Increased Effect-Site Concentration of Propofol Reduces EC50 of Remifentanil for Successful Intubation Using the Shikani Optical Stylet without Neuromuscular Blockade

Abstract

Objective For short-duration surgery, propofol and remifentanil are the drugs of choice for intubation without neuromuscular blockade. The Shikani Optical Stylet (SOS) is a novel semi-rigid type fiberoptic laryngoscope. In this study, we determined the clinically required effect-site concentration of remifentanil for intubation using SOS without neuromuscular blockade depending on propofol effect-site concentration. Methods We enrolled patients scheduled for elective surgery with general anesthesia, and assigned them into two groups by a randomized, double-blind method: concentration of propofol 3.5 μg/mL (group PRO 3.5) and 7.0 μg/mL (group PRO 7.0). Anesthesia was conducted with target-controlled infusion in predetermined target effect-site concentrations of propofol. The concentration of remifentanil for successful intubation using SOS in 50% of patients (EC50) was determined using a modified Dixon’s up-and-down method. Results The mean±standard deviation EC50 of remifentanil was 5.07±0.40 ng/mL in group PRO 3.5 and 1.79±0.44 ng/mL in group PRO 7.0. From probit analysis, EC50 and EC95 of remifentanil in group PRO 3.5 were 4.85 ng/mL (95% confidence interval [CI], 4.44–5.16 ng/mL) and 5.42 ng/mL (95% CI, 5.13–7.47 ng/mL) respectively, and EC50 and EC95 of remifentanil in group PRO 7.0 were 1.68 ng/mL (95% CI, 1.22–2.01 ng/mL) and 2.29 ng/mL (95% CI, 1.98–4.05 ng/mL), respectively. Conclusion Increased concentration of propofol reduced EC50 of remifentanil for successful intubation using SOS without neuromuscular blockade.