ACID-BASE BALANCE AND NEOSTIGMINE ANTAGONISM OF PANCURONIUM NEUROMUSCULAR BLOCKADE

In 40 cats anaesthetized with chloralose and urethane, pancuroniumwas infused i.v. at a constant rate to produce and maintain90% depression of twitch tension of the anterior tibialis musclefollowing supramaximal stimulation of the peroneal nerve. Neitherrespiratory alkalosis nor metabolic acidosis influenced theinfusion rate required to produce 90% depression of twitch tensionor antagonism of this depression by neostigmine. Respiratoryacidosis (pH 7.15; Pa_CO2, 10 kPa) did not alter the requiredinfusion rate but did prevent complete antagonism by neostigmine.Metabolic alkalosis (pH 7.65; Pa^CO2, 4.8 kPa) reduced both therequired infusion rate and prevented complete restoration oftwitch tension by neostigmine. The duration of neostigmine antagonismwas shortened by metabolic alkalosis. We conclude that respiratoryacidosis and metabolic alkalosis prevent antagonism of pancuroniumby neostigmine.