BACKGROUND: Many studies have demonstrated that lidocaine directly relaxes airway smooth muscle by decreasing Ca²⁺. Lidocaine is well known as an agent to decrease the neuromuscular transmission and potentiate the neuromuscular block of muscle relaxants. The purpose of this study was to examine the influence of lidocaine on the onset time of rocuronium and intubating conditions in children.

METHODS: 84 children, ASA physical status 1 or 2, were randomly divided into 3 groups (Group 1, 2 and 3). Anesthesia was induced with fentanyl 1 µg/kg and propofol 3 mg/kg and we maintained anesthetic states with 10 mg/kg/h of propofol. We intravenously injected saline 1.0 ml/kg to Group 1, lidocaine 1.0 mg/kg to Group 2 and lidocaine 1.5 mg/kg to Group 3. After 2 minutes, all patients received rocuronium 0.6 mg/kg. Intubation was performed 2 minutes after the administration of rocuronium, and intubating conditions were evaluated. Neuromuscular blockades were assessed by train-of-four (TOF) at the adductor pollicis muscle with supramaximal stimulation of the ulnar nerve (2 Hz, 0.2 msec) every 15 second.

RESULTS: There was no difference between the onset time of Group 1 (107.8 ± 54.4 sec), Group 2 (112.0 ± 39.3 sec) and Group 3 (90.0 ± 39.5 sec). Intubating conditions and hemodynamic response to tracheal intubation were similar in all groups.

CONCLUSIONS: Additional 1.5 mg/kg lidocaine to 0.6 mg/kg rocuronium neither influences intubating condition nor accelerate the onset of rocuronium during induction of anesthesia in the children.