A comparison of cisatracurium and atracurium: onset of neuromuscular block after bolus injection and recovery after subsequent infusion.

Cisatracurium is a new nondepolarizing muscle relaxant. In patients randomized to receive either cisatracurium (n = 40) or atracurium (n = 20) we compared the time course of neuromuscular block. The initial bolus dose of cisatracurium was 0.1 mg/kg, that of atracurium 0.5 mg/kg. Neuromuscular block, maintained with an infusion of either drug, was reversed with neostigmine 45 micrograms/kg and atropine 20 micrograms/kg in one half of the patients. Neuromuscular transmission was assessed by recording the mechanical twitch response to train-of-four nerve stimulation. Onset times were 3.1 +/- 1.0 min with cisatracurium and 2.3 +/- 1.1 min with atracurium (P = 0.008). The infusion rates for a 95% +/- 4% neuromuscular block were 1.5 +/- 0.4 micrograms.kg-1.min-1 for cisatracurium and 6.6 +/- 1.7 micrograms.kg-1.min-1 for atracurium, 3.3 times those of cisatracurium when referenced to the active cations. After the infusion, the spontaneous recovery intervals 25%-75% of 18 +/- 11 min and 18 +/- 8 min for cisatracurium and atracurium (P = 0.896) were shortened to 5 +/- 2 min and 4 +/- 3 min (P = 0.921) after neostigmine. While attributing different onset times also to differences in the initial doses, we conclude that time profiles for neuromuscular block of both muscle relaxants, when given in equipotent doses, are not different.