1. RECOVERY OF HORSES FROM ISOFLURANE ANAESTHESIA: A COMPARATIVE STUDY OF THE EFFECTS OF XYLAZINE, ROMIFIDINE AND DETOMIDINE Authors: Gabriele Niedermaier * Dr.; Bettina Wollanke*, Dr. PD; Hartmut Gerhards * Prof. Dr. Institute: * Equine Clinic, Ludwig-Maximilians-University of Munich Adress of the presenting author: Gabriele Niedermaier, Klinik für Pferde der LMU München, Veterinärstr. 13, 80539 München, German. Fax: -49 89 394272; e-mail: g.niedermaier@web.de In this double-blind study totally 131 horses and ponies (fig 1) underwent a general anaesthesia for a standardized elective eye surgery (vitrectomy) and were randomly devided into 6 different groups (table 1). Group Premedication: Levo- methadon (0.075mg/kg) AND Postanaesthetic medication 1a (n=20) Xylazine (0.55 mg/kg)Placebo 1b (n=23) Xylazine (0.55 mg/kg)Xylazine (0.275 mg/kg) 2a (n=23) Romifidine (0.04 mg/kg)Placebo 2b (n=22) Romifidine (0.04 mg/kg)Romifidine (0.02 mg/kg) 3a (n=21) Detomidine (0.01 mg/kg)Placebo 3b (n=22) Detomidine (0.01 mg/kg)Detomidine (0.005 mg/kg) All animals were premedicated with levomethadone (0.075 mg/kg) and either xylazine (0.55 mg/kg), romifidine (0.04 mg/kg), or detomidine (0.01 mg/kg) intravenously (IV). Anaesthesia was induced with ketamine and guaifenesin and maintained with isoflurane vaporised in oxygen. Mean duration time of anaesthesia was 39.1 ± 6.4 minutes. Immediately before moving into the recovery stall the horses were administered either isotonic saline solution (placebo group) or half of the dosage of the same α2-adrenoceptor-agonist used for premedication (sedation group) IV (table 1). Preceded studies showed that postanaesthetic sedation with α 2 - adrenoceptor-agonists leads to a prolonged but safer recovery of horses after inhalant anaesthesia. The attempt of this study was to find out if there exists any differences between xylazine, romifidine or detomidine in their effects on recovery from inhalant anaesthesia with isoflurane. The recovery quality (general attidude, activity, injury risk, coordination and balance) was scored on 1 to 5 category scoring system (1 = best, 5 = worst). One blinded evaluator used a standardized protocol. The time it took the horses to reach their final standing position was recorded as was the number of attempts required to sternal and stand. The latter were account for the recovery score (number = #). The times and attempts to standing position as well as the recovery scores were compared using the Mann-Whitney U test. A p of <0.05 was considered significant. Horses in all sedation groups had shorter mean times to standing than those in the respective placebo groups (table 2; fig 2, 3, 4). Horses administered postanaesthetic sedation with xylazine or detomidine required less attempts to stand and achieved a lower recovery score than horses in the respective placebo groups (table 2; fig 3, 4). In the placebo group the recovery score for horses premedicated with romifidine was significantly lower than for those premedicated with xylazine (table 2, fig 4). Fig 1. Gender, age and breed of the horses Warmblood 50% Mares 32% Geldings 53% Stallions 15% Various 14% Ponies 18% Thorough- bred 7% Quarter Horses 11% Fig 4: Mean recovery scores for horses in the placebo and sedation group. Fig 2. Mean attempts to standing position for horses in the placebo and sedation group. [group] Fig 3. Mean times to standing position for horses in the placebo and sedation group. [group] Group Time to standing Attempts to standing Recovery score Xylazine Placebo11,0 ± 5,33,7 ± 2,430,6 ± 8,2 † Xylazine Sedation23,0 ± 6,3 *1,7 ± 1,6 *17,2 ± 7,2 * Romifidine Placebo16,1 ± 6,93,2 ± 3,124,0 ± 11,1 Romifidine Sedation24,6 ± 10,7 *2,4 ± 2,119,3 ± 8,9 Detomidine Placebo12,1 ± 4,93,2 ± 3,026,9 ± 10,8 Detomidine Sedation23,3 ± 10,7 *1,7 ± 1,3 *17,7 ± 6,6 * * significantly different from the placebo group on the same α 2 -adrenoceptor- agonist; † significantly different from the romifidine placebo group. RESULTS Table 1: Classification in groups MATERIAL AND METHODS GENDERBREEDAGE Table. 2: Mean times ± s.d. and mean ± s.d. attempts to standing position and mean ± s.d. recovery score. [group] INTRODUCTION XylazineRomifidineDetomidine Xylazine RomifidineDetomidine XylazineRomifidineDetomidine