This study examined the association between cardiopulmonary bypass (CPB) hematocrit and postoperative acute renal failure (ARF) in patients undergoing aortic arch surgery with hypothermic circulatory arrest.

The Society of Thoracic Surgeons Adult Cardiac Surgery Database was queried from 2011 to 2019 for patients undergoing aortic arch surgery with hypothermic circulatory arrest. A multivariable logistic regression model estimated the adjusted odds of postoperative ARF on the basis of CPB hematocrit. Effects were stratified by preoperative kidney function and the duration of hypothermic circulatory arrest by using interaction terms. The study also investigated the association between postoperative ARF and major postoperative outcomes by using multivariable regression models.

On adjusted analysis, higher CPB hematocrit (>20%-25%, >25%-30%, >30%) was associated with lower odds of ARF as compared with lower CPB hematocrit (≤20%) (>20-25%, aOR, 0.78; 95% CI, 0.65-0.93; P = .006; >25%-30%, aOR, 0.65; 95% CI, 0.50-0.84; P = .0007; >30%, aOR, 0.45; 95% CI, 0.28-0.72; P = .0008). The predicted probability of postoperative ARF by CPB hematocrit was higher in patients with lower preoperative renal function (estimated glomerular filtration rate, <60 mL/min/1.73 m²) (interaction P = .03). The association between hematocrit and postoperative ARF was not significantly modified by hypothermic circulatory arrest time (interaction P = .74). All postoperative outcomes were significantly worse in patients with postoperative ARF (all P < .0001).

Among 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.