INTERNATIONAL JOURNAL OF AGRICULTURE & BIOLOGY 1560–8530/2003/05–3–316–321 http://www.ijab.org Effects of Detomidine with Chloral Hydrate Anaesthesia in Horses MUHAMMAD ARIF KHAN, MUHAMMAD ASHRAF, KHALID PERVEZ, H.A. HASHMI AND ASIM K. MAHMOOD Department of Clinical Medicine and Surgery, University of Veterinary and Animal Sciences, Lahore–Pakistan ABSTRACT Effect of detomidine with chloral hydrate was studied in 18 local bred horses. Three treatments were given to separate groups of horses, i.e. A= chloral hydrate alone @ 100 mg kg –1 body weight intravenously, B= detomidine @ 50 μg kg –1 body weight intravenously 10 min before chloral hydrate (100 mg kg –1 body weight) administration, C= chloral hydrate @ 60 mg kg –1 body weight with the same dose rate of detomidine used as in group B. The results of group B were quite encouraging in terms of ideal anaesthesia which is normally required for major surgical intervention in Horses. The treatment used in group C also proved better but the duration of surgical anaesthesia was shorter. Key Words: Detomidine; Chloride hydrate; Anaesthesia; Horse INTRODUCTION The use of horse in race, polo, riding, tent pegging and draft purpose has made it an important part of livestock in Pakistan. This particular species often suffers from certain problems, which require surgical manipulation as a sole remedy. To serve the purpose of anaesthesia to perform various surgical exercises in horses, chloral hydrate has been a drug of choice due to the unavailability of proper anaesthetics in field practice. The drug is also being used now a days by an average practitioner engaged in equine practice. Chloral hydrate was first introduced in 1869 by Liebrick as a somificient. It was the first drug used as intravenous anaesthetic (Oehme & Prier, 1974). Malone (1917) first time reported its use as an intravenous general anaesthetic after a number of trials in horses. The drug is found in colorless crystals with penetrating odour and bitter taste. The hypnotic effect of chloral hydrate is due to the formation of trichloroethanol after metabolism in liver. The sensory routes are mildly affected which results into loss of muscle control leading to frightening and struggling. The drug also depresses respiration and blood pressure and has prolonged recovery period, incordination and less safety margin (Booth & McDonald, 1988). Various drugs have been tried in the past as pre- anaesthetics in equine to overcome the side effects of the general anaesthetics. Detomidine HCl (Domosedan) is a potent sedative and analgesic for use in veterinary practice (Hall & Clark, 1991). The drug has been tried as pre- anaesthetic with chloral hydrate anaesthesia in this project. The sedative and analgesic actions of detomidine are related to CNS depressions mediated by stimulation of alpha two receptors (Anonymous, 1996). This study was conducted to evaluate the problems associated with chloral hydrate anaesthesia, to evaluate the effect of detomidine premedication and to observe reduction in the dose rate of chloral hydrate. MATERIALS AND METHODS Source of animals. The study was conducted on 18 local bred horses between the age of 5-6 years. The horses were kept at indoor hospital, Department of Clinical Medicine and Surgery, University of Veterinary and Animal Sciences, Lahore. The health status was judged to find out any abnormality. A week prior to study, the animals were treated for ecto and endo parasites. The horses were provided normal feed and water as per routine. Pre-anaesthetic considerations. General health status of the animal was assessed before the administration of anaesthetic by recording body temperature, pulse rate, respiration rate and auscultation of heart and lungs. The induction and recovery were managed in quiet and isolated place, well padded to prevent the chances of injuries and bruises to the animals. Fasting. All the animals were kept fast at least 12-18 h before the administration of anaesthetic agents. This was infact done to minimize the hazards of casting i.e. to reduce vigourness, to decrease the mechanical compression of lungs by full gastro-intestinal tract. Medicine used Detomidine. Detomidine [4-(5)-(2,3 dimethyl benzyle) imidazole HCl] is a newly developed potent sedative and analgesic for use in veterinary practice. It is found in the form of colourless clear solution, which can be administered intravenously and intramuscularly in various animals. The drug is available with a trade name “Domosedan” containing 10 mg/mL detomidine HCl. It is the product of Orion Pharmaceutical Company, Turku, Finland. Detomidine was used at the dose rate of 50 μg kg –1 body weight intravenously in this project. Chloral hydrate. Chloral hydrate (Trichloroacetyl aldehyde: CCl 3 . CHO) is a non-selective CNS depressant. It is readily soluble in water but solutions are irritant. Chloral hydrate was used in the form of intravenous injection