotensin II receptor blockers. With the emphasis on opioid-sparing analgesics, it is particularly important to assess the risk of AKI if nonsteroidal anti-inflammatory drugs are part of the pain control plan.

Nephrology referral may help, especially for patients with a GFR less than 45 mL/min. This information enables more informed decision-making regarding the risks of adverse outcomes related to kidney disease.

WHAT TOOLS DO WE HAVE TO DIAGNOSE RENAL INJURY?

Several risk-prediction models have been developed to assess the postoperative risk of AKI in both cardiac and major noncardiac surgery patients. Although these models can identify risk factors, their clinical accuracy and utility have been questioned.

Biomarkers

Early diagnosis is the first step in managing AKI, allowing time to implement measures to minimize its impact.

Serum creatinine testing is widely used to measure renal function and diagnose AKI; however, it does not detect small reductions in renal function, and there is a time lag between renal insult and a rise in creatinine. The result is a delay to diagnosis of AKI.

Biomarkers other than creatinine have been studied for early detection of intraoperative and postoperative renal insult. These novel renal injury markers include the following:

Neutrophil gelatinase-associated lipocalin (NGAL). Two studies looked at plasma NGAL as an early marker of AKI in patients with CKD who were undergoing cardiac surgery.^39,40 One study found that by using NGAL instead of creatinine, postoperative AKI could be diagnosed an average of 20 hours earlier.³⁹ In addition, NGAL helped detect renal recovery earlier than creatinine.⁴⁰ The diagnostic cut-off values of NGAL were different for patients with CKD than for those without CKD.^39,40

Other novel markers include:

• Kidney injury marker 1
• N-acetyl-beta-D-glucosaminidase
• Cysteine C.

Although these biomarkers show some ability to detect renal injury, they provide only modest discrimination and are not widely available for clinical use.⁴¹ Current evidence does not support routine use of these markers in clinical settings.

Interventions to prevent or ameliorate the impact of CKD and AKI on surgical outcomes have been studied most extensively in cardiac surgery patients.

Aspirin. A retrospective study of 3,585 cardiac surgery patients with CKD found that preoperative aspirin use significantly lowered the incidence of postoperative AKI and 30-day mortality compared with patients not using aspirin.⁴² Aspirin use reduced 30-day mortality in CKD stages 1, 2, and 3 by 23.3%, 58%, and 70%, respectively. On the other hand, in the Perioperative Ischemic Evaluation (POISE) trial, in noncardiac surgery patients, neither aspirin nor clonidine started 2 to 4 hours preoperatively and continued up to 30 days after surgery altered the risk of AKI significantly more than placebo.⁴³

Statins have been ineffective in reducing the incidence of AKI in cardiac surgery patients. In fact, a meta-analysis of 8 interventional trials found an increased incidence of AKI in patients in whom statins were started perioperatively.⁴⁴ Erythropoietin was also found to be ineffective in the prevention of perioperative AKI in cardiac surgery patients in a separate study.⁴⁵

The evidence regarding other therapies has also varied.

N-acetylcysteine in high doses reduced the incidence of AKI in patients with CKD stage 3 and 4 undergoing CABG.⁴⁶ Another meta-analysis of 10 studies in cardiac surgery patients published recently did not show any benefit of N-acetylcysteine in reducing AKI.⁴⁷

Human atrial natriuretic peptide, given preoperatively to patients with CKD, reduced the acute and long-term creatinine rise as well as the number of cardiac events after CABG; however, it did not reduce mortality rates.⁴⁸

Renin-angiotensin system inhibitors, given preoperatively to patients with heart failure was associated with a decrease in the incidence of AKI in 1 study.⁴⁹

Dexmedetomidine is a highly selective alpha 2 adrenoreceptor agonist. A recent meta-analysis of 10 clinical trials found it beneficial in reducing the risk of perioperative AKI in cardiac surgery patients.⁵⁰ An earlier meta-analysis had similar results.⁵¹

Levosimendan is an inotropic vasodilator that improves cardiac output and renal perfusion in patients with systolic heart failure, and it has been hypothesized to decrease the risk of AKI after cardiac surgery. Previous data demonstrated that this drug reduced AKI and mortality; however, analysis was limited by small sample size and varying definitions of AKI.⁵² A recent meta-analysis showed that levosimendan was associated with a lower incidence of AKI but was also associated with an increased incidence of atrial fibrillation and no reduction in 30-day mortality.⁵³

Remote ischemic preconditioning is a procedure that subjects the kidneys to brief episodes of ischemia before surgery, protecting them when they are later subjected to prolonged ischemia or reperfusion injury. It has shown initial promising results in preventing AKI. In a randomized controlled trial in 240 patients at high risk of AKI, those who received remote ischemic preconditioning had an AKI incidence of 37.5% compared with 52.5% for controls (P = .02); however, the mortality rate was the same.⁵⁴ Similarly, remote ischemic preconditioning significantly lowered the incidence of AKI in nondiabetic patients undergoing CABG surgery compared with controls.⁵⁵

Fluid management. Renal perfusion is intimately related to the development of AKI, and there is evidence that both hypovolemia and excessive fluid resuscitation can increase the risk of AKI in noncardiac surgery patients.⁵⁶ Because of this, fluid management has also received attention in perioperative AKI. Goal-directed fluid management has been evaluated in noncardiac surgery patients, and it did not show any benefit in preventing AKI.⁵⁷ However, in a more recent retrospective study, postoperative positive fluid balance was associated with increased incidence of AKI compared with zero fluid balance. Negative fluid balance did not appear to have a detrimental effect.⁵⁸

RECOMMENDATIONS

No prophylactic therapy has yet been shown to definitively decrease the risk of postoperative AKI in all patients. Nevertheless, it is important to identify patients at risk during the preoperative visit, especially those with CKD. Many patients undergoing surgery have CKD, placing them at high risk of developing AKI in the perioperative period. The risk is particularly high with cardiac surgery.

Serum creatinine and urine output should be closely monitored perioperatively in at-risk patients. If AKI is diagnosed, practitioners need to identify and ameliorate the cause as early as possible.

Recommendations from KDIGO for perioperative prevention and management of AKI are listed in Table 4.¹⁵ These include avoiding additional nephrotoxic medications and adjusting the doses of renally cleared medications. Also, some patients may benefit from preoperative counseling and specialist referral.

Chronic kidney disease (CKD) is estimated to affect 14% of Americans, but it is likely underdiagnosed because it is often asymptomatic.^1,2 Its prevalence is even higher in patients who undergo surgery—up to 30% in cardiac surgery.³ Its impact on surgical outcomes is substantial.⁴ Importantly, patients with CKD are at higher risk of postoperative acute kidney injury (AKI), which is also associated with adverse outcomes. Thus, it is important to recognize, assess, and manage abnormal renal function in surgical patients.

WHAT IS THE IMPACT ON POSTOPERATIVE OUTCOMES?

Cardiac surgery outcomes

Moreover, in patients undergoing coronary artery bypass grafting (CABG), the worse the renal dysfunction, the higher the long-term mortality rate. Patients with moderate (stage 3) CKD had a 3.5 times higher odds of in-hospital mortality compared with patients with normal renal function, rising to 8.8 with severe (stage 4) and to 9.6 with dialysis-dependent (stage 5) CKD.¹¹

The mechanisms linking CKD with negative cardiac outcomes are unclear, but many possibilities exist. CKD is an independent risk factor for coronary artery disease and shares underlying risk factors such as hypertension and diabetes. Cardiac surgery patients with CKD are also more likely to have diabetes, left ventricular dysfunction, and peripheral vascular disease.

Noncardiac surgery outcomes

CKD is also associated with adverse outcomes in noncardiac surgery patients, especially at higher levels of renal dysfunction.^12–14 For example, in patients who underwent major noncardiac surgery, compared with patients in stage 1 (estimated GFR > 90 mL/min/1.73 m²), the odds ratios for all-cause mortality were as follows:

• 0.8 for patients with stage 2 CKD
• 2.2 in stage 3a
• 2.8 in stage 3b
• 11.3 in stage 4
• 5.8 in stage 5.¹⁴

The association between estimated GFR and all-cause mortality was not statistically significant (P = .071), but statistically significant associations were observed between estimated GFR and major adverse cardiovascular events (P < .001) and hospital length of stay (P < .001).

The association of CKD with major adverse outcomes and death in both cardiac and noncardiac surgical patients demonstrates the importance of understanding this risk, identifying patients with CKD preoperatively, and taking steps to lower the risk.

WHAT IS THE IMPACT OF ACUTE KIDNEY INJURY?

AKI is a common and serious complication of surgery, especially cardiac surgery. It has been associated with higher rates of morbidity, mortality, and cardiovascular events, longer hospital length of stay, and higher cost.

Several groups have proposed criteria for defining AKI and its severity; the KDIGO criteria are the most widely accepted.¹⁵ These define AKI as an increase in serum creatinine concentration of 0.3 mg/dL or more within 48 hours or at least 1.5 times the baseline value within 7 days, or urine volume less than 0.5 mL/kg/hour for more than 6 hours. There are 3 stages of severity:

• Stage 1—an increase in serum creatinine of 1.5 to 1.9 times baseline, an absolute increase of at least 0.3 mg/dL, or urine output less than 0.5 mL/kg/hour for 6 to 12 hours
• Stage 2—an increase in serum creatinine of 2.0 to 2.9 times baseline or urine output less than 0.5 mmL/kg/hour for 12 or more hours
• Stage 3—an increase in serum creatinine of 3 times baseline, an absolute increase of at least 4 mg/dL, initiation of renal replacement therapy, urine output less than 0.3 mL/kg/hour for 24 or more hours, or anuria for 12 or more hours.¹⁵

Multiple factors associated with surgery may contribute to AKI, including hemodynamic instability, volume shifts, blood loss, use of heart-lung bypass, new medications, activation of the inflammatory cascade, oxidative stress, and anemia.

