959-101 Antioxidant Enzymes Attenuate Free Radical Generation After Direct Current Countershocks

Previous work in our lab has shown that direct current (DC) shocks generate free radicals, which may be toxic to the myocardium. We hypothesized that administration of free radical scavenging enzymes prior to shock delivery would attenuate the generation of free radicals. We used a newly developed and validated technique for real time quantitation of free radical production: ascorbyl free radical (AFR) concentration in coronary sinus blood, measured by electron paramagnetic resonance. In 10 open-chest dogs, 75J and 100J epicardial shocks were administered during NSR. Then superoxide dismutase (SOD, 15,000 μ/kg).and catalase (CAT. 55,000 u/kg) were given as a continuous infusion. Ten mins. after initiating the SOD/CAT infusion, 75J and 100J shocks were repeated. Four control dogs received normal saline instead of SOD/CAT. Results % Δ AFR Area AFR Energy Pre SOD Post SOD Pre SOD Post SOD 75 J 17 ± 4 5 ± 2 * 150 ± 39 37 ± 8 * 100 J 20 ± 5 6 ± 2 * 184 ± 26 53 ± 17 * x ± SO. * p l 0,05 post vs. pre. Area = integrated area under AFR concentration vs. time curve The 4 control dogs showed no significant differences in AFR generation when comparing shocks administered before and after saline infusion rather than SOD/CAT. Conclusion antioxidant enzymes markedly attenuate free radical generation by DC shocks. If free radicals are a mechanism of defibrillation injury in patients, drugs with free radical inhibiting or scavenging properties may prevent such injury.