Factors that confound the prediction of renal medullary oxygenation and risk of acute kidney injury from measurement of bladder urine oxygen tension

Abstract

Aim: Urinary oxygen tension (uPO2) may provide an estimate of renal medullary PO2 (mPO2) and thus risk of acute kidney injury (AKI). We assessed the potential for variations in urine flow and arterial PO2 (aPO2) to confound these estimates. Methods: In 28 sheep urine flow, uPO2, aPO2 and mPO2 were measured during development of septic AKI. In 65 human patients undergoing cardiac surgery requiring cardiopulmonary bypass (CPB) uPO2 and aPO2 were measured continuously during CPB, and in a subset of 20 patients, urine flow was estimated every 5 minutes. Results: In conscious sheep breathing room air, uPO2 was more closely correlated with mPO2 than with aPO2 or urine flow. The difference between ..