Lean body weight-indexed O₂delivery during cardiopulmonary bypass and acute kidney injury

Introduction: Monitoring indexed oxygen delivery (DO₂i) is recommended during cardiopulmonary bypass (CPB) and a predictor of acute kidney injury (AKI). The use of lean body mass-adjusted blood flow rates in obese patients during CPB may provide a valid representation of metabolic demand, however, the risk of AKI with this approach has not been reported. This study aimed to investigate the influence of lean body mass-adjusted DO₂i values in the risk of AKI following CPB. 

Methods: Utilizing the Australian and New Zealand Collaborative Perfusion Registry dataset, 12,811 cardiac patients were divided into 2 groups; non-obese (BMI <30) and obese (BMI >30). Obese patients’ lean mass was derived from their recalculation to a BMI of 25 and used for the calculation of DO₂i. Postoperative AKI was classified using the RIFLE criteria. 

Results: Incidence of AKI was higher in the obese compared to non-obese group (15% vs 11%, p < 0.001). Decreasing minimum lean body weight adjusted DO₂i was significantly associated with an increased risk of AKI (OR, 0.998; [0.997–0.999], p < 0.001) with an optimal threshold value of 292 ml/min/m². 

Conclusions: Lean body weight-adjusted O₂ delivery remains an independent risk factor for AKI. The critical minimum DO₂i threshold of 292 mL/min/m² is within the range of previously reported values, inferring that lean-based blood flow monitoring may offer a reasonable approach to CPB practice.