Perioperative Acute Kidney Injury

Sam D. Gumbert, M.D.; Felix Kork, M.D., M.Sc.; Maisie L. Jackson, M.D.; Naveen Vanga, M.D.; Semhar J. Ghebremichael, M.D.; Christy Y. Wang, M.D.; Holger K. Eltzschig, M.D., Ph.D.

Disclosures

Anesthesiology. 2019;132(1):180-204. 

In This Article

Surgery-associated Risk Factors for Perioperative Acute Kidney Injury

Acute kidney injury is a dangerous complication in both cardiac and noncardiac surgeries and independently associated with emergency surgery.[58] One third of acute kidney injury cases that occurred among patients who are critically ill have a previous history of major surgery.[63]

Acute Kidney Injury in Cardiac and Vascular Surgery

In vascular and cardiac surgeries, acute kidney injury is a well established obstacle. Within these surgical settings, acute kidney injury is correlated with prolonged aortic cross-clamp and ischemia time, the creation of micro- and macroemboli, low cardiac output state, prolonged hypotension, and the use of vasopressors and inotropes. In addition to low mean arterial pressure during cardiopulmonary bypass (CPB), there are reports of contact-activated systemic inflammation, triggered by blood flow across the artificial surface of the bypass circuit. These damaging elements of CPB compromise renal blood flow and lead to renin–angiotensin–aldosterone system activation, decline of renal perfusion pressure, and worsening renal insult.[64] Furthermore, the components of CPB (pump, oxygenator, suction, filters) impose mechanical damage to the circulating erythrocytes, leading to intraoperative hemolysis and release of free hemoglobin. Free hemoglobin can cause direct injury to the renal epithelium via generation of free-radical species and obstructive cast formation.[65] Strategies to minimize renal injury with CPB have been explored and include a goal-directed oxygen delivery threshold for adjusting arterial pump flow according to the hematocrit value and when necessary by blood transfusion when thresholds cannot be maintained with increased pump flow.[66] Similar to a goal-directed oxygen delivery strategy, maintenance of a mixed venous oxygen saturation target above 75% during CPB is hypothesized to optimize system perfusion and may be linked with a lower risk of postoperative acute kidney injury.[67] Further investigations are still needed to understand the optimal strategies necessary to reduce acute kidney injury risk during CPB among high-risk cases.

With the apparent renal implications of CPB, it may appear intuitive that off-pump coronary artery bypass would exhibit renal sparing effect compared with the traditional on-pump coronary artery bypass graft (CABG) surgery. To date, however, clear consensus has not been reached. The CABG Off or On Pump Revascularization Study (CORONARY) randomized 4,752 patients from 2006 through 2011 at 79 centers in 19 countries to on-pump or off-pump technique. The study found no significant difference in new renal failure requiring dialysis at 30 days, but a substantial decrease in the incidence of acute kidney injury was observed (28.0% vs. 32.1%; relative risk, 0.87; 95% CI, 0.80 to 0.96; P = 0.01) in the off-pump group.[68] In contrast, the German Off Pump Coronary Artery Bypass Grafting in Elderly Patients (GOPCABE) trial randomized 1,593 elderly patients to either on or off technique from 2008 through 2011 and found that off-pump CABG surgery was not correlated with a decreased incidence or reduced severity of acute kidney injury (P = 0.174).[69] Current evidence does not demonstrate a consistent reduction in the relative risk of acute kidney injury or dialysis with an off-pump revascularization technique. Given the lack of supporting evidence, off-pump CABG surgery should not routinely be recommended for all CABG patients at risk of perioperative acute kidney injury, especially in light of associated lower off-pump CABG revascularization success rates.[68,70]

Acute Kidney Injury in Noncardiac Surgery

Occurrence of acute kidney injury among noncardiac and nonvascular surgeries has been studied less extensively than during cardiac surgery, probably because of its overall lower incidence. According to the American College of Surgeons–National Surgical Quality Improvement Program national data collection, complications caused by acute kidney injury occur in approximately 1% of general surgery cases, resulting in an eight-fold increase in all-cause 30-day mortality.[58] Within the general surgery category, intraperitoneal surgery is an established risk for developing perioperative acute kidney injury.[58] Procedure-related factors in abdominal surgery include intraoperative blood transfusions, episodes of intraoperative hemodynamic instability, and the use of vasopressors and diuretics.[28,71] Increase in intraabdominal pressure, often caused by an excessive fluid administration or rapid fluid shift, is predictive of postoperative renal impairment.[72,73] The reduction in perfusion pressure is attributed to mechanical compression of renal vasculature, causing a decreasing renal perfusion pressure and inducing renal ischemia.[72,73] Of note, laparoscopic surgery with transient elevations in intraabdominal pressure caused by pneumoperitoneum may result in a clinical decline in urine output, without causing an increase in postoperative acute kidney injury rates.[29,71]

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