Myocardial vitamin E is consumed during cardiopulmonary bypass: indirect evidence of free radical generation in human ischemic heart

Although a role for free radicals in myocardial damage during cardiopulmonary bypass for open heart surgery has been postulated, direct evidence of free radical production as well as consumption of tissue antioxidants such as vitamin E is still lacking. Twenty patients (age 26-66 yr, mean 48) undergoing elective open heart surgery with moderate hypothermia, and cold crystalloid cardioplegia, were studied. Cardiopulmonary bypass time was 61.4 +/- 31.2 min. The specimens of atrial tissue collection before and after cardiopulmonary bypass, were immediately frozen in liquid nitrogen. Mean vitamin E atrial content, measured by reverse phase HPLC, was 355 +/- 249 pmol/mg of dry weight basally, 135 +/- 85 pmol/mg (p0.05) at the end of the ischemic period and 405 +/- 288 pmol/mg after the reperfusion period (p0.01). Microscopic examination of right atrial biopsies ruled out differences in fibrosis or cellular damage as the cause of vitamin E changes. Although a great basal variability in atrial vitamin E content was observed, which was independent of age, sex and clinical status, a reproducible and substantial decrease in atrial vitamin E content after cardiopulmonary bypass occurred (mean reduction 45 +/- 17% and 55 +/- 22%, respectively, after ischemia and after reperfusion). This was directly related to the aorta cross-clamping duration and partially to the minimum temperature achieved. In conclusion, apart from the great variability observed in basal vitamin E tissue content, vitamin E was always reduced during cardiopulmonary bypass, suggesting an oxidative stress on the myocardium during open heart surgery.