Effect of pentobarbital anesthesia on ventricular defibrillation threshold in dogs

Abstract

The effect of pentobarbital anesthesia upon the minimal voltage and current required for electrical ventricular defibrillation (the defibrillation threshold) was investigated in dogs. Threshold current, energy, and charge in five dogs averaged 2 per cent, 13 per cent, and 6 per cent less under surgical levels of pentobarbital anesthesia than thresholds in the same animals in the awake, unanesthetized state. In dogs given sufficient pentobarbital to produce apnea and supported by mechanical ventilation, threshold current, energy, and charge averaged 3 per cent, 17 per cent, and 2 per cent less than comparable awake values. These differences were far from statistically significant. In a second study, five dogs were kept for 8 to 10 hours at a surgical level of anesthesia with pentobarbital sodium. Defibrillation threshold current, determined at hourly intervals, did not drift outside ± 10 per cent limits. Arterial blood gas measurements revealed a stable, compensated metabolic acidosis in all animals (pH 7.36 ± 0.06, pCO 2 33 ± 4 mm. Hg, pO 2 71 ± 9 mm. Hg). These data support the validity of defibrillation studies using animals anesthetized with pentobarbital and indicate the stability of the defibrillation threshold under controlled experimental conditions.

The effect of newer antiarrhythmic drugs on defibrillation threshold

“…Pentobarbital anesthesia was selected because it does not itself alter the defibrillation thresh-old. 6 Lead II ECG was monitored using subdermal pin electrodes. A femoral vein was catheterized for administration of additional doses of pentobarbital to maintain anesthesia, as well as for administration of the antiarrhythmic drugs.…”

Elevation of ventricular defibrillation threshold in dogs by antiarrhythmic drugs

“…This anesthetic was chosen because we have previously shown that it does not alter the defibrillation threshold [10]. The details of anesthesia and monitoring have been described previously [11].…”

Activation during ventricular defibrillation in open-chest dogs. Evidence of complete cessation and regeneration of ventricular fibrillation after unsuccessful shocks.

“…1 mongrel dogs (mean weight±standard deviation [SD], 19.3±2.2 kg) were anesthetized with pentobarbital (30)(31)(32)(33)(34)(35) mg/kg) (13,14) and succinylcholine (1 mg/kg). Each was intubated with a cuffed endotracheal tube and ventilated with 30-60% oxygen through a Harvard respirator (Harvard Apparatus Co., Inc., S. Natick, MA).…”