Effect of ketorolac tromethamine on atracurium-induced neuromuscular blockade in anesthetized dogs.

OBJECTIVE

The purpose of this study was to determine the effect of ketorolac tromethamine or placebo on the neuromuscular blockade induced by an infusion of atracurium in isoflurane-anesthetized dogs.

DESIGN

Randomized, controlled trial.

ANIMALS

Six healthy, adult mixed-breed dogs (five female, one male) weighing 24.8 +/- 2.8 kg.

METHODS

Dogs were studied on two occasions with a minimum of 7 days between studies. Dogs were induced with 5% isoflurane in oxygen and maintained with 1.6 x minimum alveolar concentration (MAC) end-tidal isoflurane. Neuromuscular blockade was assessed using the train-of-four response. Once 50% depression of the first twitch (T1) was achieved, the atracurium infusion rate was held constant for 30 minutes. Then ketorolac, 0.5 mg/kg, or the same volume of placebo (0.9% sodium chloride solution) was administered intravenously and the atracurium infusion maintained for an additional 60 minutes. Before and at 2, 5, 10, 15, 30, and 60 minutes after ketorolac or placebo, the percent depression of T1 and the fourth twitch to the first twitch (T4/T1) ratio were recorded. The atracurium infusion was discontinued and the time for T1 to recover from 50% to 75% of its original value was recorded. At 75% T1, edrophonium, 0.5 mg/kg intravenously, was administered to antagonize the residual blockade.

RESULTS

There was no significant difference in T1%, T4/T1 ratio, or recovery time after ketorolac administration compared with placebo.

CONCLUSIONS

Ketorolac, 0.5 mg/kg intravenously, has no significant effect on either atracurium-induced neuromuscular blockade or recovery time for T1 in isoflurane-anesthetized dogs.

CLINICAL RELEVANCE

The concurrent use of atracurium should not be a contraindication for the administration of ketorolac for intraoperative or postoperative analgesia.