Cisatracurium in a myasthenic patient undergoing thymectomy

Purpose: The report investigates cisatracurium neuromuscular block in a mya sthenic patient undergoing thymectomy. Clinical Features: A myasthenic patient (Osserman II B) was prepared preope ratively with 240 mg.day(-1) pyridostigmine. The neuromuscular block produc ed by 0.05 mg.kg(-1) cisatracurium was monitored by Datex electromyography. The electromyographic response was compared with that in a control group o f five non-myasthenic patients. In the myasthenic patient, cisatracurium re sulted in a rapid onset of complete (97-98%) neuromuscular block, while a s low onset of partial (80-90%) block was achieved in the control group. Also , administration of 0.05 mg.kg(-1) neostigmine at the end of surgery revers ed the neuromuscular block of cisatracurium in the non-myasthenic patients, but did not change the rate of spontaneous recovery in the myasthenic pati ent. Conclusion: The myasthenic patient is sensitive to cisatracurium, as eviden ced by a more rapid onset and more marked neuromuscular block compared with the control non-myasthenic patients. This may be attributed to the decreas ed number of functional endplate acetylcholine receptors in the myasthenic patient, with a consequent decrease of the safety margin of neuromuscular t ransmission. Also, in contrast with the control group, the rate of recovery from neuromuscular block in the myasthenic patient was not enhanced by neo stigmine at the end of surgery. This may be attributed to the prior inhibit ion of acetylcholinesterase by the preoperative pyridostigmine, as well as by possible desensitization of the cholinergic receptors secondary to prolo nged pyridostigmine therapy.