GASTRIC-MUCOSAL OXYGEN DELIVERY DECREASES DURING CARDIOPULMONARY BYPASS DESPITE CONSTANT SYSTEMIC OXYGEN DELIVERY

Previous studies report a decrease in gastric mucosal oxygen delivery during cardiopulmonary bypass (CPB). However, in these studies, CPB wa s associated with a reduction in systemic oxygen delivery (DO2). Conce ivably, this decrease in DO2 could have contributed to the observed de crease in gastric mucosal oxygen delivery. Thus, in the present study, we assessed the effects of the maintenance of DO2 (at pre-CPB values) during hypothermic (30-32 degrees C) CPB on the gastric mucosal red b lood cell flux (GMRBC flux) using laser Doppler flowmetry. In 11 patie nts requiring cardiac surgery, the pump flow rate during CPB was initi ally set at 2.4 L.min(-1).m(-2) and was adjusted to maintain DO2 at pr e-CPB values (flow 2.5-2.7 L.min(-1).m(-2)). Despite a constant DO2, t he GMRBC flux was decreased during CPB. These decreases averaged 50% /- 16% after 10 min, 50% +/- 18% after 20 min, 49% +/- 21% after 30 mi n, and 49% +/- 19% after 40 min of CPB. The rewarming period was assoc iated with an increase in GMRBC flux. Thus, maintaining systemic DO2 d uring CPB seems to be an ineffective strategy to improve gastric mucos al oxygen delivery. Implications: Ln the present study, we tested the hypothesis that gastric mucosal red blood cell flux assessed by laser Doppler flowmetry could be improved by maintaining baseline systemic f low and oxygen delivery during hypothermic cardiopulmonary bypass. Des pite this strategy, gastric mucosal red blood cell flux decreased by 5 0% during hypothermic cardiopulmonary bypass.