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Dose-response for atropine and heart rate in infants and children anesthetized with halothane and nitrous oxide
B W Palmisano1, M A Setlock, M P Brown
1Department of Anesthesiology, Medical College of Wisconsin, Milwaukee 53226.
Insights
Atropine effectively increases heart rate in anesthetized children in a dose-dependent manner up to 30 micrograms per kilogram. Younger children experienced higher heart rates, while older children showed a greater heart rate increase after atropine administration.
Area of Science:
- Anesthesiology
- Pediatric Pharmacology
- Cardiovascular Physiology
Background:
- Dose recommendations for atropine in pediatric anesthesia are variable.
- The precise dose-response relationship between atropine and heart rate in children is not well-defined.
Purpose of the Study:
- To determine the dose-response relationship of atropine on heart rate in anesthetized children.
- To compare the effects of different atropine doses on heart rate, rhythm, and blood pressure.
- To analyze age-related differences in atropine's cardiovascular effects.
Main Methods:
- 181 healthy children undergoing anesthesia received intravenous atropine at doses of 5, 10, 20, 30, or 40 micrograms per kilogram.
- Heart rate, rhythm, and systolic blood pressure were monitored.
- Dose-response curves were constructed, and effects were compared between age groups (infants < 6 months vs. children ≥ 2 years).
Main Results:
- Atropine increased heart rate in a dose-related manner up to 30 micrograms per kilogram, with 50% and 90% maximal response at 9 and 26 micrograms per kilogram, respectively.
- Systolic blood pressure increased significantly with doses above 5 micrograms per kilogram.
- While younger infants had higher baseline and peak heart rates, older children exhibited a greater absolute change in heart rate following atropine administration.
Conclusions:
- Atropine demonstrates a predictable dose-response for heart rate elevation in anesthetized children.
- Doses of 20-30 micrograms per kilogram appear effective for achieving a significant heart rate increase.
- Age influences the magnitude of heart rate response to atropine, with older children showing a more pronounced increase.
Abstract:
The dose recommendations for atropine in anesthetized children vary, and the dose-response for heart rate has not been defined. We determined the dose-response for atropine and heart rate in 181 healthy children anesthetized with halothane and nitrous oxide. After induction of anesthesia, atropine in a dose of 5, 10, 20, 30, or 40 micrograms.kg-1 was administered by rapid intravenous infusion of each subject. The effects of atropine on heart rate, heart rhythm, and systolic blood pressure were compared among dosage groups, and a dose-response curve for peak heart rate was constructed. The effects of atropine were compared also between younger and older subjects. For the group of all 181 subjects, atropine increased heart rate in a dose-related manner up to 30 micrograms.kg-1. Fifty percent maximal response corresponded to 9 micrograms.kg-1, and 90% maximal response corresponded to 26 micrograms.kg-1. Some subjects had nonsinus supraventricular rhythms before atropine, but none had nonsinus rhythm after atropine except after the smallest dose, 5 micrograms.kg-1. Systolic blood pressure increased significantly after all doses of atropine except 5 mu.kg-1. Subjects less than 6 months old had higher control and peak heart rates than did subjects greater than or equal to 2 yr old, but the older subjects had greater change in heart rate after atropine. For subjects greater than or equal to 2 yr old, all doses of atropine produced a significant increase in heart rate. The same was true for younger subjects, less than 6 months old, except that 5 micrograms.kg-1 did not increase heart rate.(ABSTRACT TRUNCATED AT 250 WORDS)