Halothane-induced cardiac arrhythmias following administration of aminophylline in experimental animals

Cardiac arrhythmias often occur when patients receiving aminophylline are anesthetized with halothane. This animal study was designed to define what constitute arrhythmogenic doses of aminophylline when administered before halothane anesthesia. One group of six dogs was given aminophylline, 10 mg/kg IV, followed in 3 minutes by inhalation of 1% halothane. In two additional groups of dogs the same experimental protocols were used except that aminophylline doses were 25 mg/kg and 50 mg/kg. In the first group, two of six dogs developed ventricular arrhythmias during induction of halothane anesthesia. One of six dogs given 25 mg/kg of aminophylline developed a ventricular arrhythmia. Three of six dogs given 50 mg/kg of aminophylline developed ventricular arrhythmias. Sustained ventricular arrhythmias occurred in 33% of the animals with "therapeutic" serum theophylline levels and in 33% of the animals with "toxic" levels. Induction of halothane anesthesia within 15 minutes of aminophylline administration may be dangerous and is likely to result in severe and persistent ventricular arrhythmias.