The 50% and 95% effective doses of desflurane for removal of the classic laryngeal mask airway after suction of the upper airway, in anaesthetised spontaneously breathing adult patients, are not known. To determine these, we studied 38 healthy patients, aged between 18 and 44 years. The target desflurane concentration in each individual patient was determined by the Dixon up-and-down method. When the predetermined target end-tidal desflurane concentration reached steady state, we kept a constant end-expiratory partial pressure between the alveolus and the brain for 10 min before attempting to remove the classic laryngeal mask airway after suctioning the upper airway. The initial desflurane target concentration was set at 6% and up-down desflurane increments were 0.1%. This continued until there were at least six crossover pairs. From the probit analysis, the 50% effective dose of desflurane was 5.29% (95% CI 5.132-5.379%) and the 95% effective dose was 5.55% (95% CI 5.429-6.394%).
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