Brainstem and middle latency auditory evoked responses in rabbits with halothane anaesthesia

The effects of different concentrations of halothane (0.5, 1 and 1.5%) in brainstem and middle latency auditory evoked responses were studied in 14 adult rabbits. The animals were firstly curarized, tracheostomized and ventilated mechanically. Various recording were made under these conditions for control purposes. During the experiment, arterial pressure, temperature, arterial concentrations of O2, CO2 and pH were monitored. Halothane produce an increase in latency a decrease in amplitude and at higher concentrations even abolished the later waves of middle latency auditory evoked responses. Brainstem potentials are stable, but slight changes in latency were observed at high concentrations (1.5%). Modifications of these potentials as a result of the different concentrations of this anaesthetic in relation with the recordings obtained in the animals curarized without anaesthesia are discussed and the results compared with previous reports in humans.