Effect of Allopurinol on Myocardial Oxygen Free Radical Production in Coronary Bypass Surgery

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Abstract
Objectives - Allopurinol protects the heart from reperfusion injury. The aim of this study was to investigate myocardial free radical production during reperfusion with and without allopurinol treatment in coronary artery bypass grafting patients randomized into allopurinol (n = 14) or placebo (n = 13) groups. Design - Allopurinol (1 g) was given blind prior to cardiopulmonary bypass and prior to opening the aorta. Oxygen free radicals were measured before anesthesia in arterial blood, before cross-clamping and 1 and 10 min after reperfusion in arterial and coronary sinus blood. Levels were measured as relative concentrations by the electron spin resonance method. Results - One minute after reperfusion the level of spin-trapped radicals in arterial blood was elevated significantly (p = 0.016) in the allopurinol group, from 7.7 (SE:0.8) to 8.6 (1.4) and non-significantly (p = 0.074) in the placebo group, from 7.3 (0.7) to 8.3 (0.8). Ten minutes after reperfusion the arterial values were 8.6 (1.5) in the allopurinol and 7.6 (0.7) in the placebo group, the sinus values being 7.6 (1.3) and 8.3 (0.8), respectively. Myocardial free radical production was-0.94 (1.21) in the allopurinol and +0.79 (0.96) in the placebo group after 10 min reperfusion, the difference being significant (p = 0.043). Conclusions - All patients in both groups had an increasing tendency to free radical production during early reperfusion. Patients treated with allopurinol showed less myocardial production of free radicals, indicating that its protective effect may be due to its antioxidative properties.