Impact of Different Cardiopulmonary Bypass Strategies on Renal Injury After Pediatric Heart Surgery

Abstract

Background: The purpose of this study is to compare the incidence and severity of acute kidney injury (AKI) after open heart surgery in neonates and infants for two different cardiopulmonary bypass (CPB) strategies.

Methods: In all, 151 infants undergoing cardiac surgery were prospectively enrolled between June 2017 and June 2018 at two centers, one using conventional CPB (2.4 L · min^-1 · m^-2, 150 mL · kg^-1 · min^-1) with reduction of flow rates with moderate hypothermia and with a targeted hematocrit greater than 25% (center 1, n = 91), and the other using higher bypass flow rates (175 to 200 mL · kg^-1 · min^-1) and higher minimum hematocrit (greater than 32%) CPB (center 2, n = 60). The primary endpoint was the incidence of postoperative AKI as defined by Acute Kidney Injury Network criteria and risk factors associated with AKI.

Results: Preoperative characteristics and complexity of surgery were comparable between centers. The overall incidence of early postoperative AKI was 10.6% (16 of 151), with 15.4% (14 of 91) in center 1 and 3.3% (2 of 60) in center 2 (P = .02). Mean lowest flow rates on CPB were 78 mL · kg^-1 · min^-1 vs 118 mL · kg^-1 · min^-1 and mean highest hematocrit on separation from CPB were 33% vs 43% at center 1 and 2, respectively (P < .001). Center 1 used less packed red blood cells but more fresh frozen plasma than center 2 (P = .001). By multivariate analysis, only lower flows on CPB (78 vs 96 mL · kg^-1 · min^-1, P = .043) and lower hematocrit at the end of CPB (33% vs 37%, P = .007) were associated with AKI.

Conclusions: In this contemporary comparative study, higher flow rates and higher hematocrit during cardiopulmonary bypass were associated with better preservation of renal function.