Sevoflurane and oxygen anaesthesia following administration of atropine-xylazine-guaifenesin-thiopental in spontaneously breathing horses.

The effects of sevoflurane-oxygen anaesthesia at a light-surgical depth on clinically important features were evaluated in spontaneously breathing horses that received atropine, xylazine, and guaifenesin-thiopental. Mean end-tidal concentrations of sevoflurane ranged from 1.6 to 2.3% during 90 min maintenance. Recovery from anaesthesia was extremely rapid and smooth. Heart rates did not significantly change after anaesthesia. Arrhythmia was not observed. Mean arterial pressure (mean +/- SD) ranged from 86 +/- 17 to 98 +/- 5 mmHg during anaesthesia. Minute ventilation was low due to decreased respiratory rates during anaesthesia. Changes in arterial blood gases and pH demonstrated respiratory acidosis during anaesthesia. Haematological findings revealed haemodilution during anaesthesia. Serum potassium decreased slightly during anaesthesia, but other serum biochemical values did not significantly change for 7 days post-anaesthesia. These results suggest that sevoflurane may be an effective inhalant anaesthetic which produces a rapid recovery from anaesthesia in horses.