[Comparison of recovery time of bolus and continuous infusion mivacurium.].

BACKGROUND AND OBJECTIVES Mivacurium is a short-acting neuromuscular blocker (NMB), with total duration not exceeding 24 minutes. Early publications have reported no significant differences in recovery time, regardless of the route administration. However, clinical experience points out to longer recovery times when the drug is administered in continuous infusion. This study aimed at comparing recovery time of bolus administration and continuous infusion of mivacurium in a group of young adult patients. METHODS Forty young patients with no neuromuscular disease were enrolled in the study. Patients were premedicated with midazolam and monitored in the OR with ECG in D II and non-invasive automatic blood pressure. All patients received propofol and fentanyl and anesthesia was maintained with isoflurane, nitrous oxide and oxygen. Accelerometric neuromuscular transmission monitor was installed after induction and capnograph and gases analyzer were installed after intubation. Patients were divided in 2 equal groups according to mivacurium administration regimen: group 1 received initial bolus dose alone, and group 2, after the initial bolus dose and having recovered 10% of T1, received continuous infusion to maintain T1 within this value. For both groups, T1 and T4/T1 values were recorded during recovery, as from T1 in 10% of initial response, every minute up to 30 minutes. RESULTS Demographics were homogeneous between groups. Group 2 had slower recovery as compared to group 1. There have been major variations in infusion doses among patients and for the same patient during infusion. CONCLUSION In young adult patients without evidences of disease, mivacurium recovery is longer after continuous infusion as compared to bolus infusion. As a consequence of infusion dose variation among patients and for each patient, we recommend the use of neuromuscular transmission monitor to maintain constant and stable relaxation.