AKI in cardiac surgery

The incidence of AKI is high in cardiac surgery. In a meta-analysis of 46 studies (N = 242,000), its incidence in cardiopulmonary bypass surgery was about 18%, with 2.1% of patients needing renal replacement therapy.¹⁶ However, the incidence varied considerably from study to study, ranging from 1% to 53%, and was influenced by the definition of AKI, the type of cardiac surgery, and the patient population.¹⁶

Cardiac surgery-associated AKI adversely affects outcomes. Several studies have shown that cardiac surgery patients who develop AKI have higher rates of death and stroke.^16–21 More severe AKI confers higher mortality rates, with the highest mortality rate in patients who need renal replacement therapy, approximately 37%.¹⁷ Patients with cardiac surgery-associated AKI also have a longer hospital length of stay and significantly higher costs of care.^17,18

Long-term outcomes are also negatively affected by AKI. In cardiac surgery patients with AKI who had completely recovered renal function by the time they left the hospital, the 2-year incidence rate of CKD was 6.8%, significantly higher than the 0.2% rate in patients who did not develop AKI.¹⁹ The 2-year survival rates also were significantly worse for patients who developed postoperative AKI (82.3% vs 93.7%). Similarly, in patients undergoing CABG who had normal renal function before surgery, those who developed AKI postoperatively had significantly shorter long-term survival rates.²⁰ The effect does not require a large change in renal function. An increase in creatinine as small as 0.3 mg/dL has been associated with a higher rate of death and a long-term risk of end-stage renal disease that is 3 times higher.²¹

Cardiac surgery

CKD is a risk factor not only after cardiac surgery but also after percutaneous procedures. In a meta-analysis of 4,992 patients with CKD who underwent transcatheter aortic valve replacement, both moderate and severe CKD increased the odds of AKI, early stroke, the need for dialysis, and all-cause and cardiovascular mortality at 1 year.^22,23 Increased rates of AKI also have been found in patients with CKD undergoing CABG surgery.²⁴ These results point to a synergistic effect between AKI and CKD, with outcomes much worse in combination than alone.

In cardiac surgery, the most important patient risk factors associated with a higher incidence of postoperative AKI are age older than 75, CKD, preoperative heart failure, and prior myocardial infarction.^19,25 Diabetes is an additional independent risk factor, with type 1 conferring higher risk than type 2.²⁶ Preoperative use of angiotensin-converting enzyme (ACE) inhibitors may or may not be a risk factor for cardiac surgery-associated AKI, with some studies finding increased risk and others finding reduced rates.^27,28

Anemia, which may be related to either patient or surgical risk factors (eg, intraoperative blood loss), also increases the risk of AKI in cardiac surgery.^29,30 A retrospective study of CABG surgery patients found that intraoperative hemoglobin levels below 8 g/dL were associated with a 25% to 30% incidence of AKI, compared with 15% to 20% with hemoglobin levels above 9 g/dL.²⁹ Additionally, having severe hypotension (mean arterial pressure < 50 mm Hg) significantly increased the AKI rates in the low-hemoglobin group.²⁹ Similar results were reported in a later study.³⁰

Among surgical factors, several randomized controlled trials have shown that off-pump CABG is associated with a significantly lower risk of postoperative AKI than on-pump CABG; however, this difference did not translate into any long-term difference in mortality rates.^31,32 Longer cardiopulmonary bypass time is strongly associated with a higher incidence of AKI and postoperative death.³³

Noncardiac surgery

AKI is less common after noncardiac surgery; however, outcomes are severe in patients in whom it occurs. In a study of 15,102 noncardiac surgery patients, only 0.8% developed AKI and 0.1% required renal replacement therapy.³⁴

Risk factors after noncardiac surgery are similar to those after cardiac surgery (Table 3).^34–36 Factors with the greatest impact are older age, peripheral vascular occlusive disease, chronic obstructive pulmonary disease necessitating chronic bronchodilator therapy, high-risk surgery, hepatic disease, emergent or urgent surgery, and high body mass index.

Surgical risk factors include total vasopressor dose administered, use of a vasopressor infusion, and diuretic administration.³⁴ In addition, intraoperative hypotension is associated with a higher risk of AKI, major adverse cardiac events, and 30-day mortality.³⁷

Noncardiac surgery patients with postoperative AKI have significantly higher rates of 30-day readmissions, 1-year progression to end-stage renal disease, and mortality than patients who do not develop AKI.³⁵ Additionally, patients with AKI have significantly higher rates of cardiovascular complications (33.3% vs 11.3%) and death (6.1% vs 0.9%), as well as a significantly longer length of hospital stay.^34,36

CAN WE DECREASE THE IMPACT OF RENAL DISEASE IN SURGERY?

Before surgery, practitioners need to identify patients at risk of AKI, implement possible risk-reduction measures, and, afterward, treat it early in its course if it occurs.

The preoperative visit is the ideal time to assess a patient’s risk of postoperative renal dysfunction. Laboratory tests can identify risks based on surgery type, age, hypertension, the presence of CKD, and medications that affect renal function. However, the basic chemistry panel is abnormal in only 8.2% of patients and affects management in just 2.6%, requiring the clinician to target testing to patients at high risk.³⁸

Patients with a significant degree of renal dysfunction, particularly those previously undiagnosed, may benefit from additional preoperative testing and medication management. Perioperative management of medications that could adversely affect renal function should be carefully considered during the preoperative visit. In addition, the postoperative inpatient team needs to be informed about potentially nephrotoxic medications and medications that are renally cleared. Attention needs to be given to the renal impact of common perioperative medications such as nonsteroidal anti-inflammatory drugs, antibiotics, intravenous contrast, low-molecular-weight heparins, diuretics, ACE inhibitors, and angiotensin II receptor blockers. With the emphasis on opioid-sparing analgesics, it is particularly important to assess the risk of AKI if nonsteroidal anti-inflammatory drugs are part of the pain control plan.

Nephrology referral may help, especially for patients with a GFR less than 45 mL/min. This information enables more informed decision-making regarding the risks of adverse outcomes related to kidney disease.

WHAT TOOLS DO WE HAVE TO DIAGNOSE RENAL INJURY?

Several risk-prediction models have been developed to assess the postoperative risk of AKI in both cardiac and major noncardiac surgery patients. Although these models can identify risk factors, their clinical accuracy and utility have been questioned.

Biomarkers

Early diagnosis is the first step in managing AKI, allowing time to implement measures to minimize its impact.

Serum creatinine testing is widely used to measure renal function and diagnose AKI; however, it does not detect small reductions in renal function, and there is a time lag between renal insult and a rise in creatinine. The result is a delay to diagnosis of AKI.

Biomarkers other than creatinine have been studied for early detection of intraoperative and postoperative renal insult. These novel renal injury markers include the following:

Neutrophil gelatinase-associated lipocalin (NGAL). Two studies looked at plasma NGAL as an early marker of AKI in patients with CKD who were undergoing cardiac surgery.^39,40 One study found that by using NGAL instead of creatinine, postoperative AKI could be diagnosed an average of 20 hours earlier.³⁹ In addition, NGAL helped detect renal recovery earlier than creatinine.⁴⁰ The diagnostic cut-off values of NGAL were different for patients with CKD than for those without CKD.^39,40

Other novel markers include:

• Kidney injury marker 1
• N-acetyl-beta-D-glucosaminidase
• Cysteine C.

Although these biomarkers show some ability to detect renal injury, they provide only modest discrimination and are not widely available for clinical use.⁴¹ Current evidence does not support routine use of these markers in clinical settings.

Interventions to prevent or ameliorate the impact of CKD and AKI on surgical outcomes have been studied most extensively in cardiac surgery patients.

Aspirin. A retrospective study of 3,585 cardiac surgery patients with CKD found that preoperative aspirin use significantly lowered the incidence of postoperative AKI and 30-day mortality compared with patients not using aspirin.⁴² Aspirin use reduced 30-day mortality in CKD stages 1, 2, and 3 by 23.3%, 58%, and 70%, respectively. On the other hand, in the Perioperative Ischemic Evaluation (POISE) trial, in noncardiac surgery patients, neither aspirin nor clonidine started 2 to 4 hours preoperatively and continued up to 30 days after surgery altered the risk of AKI significantly more than placebo.⁴³

Statins have been ineffective in reducing the incidence of AKI in cardiac surgery patients. In fact, a meta-analysis of 8 interventional trials found an increased incidence of AKI in patients in whom statins were started perioperatively.⁴⁴ Erythropoietin was also found to be ineffective in the prevention of perioperative AKI in cardiac surgery patients in a separate study.⁴⁵

The evidence regarding other therapies has also varied.

