Low cardiopulmonary bypass perfusion temperatures are associated with acute kidney injury following coronary artery bypass surgery.

Objective: Acute kidney injury (AKI) is a common complication after coronary artery bypass surgery (CABG). The role of hypothermia in postoperative renal function remains controversial. We set out to examine the effect of varying cardiopulmonary bypass (CPB) temperatures on early postoperative renal function.

Methods: Patients undergoing first-time CABG between 2002 and 2006 and without evidence of preoperative renal insufficiency (estimated creatinine clearance >or=50 ml min(-1), calculated by the Cockcroft-Gault formula) were studied. Medical history and intra-operative variables, including lowest nasopharyngeal and arterial CPB perfusion temperatures, were collected prospectively. Primary endpoint was the development of early postoperative AKI (defined as creatinine clearance <50 ml min(-1)), which was assessed using multivariate and propensity score analyses.

Results: This study included 1072 patients. AKI occurred in 175 (16%). Univariate analysis demonstrated that lower arterial CPB perfusion temperatures, and not nasopharyngeal ones, were significantly associated with renal dysfunction following CABG. Multivariate regression analysis identified reduced arterial perfusion temperature as an independent risk factor for AKI (odds ratio (OR) 0.92, 95% confidence interval (CI): 0.86-0.98, p=0.012), along with age (OR 1.07, 95% CI: 1.04-1.10, p<0.001) and depressed preoperative creatinine clearance (OR 0.89, 95% CI: 0.87-0.91, p<0.001). Propensity score adjustment confirmed that lower CPB perfusion temperatures (<27 degrees C) were associated with postoperative AKI (OR 1.66, 95% CI: 1.16-2.39, p=0.0056).

Conclusions: Lower CPB perfusion temperatures are significantly associated with AKI following CABG. In addition to the known age-related decline in renal function, it appears that hypothermia may contribute to renal injury during cardiac surgery.