The minimum alveolar concentration of enflurane for laryngeal mask airway extubation in deeply anesthetized children.
The end-tidal anesthetic gas concentration required to prevent the anesthetized patient from coughing or moving during or immediately after the laryngeal mask airway (LMA) extubation is not known. We sought to determine the minimum alveolar concentration of enflurane required for the removal of the LMA in children. We studied 21 nonpremedicated children between 4 and 11 yr of age, ASA physical status I, undergoing procedures below the umbilicus. General anesthesia was induced with a mask by using sevoflurane, nitrous oxide, and oxygen, and the LMA was inserted. Anesthesia was maintained with enflurane, nitrous oxide, and oxygen. At the end of surgery, a predetermined end-tidal enflurane concentration was achieved, and the LMA was removed. Each concentration at which the LMA extubation was attempted was predetermined by the up-and-down method (with 0.1% as a step size). When LMA removal was accomplished without coughing, clenching teeth, or gross purposeful muscular movements during or within 1 min after removal, it was considered a successful LMA removal. Removal was considered to be unsuccessful in patients who developed breath holding or laryngospasm during or immediately after LMA removal. The minimum alveolar concentration of enflurane at which 50% of children had a successful LMA removal was found to be 1.02% (95% CL, 0.95%-1.11%), and the 95% effective dose for successful extubation was 1.14% (95% CL, 1.07%-1.66%). In conclusion, the LMA removal may be accomplished without coughing or moving at 1.02% end-tidal enflurane concentration in 50% of anesthetized children aged 4-11 yr.


CONCLUSIONS
There may be fewer problems associated with the laryngeal mask airway extubation when patients are deeply anesthetized. The purpose of this study was to determine the minimum concentration of enflurane for successful removal of the laryngeal mask in children.
Xiao
W
W
Department of Anesthesiology, Plastic Surgery Hospital, The Chinese Academy of Medical Sciences, Peking Union Medical College, Beijing, China. xiao-wenjing@263.net
Deng
X
X
D000769:Anesthesia, Inhalation / Q000379:methods; D000777:Anesthetics; D018685:Anesthetics, Inhalation / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000494:pharmacology*; D002648:Child; D002675:Child, Preschool; D004305:Dose-Response Relationship, Drug; D004737:Enflurane / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000494:pharmacology*; D005260:Female; D006801:Humans; D017214:Laryngeal Masks; D008297:Male; D011650:Pulmonary Alveoli / Q000378:metabolism*; D013990:Tidal Volume
D000777:Anesthetics; D018685:Anesthetics, Inhalation; D004737:Enflurane