N-acetylcysteine in high doses reduced the incidence of AKI in patients with CKD stage 3 and 4 undergoing CABG.⁴⁶ Another meta-analysis of 10 studies in cardiac surgery patients published recently did not show any benefit of N-acetylcysteine in reducing AKI.⁴⁷

Human atrial natriuretic peptide, given preoperatively to patients with CKD, reduced the acute and long-term creatinine rise as well as the number of cardiac events after CABG; however, it did not reduce mortality rates.⁴⁸

Renin-angiotensin system inhibitors, given preoperatively to patients with heart failure was associated with a decrease in the incidence of AKI in 1 study.⁴⁹

Dexmedetomidine is a highly selective alpha 2 adrenoreceptor agonist. A recent meta-analysis of 10 clinical trials found it beneficial in reducing the risk of perioperative AKI in cardiac surgery patients.⁵⁰ An earlier meta-analysis had similar results.⁵¹

Levosimendan is an inotropic vasodilator that improves cardiac output and renal perfusion in patients with systolic heart failure, and it has been hypothesized to decrease the risk of AKI after cardiac surgery. Previous data demonstrated that this drug reduced AKI and mortality; however, analysis was limited by small sample size and varying definitions of AKI.⁵² A recent meta-analysis showed that levosimendan was associated with a lower incidence of AKI but was also associated with an increased incidence of atrial fibrillation and no reduction in 30-day mortality.⁵³

Remote ischemic preconditioning is a procedure that subjects the kidneys to brief episodes of ischemia before surgery, protecting them when they are later subjected to prolonged ischemia or reperfusion injury. It has shown initial promising results in preventing AKI. In a randomized controlled trial in 240 patients at high risk of AKI, those who received remote ischemic preconditioning had an AKI incidence of 37.5% compared with 52.5% for controls (P = .02); however, the mortality rate was the same.⁵⁴ Similarly, remote ischemic preconditioning significantly lowered the incidence of AKI in nondiabetic patients undergoing CABG surgery compared with controls.⁵⁵

Fluid management. Renal perfusion is intimately related to the development of AKI, and there is evidence that both hypovolemia and excessive fluid resuscitation can increase the risk of AKI in noncardiac surgery patients.⁵⁶ Because of this, fluid management has also received attention in perioperative AKI. Goal-directed fluid management has been evaluated in noncardiac surgery patients, and it did not show any benefit in preventing AKI.⁵⁷ However, in a more recent retrospective study, postoperative positive fluid balance was associated with increased incidence of AKI compared with zero fluid balance. Negative fluid balance did not appear to have a detrimental effect.⁵⁸

RECOMMENDATIONS

No prophylactic therapy has yet been shown to definitively decrease the risk of postoperative AKI in all patients. Nevertheless, it is important to identify patients at risk during the preoperative visit, especially those with CKD. Many patients undergoing surgery have CKD, placing them at high risk of developing AKI in the perioperative period. The risk is particularly high with cardiac surgery.

Serum creatinine and urine output should be closely monitored perioperatively in at-risk patients. If AKI is diagnosed, practitioners need to identify and ameliorate the cause as early as possible.

Recommendations from KDIGO for perioperative prevention and management of AKI are listed in Table 4.¹⁵ These include avoiding additional nephrotoxic medications and adjusting the doses of renally cleared medications. Also, some patients may benefit from preoperative counseling and specialist referral.

First described in 2000 in a case series of 15 patients, nephrogenic systemic fibrosis (NSF) is a rare scleroderma-like fibrosing skin condition associated with gadolinium exposure in end stage renal disease (ESRD).¹ Patients with advanced chronic kidney disease (CKD) or ESRD are at the highest risk for this condition when exposed to gadolinium-based contrast dyes.

Nephrogenic systemic fibrosis is a devastating and rapidly progressive condition, making its prevention in at-risk populations of utmost importance. In this article, the authors describe a case of a patient who developed NSF in the setting of gadolinium exposure and multiple inflammatory dermatologic conditions. This case illustrates the possible role of a pro-inflammatory state in predisposing to NSF, which may help further elucidate its mechanism of action.

Case Presentation

A 61-year-old Hispanic male with a history of IV heroin use with ESRD secondary to membranous glomerulonephritis on hemodialysis and chronic hepatitis C infection presented to the West Los Angeles VAMC with fevers and night sweats that had persisted for 2 weeks. His physical examination was notable for diffuse tender palpable purpura and petechiae (including his palms and soles), altered mental status, and diffuse myoclonic jerks, which necessitated endotracheal intubation and mechanical ventilation for airway protection. Blood cultures were positive for methicillin-sensitive Staphylococcus aureus (MSSA). Laboratory results were notable for an elevated sedimentation rate of 53 mm/h (0-10 mm/h), C-reactive protein of 19.8 mg/L (< 0.744 mg/dL), and albumin of 1.2 g/dL (3.2-4.8 g/dL). An extensive rheumatologic workup was unrevealing, and a lumbar puncture was unremarkable. A biopsy of his skin lesions was consistent with leukocytoclastic vasculitis.

The patient’s prior hemodialysis access, a tunneled dialysis catheter in the right subclavian vein, was removed given concern for line infection and replaced with an internal jugular temporary hemodialysis line. Given his altered mental status and myoclonic jerks, the decision was made to pursue a magnetic resonance imaging (MRI) scan of the brain and spine with gadolinium contrast to evaluate for cerebral vasculitis and/or septic emboli to the brain.

The patient received 15 mL of gadoversetamide contrast in accordance with hospital imaging protocol. The MRI revealed only chronic ischemic changes. The patient underwent hemodialysis about 18 hours later. The patient was treated with a 6-week course of IV penicillin G. His altered mental status and myoclonic jerks resolved without intervention, and he was then discharged to an acute rehabilitation unit.

Eight weeks after his initial presentation the patient developed a purulent wound on his right forearm (Figure 1) 

The patient was discharged to continue physical and occupational therapy to preserve his functional mobility, as no other treatment options were available. 

Discussion

Nephrogenic systemic fibrosis is a poorly understood inflammatory condition that produces diffuse fibrosis of the skin. Typically, the disease begins with progressive skin induration of the extremities. Systemic involvement may occur, leading to fibrosis of skeletal muscle, fascia, and multiple organs. Flexion contractures may develop that limit physical function. Fibrosis can become apparent within days to months after exposure to gadolinium contrast.

Beyond renal insufficiency, it is unclear what other risk factors predispose patients to developing this condition. Only a minority of patients with CKD stages 1 through 4 will develop NSF on exposure to gadolinium contrast. However, the incidence of NSF among patients with CKD stage 5 who are exposed to gadolinium has been estimated to be about 13.4% in a prospective study involving 18 patients.²

In a 2015 meta-analysis by Zhang and colleagues, the only clear risk factor identified for the development of NSF, aside from gadolinium exposure, was severe renal insufficiency with a glomerular filtration rate of < 30 mL/min/1.75m².³ Due to the limited number of patients identified with this disease, it is difficult to identify other risk factors associated with the development of NSF. Based on in vitro studies, it has been postulated that a pro-inflammatory state predisposes patients to develop NSF.^4,5 The proposed mechanism for NSF involves extravasation of gadolinium in the setting of vascular endothelial permeability.^5,6 Gadolinium then interacts with tissue macrophages, which induce the release of inflammatory cytokines and the secretion of smooth muscle actin by dermal fibroblasts.^6,7

Treatment of NSF has been largely unsuccessful. Multiple modalities of treatment that included topical and oral steroids, immunosuppression, plasmapheresis, and ultraviolent therapy have been attempted, none of which have been proven to consistently limit progression of the disease.⁸ The most effective intervention is early physical therapy to preserve functionality and prevent contracture formation. For patients who are eligible, early renal transplantation may offer the best chance of improved mobility. In a case series review by Cuffy and colleagues, 5 of 6 patients who underwent renal transplantation after the development of NSF experienced softening of the involved skin, and 2 patients had improved mobility of joints.⁹

Conclusion

The case presented here illustrates a possible association between a pro-inflammatory state and the development of NSF. This patient had multiple inflammatory conditions, including MSSA bacteremia, leukocytoclastic vasculitis, and pyoderma gangrenosum (the latter 2 conditions were thought to be associated with his underlying chronic hepatitis C infection), which the authors believe predisposed him to endothelial permeability and risk for developing NSF. The risk of developing NSF in at-risk patients with each episode of gadolinium exposure is estimated around 2.4%, or an incidence of 4.3 cases per 1,000 patient-years, leading the American College of Radiologists to recommend against the administration of gadolinium-based contrast except in cases in which benefits clearly outweigh risks.¹⁰ However, an MRI with gadolinium contrast can offer high diagnostic yield in cases such as the one presented here in which a diagnosis remains elusive. Moreover, the use of linear gadolinium-based contrast agents such as gadoversetamide, as in this case, has been reported to be associated with higher incidence of NSF.⁵ Since this case, the West Los Angeles VAMC has switched to gadobutrol contrast for its MRI protocol, which has been purported to be a lower risk agent compared with that of linear gadolinium-based contrast agents (although several cases of NSF have been reported with gadobutrol in the literature).¹¹

Providers weighing the decision to administer gadolinium contrast to patients with ESRD should discuss the risks and benefits thoroughly, especially in patients with preexisting inflammatory conditions. In addition, although it has not been shown to effectively reduce the risk of NSF after administration of gadolinium, hemodialysis is recommended 2 hours after contrast administration for individuals at risk (the study patient received hemodialysis approximately 18 hours after).¹² Given the lack of effective treatment options for NSF, prevention is key. A deeper understanding of the pathophysiology of NSF and identification of its risk factors is paramount to the prevention of this devastating disease.

First described in 2000 in a case series of 15 patients, nephrogenic systemic fibrosis (NSF) is a rare scleroderma-like fibrosing skin condition associated with gadolinium exposure in end stage renal disease (ESRD).¹ Patients with advanced chronic kidney disease (CKD) or ESRD are at the highest risk for this condition when exposed to gadolinium-based contrast dyes.

