Infusion of a combination of propofol and medetomidine for long-term anesthesia in ponies.
OBJECTIVE
To determine the minimal infusion rate of propofol in combination with medetomidine for long-term anesthesia in ponies and the effects of atipamezole on recovery.


METHODS
12 ponies.


METHODS
Ponies were sedated with medetomidine (7 microg/kg of body weight, IV). Ten minutes later, anesthesia was induced with propofol (2 mg/kg, IV). Anesthesia was maintained for 4 hours, using an infusion of medetomidine (3.5 microg/kg per hour, IV) and propofol at a rate sufficient to prevent ponies from moving after electrical stimulation. Arterial blood pressures and blood gas analysis, heart rates, and respiratory rates were monitored. For recovery, 6 ponies were given atipamezole (60 microg/kg, IV). Induction and recovery were scored.


RESULTS
Minimal propofol infusion rates ranged from 0.06 to 0.1 mg/kg per min. Mean arterial blood pressure was stable (range, 74 to 86 mm Hg), and heart rate (34 to 51 beats/min) had minimal variations. Variable breathing patterns were observed. Mean PaO2 (range, 116 to 146 mm Hg) and mean PaCO2 (range, 48 to 51 mm Hg) did not change significantly with time, but hypoxemia was evident in some ponies (minimal PaO2, 47 mm Hg). Recovery was fast and uneventful with and without atipamezole (completed in 20.2 and 20.9 minutes, respectively).


CONCLUSIONS
Infusion of a combination of medetomidine and propofol was suitable for prolonged anesthesia in ponies. Recovery was rapid and uneventful. A combination of propofol and medetomidine may prove suitable for long-term anesthesia in horses. Monitoring of blood gases is essential because of potential hypoxemia.
Bettschart-Wolfensberger
R
R
Department of Anaesthesia, Veterinary Surgery Clinic, University of Zürich, Switzerland.
Freeman
S L
SL
Jäggin-Schmucker
N
N
Clarke
K W
KW
D000317:Adrenergic alpha-Antagonists / Q000008:administration & dosage; D000768:Anesthesia, General / Q000662:veterinary*; D018686:Anesthetics, Intravenous / Q000008:administration & dosage*; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D001831:Body Temperature / Q000187:drug effects; D004359:Drug Therapy, Combination; D006339:Heart Rate / Q000187:drug effects; D006736:Horses / Q000502:physiology*; D006993:Hypnotics and Sedatives / Q000008:administration & dosage*; D007093:Imidazoles / Q000008:administration & dosage; D007262:Infusions, Intravenous / Q000662:veterinary; D020926:Medetomidine / Q000008:administration & dosage*; D010147:Pain Measurement / Q000187:drug effects / Q000662:veterinary; D015742:Propofol / Q000008:administration & dosage*; D011897:Random Allocation
D000317:Adrenergic alpha-Antagonists; D018686:Anesthetics, Intravenous; D006993:Hypnotics and Sedatives; D007093:Imidazoles; C050701:atipamezole; D020926:Medetomidine; D015742:Propofol