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PEDIATRIC ANESTHESIA

The Hypnotic and Analgesic Effects of Oral Clonidine During Sevoflurane Anesthesia in Children: A Dose-Response Study

Shinichi Inomata, MD^*, Shin-ichi Kihara, MD^*, Masayuki Miyabe, MD^*, Kenji Sumiya, BSPharma, Yasuyuki Baba, PhD, Yukinao Kohda, PhD, and Hidenori Toyooka, MD^*

Departments of *Anesthesiology and Clinical Pharmacy, the University of Tsukuba, Tsukuba City, Ibaraki, Japan

Address correspondence and reprint requests to Shinichi Inomata, MD, Department of Anesthesiology, Institute of Clinical Medicine, University of Tsukuba, Tsukuba City, Ibaraki 305-8575, Japan. Address e-mail to inomatas{at}md.tsukuba.ac.jp

Although clonidine has both hypnotic and analgesic actions, the dose relationship for each actions is still unknown in a clinical setting when clonidine is used as a premedication in children. We studied 80 ASA physical status I children (age range, 3–8 yr). Subjects were randomly divided into two groups (minimum alveolar anesthetic concentration [MAC]-Awake group, n = 40; MAC-Tetanus group, n = 40). Each patient received one dose of clonidine from 1 to 5 µg/kg orally, 100 min before arrival at the operating room. Anesthesia was induced and maintained with sevoflurane in oxygen and air. Before tracheal intubation, end-tidal sevoflurane was decreased stepwise by 0.2% at the start of 1.2%, a verbal command was given to the patients, and MAC-awake was determined in each patient. We also investigated MAC-tetanus, determined with transcutaneous electric tetanic stimulations, after tracheal intubation in each patient by observing the motor response to a transcutaneous electric tetanic stimulus to the ulnar nerve at a sevoflurane concentration decreased stepwise by 0.25% at the start of 2.75%. The initial reduction in MAC-tetanus was not as steep as that in MAC-awake. Clonidine reduced MAC-tetanus by 40% at the maximal dose of 5 µg/kg, whereas MAC-awake was already reduced by 50% at 2 µg/kg. We conclude that separate dose-response relationships for oral clonidine are present regarding the hypnotic and analgesic effects in children undergoing sevoflurane anesthesia.

IMPLICATIONS: Separate dose-response relationships for oral clonidine were found regarding the hypnotic and analgesic effects in children undergoing sevoflurane anesthesia.