Miniaturized versus conventional cardiopulmonary bypass and acute kidney injury after cardiac surgery

Introduction: Acute kidney injury (AKI) is a serious complication after coronary artery bypass grafting (CABG). There are conflicting reports whether a miniaturized cardiopulmonary bypass (MCPB) system is associated with a lower AKI incidence compared with conventional cardiopulmonary bypass (CCPB). It is unknown if AKI risk factors differ between the two groups. We assessed if MCPB decreases AKI after CABG and compared the risk factors between both groups. Methods: Sixty-eight Asian patients presenting for elective CABG at a tertiary heart centre were enrolled. They were randomly assigned to MCPB (n=34) or CCPB group (n=34) and followed up in a single-blinded, prospective, randomized, controlled trial. The primary outcome was Acute Kidney Injury Network stage 1 AKI. Results: The AKI incidence was 21.5% and was not significantly different between patients undergoing MCPB versus CCPB (21.9% versus 21.2%, p=0.948). The first CPB haematocrit was independently associated with AKI in the MCPB group (Relative Risk [RR]=0.484, 95% Confidence Interval [CI]=0.268-0.876, p=0.016); post-operative blood loss and inflammation were independently associated with AKI in the CCPB group (RR=1.005, 95%CI=1.003-1.007, p<0.001; RR=1.018, 95%CI=1.010-1.028, p<0.001). Conclusion: The MCPB system is not associated with a lower incidence of AKI in Asian patients undergoing CABG. Risk factors for AKI differed between patients using the MCPB and CCPB systems.