The optimal effect site concentration of remifentanil in combination with intravenous midazolam and topical lidocaine for awake fibreoptic nasotracheal intubation in patients undergoing cervical spine surgery

Backgrund. Remifentanil has been suggested as a suitable agent for conscious sedation during fibreoptic intubation. We evaluated the optimal effect site concentration (Ce) of remifentanil target-controlled infusion (TCI) for awake nasotracheal fibreoptic intubation in patients undergoing elective cervical spine surgery. Methods. Nineteen ASA I-II patients were enrolled. Patients were premedicated with midazolam (<70 kg 1.5 mg; >70 kg 2.0 mg) intravenously. The EC ₅₀ and EC ₉₅ of remifentanil Ce for smooth intubation were determined using Dixon's up-and-down method and isotonic regression. Smooth intubation was considered to have failed when patients exhibited sustained and repetitive coughing with head lift during the procedure. Intubation time, number of attempts, adverse events, and hemodynamic variables were also recorded. Patients were asked to recall the procedure and grade satisfaction at postoperative 24 h. Results. The EC ₅₀ of remifentanil Ce for smooth intubation was 2.33±0.38 ng·mL-1 as calculated by Dixon's method. The estimated EC ₉₅ of remifentanil Ce was 3.38 (95% confidence interval 2.90-3.46) ng·mL ^-1. Median intubation time (min) was longer in failed smooth intubation than in smooth intubation (8.0 vs. 6.1, P=0.048). Eleven patients (58%) recalled the procedure and 16 patients (84%) rated their satisfaction score as good or excellent. Conclusion. The estimated EC ₉₅ of remifentanil Ce for smooth nasotracheal fibreoptic intubation with conscious sedation was 3.38 (95% CI 2.90-3.46) ng·mL ^-1 when used in combination with midazolam and topical lidocaine. Remifentanil TCI may provide a tolerable experience of awake fibreoptic intubation despite the high incidence of recall.