EC 50 and EC 95 of Remifentanil for Inhibiting Bronchoscopy Responses in Elderly Patients During Fiberoptic Bronchoscopy Under Ciprofol Sedation: An Up-and-Down Sequential Allocation Trial

Opioids are used to suppress cough during fiberoptic bronchoscopy (FOB). However, evidence regarding the optimal dose of remifentanil during FOB under ciprofol sedation is limited. This study aimed to investigate the effective concentration (EC) of remifentanil required to suppress bronchoscopy responses during FOB under ciprofol sedation in elderly patients. Elderly patients aged 60 to 90 years with American Society of Anesthesiologists (ASA) physical status I-III, scheduled for FOB, were enrolled. Patients were assigned to either the male or the female group. Remifentanil was administered intravenously prior to ciprofol administration. The endpoints included responses to FOB, such as vocal cords movement, coughing, and body movement. The EC and EC values of remifentanil required to alleviate the responses to FOB were calculated using Dixon's up-and-down method for both male and female groups. Probit analysis was used to generate a dose-response curve. Thirty-nine patients (19 males and 20 females) were enrolled. The EC values (plasma concentration) of remifentanil for blunting FOB responses under ciprofol sedation were 3.25 (2.75 to 3.26) ng/mL and 2.25 (1.75 to 2.25) ng/mL in males and females, respectively ( = 0.0023). Probit analysis indicated that the EC of remifentanil required to suppress responses to FOB under ciprofol sedation was 3.102 [95% confidence interval (CI):2.694 to 3.749] ng/mL and 2.052 [95% CI: 1.345 to 2.750] ng/mL in males and females, respectively. The EC of remifentanil required to suppress responses to FOB under ciprofol sedation was 3.741 [95% CI: 3.366 to 7.699] ng/mL and 2.943 [95% CI: 2.456 to 9.533] ng/mL in males and females, respectively. The results indicate differences between males and females in the EC and EC of remifentanil needed to suppress responses to FOB under ciprofol sedation while preserving spontaneous breathing in elderly patients. The study was registered with chictr.org.cn (ChiCTR2300077720; 17 November 2023).