Nephrogenic systemic fibrosis is a devastating and rapidly progressive condition, making its prevention in at-risk populations of utmost importance. In this article, the authors describe a case of a patient who developed NSF in the setting of gadolinium exposure and multiple inflammatory dermatologic conditions. This case illustrates the possible role of a pro-inflammatory state in predisposing to NSF, which may help further elucidate its mechanism of action.

Case Presentation

A 61-year-old Hispanic male with a history of IV heroin use with ESRD secondary to membranous glomerulonephritis on hemodialysis and chronic hepatitis C infection presented to the West Los Angeles VAMC with fevers and night sweats that had persisted for 2 weeks. His physical examination was notable for diffuse tender palpable purpura and petechiae (including his palms and soles), altered mental status, and diffuse myoclonic jerks, which necessitated endotracheal intubation and mechanical ventilation for airway protection. Blood cultures were positive for methicillin-sensitive Staphylococcus aureus (MSSA). Laboratory results were notable for an elevated sedimentation rate of 53 mm/h (0-10 mm/h), C-reactive protein of 19.8 mg/L (< 0.744 mg/dL), and albumin of 1.2 g/dL (3.2-4.8 g/dL). An extensive rheumatologic workup was unrevealing, and a lumbar puncture was unremarkable. A biopsy of his skin lesions was consistent with leukocytoclastic vasculitis.

The patient’s prior hemodialysis access, a tunneled dialysis catheter in the right subclavian vein, was removed given concern for line infection and replaced with an internal jugular temporary hemodialysis line. Given his altered mental status and myoclonic jerks, the decision was made to pursue a magnetic resonance imaging (MRI) scan of the brain and spine with gadolinium contrast to evaluate for cerebral vasculitis and/or septic emboli to the brain.

The patient received 15 mL of gadoversetamide contrast in accordance with hospital imaging protocol. The MRI revealed only chronic ischemic changes. The patient underwent hemodialysis about 18 hours later. The patient was treated with a 6-week course of IV penicillin G. His altered mental status and myoclonic jerks resolved without intervention, and he was then discharged to an acute rehabilitation unit.

Eight weeks after his initial presentation the patient developed a purulent wound on his right forearm (Figure 1) 

The patient was discharged to continue physical and occupational therapy to preserve his functional mobility, as no other treatment options were available. 

Discussion

Nephrogenic systemic fibrosis is a poorly understood inflammatory condition that produces diffuse fibrosis of the skin. Typically, the disease begins with progressive skin induration of the extremities. Systemic involvement may occur, leading to fibrosis of skeletal muscle, fascia, and multiple organs. Flexion contractures may develop that limit physical function. Fibrosis can become apparent within days to months after exposure to gadolinium contrast.

Beyond renal insufficiency, it is unclear what other risk factors predispose patients to developing this condition. Only a minority of patients with CKD stages 1 through 4 will develop NSF on exposure to gadolinium contrast. However, the incidence of NSF among patients with CKD stage 5 who are exposed to gadolinium has been estimated to be about 13.4% in a prospective study involving 18 patients.²

In a 2015 meta-analysis by Zhang and colleagues, the only clear risk factor identified for the development of NSF, aside from gadolinium exposure, was severe renal insufficiency with a glomerular filtration rate of < 30 mL/min/1.75m².³ Due to the limited number of patients identified with this disease, it is difficult to identify other risk factors associated with the development of NSF. Based on in vitro studies, it has been postulated that a pro-inflammatory state predisposes patients to develop NSF.^4,5 The proposed mechanism for NSF involves extravasation of gadolinium in the setting of vascular endothelial permeability.^5,6 Gadolinium then interacts with tissue macrophages, which induce the release of inflammatory cytokines and the secretion of smooth muscle actin by dermal fibroblasts.^6,7

Treatment of NSF has been largely unsuccessful. Multiple modalities of treatment that included topical and oral steroids, immunosuppression, plasmapheresis, and ultraviolent therapy have been attempted, none of which have been proven to consistently limit progression of the disease.⁸ The most effective intervention is early physical therapy to preserve functionality and prevent contracture formation. For patients who are eligible, early renal transplantation may offer the best chance of improved mobility. In a case series review by Cuffy and colleagues, 5 of 6 patients who underwent renal transplantation after the development of NSF experienced softening of the involved skin, and 2 patients had improved mobility of joints.⁹

Conclusion

The case presented here illustrates a possible association between a pro-inflammatory state and the development of NSF. This patient had multiple inflammatory conditions, including MSSA bacteremia, leukocytoclastic vasculitis, and pyoderma gangrenosum (the latter 2 conditions were thought to be associated with his underlying chronic hepatitis C infection), which the authors believe predisposed him to endothelial permeability and risk for developing NSF. The risk of developing NSF in at-risk patients with each episode of gadolinium exposure is estimated around 2.4%, or an incidence of 4.3 cases per 1,000 patient-years, leading the American College of Radiologists to recommend against the administration of gadolinium-based contrast except in cases in which benefits clearly outweigh risks.¹⁰ However, an MRI with gadolinium contrast can offer high diagnostic yield in cases such as the one presented here in which a diagnosis remains elusive. Moreover, the use of linear gadolinium-based contrast agents such as gadoversetamide, as in this case, has been reported to be associated with higher incidence of NSF.⁵ Since this case, the West Los Angeles VAMC has switched to gadobutrol contrast for its MRI protocol, which has been purported to be a lower risk agent compared with that of linear gadolinium-based contrast agents (although several cases of NSF have been reported with gadobutrol in the literature).¹¹

Providers weighing the decision to administer gadolinium contrast to patients with ESRD should discuss the risks and benefits thoroughly, especially in patients with preexisting inflammatory conditions. In addition, although it has not been shown to effectively reduce the risk of NSF after administration of gadolinium, hemodialysis is recommended 2 hours after contrast administration for individuals at risk (the study patient received hemodialysis approximately 18 hours after).¹² Given the lack of effective treatment options for NSF, prevention is key. A deeper understanding of the pathophysiology of NSF and identification of its risk factors is paramount to the prevention of this devastating disease.

First described in 2000 in a case series of 15 patients, nephrogenic systemic fibrosis (NSF) is a rare scleroderma-like fibrosing skin condition associated with gadolinium exposure in end stage renal disease (ESRD).¹ Patients with advanced chronic kidney disease (CKD) or ESRD are at the highest risk for this condition when exposed to gadolinium-based contrast dyes.

Nephrogenic systemic fibrosis is a devastating and rapidly progressive condition, making its prevention in at-risk populations of utmost importance. In this article, the authors describe a case of a patient who developed NSF in the setting of gadolinium exposure and multiple inflammatory dermatologic conditions. This case illustrates the possible role of a pro-inflammatory state in predisposing to NSF, which may help further elucidate its mechanism of action.

Case Presentation

A 61-year-old Hispanic male with a history of IV heroin use with ESRD secondary to membranous glomerulonephritis on hemodialysis and chronic hepatitis C infection presented to the West Los Angeles VAMC with fevers and night sweats that had persisted for 2 weeks. His physical examination was notable for diffuse tender palpable purpura and petechiae (including his palms and soles), altered mental status, and diffuse myoclonic jerks, which necessitated endotracheal intubation and mechanical ventilation for airway protection. Blood cultures were positive for methicillin-sensitive Staphylococcus aureus (MSSA). Laboratory results were notable for an elevated sedimentation rate of 53 mm/h (0-10 mm/h), C-reactive protein of 19.8 mg/L (< 0.744 mg/dL), and albumin of 1.2 g/dL (3.2-4.8 g/dL). An extensive rheumatologic workup was unrevealing, and a lumbar puncture was unremarkable. A biopsy of his skin lesions was consistent with leukocytoclastic vasculitis.

The patient’s prior hemodialysis access, a tunneled dialysis catheter in the right subclavian vein, was removed given concern for line infection and replaced with an internal jugular temporary hemodialysis line. Given his altered mental status and myoclonic jerks, the decision was made to pursue a magnetic resonance imaging (MRI) scan of the brain and spine with gadolinium contrast to evaluate for cerebral vasculitis and/or septic emboli to the brain.

The patient received 15 mL of gadoversetamide contrast in accordance with hospital imaging protocol. The MRI revealed only chronic ischemic changes. The patient underwent hemodialysis about 18 hours later. The patient was treated with a 6-week course of IV penicillin G. His altered mental status and myoclonic jerks resolved without intervention, and he was then discharged to an acute rehabilitation unit.

Eight weeks after his initial presentation the patient developed a purulent wound on his right forearm (Figure 1) 

The patient was discharged to continue physical and occupational therapy to preserve his functional mobility, as no other treatment options were available. 

Discussion

Nephrogenic systemic fibrosis is a poorly understood inflammatory condition that produces diffuse fibrosis of the skin. Typically, the disease begins with progressive skin induration of the extremities. Systemic involvement may occur, leading to fibrosis of skeletal muscle, fascia, and multiple organs. Flexion contractures may develop that limit physical function. Fibrosis can become apparent within days to months after exposure to gadolinium contrast.

