The 50% and 95% effective doses of desflurane for removal of the classic laryngeal mask airway in spontaneously breathing anaesthetised adults

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%).

Four cases of developmental foregut cysts

Four patients with developmental foregut cysts were seen in the Singapore General Hospital between 1991 and 1994. Three had bronchogenic cysts while one had features consistent with both enteric and bronchogenic origin. Among those patients with bronchogenic cysts, only one was symptomatic, having presented with cough and dysphagia. Two other patients presented incidentally on chest radiographs done for pre-National Service enlistment while one patient was picked up when a repeat chest radiograph was done following a course of antibiotics. The diagnosis of our first patient with the symptomatic bronchogenic cyst was based on barium swallow and a computerised tomographic scan of the thorax. Two patients were diagnosed on histology following open thoracotomy and surgical resection of the cysts to have a bronchogenic and a cyst of mixed origin as described above respectively. The last patient who underwent video-assisted thoracoscopic surgery with resection of the cyst was confirmed histologically to have a bronchogenic cyst.