We determined the dose-response for atropine and heart rate in 114 healthy children anesthetized with N2O-O2-1 MAC halothane, enflurane or isoflurane. After induction of anesthesia, atropine in does of 5, 10, 20 and 30 μg/kg was administered
successively by rapid intravascular infusion with a time interval to each subject. The effects of atropine on heart rate and systolic blood pressure were compared among anesthetic groups and dosage groups, and a dose-response curve for peak heart
rate
was constructed in each anesthetic group.
The heart rate increased in all cases following atropine medication. Among the dosage group of 5 μg/kg, the heart rate was significantly highest in children receiving isoflurane anesthesia (P<0.05). Among 10 and 20 μg/kg, the heart rate was
significantly lowest in enflurane group, the systolic blood pressured was significantly lowest in isoflurane group (P<0.05). In children anesthetized with halothane. 50% maximal response corresponded to 7.8 μg/kg, and 90% maximal response
corresponded
to 16.5 μg/kg. In enflurane group, 50% maximal response corresponded to 9.5 μg/kg, and 90% maximal response corresponded to 23.0 μg/kg. In isoflurane group, 50% maximal response corresponded to 7.5 μg/kg, and 90% maximal response corresponded
to
18.3 μg/kg.
Based on these data we conclude that 10 μg/kg, of atopine is minimally required to increase heart rate by 50% of peak heart rate in children anesthetized with N2O-O2-1 MAC halothane, enflurane or isoflurane and that this also increases systolic
blood
pressures.
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