mivacurium and Myasthenia-Gravis

Topics: Adolescent; Adult; Humans; Isoquinolines; Middle Aged; Mivacurium; Myasthenia Gravis; Neuromuscular Blockade; Neuromuscular Nondepolarizing Agents; Thoracic Surgery, Video-Assisted; Thymectomy; Young Adult

We have used mivacurium in four myasthenic patients presenting for thymectomy. Supramaximal single twitch stimulation was applied to the ulnar nerve at the wrist and the force of contraction of the adductor pollicis was measured. After an initial bolus dose of 30 micrograms kg-1 (approximately one-fifth of the normal intubating dose), we observed a mean 37.5 (SEM 5.6)% reduction in evoked twitch tension. Neuromuscular block was increased with incremental doses and maintained with repeat bolus doses of 15 micrograms kg-1 at 25% recovery. The interval between maintenance bolus doses remained constant (mean 5.9 (0.7) min). Spontaneous offset was rapid with a mean recovery index (T25-T75) of 11.9 (2.1) min. Provided anticholinesterase therapy is withheld in the immediate preoperative period, mivacurium would appear to be a safe and appropriate neuromuscular blocker in this variably sensitive group of patients. The cumulative dose required to establish full neuromuscular block varied between 60 and 90 micrograms kg-1. A maintenance infusion, commencing at 3 micrograms kg-1 min-1, is recommended, guided by neuromuscular monitoring.

Topics: Adult; Aged; Drug Administration Schedule; Female; Humans; Isoquinolines; Male; Mivacurium; Myasthenia Gravis; Nerve Block; Neuromuscular Junction; Neuromuscular Nondepolarizing Agents; Thymectomy; Time Factors

We describe the successful use of the short-acting, non-depolarizing neuromuscular blocking agent, mivacurium, in a patient with myasthenia gravis taking pyridostigmine 120 mg four times daily. Increased sensitivity to mivacurium was demonstrated using train-of-four monitoring. A dose of 0.5 times the recommended ED95 (3.0 mg) resulted in 93% block of T1. Spontaneous recovery was prolonged with a recovery index (25%-75% T1) of 20.5 min. Residual block was antagonized without difficulty using neostigmine 2.5 mg. We discuss the relationship between plasma cholinesterase, acetylcholinesterase and anticholinesterase drugs.

Topics: Aged; Anesthesia, General; Electromyography; Female; Humans; Isoquinolines; Mivacurium; Myasthenia Gravis; Nerve Block; Neuromuscular Junction; Neuromuscular Nondepolarizing Agents; Pyridostigmine Bromide

The relaxograph findings are presented in two patients. In the first, isoflurane alone is administered, and mivacurium with isoflurane is administered to the second patient with myasthenia gravis. A significantly lower dose of mivacurium is required. It was noticed that the T4:T1 ratio was 100% after mivacurium and reversal agent, but T1 did not return to normal. In the patient that only received isoflurane, T1 was 60% to 70% of the baseline, indicating the neuromuscular blocking effects of isoflurane. These cases illustrate that inhalation anesthetics are adequate for muscle relaxant effects, and if neuromuscular blockers are necessary, then a lower dose of nondepolarizer should be administered, and the patient carefully monitored. Mivacurium appears to be an ideal agent for neuromuscular blockade in myasthenia gravis as long as careful neuromuscular blockade is performed.

Topics: Adult; Anesthesia; Drug Monitoring; Drug Therapy, Combination; Electromyography; Female; Humans; Isoflurane; Isoquinolines; Mivacurium; Monitoring, Intraoperative; Myasthenia Gravis; Neuromuscular Nondepolarizing Agents; Thymectomy

Topics: Adult; Aged; Anesthesia, General; Depressive Disorder; Electroconvulsive Therapy; Female; Humans; Isoquinolines; Male; Middle Aged; Mivacurium; Myasthenia Gravis; Neuromuscular Depolarizing Agents