Ethane: a marker of lipid peroxidation during cardiopulmonary bypass in humans

The goals of this study were to (1) determine the utility of quantification of ethane as a marker of ischemia-reperfusion during human cardiopulmonary bypass (CPB); and (2) determine, using an animal model for this surgical procedure, whether the mode of surgical approach produced increases the quantity of exhaled ethane. Human CPB was initiated following standard anesthetic and monitoring regimens. Samples of gas were collected at baseline and at multiple defined time points throughout the studies. Ethane was determined using cryogenic concentration and gas chromatography. Sternotomy increased exhaled ethane compared to baseline (p < .007; 5.8 +/- 1.7 vs. 3.0 +/- 0.7 nmol/m2 x min); ethane returned to baseline levels prior to the initiation of CPB. Aortic unclamping produced ethane elevation (p < .05; 2.3 +/- 0.8 vs. 1.5 +/- 0.4 nmol/m2 x min) with the levels being related to a lower cardiac index and a higher systemic vascular resistance post aortic unclamping. Termination of CPB significantly increased ethane levels compared to baseline (p < .002; 4.8 +/- 1.7 vs. 3.0 +/- 0.7 nmol/m2 x min). Independent variables that correlated with increased ethane measurements included a higher arterial blood pH on bypass and the change in hemoglobin pre- and post-CPB. Electrocautery, but not scalpel, incision of the porcine abdominal wall increased ethane levels significantly (p < .02). These results indicate that exhaled ethane may be a valuable marker of lipid peroxidation during and following CPB.