Effect of methoxyflurane on epinephrine-induced ventricular arrhythmias.

THE EFFECT OF METHOXYFLURANE on the sensitivity of the heart to epinephrineinduced ventricular arrhythmias has not been clearly defined. On the one hand, animal experiments have been reported which found that methoxyflurane increases ventricular arrhythmias associated with epinephrine administration. 1,~ On the other hand, other studies have found that methoxyflurane protects against arrhythmias? ,4 Still other reports have found methoxyflurane to be less sensitizing than cyclopropane or halothane, but as sensitizing as chloroform or halothaneether azeotrope. 5,6 That epinephrine can be safely injected subcutaneously to secure haemostatis during operations performed under methoxyflurane 7-15 is a unanimous ff pragmatic observation. It is an observation, however, which neither defines the risk, ff any, involved in such a practice, nor contributes to our understanding of the pharmacological properties of methoxyflurane. The present study was undertaken to evaluate under controlled conditions in experimental animals (1) the effect of methoxyflurane on ventricular sensitivity to epinephrine-induced arrhythmias, and (2) the effect of methoxyflurane on severity of ventricular arrhythmias produced by epinephrine. The former was determined by measuring the effect of methoxyflurane on the time required for appearance of ventricular arrhythmias during the continuous infusion of a standard, dilute solution of epinephrine. The latter was measured as the effect of methoxyfiurane on duration of ventricular arrhythmias produced by epinephrine. Duration of ventrieular arrhythmias was equated with severity on the basis that one or two abnormal ventricular contractions are not of the same significance as well established, continuing abnormal contractions.