Renal disease and the surgical patient: Minimizing the impact
ABSTRACT
Chronic kidney disease (CKD) is common in patients scheduled for surgery and increases the risk of postoperative acute kidney injury, major adverse cardiac events, and death. Acute kidney injury is a common complication of cardiac and noncardiac surgery and negatively affects both short- and long-term outcomes. If we can detect underlying CKD and other risk factors for acute kidney injury before surgery, we may in theory be able to give preventive therapies and improve perioperative outcomes.
KEY POINTS
- Many patients undergoing surgery have CKD—up to 30% in some cardiac surgery populations.
- CKD is a risk factor for perioperative complications including acute kidney injury and death.
- Although challenging, early detection of renal injury is crucial to improving outcomes in this patient population. New biomarkers are being investigated.
- Preoperative assessment and perioperative management of renal dysfunction may reduce the risk of adverse postoperative outcomes.
CAN WE PROTECT RENAL FUNCTION?
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.
