Some metabolic and hormonal changes associated with general anaesthesia and surgery in the horse

Three different anaesthetic techniques were studied in normal, healthy Thoroughbred or Thoroughbred type horses. These were (a) acepromazine, thiopentone and suxamethonium; (b) acepromazine, glyceryl guaiacolate and a 'half-dose' of thiopentone; and (c) xylazine and ketamine. Anaesthesia was maintained with halothane vaporized in oxygen and nitrous oxide. All horses underwent either laryngeal or body surface surgery. Heart rate, packed cell volume, blood glucose and lactate, plasma non-esterified fatty acids, insulin and cortisol were measured before, during and after surgery. The greatest metabolic and hormonal changes occurred immediately after anaesthetic induction and were different in each group. The combination of acepromazine, glyceryl guaiacolate and a 'half-dose' of thiopentone was associated with the least change in the physiological and metabolic variables measured.