The influence of halothane and enflurane on the reversibility of an Org NC45 neuromuscular blockade in cats.

The pharmacodynamics of neostigmine 20 micrograms kg-1 reversing a constant neuromuscular blockade from continuous infusion of Org NC 45 was studied in 17 cats. Six cats received only intravenous thiopental anaesthesia, another five received a 1 MAC (0.73%) inhalational concentration of halothane, and the remaining six cats received 1 MAC (1.68%) enflurane. In the enflurane group statistically significantly less Org NC 45 was needed to maintain the blockade (p less than 0.05). There was no difference in the degree of reversal or in the time course of the neostigmine activity between the 3 groups (p greater than 0.05). Only the duration of action of neostigmine was prolonged under halothane anaesthesia.