Neuromuscular and cardiovascular effects of pancuronium bromide in calves anesthetized with halothane.

Pancuronium bromide was administered to calves to define the dosage level necessary to produce surgical relaxation (90% to 99% reduction of base-line evoked, hindlimb digital-extensor muscle twitch tension). Initial dosage level requirement was 43 +/- 9 micrograms/kg of body weight. Calves with this degree of relaxation required 26 +/- 14 minutes to achieve 50% recovery and 43 +/- 19 minutes to achieve complete return of base-line muscle twitch. Calves given a repeat injection of pancuronium at base-line muscle twitch required 27 +/- 9 micrograms/kg to achieve relaxation similar to that of the 1st dose. The 2nd dose did not last as long as the 1st, with complete recovery occurring in 37 +/- 12 minutes. Maximum evoked tension occurred at 200- to 400-g resting tension on the hoof. There was an absence of heart rate or blood pressure changes after injection of relaxant and a variable and inconsistent fade response to train-of-four and tetanic stimulus of the facial muscles. Acid-base values were alkalemic (pHa 7.5 +/- 0.08) when ventilation was controlled at eucapnia (PaCO2, 25 to 45 mm of Hg).