Alpha-adrenergic responsiveness correlates with epinephrine dose for arrhythmias during halothane anesthesia in dogs.

The dose of epinephrine required to elicit ventricular arrhythmias during halothane anesthesia may depend on end-organ sensitivity. We determined whether the arrhythmogenic dose for epinephrine (ADE) could be correlated with either alpha- or beta-adrenergic responsiveness. After ADE was determined in 26 dogs anesthetized with 1.2 MAC halothane, an in vivo assessment of adrenergic responsiveness was made. The alpha-adrenergic responsiveness was defined as the dose of phenylephrine required to increase mean arterial pressure by 75% (alpha 75), while the dose of isoproterenol causing a 75% increase in heart rate was a measure of beta-adrenergic responsiveness (beta 75). The correlation coefficients for alpha 75 and beta 75 vs ADE then were determined by multiple linear regression analysis. There was a highly significant correlation with the alpha 75 (F = 9.06; P less than 0.01), while no relationship existed with beta 75 (F = 0.52; P greater than 0.05). Thus the alpha-adrenergic responsiveness in individual patients may be used to predict the threshold for epinephrine-induced arrhythmias during halothane anesthesia.