Comparison of isoflurane inhalation anaesthesia, injection anaesthesia and high volume caudal epidural anaesthesia for umbilical surgery in calves; metabolic, endocrine and cardiopulmonary effects.

Objective To compare three anaesthetic protocols for umbilical surgery in calves regarding adequacy of analgesia, and cardiopulmonary and hormonal responses. Study design Prospective, randomised experimental study. Animals Thirty healthy German Holstein calves (7 female, 23 male) aged 45.9 +/- 6.4 days. Methods All calves underwent umbilical surgery in dorsal recumbency. The anaesthetic protocols were as follows: group INH (n = 10), induction 0.1 mg kg(-1) xylazine IM and 2.0 mg kg(-1) ketamine IV, maintenance isoflurane in oxygen; Group INJ (n = 10), induction 0.2 mg kg(-1) xylazine IM and 5.0 mg kg(-1) ketamine IV, maintenance 2.5 mg kg(-1) ketamine IV every 15 minutes or as required; group EPI (n = 10), high volume caudal epidural anaesthesia with 0.2 mg kg(-1) xylazine diluted to 0.6 mL kg(-1) with procaine 2%. All calves received peri-umbilical infiltration of procaine and pre-operative IV flunixin (2.2 mg kg(-1)). Cardiopulmonary variables were measured at preset intervals for up to 2 hours after surgery. The endocrine stress response was determined. Intra-operative nociception was assessed using a VAS scale. Data were compared between groups using appropriate statistical tests. A value of p < 0.05 was considered significant. Results All three protocols provided adequate anaesthesia for surgery although, as judged by the VAS scale, intra-operative response was greatest with INJ. Lowest mean cortisol levels during surgery occurred in EPI. Heart rate and cardiac output did not differ between groups, but mean arterial blood pressure, systemic vascular resistance, and partial pressure of carbon dioxide were higher and arterial pH lower in groups INH and INJ than in Group EPI. Group INJ became hypoxaemic and had a significantly greater vascular shunt than did the other groups. Conclusion and clinical relevance Groups INH and EPI both proved acceptable protocols for calves undergoing umbilical surgery, whilst INJ resulted in variable anti-nociception and in hypoxaemia. High volume caudal epidural anaesthesia provides a practical inexpensive method of anaesthesia for umbilical surgery.