High-dose rocuronium-induced paralysis of the adductor pollicis muscle facilitates detection of the timing for tracheal intubation in elderly patients: a randomized double-blind study

Purpose: To prevent coughing related to tracheal intubation and the resultant exposure of intubating staff to the patients’ expiratory aerosols, the timing of tracheal intubation needs to be precisely predicted. The aim of this study was to evaluate the hypothesis that the timing for safe tracheal intubation in elderly patients can be determined by acceleromyographically monitoring paralysis of the adductor pollicis muscle when high-dose rocuronium, given to block the respiratory muscles, is administered. Methods: Forty elderly (65–92 years) patients were enrolled in this study and randomly assigned to two groups, to receive rocuronium 0.6 mg/kg or 1 mg/kg. After induction of anesthesia and observing acceleromyographic train-of-four (TOF) responses of the adductor pollicis muscle to ulnar nerve stimulation, the patients randomly received either dose of rocuronium. The onset times from rocuronium administration to TOF counts of 0 were measured. Soon thereafter, a single anesthesiologist who was blinded to the allocated dose of rocuronium performed laryngoscopy and tracheal intubation, and assessed intubating conditions. Data were analyzed by the unpaired t-test and Chi-squared test. Results: The averaged [SD] onset time of neuromuscular blockade was significantly shorter with 1 mg/kg than 0.6 mg/kg rocuronium (104.3 [30.1] s vs. 186.8 [37.5] s, p < 0.001). Patients who received 0.6 mg/kg rocuronium variously showed either poor (n = 9) or good (n = 11) intubating conditions. However, all patients who received 1 mg/kg rocuronium had excellent intubating conditions. Conclusions: If 1 mg/kg rocuronium is administered, a TOF count of 0 acceleromyographically observed at the adductor pollicis muscle can reveal the adequate timing for tracheal intubation.