SPLANCHNIC OXYGEN-TRANSPORT AND LACTATE METABOLISM DURING NORMOTHERMIC CARDIOPULMONARY BYPASS IN HUMANS

The effect of normothermic (36.2 degrees C +/- 0.6 degrees C) nonpulsa tile cardiopulmonary bypass (CPB) on splanchnic (hepatic) blood flow ( SBF), splanchnic oxygen transport (DO2spl,,,) and oxygen consumption ( VO2spl,, splanchnic lactate uptake and gastric mucosal pH (pHi, gastri c tonometry) was studied in 12 adults (New York Heart Association clas s II, ejection fraction greater than or equal to 0.4) undergoing coron ary artery surgery. SBF was estimated with the constant-infusion indoc yanine green (ICG) technique using a hepatic venous catheter. DO2spl,, VO2spl,,,, and splanchnic lactate uptake were calculated using the Fi ck principle after the induction of anesthesia, during aortic cross-cl amping, after CPB, and 2 and 7 h after admission to the intensive care unit (ICU). SBF, DO2spl,,, VO2spl,, did not decrease during CPB but i ncreased after ICU admission, whereas pHi decreased 7 h after ICU admi ssion. Initial ICG extraction was 0.78, which decreased to 0.54 during aortic clamping and remained low thereafter. The increased arterial b lood lactate concentrations were not associated with a decreased splan chnic lactate uptake. We conclude that normothermic CPB is not associa ted with deterioration in the global intestinal oxygen supply. The inc rease of blood lactate levels and the decrease in ICG extraction, as w ell as in pHi, are consistent with a systemic inflammatory response to CPB. Implications: This study demonstrated that normothermic cardiopu lmonary bypass (at flows >2.4 L.min(-1).m(-2)) was not associated with deterioration in global intestinal oxygen delivery, which suggests th at increased blood lactate concentrations and decreased gastric mucosa l pH and indocyanine green extraction are manifestations of a systemic inflammatory response to cardiopulmonary bypass.