Intraoperative venous congestion rather than hypotension is associated with acute adverse kidney events after cardiac surgery: a retrospective cohort study

Background: The pathophysiological mechanisms by which venous congestion and hypotension lead to acute adverse kidney events after cardiac surgery with cardiopulmonary bypass have not been elucidated. We tested the hypothesis that intraoperative hypotension and venous congestion are associated with acute kidney injury and acute kidney disease. Methods: Primary exposures were venous congestion and intraoperative hypotension defined by central venous pressure >= 12, 16, or 20 mm Hg or mean arterial pressure <55, 65, or 75 mm Hg. The primary outcomes were acute kidney injury and acute kidney disease. Multivariable logistic regression and Cox proportional hazard models were used, adjusted for relevant confounding factors and multiple comparisons. Results: Of 5127 eligible subjects, 1070 (20.9%) and 327 (7.2%) developed acute kidney injury and acute kidney disease, respectively. The occurrence of acute kidney injury was statistically associated with both venous congestion and intraoperative hypotension. The cumulative incidence rate for new onset acute kidney disease was 1.34 (95% confidence interval [CI], 1.21-1.60) per 100 person-days. Acute kidney disease was significantly associated with each 10 min epoch of central venous pressure >= 12 mm Hg (hazard ratio [HR]=1.03; 99% CI, 1.01-1.06; P<0.001), >= 16 mm Hg (HR=1.04; 99% CI, 1.01-1.07; P<0.001), and >= 20 mm Hg (HR=1.07; 99% CI, 1.02-1.13; P<0.001). Venous congestion was associated with an 8-17% increased risk for de novo renal replacement therapy. In contrast, intraoperative hypotension was not associated with development of acute kidney disease. Conclusion: Although both venous congestion and intraoperative hypotension are associated with acute kidney injury, only venous congestion correlates with acute kidney disease among patients undergoing cardiac surgery requiring cardiopulmonary bypass. The reported associations are suggestive of a pathophysiological role of venous congestion in acute kidney disease.