Abstract 148: Zoniporide Combined with α-Methylnorepinephrine Appears Highly Effective for Resuscitation from Cardiac Arrest in a Rat Model of Ventricular Fibrillation

Abstract

Background: We have reported in rat and swine models of cardiac arrest that sodium hydrogen exchanger isoform-1 (NHE-1) inhibition facilitates resuscitation, ameliorates myocardial dysfunction, and improves survival. Others have reported that α-methylnorepinephrine (α-MNE) - a selective α2-adrenoreceptor agonist - is superior to epinephrine given its lack of β-agonist effects. We examined in a rat model of VF and closed-chest resuscitation the effects of combining the NHE-1 inhibitor zoniporide (ZNP) with α-MNE. Methods: VF was electrically induced in 32 male retired breeder Sprague-Dawley rats and left untreated for 8 minutes after which resuscitation was attempted by an 8 minute interval of chest compression and delivery of electrical shocks. Rats were randomized 1:1:1:1 to receive a 3 mg/kg bolus of ZNP or 0.9% NaCl before starting chest compression and a 100 μg/kg bolus of α-MNE or its vehicle at minute 2 of chest-compressions establishing 4 groups of 8 rats each. Successfully resuscitated rats were monitored for 240 minutes. Results: The number of rats that had return of spontaneous circulation and then survived 240 min were: α-MNE(-)/ZNP(-) 4 and 2; α-MNE(-)/ZNP(+) 5 and 5; α-MNE(+)/ZNP(-) 2 and 1; and α-MNE(+)/ZNP(+) 7 and 7 yielding a statistically significant effect on overall survival times corresponding to 105 ± 114, 150 ± 124, 58 ± 108, and 210 ± 85 min, respectively (p < 0.045). Post-resuscitation lactate levels were attenuated in all treatment groups with the greatest effect by the α-MNE(+)/ZNP(+) combination without major differences in hemodynamic function (Table). Conclusion: We confirm a beneficial effect resulting from the combination of ZNP (given to attenuate myocardial reperfusion injury) and α-MNE (given to augment peripheral vascular resistance during chest compression without the detrimental actions of epinephrine). The proposed combination may prove to be a highly effective novel strategy for resuscitation from cardiac arrest.