Minimum alveolar sevoflurane concentrations required for insertion of the cuffed oropharyngeal airway and the laryngeal mask airway: a comparative study

Abstract

SummaryBoth the cuffed oropharyngeal airway and the laryngeal mask airway share a similar property of being less stimulating to the upper airway than the tracheal tube. This study was conducted to compare sevoflurane concentrations required for insertion of the cuffed oropharyngeal airway and the laryngeal mask airway in elderly and young adult patients. Forty-one elderly (65-90 years) and 34 young adult (18-50 years) patients, scheduled for elective surgery during spontaneous breathing anaesthesia were randomly assigned to either the cuffed oropharyngeal airway or the laryngeal mask airway group. After a predetermined end-tidal concentration of sevoflurane had been established and maintained for at least 20 min, insertion of the device was attempted without neuromuscular relaxants or other adjuvants. Each concentration at which insertion of the device was attempted was predetermined by modification of Dixon's up-and-down method with 0.5% as the step size. Sevoflurane MAC COPA [mean 1.17 (SD 0.38)%, 0.77-1.56% (95% CI)] was significantly less than MAC LMA [2.00 (0.52)%, 1.45-2.55%, p < 0.05] for elderly patients. Similarly, sevoflurane MAC COPA [1.33 (0.38)%, 0.94-1.73%] was significantly less than MAC LMA [2.00 (0.42)%, 1.56-2.44%, p < 0.05] for young adult patients. There were no significant differences in either MAC COPA or MAC LMA between the elderly and the young adult patients. We conclude that the insertion of the cuffed oropharyngeal airway can be accomplished at a lower sevoflurane concentration, and hence, is less stimulating to the upper airway than that of the laryngeal mask airway.

End-tidal Sevoflurane Concentration for ProSeal™ versus Classic™ Laryngeal Mask Airway Insertion in Unpremedicated Anaesthetised Adult Females

“…The ET% 50 of sevoflurane for CLMA placement in our study was also found to be higher than that in a study by Tanaka et al 14 (2.72% versus 2.0%). This difference might have been due to differences in patient age and methodology.…”

Predicted values of propofol EC 50 and sevoflurane concentration for insertion of laryngeal mask Classic TM and ProSeal TM

“…Finally, actual measured values after induction of anaesthesia are often underestimated by prediction software. 16 Tanaka and colleagues 17 found the end-tidal sevo¯urane for insertion of the Classic LMA was 2.0% for both young and elderly patients. The value we found was 2.38%.…”

Efficacy of the A‐line™ AEP monitor as a tool for predicting successful insertion of a laryngeal mask during sevoflurane anesthesia

“…Other dose–response studies on EE‐sevo required for acceptable conditions for insertion of a laryngeal mask reported an ED 50 of 1.9% during steady state conditions in adults (17), and an ED 50 of 1.6% maintained for 10 min in children (18). The ED 50 reported in these studies are less than the ED 50 of 2.82% found in the present study, which may be owing to the fact that our study was not performed under steady state conditions.…”