END-TIDAL SEVOFLURANE CONCENTRATION FOR TRACHEAL EXTUBATION AND SKIN INCISION IN CHILDREN

We sought to determine minimum alveolar anesthetic concentrations for skin incision (MAC) and for tracheal extubation (MACEx) for sevofluran e and its associated awakening time and respiratory complications duri ng emergence from sevoflurane anesthesia in children. We studied 40 (2 0 in each group) unpremedicated pediatric patients ranging in age from 2 to 8 yr. For MACEx determination, anesthetic induction, tracheal in tubation, and maintenance of anesthesia were performed with sevofluran e and N2O in oxygen. However, N2O administration was discontinued at t he end of surgery. The ratio of the predetermined end-tidal to inspira tory concentration was maintained at 0.95-1.00 for at least 15 min. Th e trachea was gently extubated, and smooth tracheal extubation was def ined by the absence of gross purposeful muscular movements. Ln additio n, the respiratory complications and awakening time were investigated during emergence from anesthesia for each patient. For MAC determinati on, anesthesia induction and tracheal intubation were performed with 5 % sevoflurane in oxygen. After the predetermined end-tidal sevoflurane concentration had been established and maintained for at least 15 min , skin incision was attempted. Patients' responses to skin incision we re described as ''no movement'' or ''movements.'' The MAC or MACEx for sevoflurane was 2.22% +/- 0.13% (mean +/- so) or 1.70% +/- 0.12%, and the 95% effective dose (ED95) for smooth extubation was 1.87% (95% co nfidence limits 1.75%-2.62%), respectively, in children. During emerge nce from anesthesia, none of patients held their breath or experienced laryngospasm in the current study. One patient in a subgroup at 1.5% coughed before tracheal extubation. All 10 patients with smooth trache al extubation had hemoglobin oxygen saturation levels of greater than or equal to 98% in this study. Awakening time was 9.7 +/- 3.7 min in t he subgroup that received 1.75% sevoflurane. In conclusion, the MACEx and ED95 values of sevoflurane were 1.64% and 1.87%, respectively, in children. The MACEx to MAC ratio for sevoflurane was 0.8 in children w ithin the same age range and mean age. Implications: Because tracheal extubation of anesthetized patients may be advantageous in certain cli nical situations, we performed this study. The ratio minimum alveolar anesthetic concentrations for skin incision and for tracheal extubatio n for sevoflurane was 0.8 in children within the same age range and me an age. No patient in the current study had laryngospasm.