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Objective: To evaluate the effect of the peripherally acting α 2 -adrenoceptor antagonist vatinoxan (MK-467) on the sedative properties of medetomidine (MED) when injected intramuscularly (IM) in the same syringe and on reversal of this sedation with atipamezole in sheep., Study Design: Randomized, blinded, crossover experimental trial., Animals: Eight healthy adult female sheep., Methods: Sheep received MED (30 μg kg -1 IM) alone or combined in the same syringe with vatinoxan (300 μg kg -1 IM, MED+VAT) with a 2 week washout period. Atipamezole (150 μg kg -1 IM) was administered 30 minutes later for reversal. Sedation was assessed using two sedation scores, a visual analog score and a descriptive scale before treatments (T0) and at intervals up to 5 hours thereafter. Pulse rate (PR) was counted at T0 and at 30 (T30) and 90 (T90) minutes. Rectal temperature was measured at T0 and T90 postinjection. Plasma samples were analyzed for drug concentrations at T30 and T90., Results: The first signs of sedation were seen significantly earlier after MED+VAT (4.6 ± 1.7 minutes versus 9.4 ± 2.6 minutes after MED) and the sedation scores were significantly higher after MED+VAT than MED. All animals laid with head down 10.0 ± 3.4 minutes after MED+VAT, whereas three MED animals did not become recumbent before atipamezole was administered. The plasma concentrations of dexmedetomidine were significantly higher at T30 (2.47 ± 0.2 ng mL -1 ) and significantly lower at T90 (1.23 ± 0.3 ng mL -1 ) with MED+VAT than with MED (1.19 ± 0.8 and 1.83 ± 0.4 ng mL -1 , respectively). While no significant differences were observed between treatments in PR at T30, PR at T90 was significantly higher with MED+VAT than with MED., Conclusions and Clinical Relevance: When administered IM in the same syringe, vatinoxan hastened and intensified the initial sedative effects of MED and enhanced the sedation reversal by atipamezole., (Copyright © 2018 Association of Veterinary Anaesthetists and American College of Veterinary Anesthesia and Analgesia. Published by Elsevier Ltd. All rights reserved.)

Objective: To characterize a propofol-medetomidine-ketamine total intravenous anaesthetic in impala (Aepyceros melampus)., Study Design: Prospective clinical study., Animals: Ten adult female impala., Materials and Methods: Impala were immobilized at 1253 m above sea level with 2.0 mg thiafentanil and 2.2 mg medetomidine via projectile darts. Propofol was given to effect (0.5 mg kg -1 boluses) to allow endotracheal intubation, following which oxygen was supplemented at 2 L minute -1 . Anaesthesia was maintained with a constant-rate infusion of medetomidine and ketamine at 5 μg kg -1 hour -1 and 1.5 mg kg -1 hour -1 , respectively, and propofol to effect (initially 0.2 mg kg -1 minute -1 ) for 120 minutes. The propofol infusion was titrated according to reaction to nociceptive stimuli every 15 minutes. Cardiopulmonary parameters were monitored continuously and arterial blood gas samples were analysed intermittently. After 120 minutes' maintenance, the thiafentanil and medetomidine were antagonized using naltrexone (10:1 thiafentanil) and atipamezole (5:1 medetomidine), respectively., Results: All impala were successfully immobilized. The median dose [interquartile range (IQR)] of propofol required for intubation was 2.7 (1.9-3.3) mg kg -1 . The propofol-medetomidine-ketamine combination abolished voluntary movement and ensured anaesthesia for the 120 minute period. Propofol titration showed a generally downward trend. Median (IQR) heart rate [57 (53-61) beats minute -1 ], respiratory rate [10 (9-12) breaths minute -1 ] and mean arterial blood pressure [101 (98-106) mmHg] were well maintained. Arterial blood gas analysis indicated hypoxaemia, hyper- capnia and acidaemia. Butorphanol (0.12 mg kg -1 ) was an essential rescue drug to counteract thiafentanil-induced respiratory depression. All impala regurgitated frequently during the maintenance period. Recovery was calm and rapid in all animals. Median (IQR) time to standing from antagonist administration was 4.4 (3.2-5.6) minutes., Conclusions and Clinical Relevance: A propofol-medetomidine-ketamine combination could provide adequate anaesthesia for invasive procedures in impala. The propofol infusion should begin at 0.2 mg kg -1 minute -1 and be titrated to clinical effect. Oxygen supplementation and airway protection with a cuffed endotracheal tube are essential., (Copyright © 2016 Association of Veterinary Anaesthetists and American College of Veterinary Anesthesia and Analgesia. Published by Elsevier Ltd. All rights reserved.)

Objective: To establish a safe, reliable and reversible immobilization protocol for captive juvenile crocodiles., Study Design: Prospective, randomized, clinical study., Animals: Thirty male estuarine crocodiles (body mass 1-12.1 kg) and 10 male Australian freshwater crocodiles (body mass 4.1-12.8 kg)., Methods: An optimized dose of medetomidine (0.5 mg kg(-1)) was administered intramuscularly (IM) into the tail (Group 1; n = 5), pelvic limb (Group 2; n = 5) and thoracic limb (Groups 3 and 4; n = 5 in each group) of estuarine crocodiles weighing 3-12.1 kg. Their heart and respiratory rates and degree of immobilization were monitored every 15 minutes until recovery and daily thereafter for 3 subsequent days. In Group 4 (n = 5), medetomidine was antagonized with an optimized dose of atipamezole (2.5 mg kg(-1)) given IM into the thoracic limb and time to recovery recorded. The effects of increasing doses of medetomidine given IM in the thoracic limb (n = 4) and intravenously (n = 6) were determined in 1-2 kg estuarine crocodiles. Australian freshwater crocodiles (4.1-12.8 kg) were administered medetomidine IM into the thoracic limb in divided doses at 0.5 mg kg(-1) (n = 5) and 0.75 mg kg(-1) (n = 5) and similarly monitored., Results: Immobilization was achieved only in the estuarine crocodiles >3 kg and when medetomidine was administered into the thoracic limb. Immobilization was achieved within 30 minutes and the duration of immobilization lasted approximately 90 minutes. Immobilization in estuarine crocodiles was readily reversed with atipamezole. A dose of 0.75 g kg(-1) was required to immobilize Australian freshwater crocodiles and the onset of immobilization was longer and the duration shorter than seen in the estuarine crocodiles. The heart and respiratory rates of all immobilized animals decreased significantly and arterial blood pressure became undetectable in the animals in which it was measured., Conclusions and Clinical Relevance: Medetomidine administered in the thoracic limb of captive estuarine and Australian freshwater crocodiles, ranging from 3 to 12.8 kg, provides a predictable onset and duration of immobilization sufficient for physical examination, sample collection, short minor procedures and translocation of the animals. Atipamezole administered in the thoracic limb results in complete reversal of the effects of medetomidine in the estuarine crocodile and a rapid return to normal behaviour., (© 2012 The Authors. Veterinary Anaesthesia and Analgesia. © 2012 Association of Veterinary Anaesthetists and the American College of Veterinary Anesthesiologists.)