Torsade de Pointes and Sudden Death Induced by Thiopental and Isoflurane Anesthesia in Dogs with Cardiac Electrical Remodeling

Abstract

Background: Many anesthetic agents are known to have cardiac effects. The effects of pentobarbital, thiopental and isoflurane on dogs with electrical remodeling are lacking.

Methods and Results: We studied 12 dogs that underwent two anesthesias. First, anesthesia was induced (N=12) with intravenous thiopental (17 mg/kg) induction followed by isoflurane inhalation (1.5%-3% via endotracheal tube). For electrical remodeling, we created complete atrioventricular block (CAVB) and myocardial infarction (MI). In 6 of the 12 dogs we also infused nerve growth factor (NGF) to the right stellate ganglion. All dogs had an implantable cardioverter-defibrillator (ICD) implanted. A second anesthesia was done 66 ± 20 days later. In 8 of the 12 dogs (6 without NGF), pentobarbital was used as the only anesthetic. In the remaining 4 dogs (all with NGF), 3 received thiopental and 1 received isoflurane.

Results: During the first anesthesia, none of 12 dogs had cardiac arrhythmia. During the second anesthesia, none of the 8 dogs that received pentobarbital developed ventricular fibrillation (VF). In contrast, all the dogs receiving either thiopental or isoflurane died of VF within 2 to 3 minutes. QT and P-P intervals before VF were 440 ± 36 milliseconds and 298 ± 28 milliseconds, longer and shorter (respectively) than those obtained the day prior to surgery (315 ± 25 milliseconds, P < 0.001; 330 ± 22 milliseconds, P < 0.01, respectively).

Conclusion: Thiopental and isoflurane are not arrhythmogenic in normal dogs and dogs with acute MI and CAVB, but are extremely proarrhythmic in dogs with chronic MI and CAVB. Consistent with the results of in vitro studies, pentobarbital did not induce ventricular arrhythmia in dogs with cardiac electrical remodeling.