Oral atropine premedication in infants attenuates cardiovascular depression during halothane anesthesia.

The efficacy of oral atropine premedication in attenuation of the cardiovascular depression associated with halothane anesthesia has not been previously evaluated. A solution containing either oral atropine 0.04 mg/kg (HI), 0.02 mg/kg (LO), or a placebo (NO) was randomly administered to 36 infants 1-6 months old and 36 infants 7-15 months old 30-90 minutes before induction of anesthesia. The onset of action of atropine was approximately 25 minutes after administration as determined by a 15% increase in heart rate (HR) above baseline levels. Heart rate, systolic blood pressure (SBP), and mean arterial blood pressure (MAP) were then measured at 1-minute intervals starting just before induction of anesthesia and continuing until onset of surgical stimulation during anesthesia with halothane (up to 3%), nitrous oxide (60%), and oxygen (40%). In infants 1-6 months old, either dosage of oral atropine preserved HR and SBP as compared with placebo. In infants 7-15 months old, either dosage preserved HR but not SBP. The severity of hypotension was greatest in infants 1-6 months of age given placebos. No significant differences existed between oral atropine 0.04 mg/kg or 0.02 mg/kg in either age range. It is concluded that premedication with oral atropine 0.02 mg/kg is effective in attenuating the cardiovascular depression associated with halothane anesthesia in infants.