Mivacurium chloride for short laparoscopic procedures.

We have studied the effects of mivacurium after induction of anesthesia with fentanyl-propofol in healthy adult women. Anesthesia was maintained with nitrous oxide in oxygen and continuous infusion of propofol (6-10 mg/kg/hr.). A myorelaxograph (Datex NMT 100) measuring the responses of the adductor pollicis to Train of Four (TOF) stimulations of the ulnar nerve was installed after induction. Three bolus dosages of mivacurium were administered just after induction: 0.15 mg/kg (group A), 0.17 mg/kg (group B) and 0.19 mg/kg (group C). Intubation was attempted at 75% TI-suppression. The conditions of intubation were good to excellent in the three groups except for one patient in group A (0.15 mg/kg). Successful intubation was performed faster in group C(p = 0.017). The curarization time was significantly longer in group C(0.19 mg/kg) vs the other groups (p = 0.002). As soon as the first signs of recovery (TI increment) appeared, a continuous infusion of mivacurium (10 micrograms/kg/min) was started to maintain a complete neuromuscular block. After stopping the continuous infusion, there were no differences in spontaneous recovery between groups A and B but patients from group C showed a lenghtening of the recovery time. There is no effect of the different bolus dosages on vital signs. We conclude that a bolus dosage of 0.19 mg/kg after induction of anesthesia with fentanyl-propofol offers the best choice when a rapid sequence of induction is required. Mivacurium could be an interesting muscle relaxant in one-day surgery even if a risk of prolonged curarization exists due to its degradation by plasma cholinesterases.