Clinical Observations during Induction and Recovery of Xylazine-Midazolam-Propofol Anesthesia in Horses

Abstract

ABSTRACT. To evaluate clinical usefulness of xylazine (1.0 mg/kg)-midazolam (20 µg/kg)-propofol (3.0 mg/kg) anesthesia in horses, 6 adult Thoroughbred horses were examined. The quality of induction varied from poor to excellent and 5 out of 6 horses presented myotonus in the front half of the body. However, paddling immediately after induction observed in other reports of equine propofol anesthesia was not observed. Recovery time was 35.3 ± 9.3 min and the quality of recovery was calm and smooth in all horses. Respiration rate decreased after induction and hypoxemia was observed during lateral recumbency. Heart rate also decreased after induction, however mean arterial blood pressure was maintained above approximately 100 mmHg. KEY WORDS: equine, intravenous anesthesia, propofol.J. Vet. Med. Sci. 65 (7): [805][806][807][808] 2003 The intravenous anesthetic, propofol (2,6-diisopropylphenol) has been widely used for total intravenous anesthesia of human beings [12,20,22] and some animals [9,11,13]. The drug is characterized by short duration of action with little cumulative effects, easiness of anesthetic depth control and rapid recovery [4,12]. There is a number of reports of anesthesia using propofol also in horses [1,3,[15][16][17][18], in many of these reports, undesirable anesthesia-induction characteristics, i.e., excitement, increased muscle activities and paddling in the early recumbent phase were observed [3,[15][16][17]. For anesthesia induction in horses, safety of both personnel and horse is an important subject. Therefore, establishment of the anesthesia method without such undesirable characteristics is necessary for the clinical application of propofol to horses.In this research, midazolam, a benzodiazepine derivative, was used together with xylazine for premedication of propofol anesthesia of a horse, and the behavior of horses during anesthetic induction and recovery and their effects on the cardiopulmonary function were characterized.Six male 2-years-old (28 ± 1 months of age) healthy Thoroughbred horses trained for rearing weighing 469 ± 24 kg were used. Horses were fasted for 12 hr before anesthesia and freely given water. The experiments were conducted according to the guidelines established by the Experimental Animal Committee, Japan Racing Association.Five min after premedication with xylazine (1.0 mg/kg; Celactar, Bayer, Tokyo, Japan) follwed by midazolam (20 µg/kg; Dormicum, Yamanouchi, Tokyo, Japan) 10 min later, horses received a 3 min in duration intravenous injection of 1% propofol (3.0 mg/kg; Rapinovet, Mallinckrodt Veterinary, Mundelein, U.S.A.) solution.Horses were restrained by a swing-door induction system and propofol was administred. After the horses attained a sternal recumbency, the swing-door was opened and horses were turned to lateral recumbency. Following endotracheal intubation, horses were transported to the recovery room by hoist. In the recovery room, horses were placed in right lateral recumbency on a mat and spontaneously inhaled room air. After appearance of the ...

Comparison of high (5%) and low (1%) concentrations of micellar microemulsion propofol formulations with a standard (1%) lipid emulsion in horses

“…[5][6][7][8] The observations made in our study further support the opinion that propofol alone or in combination with xylazine is not a desirable drug protocol for routine induction of anesthesia in horses. 4,9 It is a commonly held clinical notion that recovery behavior of horses that are anesthetized on multiple occasions changes with increasing number of anesthetic episodes.…”

The Minimum Infusion Rate (MIR) of Propofol for Total Intravenous Anesthesia after Premedication with Xylazine in Horses

“…In this research, induction dose of propofol was 3.0 mg/ kg which is reported as an appropriate dose for young Thoroughbred [18]. On the other hand, induction dose of propofol was 2.0 mg/kg in the previous reports in which elder aged horses were used [16].…”

Evaluation of Bispectral Index (BIS) as an Indicator of Central Nervous System Depression in Horses Anesthetized with Propofol

“…Although chemically unrelated to the ultrashort-acting hypnotic anesthetics thiopental, methohexital, and etomidate, propofol acts by a similar mechanism of action, i.e., it potentiates -aminobutyric acid (GABA)-induced chloride current by binding with the -subunit of GABA A receptors at both spinal and supraspinal sites [18]. Propofol is unlikely to replace current induction techniques in horses such as  2 -adrenoceptor agonist-ketamine, benzodiazepine-ketamine and guaifenesin-thiopental [22,23,31]. However, recovery from anesthesia is uneventful and generally typified by good skeletal muscle strength and minimum ataxia in horses anesthetized with propofol for prolonged periods [4-7, 11, 26-29, 36, 37].…”