title: Caudal anesthesia reduces the minimum alveolar concentration of enflurane for laryngeal mask airway removal in boys.
abstract: OBJECTIVE
  To investigate the effects of caudal analgesia on the minimal alveolar concentration of enflurane for laryngeal mask airway (LMA) smooth extubation (MACex).
  
  
  METHODS
  We studied 50 nonpremedicated children, aged three to ten years, ASA physical status I, undergoing surgery for hypospadias repair. After a sevoflurane inhalation induction, children were randomized to receive LMA insertion with or without ropivacaine caudal analgesia. At the end of surgery, a predetermined end-tidal enflurane concentration was achieved, and the LMA was removed by an anesthesiologist blinded to group allocation. Each concentration at which LMA extubation was attempted was predetermined by the up-and-down method (with 0.1% as the step size). When LMA removal was accomplished without coughing, clenching teeth or gross purposeful muscular movements during or within one minute after removal, it was considered successful.
  
  
  RESULTS
  MACex of enflurane for LMA removal in the group without caudal anesthesia was 1.04% (95% confidence interval, 1.00-1.10) and the LMA MACex of enflurane in the group with caudal anesthesia was 0.74% (95% confidence interval, 0.63-0.81). Caudal analgesia significantly reduced enflurane requirements by 29% (95% confidence interval, 22-36%).
  
  
  CONCLUSIONS
  In conclusion, caudal analgesia significantly reduced the LMA MACex of enflurane by approximately 29%. Possible mechanisms may be related to the analgesic effect of caudal blockade or to the sedative properties of neuraxial anesthesia.
authors.affiliation: Department of Anesthesiology, Plastic Surgery Hospital, Chinese Academy of Medical Sciences, Peking Union Medical College, Beijing, China. wenjingxiao@sina.com
authors.forename: Wen-Jing
authors.initials: WJ
authors.lastname: Xiao
authors.forename: Xiao-Ming
authors.initials: XM
authors.lastname: Deng
authors.forename: Geng-Zhi
authors.initials: GZ
authors.lastname: Tang
authors.forename: Mao-Ping
authors.initials: MP
authors.lastname: Lu
authors.forename: Kun-Ling
authors.initials: KL
authors.lastname: Xu
mesh_terms: D000763:Anesthesia, Caudal; D018685:Anesthetics, Inhalation / Q000494:pharmacology*; D002648:Child; D002675:Child, Preschool; D004737:Enflurane / Q000493:pharmacokinetics / Q000494:pharmacology*; D006801:Humans; D017214:Laryngeal Masks; D008297:Male; D011650:Pulmonary Alveoli / Q000378:metabolism*
chemical_list: D018685:Anesthetics, Inhalation; D004737:Enflurane