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A3074
October 14, 2013
8:00:00 AM - 9:00:00 AM
Room Room 104-Area E
Do Small Doses of Atropine Cause Bradycardia in Young Children?
Lara Eisa, M.D., Yuvesh Passi, M.D., Jerrold Lerman, M.D., Christopher Heard, M.D.
Women and Children's Hospital of Buffalo, Buffalo, New York, United States
Introduction: Intravenous (IV) atropine is routinely administered at induction of anesthesia to neonates and infants to prevent bradycardia should it occur during anesthesia. Numerous texts and authoritative bodies recommend a minimum dose of 0.1 mg IV atropine1 independent of the child’s weight. This recommendation is based on a single study of five infants and children in which atropine doses < 0.1mg caused atrial arrhythmias that “correlate with atropine-induced bradycardia”, although bradycardia did not occur in that study.2 Despite the lack of evidence that small doses of atropine cause bradycardia, 0.1 mg IV atropine is the minimum dose recommended in children, independent of weight. The purpose of this study is to determine the heart rate responses to < 0.1mg atropine in neonates and children less than 2 years of age.

Methods: With IRB approval and written parental consent, thirty infants <5 kg and thirty 5-15 kg, ASA I & II, undergoing elective surgery will be enrolled. This study was registered with ClinicalTrials.gov. Standard of care monitoring was applied and anesthesia was induced with nitrous oxide and oxygen followed by 8% sevoflurane. Respiration was maintained spontaneously through a facemask at 2 MAC sevoflurane in 66% nitrous oxide after IV access was established. Once vital signs were stable, IV 5 mcg/kg atropine was administered and flushed into a fast flowing IV. The EKG was recorded continuously from 30 seconds before until five minutes after IV atropine. Heart rate, blood pressure, oxygen saturation and end-tidal pCO2 were recorded throughout the study period. Upon completion of the enrollment, a blinded observer will review all 60 EKG recordings to identify all episodes of bradycardia and arrhythmias. A sample size of 60 infants was selected to ensure that the long-run risk (upper 95% confidence interval) of zero episodes of bradycardia (if that proves to be true) in the population would be ≤5%.3 Statistical analysis of continuous hemodynamic and respiratory variables within each weight group will be analyzed using repeated-measures ANOVA with the Newman-Keuls multiple comparison test. P<0.05 was accepted.

Results: To date, 31 infants have been enrolled and completed the study. One in the <5 kg group and thirty in the 5-15 kg group. The investigators observed no episodes of bradycardia in the operating room thus far, but the blinded review of the EKG recordings will occur only after the enrollment is complete. The mean (± standard deviation) age and weight of the 30 infants in the 5-15 kg weight group were 12.4 ± 6.4 months and 9.7 ± 2.2 kg, respectively. The vital signs were unchanged throughout.

Conclusion: No episodes of bradycardia have been identified while recording the EKG in infants after 5 mcg/kg IV atropine during sevoflurane and nitrous oxide anesthesia. This zero incidence of bradycardia in 31 children suggests a 95% upper confidence interval of bradycardia in the entire population of 10%.3

References:

1. American Heart Association. 2005 American Heart Association (AHA) Guidelines for Cardiopulmonary Resuscitation (CPR) and Emergency Cardiovascular Care (ECC) of Pediatric and Neonatal Patients: Pediatric Advanced Life Support. Pediatrics 2006:117. Available at www.pediatrics.org/cgi/content/full/117/5/e1005

2. Dauchot P, Gravenstein JS. Effects of atropine on the electrocardiogram in different age groups. Clin Pharm Ther 1971:12;274-80

3. Hanley JA. Lippman-Hand A. If nothing goes wrong, is everything all right? Interpreting zero numerators. JAMA 1983:249;1743-5

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