INTUBATING CONDITIONS AND NEUROMUSCULAR BLOCK AFTER DIVIDED DOSE MIVACURIUM OR SINGLE-DOSE ROCURONIUM

Purpose: To evaluate the tracheal intubating conditions and neuromuscu lar blocking characteristics of divided close mivacurium or single dos e rocuronium. Methods: Thirty-two patients undergoing elective surgery were studies. Anaesthesia was with propofol 2 mg . kg(-1), followed b y an infusion of 150 mu g . kg(1-). min(-1). Patients were randomized to receive either mivacurium- 0.15 mg . kg(-1) followed 30 sec later b y 0.1 mg . kg(-1), or rocuronium- 0.9 mg . kg(-1), followed 30 sec lat er by placebo. Tracheal intubating conditions were assessed 90 sec aft er the initial dose of relaxant by an anaesthetist who was unaware of patient group. The electromyographic (EMG) response of the first dorsa l interosseus muscle to ulnar nerve train-of-four was measured. Result s: Successful tracheal intubation was performed in all patients after both mivacurium and rocuronium. Intubating conditions (jaw relaxation, open visible vocal cords) were judged to be good-excellent in al but one patient before insertion of the tracheal tube. However, patients r eceiving mivacurium were more likely to experience coughing and buckin g after tracheal tube insertion (10/16 patients) than those receiving rocuronium (3/16 patients, P<0.05). No patient in the rocuronium group experienced moderately vigorous coughing and bucking after insertion of the tracheal tube vs six patients in the mivacurium group (P<0.05). Time to 10 and 25% recovery of neuromuscular function as faster (P<0. 05) after divided dose mivacurium (20 +/- 1 and 23 +/- 1 min, respecti vely) than after rocuronium (45 +/- 5 and 57 +/- 8 min, respectively). Conclusion: The results suggest that, during conditions of the study, divided close mivacurium is not recommended for a 90-sec tracheal int ubation in patients where moderate coughing and bucking is deemed unac ceptable.