Splanchnic oxygen transport and lactate metabolism during normothermic cardiopulmonary bypass in humans

The effect of normothermic (36.2 degrees C +/- 0.6 degree C) nonpulsatile 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, gastric tonometry) was studied in 12 adults (New York Heart Association class II, ejection fraction > or = 0.4) undergoing coronary artery surgery. SBF was estimated with the constant-infusion indocyanine green (ICG) technique using a hepatic venous catheter. DO2spl, VO2spl, and splanchnic lactate uptake were calculated using the Fick principle after the induction of anesthesia, during aortic cross-clamping, after CPB, and 2 and 7 h after admission to the intensive care unit (ICU). SBF, DO2spl, and VO2spl did not decrease during CPB but increased after ICU admission, whereas pHi decreased 7 h after ICU admission. Initial ICG extraction was 0.78, which decreased to 0.54 during aortic clamping and remained low thereafter. The increased arterial blood lactate concentrations were not associated with a decreased splanchnic lactate uptake. We conclude that normothermic CPB is not associated with deterioration in the global intestinal oxygen supply. The increase of blood lactate levels and the decrease in ICG extraction, as well as in pHi, are consistent with a systemic inflammatory response to CPB.

This study demonstrated that normothermic cardiopulmonary bypass (at flows > 2.4 L.min-1.m-2) was not associated with deterioration in global intestinal oxygen delivery, which suggests that increased blood lactate concentrations and decreased gastric mucosal pH and indocyanine green extraction are manifestations of a systemic inflammatory response to cardiopulmonary bypass.