Optimal end-tidal sevoflurane concentration for the removal of the laryngeal mask airway in anesthetized adults

Abstract

Sevoflurane provides smooth and rapid emergence from anesthesia and can be used when the removal of a laryngeal mask airway (LMA) is required in anesthetized patients. We sought to determine the optimal end-tidal concentrations of sevoflurane required for the removal of LMA in anesthetized adults. We studied 35 adults, aged 22–64 years old with an ASA physical status I or II, who were undergoing perineal surgery. General anesthesia was induced with thiopental, and the LMA was then inserted. Anesthesia was maintained with sevoflurane, oxygen, and air. After the surgery, the target concentration was maintained for at least 10 min, and then the LMA was removed. Each target concentration at the time of removal was predetermined by the Dixon up-down method (with 0.1% as a step size) starting at 1.7% end-tidal concentra-tion of sevoflurane. The LMA removal was considered successful when there was no coughing, clenching of teeth, or gross purposeful movements during or within 1 min after removal and also if there was no breath holding, laryngospasm, or desaturation after removal. The end-tidal concentration of sevoflurane to achieve successful LMA removal in 50% of adults was 0.99% ± 0.09% (mean ± sd) and in 95% of adults was 1.18% (95% confidence limits, 1.07%–1.79%). In conclusion, we have determined that LMA removal in 50% and 95% of anesthetized adults can be safely accomplished without coughing, moving, or any other airway complications at 0.99% and 1.18% end-tidal concentrations of sevoflurane.