Mivacurium chloride and late onset congenital myopathy.

We describe the successful use of the short-acting, non-depolarizing neuromuscular blocking agent, mivacurium, in a 53-yr-old female patient with late onset congenital myopathy, undergoing elective submucous resection of the inferior turbinates. She was unable to climb stairs and walking was limited to periods of 15 min because of generalized weakness, fatigue and shortness of breath. A Datex Relaxograph was used to monitor the train-of-four count. No increase in sensitivity to mivacurium was demonstrated. A dose of 12 mg (three times the recommended ED95) resulted in 88% reduction of the first of the train-of-four count (T1) compared with control (TC). Spontaneous recovery of T1/TC to 100% took 11 min 20 s from the time maximum block was first achieved. The recovery index (25-75% T1/TC) was 4 min 40 s.