Total intravenous anaesthesia in horses using medetomidine and propofol.
OBJECTIVE
To examine the clinical suitability of medetomidine-propofol infusions for total intravenous anaesthesia in horses.


METHODS
Fifty client-owned horses of mixed breed, age [mean +/- SD (range)] 6.6 +/- 4.4 (0.04-18) years, mass 478 +/- 168.3 (80-700) kg presented for a range of operations requiring general anaesthesia.


METHODS
Pre-anaesthetic medication was intravenous (IV) medetomidine 7 mug kg(-1). Anaesthesia was induced with IV ketamine (2 mg kg(-1)) and diazepam (0.02 mg kg(-1)). 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 microg kg(-1) hour(-1)) and propofol infused IV to effect (initial dose 0.1 mg kg(-1) minute(-1)). 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 medetomidine-propofol infusion, medetomidine (2 microg kg(-1); 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: 28.0-39.2 (16-88) beats minute(-1); mean arterial blood pressure: 74.0-132.5 (42-189) mmHg; PaO2: 22.1-42.9 (4.9-67.8) kPa; [166-322 (37-508) mmHg], PaCO2: 6.7-8.1 (4.2-11.8) kPa [50-61 (32-88) mmHg] and pH 7.35-7.39 (7.15-7.48). Positive pressure ventilation was required in 23 horses. In three horses, HR values below 20 beats minute(-1) were treated with 20 microg kg(-1) atropine (IV). Mean propofol infusion rates were 98-108 microg kg(-1) minute(-1). During anaesthesia, movement occurring in 14 horses was controlled with thiopental. Duration of anaesthesia was 111.6 +/- 41.4 (46-225) minutes. Recovery in all horses was uneventful and completed within 42.2 +/- 19.8 (12-98) minutes.


CONCLUSIONS
Medetomidine-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.
Bettschart-Wolfensberger
Regula
R
Equine Clinic, Vetsuisse Faculty University of Zürich, Zürich, Switzerland. rbettschart@vetclinics.unizh.ch
Kalchofner
Karin
K
Neges
Karin
K
Kästner
Sabine
S
Fürst
Anton
A
D000759:Adjuvants, Anesthesia; D019162:Anesthetics, Combined / Q000494:pharmacology*; D000778:Anesthetics, Dissociative; D018686:Anesthetics, Intravenous / Q000494:pharmacology*; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D003975:Diazepam; D006339:Heart Rate / Q000187:drug effects; D006736:Horses / Q000502:physiology*; D006863:Hydrogen-Ion Concentration; D006993:Hypnotics and Sedatives / Q000494:pharmacology; D007442:Intubation, Intratracheal / Q000662:veterinary; D007649:Ketamine; D020926:Medetomidine / Q000494:pharmacology*; D010100:Oxygen / Q000097:blood; D010313:Partial Pressure; D015742:Propofol / Q000494:pharmacology*; D012119:Respiration / Q000187:drug effects; D016896:Treatment Outcome
D000759:Adjuvants, Anesthesia; D019162:Anesthetics, Combined; D000778:Anesthetics, Dissociative; D018686:Anesthetics, Intravenous; D006993:Hypnotics and Sedatives; D007649:Ketamine; D020926:Medetomidine; D003975:Diazepam; D010100:Oxygen; D015742:Propofol