Estimation of the median effective dose and the 95% effective dose of alfentanil required to inhibit the bronchoscopy reaction during painless bronchoscopy with i-gel supraglottic airway device: an Up-and-Down Sequential Allocation Trial

BACKGROUND: In practice, the optimal dose of alfentanil that should be used when painless bronchoscopy is performed is unknown. The purpose of this study was to investigate the effective dose of alfentanil in suppressing bronchoscopy responses to painless bronchoscopy with an i-gel supraglottic airway device. METHODS: Patients aged 18–70 years, with American Society of Anesthesiologists (ASA) physical status I–II, who planned to undergo painless bronchoscopy were recruited for this study. Alfentanil was administered intravenously 2 minutes before propofol administration. The response to bronchoscopy was measured, including oxygen saturation (SPO(2)) and changes in respiratory rhythm. The median effective dose of alfentanil (ED(50)) required to alleviate responses to the bronchoscopy was calculated using Dixon’s up-and-down method in the female and male groups. Probit analysis was used to generate a dose-response curve in each group. RESULTS: A total of 48 patients were recruited for the study including 25 females and 23 males. The ED(50) of alfentanil for suppressing responses to painless bronchoscopy in females and males was 13.68±4.75 and 17.96±3.45 µg/kg, respectively. The difference was not statistically significant between the two groups (P=0.078). Probit analysis showed the ED(50) of alfentanil in female bronchoscopy was 12.4 µg/kg [95% confidence interval (CI): 4.5 to 17 µg/kg]. In men, the ED(50) of alfentanil was 16.4 µg/kg (95% CI: 12.1 to 20.1 µg/kg). According to the probit analysis, the 95% effective dose (ED(95)) of alfentanil was 22.4 µg/kg (95% CI: 17.5 to 67.3 µg/kg) in female bronchoscopy. In men, the ED(95) of alfentanil was 23.3 µg/kg (95% CI: 19.8 to 46.2 µg/kg). CONCLUSIONS: Our data suggest that there were no obvious differences between men and women in the effective dose of alfentanil in painless bronchoscopy.