In vivo comparison of dl-sotalol-induced electrocardiographic responses among halothane anesthesia, isoflurane anesthesia with nitrous oxide, and conscious state.

We compared dl-sotalol-induced electrocardiographic responses in intact dogs using a repeated-measures design among 1% halothane anesthesia, 1.5% isoflurane anesthesia with nitrous oxide (NO), and conscious state to clarify influences of the anesthetics (n = 4). Basal PR interval was longer in halothane than either in isoflurane with NO or in conscious state, reflecting sympathetic nerve suppression for the atrioventricular node by halothane. Both anesthetics exhibited longer basal QRS width than conscious state, suggesting their ventricular I inhibition. Also, both anesthetics showed longer basal QT interval, QTcF and T-T than conscious state, indicating their ventricular I inhibition. Meanwhile, dl-sotalol prolonged PR interval similarly in isoflurane with NO and in conscious state, which was less great in halothane, suggesting further sympathetic nerve suppression for the atrioventricular node might be limited in halothane. dl-Sotalol prolonged QT interval and QTcF >3 times greater in either of the anesthetics than in conscious state; moreover, dl-sotalol prolonged T-T similarly in both anesthetics, but hardly altered it in conscious state; indicating isoflurane with NO as well as halothane may have reduced the repolarization reserve to increase the sensitivity of ventricle toward I suppression. Thus, isoflurane with nitrous oxide could be useful for in vivo I assay like halothane.