A comparison of the neuromuscular and cardiovascular effects of vecuronium, atracurium and mivacurium in sheep.

Neuromuscular and cardiovascular effects of vecuronium, atracurium and mivacurium were compared in 45 sheep. The onset and duration of neuromuscular block produced with loading doses of vecuronium (25 microg kg(-1)), atracurium (500 microg kg(-1)) and mivacurium (200 microg kg(-1)) and maintained with incremental doses (7, 170 and 70 microg kg(-1), respectively) were monitored using train-of-four stimulation of the n. facialis-m. levator nasolabialis unit. The electrocardiogram, heart rate and arterial blood pressure were recorded during onset of neuromuscular blockade. Mean loading dose onset times for atracurium (98 seconds) and mivacurium (86 seconds) were significantly shorter than vecuronium (203 seconds). Vecuronium produced significantly longer block (40 minutes) than atracurium (28 minutes) and mivacurium (15 minutes). There was no evidence of drug cumulation with atracurium or mivacurium. Cardiac dysrrhythmias were not observed in any group. Atracurium and mivacurium produced intermediate- and short-duration neuromuscular blockade, respectively. Vecuronium produced a prolonged effect after a slow onset.