Post-transfusional variation in urinary oxygen tension in surgical patients

Prior studies have suggested urinary oxygen tension (P(u)O2) as a putative index of renal blood flow (RBF) and tissue oxygenation. In the present study, we collected intraoperative data from eight anaemic, bladder-catheterized patients who received erythrocyte transfusions during various surgical procedures under general anaesthesia. Urinary and arterial blood gas analysis and co-oximetry were performed before and after transfusion, during an interval in which RBF was assumed to be constant. Pre- and post-transfusion haematocrit levels were 23 +/- 4.8 and 27 +/- 6.4%, respectively, and arterial oxygen content (C(a)O2) was 10.5 +/- 2.5 and 12.4 +/- 3.1 mL/dL, respectively (P = 0.012). Pre- and post-transfusion P(u)O2 was 90 +/- 14 and 108 +/- 20 mmHg, respectively (P = 0.036). 4. These results, although limited, suggest that under conditions of stable haemodynamics, systemic oxygenation and renal function, intraoperative blood transfusion may increase P(u)O2 in anaemic anaesthetized patients. If confirmed by subsequent clinical and laboratory studies, P(u)O2 measurement could become a simple, non-invasive way to monitor renal medullary oxygenation and tissue oxygen availability and help determine whether red blood cells should be transfused.