Effects of age on effect-site concentration of remifentanil for suppressing anesthetic emergence cough in male patients undergoing laparoscopic cholecystectomy

Background: Remifentanil infusion during emergence lowers cough. Effect-site concentration (Ce) of remifentanil using target-controlled infusion (TCI) has been evaluated in previous studies. Recent studies revealed the existence of sex-related differences in remifentanil Ce in young and elderly patients. Thus, there was the need to re-evaluate the effect of age in single sex. We investigated the remifentanil Ce for suppressing emergence cough in young and elderly male patients and evaluated the age-related differences. Patients and methods: In total, 25 young (ages between 20 and 50 years) and 24 elderly (ages between 65 and 75 years) male patients undergoing laparoscopic cholecystectomy were enrolled. Anesthesia was implemented with remifentanil using TCI and sevoflurane. The remifentanil Ce for suppressing emergence cough was estimated for each group using Dixon's up-and-down method and isotonic regression method with a bootstrapping approach. Results: The remifentanil Ce for suppressing emergence cough in 50% (EC50) and 95% (EC95) of the patients was comparable between the young and elderly patients. Isotonic regression demonstrated that the EC50 (83% confidence interval [CI]) of remifentanil was 2.56 (2.39-2.75) ng/mL in the young patients and 2.15 (1.92-2.5) ng/mL in the elderly patients. The EC95 (95% CI) of remifentanil was 3.33 (2.94-3.46) ng/mL in the young patients and 3.41 (3.18-3.48) ng/mL in the elderly patients. Dixon's up-and-down method also demonstrated that the EC50 was comparable between the two groups (2.69 +/- 0.32 ng/mL vs 2.39 +/- 0.38 ng/mL, P=0.132). Conclusion: The remifentanil Ce for suppressing emergence cough following extubation during general anesthesia was comparable between young and elderly male patients. It indicates that age-related differences in remifentanil requirement for suppressing emergence cough did not exist in male sex.