HUMANS ANESTHETIZED WITH SEVOFLURANE OR ISOFLURANE HAVE SIMILAR ARRHYTHMIC RESPONSE TO EPINEPHRINE

Background: Anesthetics can alter the dose of exogenously administered epinephrine that causes cardiac arrhythmias. The purpose of this study was to test the hypothesis that in humans anesthetized with sevoflurane, the arrhythmic response to epinephrine is not different from the response in humans anesthetized with isoflurane. Methods: We determined the arrhythmogenicity of submucosally administered epinephrine in 40 ASA physical status 1 or 2 patients who were to undergo transsphenoidal surgery. Patients were assigned randomly to be given 1.0-1.3 minimum alveolar concentration sevoflurane or isoflurane. A surgeon, blinded to the anesthetic and the concentration of epinephrine, injected into the nasal submucosa spinephrine 10, 13.3, or 20 mug/ml in saline of volume sufficient for surgical need. We defined a ''positive'' response as three or more premature ventricular contractions within 5 min after initiation of injection. Responses between anesthetic groups within each dose range of epinephrine were compared by chi-squared analysis. Results: No patient given either anesthetic developed premature ventricular contractions with doses of epinephrine less than 5 mug/kg. At larger doses of epinephrine (5-9.9 and 10-14.9 mug/kg), the frequency of arrhythmias did not differ between patients given sevoflurane and patients given isoflurane. Patients anesthetized with 1.2 minimum alveolar concentration sevoflurane had blood pressure similar to and heart rate less than those of patients anesthetized with similar concentrations of isoflurane. Blood pressure and heart rate were increased similarly in both groups after laryngoscopy and tracheal intubation and after epinephrine injection. Conclusions: Sevoflurane and isoflurane do not differ in their sensitization of the human myocardium to the arrhythmogenic effect of exogenously administered epinephrine.