Beyond renal insufficiency, it is unclear what other risk factors predispose patients to developing this condition. Only a minority of patients with CKD stages 1 through 4 will develop NSF on exposure to gadolinium contrast. However, the incidence of NSF among patients with CKD stage 5 who are exposed to gadolinium has been estimated to be about 13.4% in a prospective study involving 18 patients.²

In a 2015 meta-analysis by Zhang and colleagues, the only clear risk factor identified for the development of NSF, aside from gadolinium exposure, was severe renal insufficiency with a glomerular filtration rate of < 30 mL/min/1.75m².³ Due to the limited number of patients identified with this disease, it is difficult to identify other risk factors associated with the development of NSF. Based on in vitro studies, it has been postulated that a pro-inflammatory state predisposes patients to develop NSF.^4,5 The proposed mechanism for NSF involves extravasation of gadolinium in the setting of vascular endothelial permeability.^5,6 Gadolinium then interacts with tissue macrophages, which induce the release of inflammatory cytokines and the secretion of smooth muscle actin by dermal fibroblasts.^6,7

Treatment of NSF has been largely unsuccessful. Multiple modalities of treatment that included topical and oral steroids, immunosuppression, plasmapheresis, and ultraviolent therapy have been attempted, none of which have been proven to consistently limit progression of the disease.⁸ The most effective intervention is early physical therapy to preserve functionality and prevent contracture formation. For patients who are eligible, early renal transplantation may offer the best chance of improved mobility. In a case series review by Cuffy and colleagues, 5 of 6 patients who underwent renal transplantation after the development of NSF experienced softening of the involved skin, and 2 patients had improved mobility of joints.⁹

Conclusion

The case presented here illustrates a possible association between a pro-inflammatory state and the development of NSF. This patient had multiple inflammatory conditions, including MSSA bacteremia, leukocytoclastic vasculitis, and pyoderma gangrenosum (the latter 2 conditions were thought to be associated with his underlying chronic hepatitis C infection), which the authors believe predisposed him to endothelial permeability and risk for developing NSF. The risk of developing NSF in at-risk patients with each episode of gadolinium exposure is estimated around 2.4%, or an incidence of 4.3 cases per 1,000 patient-years, leading the American College of Radiologists to recommend against the administration of gadolinium-based contrast except in cases in which benefits clearly outweigh risks.¹⁰ However, an MRI with gadolinium contrast can offer high diagnostic yield in cases such as the one presented here in which a diagnosis remains elusive. Moreover, the use of linear gadolinium-based contrast agents such as gadoversetamide, as in this case, has been reported to be associated with higher incidence of NSF.⁵ Since this case, the West Los Angeles VAMC has switched to gadobutrol contrast for its MRI protocol, which has been purported to be a lower risk agent compared with that of linear gadolinium-based contrast agents (although several cases of NSF have been reported with gadobutrol in the literature).¹¹

Providers weighing the decision to administer gadolinium contrast to patients with ESRD should discuss the risks and benefits thoroughly, especially in patients with preexisting inflammatory conditions. In addition, although it has not been shown to effectively reduce the risk of NSF after administration of gadolinium, hemodialysis is recommended 2 hours after contrast administration for individuals at risk (the study patient received hemodialysis approximately 18 hours after).¹² Given the lack of effective treatment options for NSF, prevention is key. A deeper understanding of the pathophysiology of NSF and identification of its risk factors is paramount to the prevention of this devastating disease.

SAN FRANCISCO – Primary hyperparathyroidism was detected in 7% of 742 patients with recurrent kidney stones at a single tertiary care clinic, and the patients’ primary care physicians may have missed the diagnosis because several affected patients’ calcium levels were in the high normal range.

Of the 53 patients diagnosed with primary hyperparathyroidism (hPTH), 72% had high normal serum calcium levels. After examining the charts of those patients, researchers found that 11 of the 53 patients (21%) had been tested for parathyroid hormone and serum calcium levels and could have been identified by their primary care physicians.

SOURCE: Boyd C et al. AUA 2018, Abstract MP13-03.

SAN FRANCISCO – Primary hyperparathyroidism was detected in 7% of 742 patients with recurrent kidney stones at a single tertiary care clinic, and the patients’ primary care physicians may have missed the diagnosis because several affected patients’ calcium levels were in the high normal range.

Of the 53 patients diagnosed with primary hyperparathyroidism (hPTH), 72% had high normal serum calcium levels. After examining the charts of those patients, researchers found that 11 of the 53 patients (21%) had been tested for parathyroid hormone and serum calcium levels and could have been identified by their primary care physicians.

SOURCE: Boyd C et al. AUA 2018, Abstract MP13-03.

SAN FRANCISCO – Primary hyperparathyroidism was detected in 7% of 742 patients with recurrent kidney stones at a single tertiary care clinic, and the patients’ primary care physicians may have missed the diagnosis because several affected patients’ calcium levels were in the high normal range.

Of the 53 patients diagnosed with primary hyperparathyroidism (hPTH), 72% had high normal serum calcium levels. After examining the charts of those patients, researchers found that 11 of the 53 patients (21%) had been tested for parathyroid hormone and serum calcium levels and could have been identified by their primary care physicians.

SOURCE: Boyd C et al. AUA 2018, Abstract MP13-03.

SAN FRANCISCO – Testosterone replacement therapy was associated with heightened risk for kidney stones, according to an analysis of more than 50,000 men with low testosterone.

When researchers compared hypogonadal men to age- and comorbidity-matched controls, they found a statistically significantly higher number of clinical diagnoses of a kidney stone, or of patients undergoing a kidney stone–related procedure.

Jim Kling/MDedge News

Dr. McClintock said the study is convincing in part because it used data from TRICARE, which sets a lower testosterone level even than AUA guidelines for determining if a patient is eligible for testosterone therapy.

“It would suggest that those are the real low testosterone patients, not necessarily men who heard an ad or went to a test center,” noted Patrick Shepherd Lowry, MD, associate professor of urology at Scott & White Medical Center, Temple, Texas, who attended the presentation but was not involved in the study. “It’s preliminary, but it’s very interesting. It hasn’t been shown before.”

The Department of Defense funded the study. Dr. McClintock reported having no relevant financial disclosures.

SOURCE: McClintock T. AUA Annual Meeting. Abstract MP13-19.

SAN FRANCISCO – Testosterone replacement therapy was associated with heightened risk for kidney stones, according to an analysis of more than 50,000 men with low testosterone.

When researchers compared hypogonadal men to age- and comorbidity-matched controls, they found a statistically significantly higher number of clinical diagnoses of a kidney stone, or of patients undergoing a kidney stone–related procedure.

Jim Kling/MDedge News

Dr. McClintock said the study is convincing in part because it used data from TRICARE, which sets a lower testosterone level even than AUA guidelines for determining if a patient is eligible for testosterone therapy.

“It would suggest that those are the real low testosterone patients, not necessarily men who heard an ad or went to a test center,” noted Patrick Shepherd Lowry, MD, associate professor of urology at Scott & White Medical Center, Temple, Texas, who attended the presentation but was not involved in the study. “It’s preliminary, but it’s very interesting. It hasn’t been shown before.”

The Department of Defense funded the study. Dr. McClintock reported having no relevant financial disclosures.

SOURCE: McClintock T. AUA Annual Meeting. Abstract MP13-19.

SAN FRANCISCO – Testosterone replacement therapy was associated with heightened risk for kidney stones, according to an analysis of more than 50,000 men with low testosterone.

When researchers compared hypogonadal men to age- and comorbidity-matched controls, they found a statistically significantly higher number of clinical diagnoses of a kidney stone, or of patients undergoing a kidney stone–related procedure.

Jim Kling/MDedge News

Dr. McClintock said the study is convincing in part because it used data from TRICARE, which sets a lower testosterone level even than AUA guidelines for determining if a patient is eligible for testosterone therapy.

“It would suggest that those are the real low testosterone patients, not necessarily men who heard an ad or went to a test center,” noted Patrick Shepherd Lowry, MD, associate professor of urology at Scott & White Medical Center, Temple, Texas, who attended the presentation but was not involved in the study. “It’s preliminary, but it’s very interesting. It hasn’t been shown before.”

The Department of Defense funded the study. Dr. McClintock reported having no relevant financial disclosures.

SOURCE: McClintock T. AUA Annual Meeting. Abstract MP13-19.

BOSTON – A lot of people do well with HIV thanks to potent antiretrovirals, but there’s still at least one group that needs extra attention: HIV patients with chronic kidney disease (CKD), according to Lene Ryom, MD, PhD, an HIV researcher at the University of Copenhagen.

She was the lead investigator on a review of 2,467 HIV patients with CKD – which is becoming more common in HIV as patients live longer – and 33,427 HIV patients without CKD.

decade3d/Thinkstock

The subjects were all participants in the D:A:D project [Data Collection on Adverse Events of Anti-HIV Drugs], an ongoing international cohort study based at the University of Copenhagen, and funded by pharmaceutical companies, among others.

Dr. Ryom had no disclosures.

[email protected]

SOURCE: Ryom L et al. CROI, Abstract 75.

BOSTON – A lot of people do well with HIV thanks to potent antiretrovirals, but there’s still at least one group that needs extra attention: HIV patients with chronic kidney disease (CKD), according to Lene Ryom, MD, PhD, an HIV researcher at the University of Copenhagen.

She was the lead investigator on a review of 2,467 HIV patients with CKD – which is becoming more common in HIV as patients live longer – and 33,427 HIV patients without CKD.

decade3d/Thinkstock

The subjects were all participants in the D:A:D project [Data Collection on Adverse Events of Anti-HIV Drugs], an ongoing international cohort study based at the University of Copenhagen, and funded by pharmaceutical companies, among others.

Dr. Ryom had no disclosures.

[email protected]

SOURCE: Ryom L et al. CROI, Abstract 75.

