Ilium methadone

Sheep were pre-medicated with diazepam (0.2mg/kg IV) [Ilium Diazepam, Troy Laboratories Pty Ltd, NSW, Australia] prior to placement of an intravenous catheter [14G BD Angiocath, BD Medical, NSW, Australia] into the jugular vein. A combination of diazepam (0.1mg/kg IV) [Ilium Diazepam, Troy Laboratories Pty Ltd, NSW, Australia] and ketamine hydrochloride (5mg/kg IV) [Ilium Ketamil, Troy Laboratories Pty Ltd, NSW, Australia] was administered for anaesthetic induction. A cuffed, endotracheal tube was placed and sheep were maintained on isoflurane in 100% oxygen for the duration of the procedure. Ceftiofur sodium (5mg/kg IV BID) [Accent, Zamira Life Sciences, QLD, Australia] was administered for antibiotic prophylaxis and methadone (0.1mg/kg IV) [Ilium Methadone, Troy Laboratories Pty Ltd, NSW, Australia] and flunixin meglumine (1.1mg/kg IV) [Ilium Flunixil, Troy Laboratories Pty Ltd, NSW, Australia] were administered for analgesia after induction of anaesthesia.

For all dogs, food was removed at least eight hours prior to the procedure but access to water provided until premedication. Dog were anesthetized by a veterinary anesthesiologist (AR) using a standardized protocol. Premedication with methadone 0.3 mg/kg (Ilium Methadone 10 mg/mL, Troy Laboratories, Glendenning, NSW, Australia) IM was performed 30 min prior to induction of general anesthesia with alfaxalone (Alfaxan injection 10 mg/mL, Jurox, Glendinning, NSW, Australia) 2.2–3.2 mg/kg intramuscularly. Endotracheal intubation was used to maintain anesthesia with isoflurane (I.S.O., Veterinary Companies of Australia Pty Ltd, Kings Park, NSW, Australia) in 30% oxygen through a circle rebreathing system. End tidal isoflurane was maintained at 1.3–1.4%. Infusion of a balanced isotonic crystalloid solution (Compound Sodium Lactate, Baxter Healthcare, Toongabbie, NSW, Australia) was provided at 10 mL/kg/hour IV throughout anesthesia, along with IV fentanyl (Fentanyl injection 50 µg/mL, AstraZeneca, Macquarie Park, NSW, Australia) 2 µg/kg/hour. Arterial carbon dioxide tension was maintained between 35 and 45 mmHg by provision of mechanical ventilation by an anesthesia workstation (Datex-Ohmeda S/5 Aespire Anaesthesia Machine, GE Healthcare, Chicago, IL, USA). Active warming maintained esophageal temperature between 36.0 and 38.0 °C.