Higher Flow on Cardiopulmonary Bypass in Pediatrics is Associated With A Lower Incidence of Acute Kidney Injury

Semin Thorac Cardiovasc Surg. 2019 Aug 16. [Epub ahead of print]

Adequate perfusion is of paramount concern during cardiopulmonary bypass (CPB) and different methodologies are employed to optimize oxygen delivery. Temperature, hematocrit, and cardiac index are all modulated during CPB to ensure appropriate support. This study examines two different perfusion strategies and their impact on various outcome measures including acute kidney injury (AKI), urine output on CPB, ICU length of stay, time to extubation, and mortality. Predicated upon surgeon preference, the study institution employs two different perfusion strategies (PS) during congenital cardiac surgery requiring CPB. One method utilizes a targeted 2.4 L/min/m2 CI and nadir hematocrit of 28% (PS1), the other a 3.0 L/min/m2 CI with a nadir hematocrit of 25% (PS2). This study retrospectively examines CPB cases during which the two perfusion strategies were applied to determine potential differences in packed red blood cell administration, urine output during cardiopulmonary bypass, AKI post CPB as defined by the KDIGO criteria and operative survival as defined by the Society of Thoracic Surgeons. Significant differences were found in urine output while on CPB (p <0.01) and all combined stages of postoperative AKI (p =0.01) with the PS2 group faring better in both measures. No significant difference was found between the two groups for packed red blood cell administration, mortality, time to extubation, or ICU length of stay. Avoiding a nadir hematocrit less than 25% has been well established but maintaining anything greater than that may not be necessary to achieve adequate oxygen delivery on CPB. Our results indicate higher cardiac index and oxygen delivery on CPB is associated with a lower rate of AKI and this may be achieved with increased flow rather than increasing the hematocrit thus avoiding unnecessary transfusion.