BOSTON – A lot of people do well with HIV thanks to potent antiretrovirals, but there’s still at least one group that needs extra attention: HIV patients with chronic kidney disease (CKD), according to Lene Ryom, MD, PhD, an HIV researcher at the University of Copenhagen.

She was the lead investigator on a review of 2,467 HIV patients with CKD – which is becoming more common in HIV as patients live longer – and 33,427 HIV patients without CKD.

decade3d/Thinkstock

The subjects were all participants in the D:A:D project [Data Collection on Adverse Events of Anti-HIV Drugs], an ongoing international cohort study based at the University of Copenhagen, and funded by pharmaceutical companies, among others.

Dr. Ryom had no disclosures.

[email protected]

SOURCE: Ryom L et al. CROI, Abstract 75.

AUSTIN, TEX. – Canagliflozin can improve renal outcomes in patients with type 2 diabetes, even when they have mild or moderate kidney disease, new data from the CANVAS program suggested.

“The effect of canagliflozin on composite renal outcomes was large, particularly in people with preserved kidney function,” Brendon L. Neuen, MBBS, of University of New South Wales, Sydney, and his associates wrote in a poster. Baseline renal function also did not appear to affect the safety of canagliflozin, the investigators reported at a meeting sponsored by the National Kidney Foundation.

In patients with diabetes mellitus, increased proximal reabsorption of glucose and sodium decreases the amount of sodium reaching the macula densa in the distal convoluted tubule. This results in reduced use of adenosine triphosphate for sodium reabsorption, which thereby decreases adenosine release and vasoconstriction of afferent arterioles. Left unchecked, this dampening of the tubuloglomerular feedback mechanism increases glomerular filtration and leads to diabetic nephropathy.

Sodium glucose cotransporter 2 (SGLT2) inhibitors such as canagliflozin (Invokana) and empagliflozin (Jardiance) help mitigate this pathology by vasoconstricting afferent arterioles. Previously, in an exploratory analysis of the multicenter, placebo-controlled EMPA-REG OUTCOME (Empagliflozin, Cardiovascular Outcomes, and Mortality in Type 2 Diabetes) trial, empagliflozin led to modest but statistically significant long-term reductions in urinary albumin secretion for diabetic patients, regardless of their baseline urinary albumin to creatinine ratio (Lancet Diabetes Endocrinol. 2017 Aug;5[8]:610-21). Treatment with empagliflozin also significantly reduced the risk of developing microalbuminuria or macroalbuminuria (P less than .0001).

The multicenter, double-blind, placebo-controlled CANVAS (Canagliflozin Cardiovascular Assessment Study) and CANVAS-R (A Study of the Effects of Canagliflozin on Renal Endpoints in Adult Participants with Type 2 Diabetes Mellitus) trials included more than 10,000 adults with type 2 diabetes and high cardiovascular risk. In the primary analysis, canagliflozin significantly reduced the risk of cardiovascular death, nonfatal myocardial infarction, or nonfatal stroke compared with placebo (N Engl J Med. 2017 Aug 17;377[7]:644-57).

Dr. Neuen and his associates compared the effects of canagliflozin on renal outcomes and safety among CANVAS patients whose estimated glomerular filtration rate (eGFR) was preserved (greater than 60 mL/min per 1.73 m²) or reduced (less than 60 ml/min per 1.73 m²). Actual mean eGFRs in each of these groups were 83 mL/min per 1.73 m² and 49 mL/min per 1.73 m², respectively. Compared with placebo, canagliflozin acutely reduced eGFR in patients with either preserved (average, –2.2 mL/min per 1.73 m²) or reduced (–2.83 mL/min/1.73 m² ) baseline kidney function (P = 0.21).

SOURCE: Neuen BL et al. SCM 2018.
 

AUSTIN, TEX. – Canagliflozin can improve renal outcomes in patients with type 2 diabetes, even when they have mild or moderate kidney disease, new data from the CANVAS program suggested.

“The effect of canagliflozin on composite renal outcomes was large, particularly in people with preserved kidney function,” Brendon L. Neuen, MBBS, of University of New South Wales, Sydney, and his associates wrote in a poster. Baseline renal function also did not appear to affect the safety of canagliflozin, the investigators reported at a meeting sponsored by the National Kidney Foundation.

In patients with diabetes mellitus, increased proximal reabsorption of glucose and sodium decreases the amount of sodium reaching the macula densa in the distal convoluted tubule. This results in reduced use of adenosine triphosphate for sodium reabsorption, which thereby decreases adenosine release and vasoconstriction of afferent arterioles. Left unchecked, this dampening of the tubuloglomerular feedback mechanism increases glomerular filtration and leads to diabetic nephropathy.

Sodium glucose cotransporter 2 (SGLT2) inhibitors such as canagliflozin (Invokana) and empagliflozin (Jardiance) help mitigate this pathology by vasoconstricting afferent arterioles. Previously, in an exploratory analysis of the multicenter, placebo-controlled EMPA-REG OUTCOME (Empagliflozin, Cardiovascular Outcomes, and Mortality in Type 2 Diabetes) trial, empagliflozin led to modest but statistically significant long-term reductions in urinary albumin secretion for diabetic patients, regardless of their baseline urinary albumin to creatinine ratio (Lancet Diabetes Endocrinol. 2017 Aug;5[8]:610-21). Treatment with empagliflozin also significantly reduced the risk of developing microalbuminuria or macroalbuminuria (P less than .0001).

The multicenter, double-blind, placebo-controlled CANVAS (Canagliflozin Cardiovascular Assessment Study) and CANVAS-R (A Study of the Effects of Canagliflozin on Renal Endpoints in Adult Participants with Type 2 Diabetes Mellitus) trials included more than 10,000 adults with type 2 diabetes and high cardiovascular risk. In the primary analysis, canagliflozin significantly reduced the risk of cardiovascular death, nonfatal myocardial infarction, or nonfatal stroke compared with placebo (N Engl J Med. 2017 Aug 17;377[7]:644-57).

Dr. Neuen and his associates compared the effects of canagliflozin on renal outcomes and safety among CANVAS patients whose estimated glomerular filtration rate (eGFR) was preserved (greater than 60 mL/min per 1.73 m²) or reduced (less than 60 ml/min per 1.73 m²). Actual mean eGFRs in each of these groups were 83 mL/min per 1.73 m² and 49 mL/min per 1.73 m², respectively. Compared with placebo, canagliflozin acutely reduced eGFR in patients with either preserved (average, –2.2 mL/min per 1.73 m²) or reduced (–2.83 mL/min/1.73 m² ) baseline kidney function (P = 0.21).

SOURCE: Neuen BL et al. SCM 2018.
 

AUSTIN, TEX. – Canagliflozin can improve renal outcomes in patients with type 2 diabetes, even when they have mild or moderate kidney disease, new data from the CANVAS program suggested.

“The effect of canagliflozin on composite renal outcomes was large, particularly in people with preserved kidney function,” Brendon L. Neuen, MBBS, of University of New South Wales, Sydney, and his associates wrote in a poster. Baseline renal function also did not appear to affect the safety of canagliflozin, the investigators reported at a meeting sponsored by the National Kidney Foundation.

In patients with diabetes mellitus, increased proximal reabsorption of glucose and sodium decreases the amount of sodium reaching the macula densa in the distal convoluted tubule. This results in reduced use of adenosine triphosphate for sodium reabsorption, which thereby decreases adenosine release and vasoconstriction of afferent arterioles. Left unchecked, this dampening of the tubuloglomerular feedback mechanism increases glomerular filtration and leads to diabetic nephropathy.

Sodium glucose cotransporter 2 (SGLT2) inhibitors such as canagliflozin (Invokana) and empagliflozin (Jardiance) help mitigate this pathology by vasoconstricting afferent arterioles. Previously, in an exploratory analysis of the multicenter, placebo-controlled EMPA-REG OUTCOME (Empagliflozin, Cardiovascular Outcomes, and Mortality in Type 2 Diabetes) trial, empagliflozin led to modest but statistically significant long-term reductions in urinary albumin secretion for diabetic patients, regardless of their baseline urinary albumin to creatinine ratio (Lancet Diabetes Endocrinol. 2017 Aug;5[8]:610-21). Treatment with empagliflozin also significantly reduced the risk of developing microalbuminuria or macroalbuminuria (P less than .0001).

The multicenter, double-blind, placebo-controlled CANVAS (Canagliflozin Cardiovascular Assessment Study) and CANVAS-R (A Study of the Effects of Canagliflozin on Renal Endpoints in Adult Participants with Type 2 Diabetes Mellitus) trials included more than 10,000 adults with type 2 diabetes and high cardiovascular risk. In the primary analysis, canagliflozin significantly reduced the risk of cardiovascular death, nonfatal myocardial infarction, or nonfatal stroke compared with placebo (N Engl J Med. 2017 Aug 17;377[7]:644-57).

Dr. Neuen and his associates compared the effects of canagliflozin on renal outcomes and safety among CANVAS patients whose estimated glomerular filtration rate (eGFR) was preserved (greater than 60 mL/min per 1.73 m²) or reduced (less than 60 ml/min per 1.73 m²). Actual mean eGFRs in each of these groups were 83 mL/min per 1.73 m² and 49 mL/min per 1.73 m², respectively. Compared with placebo, canagliflozin acutely reduced eGFR in patients with either preserved (average, –2.2 mL/min per 1.73 m²) or reduced (–2.83 mL/min/1.73 m² ) baseline kidney function (P = 0.21).

SOURCE: Neuen BL et al. SCM 2018.
 

