Lipid peroxidation, antioxidant status and troponin-T following cardiopulmonary bypass. A comparison between intermittent crossclamp with fibrillation and crystalloid cardioplegia

OBJECTIVE: Intermittent crossclamp with fibrillation affords equivalent myocardial protection to cold crystalloid cardioplegia in patients undergoing elective coronary artery surgery. This study is a direct comparison between the two techniques with regards to free radical activity. METHODS: The study design was part of a prospective randomised trial. We studied 24 consecutive patients with ejection fraction of 30% or greater undergoing elective coronary artery surgery. Patients were randomised into two groups. In group 1 (n = 13) the myocardium was protected by intermittent aortic cross clamping with fibrillation and group 2 (n = 11) by antegrade cold crystalloid cardioplegia. The determinants of free radical activity were serial peripheral venous samples for lipid peroxidation and plasma antioxidant status (before and at 1, 6, 24 and 72 h after the end of cardiopulmonary bypass). The determinant of the efficacy of myocardial protection was serial peripheral venous samples of cardiactroponin-T taken at the same time intervals. RESULTS: The groups were similar with respect to age, sex distribution, preoperative ventricular function, left main stem disease, number of grafts and bypass times. Lipidperoxidation measurements at the 1 h time point were higher thanpreoperative values (7.24 ± 1.19 vs. 4.48 ± 0.69 and 9.36 ± 1.46 vs.4.98 ± 1.02 (mean ± S.E) in groups 1 and 2, respectively (units inmmol/l) thereafter values decreased to near preoperative values by 72 h. There was no significant difference between the groups (P = 0.42). Totalplasma antioxidant status values at the 1 h time point were lower than the preoperative values for all patients (1.33 ± 0.07 vs. 1.63 ± 0.06 and 1.42 ± 0.07 vs. 1.63 ± 0.05 (mean ± standard error) in groups 1 and 2, respectively, (units in mmol/l) and thereafter at the subsequent time points increased but never attained their preoperative value. There was nostatistically significant difference between the two groups (P = 0.59). Troponin-T measurements showed no significant difference between the two groups at all time points (P = 0.2217). CONCLUSIONS: This study shows that lipid peroxidation is initially elevated and the defence mechanisms against oxygen free radicals-‘antioxidant status’-are depressed following cardiopulmonary bypass. The degree of oxygen free radical activity produced during ischaemia and reperfusion was similar in both types of myocardia lprotection employed in this study.