Use of mivacurium chloride by constant infusion in the anephric patient

Twenty anephric and 20 healthy patients received a bolus dose of mivacurium 150 micrograms kg-1. When the first EMG response (T1) of the train-of-four had recovered to 5% of control (T0), an infusion of mivacurium 10 micrograms kg-1 min-1 was started and adjusted to keep T1 at 5%. Ten patients in each group were given neostigmine 35 micrograms kg-1 when the infusion was stopped when T1/T0 had recovered to 20%; in the others recovery was spontaneous. After the bolus dose of mivacurium, mean (SD) depression of T1 was greater in the anephric group than in the normal group (98.4 (3.5) vs 96.8 (4.4)%; P less than 0.01) and recovery of T1/T0 to 5% was slower (15.3 (6.9) vs 9.8 (3.5) min; P less than 0.01). Anephric patients required a slower infusion rate (6.3 (1.9) vs 10.4 (2.8) micrograms kg-1 min-1; P less than 0.001). Neostigmine hastened recovery of both T1/T0 and T4/T1 in both groups. Spontaneous recovery of T1/T0 (from 25% to 75%) after the infusion was also slower in anephric patients (12.2 (8.2) vs 7.7 (1.2) min; P less than 0.05). Plasma cholinesterase activity was less in the anephric group (785 (207) vs 943 (217) iu litre-1; P less than 0.05) and there was a (negative) correlation overall between cholinesterase activity and time to 5% recovery of T1/T0 after the bolus dose (r = -0.42; P less than 0.02). We conclude that patients with chronic renal failure may require a reduced dose of mivacurium.