Compared with a liberal fluid regimen, a restrictive perioperative regimen that was aimed at zero balance did not improve disability-free survival among high-risk patients undergoing major abdominal surgery and led to a significantly increased risk of acute kidney injury, researchers reported.

dtimiraos/iStock/Getty Images

In an international, randomized trial with 366 median days of follow-up, estimated 1-year rates of disability-free survival were 81.9% with the restrictive intravenous fluid regimen and 82.3% with the liberal regimen (hazard ratio for death or disability, 1.05; P = .61), according to Paul S. Myles, MPH, DSc, and his associates.

Rates of acute renal injury were 8.6% in the restrictive IV fluid group and 5.0% with the liberal fluid therapy (P less than .001), the researchers reported online May 10 in the New England Journal of Medicine.

Guidelines recommend a restrictive intravenous fluid strategy to promote early recovery after major abdominal surgery, noted Dr. Myles of Alfred Hospital in Melbourne and his colleagues. “However, the supporting evidence is limited, and there is concern about impaired organ perfusion.”

Therefore, they randomly assigned, 3,000 patients to receive either the restrictive fluid regimen or a liberal regimen during major abdominal surgery and up to 24 hours after. Median intravenous volume was 3.7 L (interquartile range, 2.9-4.9 L) in the restrictive group and 6.1 L (IQR, 5.0-7.4 L) in the liberal fluid group. All patients were deemed high risk based on their age (at least 70 years) or because they had heart disease, diabetes, kidney disease, or morbid obesity.

Patients who received the restrictive regimen had higher rates of surgical site infection (16.5% vs. 13.6% with liberal fluids; P = .02) and were more likely to receive renal replacement therapy (0.9% vs. 0.3%; P = .048). However, these trends were no longer significant after the researchers controlled for the effects of testing for multiple variables.

“Our findings should not be used to support excessive administration of intravenous fluid,” the researchers cautioned. “Rather, they show that a regimen that includes a modestly liberal administration of fluid is safer than a restrictive regimen.”

Funders included the Australian National Health and Medical Research Council (NHMRC), the Health Research Council of New Zealand, the Australian and New Zealand College of Anaesthetists, and Monash University, Melbourne. Dr. Myles reported receiving grant support from NHMRC. He had no other disclosures.

SOURCE: Myles PS et al. New Engl J Med. 2018 May 10. doi: 10.1056/NEJMoa1801601.

Compared with a liberal fluid regimen, a restrictive perioperative regimen that was aimed at zero balance did not improve disability-free survival among high-risk patients undergoing major abdominal surgery and led to a significantly increased risk of acute kidney injury, researchers reported.

dtimiraos/iStock/Getty Images

In an international, randomized trial with 366 median days of follow-up, estimated 1-year rates of disability-free survival were 81.9% with the restrictive intravenous fluid regimen and 82.3% with the liberal regimen (hazard ratio for death or disability, 1.05; P = .61), according to Paul S. Myles, MPH, DSc, and his associates.

Rates of acute renal injury were 8.6% in the restrictive IV fluid group and 5.0% with the liberal fluid therapy (P less than .001), the researchers reported online May 10 in the New England Journal of Medicine.

Guidelines recommend a restrictive intravenous fluid strategy to promote early recovery after major abdominal surgery, noted Dr. Myles of Alfred Hospital in Melbourne and his colleagues. “However, the supporting evidence is limited, and there is concern about impaired organ perfusion.”

Therefore, they randomly assigned, 3,000 patients to receive either the restrictive fluid regimen or a liberal regimen during major abdominal surgery and up to 24 hours after. Median intravenous volume was 3.7 L (interquartile range, 2.9-4.9 L) in the restrictive group and 6.1 L (IQR, 5.0-7.4 L) in the liberal fluid group. All patients were deemed high risk based on their age (at least 70 years) or because they had heart disease, diabetes, kidney disease, or morbid obesity.

Patients who received the restrictive regimen had higher rates of surgical site infection (16.5% vs. 13.6% with liberal fluids; P = .02) and were more likely to receive renal replacement therapy (0.9% vs. 0.3%; P = .048). However, these trends were no longer significant after the researchers controlled for the effects of testing for multiple variables.

“Our findings should not be used to support excessive administration of intravenous fluid,” the researchers cautioned. “Rather, they show that a regimen that includes a modestly liberal administration of fluid is safer than a restrictive regimen.”

Funders included the Australian National Health and Medical Research Council (NHMRC), the Health Research Council of New Zealand, the Australian and New Zealand College of Anaesthetists, and Monash University, Melbourne. Dr. Myles reported receiving grant support from NHMRC. He had no other disclosures.

SOURCE: Myles PS et al. New Engl J Med. 2018 May 10. doi: 10.1056/NEJMoa1801601.

Compared with a liberal fluid regimen, a restrictive perioperative regimen that was aimed at zero balance did not improve disability-free survival among high-risk patients undergoing major abdominal surgery and led to a significantly increased risk of acute kidney injury, researchers reported.

dtimiraos/iStock/Getty Images

In an international, randomized trial with 366 median days of follow-up, estimated 1-year rates of disability-free survival were 81.9% with the restrictive intravenous fluid regimen and 82.3% with the liberal regimen (hazard ratio for death or disability, 1.05; P = .61), according to Paul S. Myles, MPH, DSc, and his associates.

Rates of acute renal injury were 8.6% in the restrictive IV fluid group and 5.0% with the liberal fluid therapy (P less than .001), the researchers reported online May 10 in the New England Journal of Medicine.

Guidelines recommend a restrictive intravenous fluid strategy to promote early recovery after major abdominal surgery, noted Dr. Myles of Alfred Hospital in Melbourne and his colleagues. “However, the supporting evidence is limited, and there is concern about impaired organ perfusion.”

Therefore, they randomly assigned, 3,000 patients to receive either the restrictive fluid regimen or a liberal regimen during major abdominal surgery and up to 24 hours after. Median intravenous volume was 3.7 L (interquartile range, 2.9-4.9 L) in the restrictive group and 6.1 L (IQR, 5.0-7.4 L) in the liberal fluid group. All patients were deemed high risk based on their age (at least 70 years) or because they had heart disease, diabetes, kidney disease, or morbid obesity.

Patients who received the restrictive regimen had higher rates of surgical site infection (16.5% vs. 13.6% with liberal fluids; P = .02) and were more likely to receive renal replacement therapy (0.9% vs. 0.3%; P = .048). However, these trends were no longer significant after the researchers controlled for the effects of testing for multiple variables.

“Our findings should not be used to support excessive administration of intravenous fluid,” the researchers cautioned. “Rather, they show that a regimen that includes a modestly liberal administration of fluid is safer than a restrictive regimen.”

Funders included the Australian National Health and Medical Research Council (NHMRC), the Health Research Council of New Zealand, the Australian and New Zealand College of Anaesthetists, and Monash University, Melbourne. Dr. Myles reported receiving grant support from NHMRC. He had no other disclosures.

SOURCE: Myles PS et al. New Engl J Med. 2018 May 10. doi: 10.1056/NEJMoa1801601.

Coaching adults with stage 3 chronic kidney disease (CKD) to increase water intake did not significantly slow decline in kidney function, results of a randomized clinical trial show.

Compared with coaching to maintain water intake, coaching to increase water intake did in fact increase water intake but did not prevent a decrease in estimated glomerular filtration rate (eGFR) over 1 year, according to findings of the study, which was published in JAMA..

However, the study may have been underpowered to detect a clinically important difference in this primary endpoint, and certain secondary endpoints did suggest a favorable effect of the intervention, according to William F. Clark, MD, of the London (Ontario) Health Sciences Centre and his coauthors.

“The increased water intake achieved in this trial was sufficient to lower vasopressin secretion, as assessed by plasma copeptin concentrations,” Dr. Clark and his colleagues said in their report

An increasing number of studies suggest that drinking water may benefit the kidneys. In some human studies, water intake was associated with reduced risk of kidney stones and better kidney function.

However, it remains unknown whether increasing water intake would benefit patients with CKD. To evaluate this question, Dr. Clark and colleagues initiated CKD WIT (Chronic Kidney Disease Water Intake Trial), a randomized clinical trial conducted in 9 centers in Ontario.

The study included 631 patients with stage 3 CKD and a 24-hour urine volume below 3 L. Patients randomized to the hydration group were coached to increase water intake gradually to 1-1.5 L/day for 1 year, while those randomized to the control group were coached to maintain their usual water intake.

SOURCE: Clark WF et al. JAMA. 2018;319(18):1870-9.

Coaching adults with stage 3 chronic kidney disease (CKD) to increase water intake did not significantly slow decline in kidney function, results of a randomized clinical trial show.

Compared with coaching to maintain water intake, coaching to increase water intake did in fact increase water intake but did not prevent a decrease in estimated glomerular filtration rate (eGFR) over 1 year, according to findings of the study, which was published in JAMA..

However, the study may have been underpowered to detect a clinically important difference in this primary endpoint, and certain secondary endpoints did suggest a favorable effect of the intervention, according to William F. Clark, MD, of the London (Ontario) Health Sciences Centre and his coauthors.

“The increased water intake achieved in this trial was sufficient to lower vasopressin secretion, as assessed by plasma copeptin concentrations,” Dr. Clark and his colleagues said in their report

An increasing number of studies suggest that drinking water may benefit the kidneys. In some human studies, water intake was associated with reduced risk of kidney stones and better kidney function.

