Epinephrine-induced arrhythmias during enflurane anesthesia in man: a nonlinear dose-response relationship and dose-dependent protection from lidocaine.

Forty-eight patients undergoing transsphenoidal pituitary surgery under enflurane anesthesia received submucosal injections of 1:150,000 or 1:200,000 epinephrine in saline, 0.5% lidocaine, or 1.0% lidocaine. The threshold doses for ventricular irritability, defined as 3 or more premature ventricular contractions during or in the 3 to 5 minutes following injection, were 1.3 microgram/kg with saline, 2.5 microgram/kg with 0.5% lidocaine, and 4.9 microgram/kg with 1.0% lidocaine. There was no consistent relationship between epinephrine dose and occurrence of ventricular irritability within or among groups. The data show a protective effect of lidocaine against epinephrine-induced ventricular irritability during enflurane anesthesia and suggest a qualitative as well as quantitative difference between enflurane and other volatile anesthetics in their interaction with epinephrine.