RESUMO
Objective:To determine the median effective dose(ED 50) of alfentanil combined with propofol inhibiting responses to the laryngeal mask airway(LMA) insertion in children. Methods:American Society of Anesthesiologists Physical Status classification Ⅰ children, aged 6-10 yr, with body mass index of 18-24 kg/m 2, undergoing facial skin pigmented nevus resection, were selected. Propofol(target plasma concentration 3 μg/ml) was given by the target-controlled infusion, alfentanil was intravenously injected, 2 min later LMA was inserted, and anesthesia was maintained with 2%-3% sevoflurane until the end of surgery. The dose of alfentanil was determined by the up-and-down sequential method, the initial dose of alfentanil was 15 μg/kg, when the response to LMA insertion was positive/negative, the dose of alfentanil increased/decreased by 1 μg/kg in the next case. The LMA insertion response was defined as swallowing, bucking, body movement occurred during insertion of the LMA, and this process was repeated until 7th turning points appeared. The ED 50 and 95% confidence interval of alfentanil combined with propofol inhibiting responses to LMA insertion in children were calculated using probit method. Results:The ED 50 of alfentanil combined with propofol inhibiting responses to LMA insertion was 13.18(95% confidence interval 12.43-13.79) μg/kg in children. Conclusions:The ED 50 of alfentanil combined with propofol inhibiting responses to LMA insertion is 13.18 μg/kg in children.
RESUMO
Objective:To determine the value of ultrasonographic measurement of submental soft tissue distance in predicting poor ventilation with laryngeal mask airway (LMA).Methods:A total of 272 American Society of Anesthesiologists physical status Ⅰ or Ⅱ patients, aged 25-78 yr, weighing 40-85 kg, with mechanical ventilation time 30-120 min, scheduled for elective lower limb vascular surgery or lithotripsy under general anesthesia with LMA, were selected.The parameters of submental soft tissue of tongue thickness (TT), distance from skin to the hyoid bone (DSHB), distance from skin to epiglottis midway (DSEM) and distance from skin to anterior commissure of the vocal cords (DSAC) were measured using ultrasonography before operation.The type of LMA was chosen according to the instruction book.The development of failure of LMA placement at the first attempt, air leakage around LMA cuff during mechanical ventilation, peak airway pressure >20 cmH 2O and gastric insufflation detected by ultrasonography were recorded.The development of one or more adverse events mentioned above was considered to be poor ventilation.The patients were divided into normal ventilation group (N group) and poor ventilation group (P group) according to whether poor ventilation occurred.The receiver operating characteristic curve for ultrasonographic measurement of submental soft tissue distance in predicting poor ventilation with LMA was drawn, and the area under the curve (AUC) and 95% confidence interval (CI), sensitivity and specificity and cut-off value were calculated.The risk factors of which P values were less than 0.05 would enter the logistic regression analysis to stratify the risk factors for poor ventilation with LMA. Results:The AUC for TT, DSHB, DSEM and DSAC measured using ultrasonography in predicting poor ventilation with LMA (95%CI) was 0.866 (0.813-0.919), 0.755 (0.683-0.827), 0.835 (0.772-0.899) and 0.705 (0.628-0.782) ( P<0.05 or 0.01), respectively.The results of logistic regression analysis showed that TT≥6.140 cm, DSHB≥1.145 cm, DSEM≥2.175 cm and DSAC≥1.075 cm were risks factor for poor ventilation with LMA. Conclusion:Ultrasonographic measurement of TT, DSHB, DSEM and DSAC can predict the development of poor ventilation with LMA.