A COMPARISON OF THE INTUBATION CONDITIONS BETWEEN MIVACURIUM AND ROCURONIUM DURING BALANCED ANESTHESIA

Background: Comparisons of the intubation conditions with mivacurium a nd rocuronium from previous reports are confounded by the use of varie d induction regimens. The authors compared intubation conditions of mi vacurium, rocuronium, and a placebo at 90 s and their recovery profile s during anesthesia with nitrous oxide, oxygen, and propofol. Methods: After induction with midazolam, fentanyl, and propofol in a randomize d blinded study, 100 patients received one of the following treatments : 0.25 mg/kg mivacurium in divided doses (0.15 mg/kg followed by 0.1 m g/kg 30 s later); 0.45, 0.6, 0.9, or 1.2 mg/kg rocuronium; or placebo, Evoked thumb adduction was measured throughout. Intubation was attemp ted 90 s after the initial dose of mivacurium and other treatment dose s by a ''blinded'' physician. Intubating conditions were graded as exc ellent, good, poor, or not possible. Spontaneous recovery was studied until a 25% initial twitch height was reached. Mean arterial blood pre ssure and heart rate changes between groups were determined before ind uction through 6 min after administration of the study drugs. Results: There were no important changes or intergroup differences in mean art erial blood pressure and heart rate. Intubation conditions were good o r excellent for both mivacurium and rocuronium at the 0.9 mg/kg dose ( 93%) and at the 1.2 mg/kg dose (100%). Rocuronium at the 0.6 mg/kg dos e was excellent in 27% of patients, whereas rocuronium at the 0.45 mg/ kg dose had the least number of excellent conditions and the most poor or not possible assessments. Patients given placebo could not be intu bated, Times to maximum blockade for 0.9 and 1.2 mg/kg rocuronium were the shortest, The times to 25% recovery for 0.6 mg/kg rocuronium (mea n +/- SD = 27 +/- 8.6 min), 0.9 mg/kg (43.1 +/- 10.8), and 1.2 mg/kg ( 62.3 +/- 17.4 min) mere significantly longer than were those for mivac urium (17.4 +/- 6.2 min). Conclusions: Mivacurium in a 0.25 mg/kg divi ded dose and rocuronium at 0.9 mg/kg and 1.2 mg/kg provide good or exc ellent intubation conditions at 90 s in most patients. Rocuronium was faster in onset at the higher doses (0.9 and 1.2 mg/ kg) but had more prolonged recovery times to 25% single twitch height.