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Optimal end-tidal concentration of sevoflurane to test an ankle clonus in children
Chul Ho Chang1, Seung Ho Choi, Yon Hee Shim
1Department of Anesthesiology and Pain Medicine, and Anesthesia and Pain Research Institute, Yonsei University College of Medicine, CPO Box 1217, Seoul 120-752, Republic of Korea.
Study Design:
A prospective randomized study on the end-tidal concentrations of sevoflurane at which ankle clonus existed.
Summary Of Background Data:
The ankle clonus reflex is a transient neurologic abnormality, which normally occurs in patients during emergence from general anesthesia.
Objective:
To determine the optimal end-tidal concentration of sevoflurane to test an ankle clonus in children during emergence from general anesthesia.
Methods:
We studied 30 children (aged 5-15 years). General anesthesia was induced with thiopental sodium. Anesthesia was maintained with sevoflurane, oxygen, and air. At completion of surgery, 3% volume of the end-tidal sevoflurane concentration was maintained for at least 10 minutes. Ankle clonus was checked at 1.0% to 0.1% volume of the end-tidal sevoflurane concentration with an interval of 0.05% volume.
Results:
Of children, 80% had bilateral ankle clonus, which was found most frequently when patients responded poorly to verbal commands. The median of the end-tidal sevoflurane concentration for a reactive ankle clonus was 0.45% volume (interquartile range 0.5% to 0.4% volume).
Conclusions:
The ankle clonus should be tested at 0.45% volume of end-tidal sevoflurane concentration in children undergoing scoliosis surgery during emergence from the general anesthesia.
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