Comparison of three injectable anaesthetic techniques in pigs

Forty-six near-adult pigs (mean age 10 months, mean weight 156 kg) were anaesthetised for laparoscopy. After intramuscular azaperone (1.0 mg/kg) and ketamine (2.5 mg/kg), 14 of the pigs received intravenous etomidate (200 mu g/kg) and midazolam (100 mu g/kg) and 17 were given ketamine (2 mg/kg) and midazolam (100 mu g/kg). The other 15 pigs were anaesthetised with pentobarbitone (15 to 20 mg/kg) without pre-anaesthetic medication. The duration and adequacy of anaesthesia, recovery rate, and seven physiological variables (ECG, heart rate, indirect arterial blood pressure, respiratory rate, minute volume, mean end-tidal carbon dioxide concentration and percentage oxygen saturation of haemoglobin) were compared. Repeated injections were needed in 29 of the 46 cases. Pentobarbitone was the least satisfactory drug because although the haemodynamic variables were greater, it caused more respiratory depression and a higher overall complication rate than the other methods. Apnoea occurred in two pigs, and was fatal in one, and positive pressure ventilation with oxygen was needed in three others. Intubation conditions were poorer and the times to standing, walking and rooting were longer in the pigs anaesthetised with pentobarbitone.