Low-dose rocuronium: Time course of neuromuscular blockade and intubating conditions

Background: Rocuronium is a non-depolarising neuromuscular blocking agent s tructurally related to vecuronium. The compound has a rapid onset and an in termediate duration of action. The rapid onset is of importance in patients at risk for pulmonary aspiration, for elective induction of anaesthesia sl ower onset properties generally are accepted. In this context, we asked whe ther the induction dose of rocuronium may be reduced to doses smaller than 2XED(95) in situations in which slower onset properties may be acceptable. Methods: The rime course of neuromuscular block and intubating conditions o f two different doses rocuronium, 2XED(95) (0.6 mg/kg) and 1.3XED(95) (0.4 mg/kg), were investigated in 90 patients. We first determined the time cour se of neuromuscular block using electromyography (EMG), n=l5 for each group . In the second pan the intubating conditions 3 min after injection of eith er rocuronium 0.6 mg/kg or rocuronium 0.4 mg/kg were evaluated, n=30 for ea ch group. Results: In the present study reduction of the dose of rocuronium led to a slower onset (148+/-32 s vs. 220+/-30 s; P<0.05) and a shorter clinical dur ation (21 min+/-4 vs. 36+/-7 min; P<0.05). The recovery index was modified by the dose reduction: 11+/-3 min after 0.6 mg/kg rocuronium and 9+/-2 min after 0.4 mg/kg. After both doses of rocuronium the intubating conditions w ere good to excellent, no difference between both rocuronium groups were fo und. Conclusion: In the present study dose reduction from 0.6 mg/kg rocuronium t o 0.4 mg/kg rocuronium led to a slower onset and reduced clinical duration. However, the intubating conditions, evaluated 3 min after injection of the muscle relaxant were comparable. This offers new possibilities for muscle relaxation for surgical or diagnostic procedures of short duration and may reduce costs.