However, it remains unknown whether increasing water intake would benefit patients with CKD. To evaluate this question, Dr. Clark and colleagues initiated CKD WIT (Chronic Kidney Disease Water Intake Trial), a randomized clinical trial conducted in 9 centers in Ontario.

The study included 631 patients with stage 3 CKD and a 24-hour urine volume below 3 L. Patients randomized to the hydration group were coached to increase water intake gradually to 1-1.5 L/day for 1 year, while those randomized to the control group were coached to maintain their usual water intake.

SOURCE: Clark WF et al. JAMA. 2018;319(18):1870-9.

Coaching adults with stage 3 chronic kidney disease (CKD) to increase water intake did not significantly slow decline in kidney function, results of a randomized clinical trial show.

Compared with coaching to maintain water intake, coaching to increase water intake did in fact increase water intake but did not prevent a decrease in estimated glomerular filtration rate (eGFR) over 1 year, according to findings of the study, which was published in JAMA..

However, the study may have been underpowered to detect a clinically important difference in this primary endpoint, and certain secondary endpoints did suggest a favorable effect of the intervention, according to William F. Clark, MD, of the London (Ontario) Health Sciences Centre and his coauthors.

“The increased water intake achieved in this trial was sufficient to lower vasopressin secretion, as assessed by plasma copeptin concentrations,” Dr. Clark and his colleagues said in their report

An increasing number of studies suggest that drinking water may benefit the kidneys. In some human studies, water intake was associated with reduced risk of kidney stones and better kidney function.

However, it remains unknown whether increasing water intake would benefit patients with CKD. To evaluate this question, Dr. Clark and colleagues initiated CKD WIT (Chronic Kidney Disease Water Intake Trial), a randomized clinical trial conducted in 9 centers in Ontario.

The study included 631 patients with stage 3 CKD and a 24-hour urine volume below 3 L. Patients randomized to the hydration group were coached to increase water intake gradually to 1-1.5 L/day for 1 year, while those randomized to the control group were coached to maintain their usual water intake.

SOURCE: Clark WF et al. JAMA. 2018;319(18):1870-9.

How to handle opioid constipation. Bath emollients are a washout for childhood eczema. Does warfarin cause acute kidney injury? And there may be a new option for postpartum depression.

Listen to the MDedge Daily News podcast for all the details on today’s top news.


 

How to handle opioid constipation. Bath emollients are a washout for childhood eczema. Does warfarin cause acute kidney injury? And there may be a new option for postpartum depression.

Listen to the MDedge Daily News podcast for all the details on today’s top news.


 

How to handle opioid constipation. Bath emollients are a washout for childhood eczema. Does warfarin cause acute kidney injury? And there may be a new option for postpartum depression.

Listen to the MDedge Daily News podcast for all the details on today’s top news.


 

A 45-year-old man with end-stage renal disease secondary to hypertension presented with abdominal pain, nausea, vomiting, and fever. He had been on peritoneal dialysis for 15 years.

Results of initial laboratory testing were as follows:

• Sodium 137 mmol/L (reference range 136–144)
• Potassium 3.7 mmol/L (3.5–5.0)
• Bicarbonate 31 mmol/L (22–30)
• Creatinine 17.5 mg/dL (0.58–0.96)
• Blood urea nitrogen 57 mg/dL (7–21)
• Lactic acid 1.7 mmol/L (0.5–2.2)
• White blood cell count 14.34 × 10⁹/L (3.70–11.0).

Blood cultures were negative. Peritoneal fluid analysis showed a white blood cell count of 1.2 × 10⁹/L (reference range < 0.5 × 10⁹/L) with 89% neutrophils, and an amylase level less than 3 U/L (reference range < 100). Fluid cultures were positive for coagulase-negative staphylococci and Staphylococcus epidermidis.

CAUSES AND CLINICAL FEATURES

Encapsulating peritoneal sclerosis is a devastating complication of peritoneal dialysis, occurring in 3% of patients on peritoneal dialysis. The mortality rate is above 40%.^1,2 It is characterized by an initial inflammatory phase followed by extensive intraperitoneal fibrosis and encasement of bowel. Causes include prolonged exposure to peritoneal dialysis or glucose degradation products, a history of severe peritonitis, use of acetate as a dialysate buffer, and reaction to medications such as beta-blockers.³

Clinical features result from inflammation, ileus, and peritoneal adhesions and include abdominal pain, nausea, and vomiting. A high peritoneal transport rate, which often heralds development of encapsulating peritoneal sclerosis, leads to failure of ultrafiltration and to fluid retention.

CT is recommended for diagnosis and demonstrates peritoneal calcification with bowel thickening and dilation.

TREATMENT

Treatment entails stopping peritoneal dialysis, changing to hemodialysis, bowel rest, and corticosteroids. Successful treatment has been reported with a combination of corticosteroids and azathioprine.^4,5 A retrospective study showed that adding the antifibrotic agent tamoxifen was associated with a decrease in the mortality rate.⁶ Bowel obstruction is a common complication, and surgery may be indicated. Enterolysis is a new surgical technique that has shown improved outcomes.⁷         

A 45-year-old man with end-stage renal disease secondary to hypertension presented with abdominal pain, nausea, vomiting, and fever. He had been on peritoneal dialysis for 15 years.

Results of initial laboratory testing were as follows:

• Sodium 137 mmol/L (reference range 136–144)
• Potassium 3.7 mmol/L (3.5–5.0)
• Bicarbonate 31 mmol/L (22–30)
• Creatinine 17.5 mg/dL (0.58–0.96)
• Blood urea nitrogen 57 mg/dL (7–21)
• Lactic acid 1.7 mmol/L (0.5–2.2)
• White blood cell count 14.34 × 10⁹/L (3.70–11.0).

Blood cultures were negative. Peritoneal fluid analysis showed a white blood cell count of 1.2 × 10⁹/L (reference range < 0.5 × 10⁹/L) with 89% neutrophils, and an amylase level less than 3 U/L (reference range < 100). Fluid cultures were positive for coagulase-negative staphylococci and Staphylococcus epidermidis.

CAUSES AND CLINICAL FEATURES

Encapsulating peritoneal sclerosis is a devastating complication of peritoneal dialysis, occurring in 3% of patients on peritoneal dialysis. The mortality rate is above 40%.^1,2 It is characterized by an initial inflammatory phase followed by extensive intraperitoneal fibrosis and encasement of bowel. Causes include prolonged exposure to peritoneal dialysis or glucose degradation products, a history of severe peritonitis, use of acetate as a dialysate buffer, and reaction to medications such as beta-blockers.³

Clinical features result from inflammation, ileus, and peritoneal adhesions and include abdominal pain, nausea, and vomiting. A high peritoneal transport rate, which often heralds development of encapsulating peritoneal sclerosis, leads to failure of ultrafiltration and to fluid retention.

CT is recommended for diagnosis and demonstrates peritoneal calcification with bowel thickening and dilation.

TREATMENT

Treatment entails stopping peritoneal dialysis, changing to hemodialysis, bowel rest, and corticosteroids. Successful treatment has been reported with a combination of corticosteroids and azathioprine.^4,5 A retrospective study showed that adding the antifibrotic agent tamoxifen was associated with a decrease in the mortality rate.⁶ Bowel obstruction is a common complication, and surgery may be indicated. Enterolysis is a new surgical technique that has shown improved outcomes.⁷         

A 45-year-old man with end-stage renal disease secondary to hypertension presented with abdominal pain, nausea, vomiting, and fever. He had been on peritoneal dialysis for 15 years.

Results of initial laboratory testing were as follows:

• Sodium 137 mmol/L (reference range 136–144)
• Potassium 3.7 mmol/L (3.5–5.0)
• Bicarbonate 31 mmol/L (22–30)
• Creatinine 17.5 mg/dL (0.58–0.96)
• Blood urea nitrogen 57 mg/dL (7–21)
• Lactic acid 1.7 mmol/L (0.5–2.2)
• White blood cell count 14.34 × 10⁹/L (3.70–11.0).

Blood cultures were negative. Peritoneal fluid analysis showed a white blood cell count of 1.2 × 10⁹/L (reference range < 0.5 × 10⁹/L) with 89% neutrophils, and an amylase level less than 3 U/L (reference range < 100). Fluid cultures were positive for coagulase-negative staphylococci and Staphylococcus epidermidis.

CAUSES AND CLINICAL FEATURES

Encapsulating peritoneal sclerosis is a devastating complication of peritoneal dialysis, occurring in 3% of patients on peritoneal dialysis. The mortality rate is above 40%.^1,2 It is characterized by an initial inflammatory phase followed by extensive intraperitoneal fibrosis and encasement of bowel. Causes include prolonged exposure to peritoneal dialysis or glucose degradation products, a history of severe peritonitis, use of acetate as a dialysate buffer, and reaction to medications such as beta-blockers.³

Clinical features result from inflammation, ileus, and peritoneal adhesions and include abdominal pain, nausea, and vomiting. A high peritoneal transport rate, which often heralds development of encapsulating peritoneal sclerosis, leads to failure of ultrafiltration and to fluid retention.

CT is recommended for diagnosis and demonstrates peritoneal calcification with bowel thickening and dilation.

TREATMENT

Treatment entails stopping peritoneal dialysis, changing to hemodialysis, bowel rest, and corticosteroids. Successful treatment has been reported with a combination of corticosteroids and azathioprine.^4,5 A retrospective study showed that adding the antifibrotic agent tamoxifen was associated with a decrease in the mortality rate.⁶ Bowel obstruction is a common complication, and surgery may be indicated. Enterolysis is a new surgical technique that has shown improved outcomes.⁷