Real-time monitoring of endogenous lipid peroxidation by exhaled ethylene in patients undergoing cardiac surgery

Abstract

Pulmonary and systemic organ injury produced by oxidative stress including lipid peroxidation is a fundamental tenet of ischemia-reperfusion injury, inflammatory response to cardiac surgery, and cardiopulmonary bypass (CPB) but is not routinely measured in a surgically relevant time frame. To initiate a paradigm shift toward noninvasive and real-time monitoring of endogenous lipid peroxidation, we have explored pulmonary excretion and dynamism of exhaled breath ethylene during cardiac surgery to test the hypothesis that surgical technique and ischemia-reperfusion triggers lipid peroxidation. We have employed laser photoacoustic spectroscopy to measure real-time trace concentrations of ethylene from the patient breath and from the CPB machine. Patients undergoing aortic or mitral valve surgery-requiring CPB (n = 15) or off-pump coronary artery bypass surgery (OPCAB) (n = 7) were studied. Skin and tissue incision by diathermy caused striking (> 30-fold) increases in exhaled ethylene resulting in elevated levels until CPB. Gaseous ethylene in the CPB circuit was raised upon the establishment of CPB (> 10-fold) and decreased over time. Reperfusion of myocardium and lungs did not appear to enhance ethylene levels significantly. During OPCAB surgery, we have observed increased ethylene in 16 of 30 documented reperfusion events associated with coronary and aortic anastomoses. Therefore, novel real-time monitoring of endogenous lipid peroxidation in the intraoperative setting provides unparalleled detail of endogenous and surgery-triggered production of ethylene. Diathermy and unprotected regional myocardial ischemia and reperfusion are the most significant contributors to increased ethylene.

Keywords: cardiopulmonary bypass; ischemia-reperfusion injury; off-pump coronary artery bypass grafting; oxidative stress.

Copyright © 2014 the American Physiological Society.

Figures

Fig. 1.

Intraoperative real-time monitoring of ethylene measured in patients undergoing cardiac surgery with cardiopulmonary bypass (CPB). Sampling line was positioned in the expiratory limb of the ventilator circuit prior to and at the end of CPB and following CPB and to the exhaust of the oxygenator of CPB machine during CPB. Box plots represent 3–5 min ethylene averages. *P < 0.05 compared with patient baseline for ventilated groups. #P < 0.05 among CPB groups.

Fig. 2.

Impact of sternotomy (A) and cardiopulmonary bypass (B) on gaseous ethylene. A: typical example of real-time monitoring of ethylene following initial diathermy (DT) for skin incision and sternotomy (ST). P, patient baseline; V, ventilation hold. B: example of real-time monitoring of ethylene at onset of CPB showing influence of changing fresh gas flow, temperature (T), rewarming, and aortic cross-clamp release (XC).

Fig. 3.

Example of real-time monitoring of ethylene during off-pump coronary artery bypass surgery (OPCAB) grafting showing the reperfusion events associated with completing of distal and proximal aortic anastomoses. LAD, left anterior descending, PDA, posterior descending; CFX, circumflex coronary artery; ASC, aortic side clamp; OM, obtuse marginal.

Fig. 4.

Summary data of real-time monitoring of ethylene during OPCAB grafting showing the major clinical and reperfusion events associated with completing of distal anastomoses and proximal aortic anastomoses. Box plots represent 3–5 min ethylene averages. *P < 0.05 compared with patient baseline.