Abstract 11100: Effect of Different Oxygen Concentrations on Post Resuscitation Myocardial Oxidative Stress and Myocardial Function in a Rat Model of CPR

Background: Lipid peroxidation induced by oxygen free radicals plays a prominent role in myocardial injury after global ischemia. The present study investigated whether ventilation with lower concentration of inspired oxygen would decrease the severity of myocardial lipid peroxidation and post resuscitation myocardial dysfunction. Methods: Ventricular fibrillation was induced and untreated for 8 mins in 46 male Sprague-Dawley rats. Defibrillation was attempted after 8 mins of CPR. The animals were randomized into 3 groups: mechanical ventilation with 100% O2, 50% O2 or 21% O2 during CPR and one hr following return of spontaneous circulation. Normoxic ventilation was maintained thereafter. The level of 8-iso-Prostaglandin F2α (8-iso-PGF2α) in myocardium was evaluated using the enzyme-linked immunosorbent assay (ELISA). Blood gases, post resuscitation myocardial function and the duration of survival were monitored in all animals. Results: Compared with the 100% and 21% groups, the 50% group showed a lower 8-iso-PGF2α level at 4 hrs post resuscitation (Table). Significantly greater oxygen extraction rate, lower lactate, better myocardial ejection fraction and myocardial performance index were observed in the 50% group (Table). A significantly shorter duration of survival was observed in the 21% group when compared with the other two groups (Table). There was a trend in the 50% group towards an increased duration of survival when compared with the 100% group. Conclusions: In a rat cardiac arrest model, ventilation with 50% inspired oxygen during early post-ischemic reperfusion contributed to a decreased lipid peroxidation, a better oxygenation, myocardial function and duration of survival.