A retrospective survey of anaesthesia in horses with colic

The purpose of this survey was to identify complications occurring in horses with colic during anaesthesia and recovery from anaesthesia; and to determine any relationships between these complications and drugs used for induction or maintenance of anaesthesia. Two hundred and thirty nine horses were anaesthetised on a total of 250 occasions for colic surgery between January 1985 and May 1987. Of these, 189 recovered from 200 anaesthetic episodes. Most horses received xylazine and guaifenesin with either thiobarbiturate (68 per cent) or ketamine (24 per cent) and anaesthesia was maintained with either halothane (51 per cent), isoflurane (43 per cent), or first halothane then isoflurane (6 per cent). Sixty nine per cent also received an opioid. Hypotension or tachycardia were recorded in 15 and 13 per cent of anaesthesias, respectively. Arterial PO2 was less than 13.3 kPa in 17 per cent of 175 anaesthesias. None of these complications was associated with a specific anaesthetic agent. Hypertension was recorded in 11.5 per cent of anaesthesias and occurred more frequently during isoflurane anaesthesia (P < 0.05). The mean duration of anaesthesia was 126 mins (range, 50-270 mins), and was not different for horses receiving thiobarbiturate or ketamine, halothane or isoflurane. The time taken to stand after anaesthesia recorded on 149 occasions and was 63 +/- 24 mins (range, 15-135 mins). This was not different for the different anaesthetic agents. Horses that were excited or had difficulty standing up during recovery had a significantly longer duration of anaesthesia (165 +/- 51 mins) (P < 0.05) but no specific anaesthetic agent was involved. Of the 189 horses, 148 (75 per cent) survived and were discharged from the hospital. Horses that did not survive had a significantly increased prevalence of anaesthetic complications, and longer durations of anaesthesia.