Comparison of the trapezius squeezing test and jaw thrust as indicators for laryngeal mask airway insertion in adults.

BACKGROUND: The purpose of this study was to compare the effectiveness of the trapezius squeezing test with that of the jaw thrust maneuver as clinical indicators of adequate conditions for laryngeal mask airway (LMA) insertion in adults under sevoflurane anesthesia. METHODS: One hundred adult patients of ASA physical status 1 or 2 undergoing minor surgical procedures were randomly allocated to the T (trapezius squeezing, n = 50) group or the J (jaw thrust, n = 50) group. The LMA was inserted immediately after the loss of response to trapezius squeezing or jaw thrust. Successful and unsuccessful attempts were recorded. An unsuccessful attempt was defined as the occurrence of coughing, gagging, gross purposeful movements, breath-holding, laryngospasm, or an SpO(2) < 90% during LMA insertion. Insertion time, end-tidal sevoflurane concentration, mean arterial pressure, and heart rate were recorded. RESULTS: The incidence of successful attempts was significantly higher in the T than in the J group (48/50 vs. 36/50, respectively). CONCLUSIONS: The trapezius squeezing test is a superior indicator of an adequate condition for LMA insertion compared to the jaw thrust maneuver in adults under sevoflurane anesthesia.

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

UNLABELLED: 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 concentration 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. IMPLICATIONS: Because the removal of the laryngeal mask airway (LMA) in the anesthetized state is required in some clinical situations, we sought to determine the end-tidal concentration of sevoflurane to safely remove the LMA in anesthetized adults.

Estimation of the length of the nares-vocal cord.

The nasal route is preferred for fiberoptic intubation. Placing a lubricated endotracheal tube through the nostril can guide the fiberoptic scope towards the larynx. It would be helpful for optimal visualization of the vocal cord when the scope is passed through the endotracheal tube if the length of nares-vocal cord (NV length) could be predicted and the tip of the endotracheal tube could be placed close to the vocal cord. In this study we measured the NV length and examined the relationship between the NV length and various external measurements. Using a fiberoptic scope, the NV lengths were measured in 50 male and 45 female patients scheduled to undergo elective surgery under general anesthesia. In addition, the distances from the lateral border of the nares to tragus of the ear (NE distance) and to the angle of the mandible (NM distance) were measured. The age, height, and weight of all the patients were recorded. The NV length of the males was 18.3 +/- 0.8 cm, and that of the females was 16.3 +/- 0.7 cm. The relationship between the NV length and body height (P < 0.001, r = 0.755) and the NE distance (P < 0.001, r = 0.636) showed a significant correlation but NM distance did not (P = 0.075). The length of the NV cord can be predicted using the body height or the NE distance.