Evaluation of thiopentone-midazolam-fentanyl anaesthesia in pigs.

Induction of anaesthesia in swine by thiopentone (27.1-35.7 mg/kg, mean 29.9 mg/kg) was followed by bolus doses and continuous infusion of midazolam and fentanyl (0.90 mg/kg followed by 0.90 mg/kg/h and 0.025 mg/kg followed by 0.025 mg/kg/h, respectively). This produced good anaesthesia and analgesia for up to 2 h in 6 Norwegian Landrace pigs (wt: 17-42 kg), based on responses to painful stimuli elicited by pinching the nasal septum, the mouth, the forefoot and the perineal skin area. The first responses occurred after 110 min of anaesthesia. No significant drop in rectal temperature due to the regimen was noted during monitoring periods (140-180 min). This combined intravenous anaesthetic regimen gave good anaesthesia and analgesia to pigs for up to 2 h as monitored by clinical signs. The regimen may not be sufficient for longer time periods. We cannot advocate the incorporation of neuromuscular blocking agents in this regimen.