CARDIOVASCULAR ANESTHESIA SOCIETY OF CARDIOVASCULARANESTHESIOLOGISTS SECTION EDITOR KENNETH J. TUMAN Gastric Mucosal Oxygen Delivery Decreases During Cardiopulmonary Bypass Despite Constant Systemic Oxygen Delivery Jean-Charles Sicsic, MD*, Jacques Duranteau, MDS, Her& Corbineau, MDt, Sami Antoun, MDS, Pascal Menestret, MD*, Philippe Sitbon, MDS, Alain Leguerrier, MDt, Yves Logeais, Mm, and Claude Ecoffey, MD* Departments of *Anesthesiology and Surgical Intensive Care 2 and tcardiothoracic Surgery, Hopital Pontchaillou, Universite de Rennes I, Rennes; and SDepartment of Anesthesiology and Surgical Intensive Care, Hopital Bicetre, Kremlin Bicetre, France Previous studies report a decrease in gastric mucosal oxygen delivery during cardiopulmonary bypass (CPB). However, in these studies, CPB was associated with a reduction in systemic oxygen delivery (DO,). Conceivably, this decrease in DO, could have contrib- uted to the observed decrease in gastric mucosal oxy- gen delivery. Thus, in the present study, we assessed the effects of the maintenance of DO, (at pre-CPB val- ues) during hypothermic (30-32”(Z) CPB on the gastric mucosal red blood cell flux (GMRBC flux) using laser Doppler flowmetry. In 11 patients requiring cardiac surgery, the pum flow rate during CPB was initially setat2.4L*minP*m-’ and was adjusted to maintain DO, at pre-CPB values (flow 2.5-2.7 L * rnin~’ * rn-‘). Despite a constant DO,, the GMRBC flux was decreased during CPB. These decreases averaged 50% ? 16% after 10 min, 50% 2 18% after 20 min, 49% + 21% after 30 min, and 49% ? 19% after 40 min of CPB. The rewarming period was associated with an in- crease in GMRBC flux. Thus, maintaining systemic DO, during CPB seems to be an ineffective strategy to im- prove gastric mucosal oxygen delivery. Implications: In the present study, we tested the hypothesis that gas- tric mucosal red blood cell flux assessed by laser Dopp- ler flowmetry could be improved by maintaining base- line systemic flow and oxygen delivery during hypothermic cardiopulmonary bypass. Despite this strategy, gastric mucosal red blood cell flux decreased by 50% during hypothermic cardiopulmonary bypass. (Anesth Analg 1998;86:455-60) P atients undergoing cardiopulmonary bypass (CPB) are at risk of developing gut ischemia (1,2) and the gut mucosal layer is known to be ex- tremely susceptible to hypoxia (3,4). The laser Doppler (LD) flowmetry technique can be applied to patients to provide a direct and continuous evaluation of the gastric mucosal red blood cell flux (GMRBC flux). The LD flowmetry signal is proportional to the number and mean velocity of red blood cells in the tissue volume studied. Thus, LD flowmetry measures the flux of red blood cells in the tissue, rather than actual tissue blood flow. Because oxygen delivery is related to the flux of red blood cells rather than to plasma Accepted for publication November 25, 1997. Address correspondence and reprint requests to J. C. Sicsic, MD, Service d’Anesth&ie-Reanimation Chirurgicale 2, HBpital Pont- chaillou, rue Henri le Guilloux, 35033 Rennes Cedex 9, France. flow, LD flowmetry can continuously provide infor- mation on the local oxygen delivery in the volume of tissue studied. Using this technique in patients under- going CPB, previous studies have found a decrease in the GMRBC flux during CPB (5,6). The prevalence of gastric mucosal acidosis (7,8) with increased intestinal mucosal permeability (5) reported after CPB suggests that an inadequacy between gut oxygen delivery and gut metabolic demands could occur during CPB. Many different mechanisms may contribute to the CPB-induced decrease in gastric oxygen delivery. However, in all the studies that reported a CPB- induced reduction of gastric mucosal oxygen delivery, reduced systemic oxygen delivery (DO,) was appar- ent during CPB. It is conceivable that this decrease in DO, contributed to the observed decrease in gastric mucosal oxygen delivery. In this regard, a fundamental question is whether GMRBC flux can be improved when systemic DO, is 01998 by the International Anesthesia Research So&Q 0003-2999/98/$5.00 Anesth Analg 1998;86:45540 455