Hematocrit and Renal Failure in Aortic Arch Surgery: A Society of Thoracic Surgeons Database Study

BACKGROUNDWe examined the association between cardiopulmonary bypass (CPB) hematocrit and postoperative acute renal failure (ARF) in patients undergoing aortic arch surgery with hypothermic circulatory arrest.METHODSThe Society of Thoracic Surgeons Adult Cardiac Surgery Database was queried from 2011-2019 for patients undergoing aortic arch surgery with hypothermic circulatory arrest. A multivariable logistic regression model estimated the adjusted odds of postoperative ARF based on CPB hematocrit. Effects were stratified by preoperative kidney function and duration of hypothermic circulatory arrest using interaction terms. We also investigated the association between postoperative ARF and major postoperative outcomes using multivariable regression models.RESULTSOn adjusted analysis, higher CPB hematocrit (>20-25%, >25-30%, >30%) was associated with lower odds of ARF as compared to lower CPB hematocrit (≤20%) [>20-25%: aOR=0.78(0.65-0.93), p=0.006, >25-30%: aOR=0.65(0.50-0.84), p=0.0007, >30%: aOR=0.45(0.28-0.72), p=0.0008]. The predicted probability of postoperative ARF by CPB hematocrit was higher in patients with lower preoperative renal function (<60 mL/min/1.73m2) (interaction p=0.03). The association between hematocrit and postoperative ARF was not significantly modified by hypothermic circulatory arrest time (interaction p= 0.74). All postoperative outcomes were significantly worse in patients with postoperative ARF (all p<0.0001).CONCLUSIONSAmong patients undergoing aortic arch surgery, a higher CPB hematocrit level is associated with reduced likelihood of postoperative ARF. Preoperative renal function, but not hypothermic circulatory arrest duration, significantly modified this association. The maintenance of higher CPB hematocrit may reduce the incidence of postoperative ARF, especially for patients with poor preoperative renal function.