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Caudal anesthesia reduces the minimum alveolar concentration of enflurane for laryngeal mask airway removal in boys

[L'anesthésie caudale permet de réduire la concentration alvéolaire minimale d'enflurane pendant le retrait du masque laryngé chez des garçons]

From the Department of Anesthesiology, Plastic Surgery Hospital, Chinese Academy of Medical Sciences, Peking Union Medical College, Beijing, China.

Address correspondence to: Dr. Wen-Jing Xiao, Department of Anesthesiology, Plastic Surgery Hospital, Chinese Academy of Medical Sciences, Peking Union Medical College, Beijing, China, 100041. E-mail: wenjingxiao{at}sina.com

Purpose: 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%).

Conclusion: 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.

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