Antagonism of Mivacurium Neuromuscular Block

This study was designed to compare the effectiveness of antagonism of mivacurium blockade with either neostigmine, edrophonium, or spontaneous recovery. Thirty ASA physical status I or II patients provided informed consent and were randomized to one of the following groups: Group 1, placebo saline; Group 2, edrophonium (1 mg/kg); and Group 3, neostigmine (70 micrograms/kg) (n = 10/group). All studied patients had anesthesia induced with propofol and maintained with propofol/N2O/fentanyl. Mivacurium bolus of 0.2 mg/kg was used for endotracheal intubation and an infusion titrated to maintain deep levels of block (T1% = 1%-5%) (T1% = first response/control response x 100). The antagonist was injected at a deep level of the block (T1% = 1%-8%) and neuromuscular (NM) recovery was evaluated by train-of-four twitches (TOF). T1% was used during maintenance, whereas both T1% and TOF% (fourth response/first response x 100) were used during recovery. Investigators were blinded to the antagonist used. Plasma cholinesterase activity was measured prior to antagonist administration (0 min), as well as 15, 30, and 60 min after. Plasma cholinesterase activity was decreased to 29% of control at 15 min and remained at approximately 60% of the control after neostigmine administration. Edrophonium did not affect plasma cholinesterase activity. Clinically adequate spontaneous recovery (TOF% > or = 70%) of the mivacurium block with placebo required 15-18 min. On average, clinically adequate antagonism of mivacurium by edrophonium was 50% faster than placebo and 30%-40% faster than with neostigmine. In summary, the speed of antagonism with edrophonium is faster than with neostigmine when antagonizing deep mivacurium NM block.(ABSTRACT TRUNCATED AT 250 WORDS)