Mivacurium infusion during nitrous oxide-isoflurane anesthesia: a comparison with nitrous oxide-opioid anesthesia.

STUDY OBJECTIVE

To determine the potentiation of the neuromuscular blockade induced by a titrated infusion of mivacurium in the presence of isoflurane versus a nitrous oxide (N2O)-opioid anesthesia.

DESIGN

An open-label, controlled study.

SETTING

The inpatient anesthesia service of two university medical centers.

PATIENTS

Thirty adults divided into two groups.

INTERVENTION

An intravenous infusion of mivacurium during anesthesia with N2O-opioid or N2O-isoflurane.

MEASUREMENTS AND MAIN RESULTS

A neuromuscular blockade was monitored by recording the electromyographic activity of the adductor pollicis muscle resulting from supramaximal stimulation at the ulnar nerve at 2 Hz for 2 seconds at 10-second intervals. The mivacurium infusion rate was significantly less in the presence of isoflurane [4.0 +/- 0.8 micrograms/kg/min (mean +/- SEM)] than during N2O-opioid anesthesia (6.4 +/- 0.6 micrograms/kg/min). The recovery rates did not differ between anesthetic groups. After the termination of the infusion, spontaneous recovery to T4/T1 of at least 0.75 occurred in an average of 17.9 +/- 1.5 minutes, with a mean recovery index (T25-75) of 6.0 +/- 0.7 minutes.

CONCLUSION

Isoflurane anesthesia reduces the infusion rate of mivacurium required to produce about 95% depression of neuromuscular function.