DL and D Sotalol Decrease Defibrillation Energy Requirements

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Abstract
We examined the acute effects of intravenous DL and D sotalol on the energy requirements for internal defibrillation (DF) in 44 dogs anesthetized with pentobarbital (n = 18), enflurane (n = 8), and fentanyl (n = 18). Multiple shocks of varying energies were applied through left and right ventricular epicardial patch electrodes to relate delivered energy to percent success in DF. The energies required for 50% success in DF (E) were estimated by logistic regression. DL or D sotalol was administered in a loading (4 mg/kg over 10 min) and maintenance (1.5 mg/kg/hr) infusion and the energy--success curve was again measured 30 minutes after drug administration. The effect of DL and D sotalol on E50 was compared to controls given saline. Both DL and D sotalol significantly lowered E50 by 16% +/- 14% (P less than 0.05) and 24.5% +/- 8.2% (P less than 0.05), respectively, in fentanyl anesthetized animals; this was accompanied by a 22% +/- 8% (P less than 0.05) and 16% +/- 5% (P less than 0.01) increase in ventricular effective refractory period (VERP), respectively. In pentobarbital anesthetized dogs, DL and D sotalol decreased E50 by 16% +/- 27% (P = ns) and 11% +/- 16% (P less than 0.05), respectively, and were associated with a 23% +/- 5% (P less than 0.01) and 12 +/- 4% (P less than 0.05) prolongation of VERP. DL and D sotalol decrease defibrillation energy requirements, possibly as a result of their Class III antiarrhythmic drug action.