Oral Clonidine Premedication Blunts the Heart Rate Response to Intravenous Atropine in Awake Children

Abstract

Comment Apparently two separate groups of Japanese researchers are simultaneously investigating the premedicating potential of oral clonidine, a centrally acting α-agonist. In awake adults, oral clonidine can cause bradycardia and hypotension and reduces the chronotropic response to intravenous atropine (Nishikawa et al.). In this investigation, high-dose (4 μg/kg) oral clonidine premedication in children, 10.8 ± 1.6 yr, also attenuated the increase in heart rate (HR) produced by intravenous atropine (10 μg/ kg) but did not cause significant changes in HR or blood pressure (BP) at the same or lower (2 M-g/kg) doses. No adverse effects of atropine were reported in this study, even though atropine doses as high as 30 μg/kg were required to increase HR 20 bpm in low-dose study patients, and atropine doses of 40 μg/kg were ineffective in 2 of 16 patients in the high-dose group. In addition, premedication with high-dose oral clonidine produced significandy higher (p <0.05, test statistic unreported) sedation scores than premedication with placebo or low-dose (2 μg/kg) oral clonidine. The authors concluded that effective (4 μg/kg) premedicating doses of oral clonidine can suppress the HR response to intravenous atropine in awake children; large doses (30–40+ μg/kg) of atropine may be required to increase HR 20 bpm in children