Atracurium administration, as an infusion, to induce neuromuscular blockade in clinically normal and temporarily immune-suppressed cats.

Atracurium besylate, a nondepolarizing neuromuscular blocking agent, was administered by infusion to 10 cats that were anesthetized with isoflurane and oxygen to allow transplantation of a myocutaneous flap. Five of the cats were given cyclosporine (20 mg/kg of body weight, PO q 12 h in divided doses) for 2 days prior to anesthesia, and prednisolone (0.25 mg/kg, PO) on the morning of surgery. The other 5 cats were not given either drug. Neuromuscular blockade was assessed, using the train-of-four stimulation, and throughout surgery, the infusion rate was adjusted to maintain the first-twitch response (T1) at 90 to 95% depression from baseline. At completion of surgery, atracurium was discontinued, and the infusion rate and the time for recovery (the time for the train-of-four ratio to increase from 50 to 75%) were recorded. Once the train-of-four ratio had been stable for 10 minutes, edrophonium (0.5 mg/kg), a cholinesterase inhibitor, was administered IV, and neuromuscular blockade was monitored for another 10 minutes. Mean (+/- SD) duration of the atracurium infusion was 302.1 +/- 70.5 minutes for the control group and was 323.9 +/- 61.7 minutes for the cats given cyclosporine and prednisolone. In the cats of the control group, the infusion rate required to induce 90 to 95% T1 depression from baseline was 3.7 +/- 0.7 micrograms/kg/min. This rate was not significantly different from that of 2.8 +/- 1.2 micrograms/kg/min in cats given cyclosporine and prednisolone. Significant difference in recovery time was not evident between the control group and the treated group (6.4 +/- 4.5 minutes vs 6.2 +/- 2.5 minutes).(ABSTRACT TRUNCATED AT 250 WORDS)