Strategies that improve renal medullary oxygenation during experimental cardiopulmonary bypass may mitigate postoperative acute kidney injury

Abstract

Renal medullary hypoxia may contribute to cardiac surgery–associated acute kidney injury (AKI). However, the effects of cardiopulmonary bypass (CPB) on medullary oxygenation are poorly understood. Here we tested whether CPB causes medullary hypoxia and whether medullary oxygenation during CPB can be improved by increasing pump flow or mean arterial pressure (MAP). Twelve sheep were instrumented to measure whole kidney, medullary, and cortical blood flow and oxygenation. Five days later, under isoflurane anesthesia, CPB was initiated at a pump flow of 80 mL kg–1min–1 and target MAP of 70 mm Hg. Pump flow was then set at 60 and 100 mL kg–1min–1, while MAP was maintained at approximately 70 mm ..