|Fifty client-owned horses of mixed breed, age [mean Â± SD (range)] 6.6 Â± 4.4 (0.04Â–18) years, mass 478 Â± 168.3 (80Â–700) kg presented for a range of operations requiring general anaesthesia.
Pre-anaesthetic medication was intravenous (IV) medetomidine 7 μg kg1.
Anaesthesia was induced with IV ketamine (2 mg kg1) and diazepam (0.02 mg kg1).
After endotracheal intubation, O2 was delivered (FiO2 > 0.85).
Positive pressure ventilation was initiated if breath-holding in excess of 1 minute occurred. Anaesthesia was maintained with a constant rate medetomidine infusion (3.5 μg kg1 hour1) and propofol infused IV to effect (initial dose 0.1 mg kg1 minute1).
Heart (HR) respiratory (fr) and propofol administration rates, and systemic arterial blood pressures were recorded at 5-minute intervals.
Arterial blood gas (O2 and CO2) tensions and pH values were recorded every 15 minutes.
Ten minutes after ending medetomidineÂ–propofol infusion, medetomidine (2 μg kg1; IV) was given.
Cardiopulmonary data were analysed using descriptive statistical techniques.
Results: Thirty-three orthopaedic, seven integumentary and 10 elective abdominal operations were performed.
Cardiopulmonary data, presented as range of mean individual (and absolute individual minimum and maximum values) were: HR: 28.0Â–39.2 (16Â–88) beats minute1; mean arterial blood pressure: 74.0Â–132.5 (42Â–189) mmHg; PaO2: 22.1Â–42.9 (4.9Â–67.8) kPa; [166Â–322 (37Â–508) mmHg], PaCO2: 6.7Â–8.1 (4.2Â–11.8) kPa [50Â–61 (32Â–88) mmHg] and pH 7.35Â–7.39 (7.15Â–7.48).
Positive pressure ventilation was required in 23 horses.
In three horses, HR values below 20 beats minute1 were treated with 20 μg kg1 atropine (IV). Mean propofol infusion rates were 98Â–108 μg kg1 minute1.
During anaesthesia, movement occurring in 14 horses was controlled with thiopental. Duration of anaesthesia was 111.6 Â± 41.4 (46Â–225) minutes.
Recovery in all horses was uneventful and completed within 42.2 Â± 19.8 (12Â–98) minutes.
MedetomidineÂ–propofol infusion produces adequate conditions for a range of surgical procedures. Cardiovascular function was adequate, as no pressor agents were required. Positive pressure ventilation was required in 23 horses.
Source: Bettschart-Wolfensberger, Regula, Kalchofner, Karin, Neges, Karin, KÃ¤stner, Sabine & FÃ¼rst, Anton (2005): Total intravenous anaesthesia in horses using medetomidine and propofol. In: Veterinary Anaesthesia and Analgesia 32 (6), 348-354.
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