Comparison of three different sedative-anaesthetic protocols (ketamine, ketamine-medetomidine and alphaxalone) in common marmosets (Callithrix jacchus)

BMC Veterinary Research Comparison of three different sedative- anaesthetic protocols (ketamine, ketamine- medetomidine and alphaxalone) in common marmosets (Callithrix jacchus) Jaco Bakker 0 Joost J Uilenreef 2 Eva RJ Pelt 2 Herbert PM Brok 0 Edmond J Remarque 1 Jan AM Langermans 0 0 Animal Science Department, Biomedical Primate Research Centre , Lange Kleiweg 161, 2288 GJ, Rijswijk , The Netherlands 1 Department of Parasitology, Biomedical Primate Research Centre , Lange Kleiweg 161, 2288 GJ, Rijswijk , The Netherlands 2 Department of Clinical Sciences of Companion Animals, Faculty of Veterinary Medicine, University of Utrecht , Yalelaan 106, 3584 CM, Utrecht , The Netherlands Background: Handling of common marmoset (Callithrix jacchus) usually requires chemical restraint. Ketamine has been associated with muscle damage in primates, while common marmosets, compared to other primates, additionally display an exceptional high sensitivity to ketamine-associated side-effects. Notably, muscle twitching movements of limbs and hands, and a marked increase in salivation are observed. We investigated two alternative intramuscular (i.m.) immobilisation protocols against ketamine (50 mg/kg; protocol 1) in a double-blind randomised crossover study in ten healthy adult common marmosets for use as a safe reliable, short-term immobilisation and sedation. These protocols comprised: alphaxalone (12 mg/kg; protocol 2) and 25 mg/kg ketamine combined with 0.50 mg/kg medetomidine (reversal with 2.5 mg/kg atipamezole; protocol 3A). Following completion and unblinding, the project was extended with an additional protocol (3B), comprising 25 mg/kg ketamine combined with 0.05 mg/kg medetomidine (reversal with 0.25 mg/kg atipamezole, twice with 35 min interval). Results: All protocols in this study provided rapid onset (induction times <5 min) of immobilisation and sedation. Duration of immobilisation was 31.23 22.39 min, 53.72 13.08 min, 19.73 5.74 min, and 22.78 22.37 min for protocol 1, 2, 3A, and 3B, respectively. Recovery times were 135.84 39.19 min, 55.79 11.02 min, 405.46 29.81 min, and 291.91 80.34 min, respectively. Regarding the quality, and reliability (judged by pedal withdrawal reflex, palpebral reflex and muscle tension) of all protocols, protocol 2 was the most optimal. Monitored vital parameters were within clinically acceptable limits during all protocols and there were no fatalities. Indication of muscle damage as assessed by AST, LDH and CK values was most prominent elevated in protocol 1, 3A, and 3B. Conclusions: We conclude that intramuscular administration of 12 mg/kg alphaxalone to common marmosets is preferred over other protocols studied. Protocol 2 resulted in at least comparable immobilisation quality with acceptable and less frequent side effects and superior recovery quality. In all protocols, supportive therapy, such as external heat support, remains mandatory. Notably, an unacceptable long recovery period in both ketamine/ medetomidine protocols (subsequently reversed with atipamezole) was observed, showing that -2 adrenoreceptor agonists in the used dose and dosing regime is not the first choice for sedation in common marmosets in a standard research setting. Alphaxalone; Atipamezole; Common marmoset; Immobilisation; Induction; Ketamine; Medetomidine; Recovery; Sedation - Background The common marmoset (Callithrix jacchus) is frequently used in biomedical research [1,2]. Although certain procedures can sometimes be performed without sedation, more complex procedures require immobilisation. However, limited information is available in the literature on marmoset chemical restraints [3]. The use of inhalation techniques is impractical when dealing with large numbers of animals simultaneously in environments without an operating theatre. Therefore, ketamine is commonly used for immobilisation, either alone or combined with other sedatives and/or analgesics [3-5]. The main disadvantages of ketamine are poor muscle relaxation, grasping movements of limbs and hands, and a marked increase in salivation [4,6]. In addition, ketamine has been associated with muscle damage in primates [7-9]. Alternatively, sedation with alphaxalone-alphadolone (SaffanW, AlthesinW) was recommended for marmosets [3,5,10]. Despite the relatively large injection volume, no muscle damage was observed [5]. Alphaxalonealphadolone was solubilised with CremophorW-EL, which resulted in adverse effects in dogs, cats, and humans [11,12] and consequently it was withdrawn from the market. Recently, a new formulation of alphaxalone without alphadalone and solubilised with the aid of cyclodextrin rather than CremophorW-EL became available (AlfaxanW). This is a short-acting, injectable anaesthetic agent for the induction and maintenance of general anaesthesia in dogs and cats [13-15]. Its clinical off-label administration has been described in several species, including ponies, pigs, and goats [16-22]. A short-term anaesthesia regimen frequently used in dogs and cats is ketamine combined with medetomidine [23,24]. Concurrent use of medetomidine reduces the amount of ketamine required, induces additional analgesia as well as curtailing increased muscle tone and salivation. An important advantage is the quick recovery to normal function following reversal of medetomidine with the specific antagonist atipamezole in dogs and cats [23-26]. In addition, the combination ketamine/ medetomidine caused markedly less damage to muscle tissue at injection sites than did the single use of ketamine in rats [27]. The use of ketamine/medetomidine has been described in several primate species [27-35], but these reports offer little guidance related to its practical implementation in the common marmoset. Due to the lack of knowledge on safe, reliable and shortterm sedation protocols in the common marmoset, we designed a crossover study to assess and compare the effects of ketamine, ketamine-medetomidine (reversed with atipamezole) and alphaxalone administered i.m. for allowing the undertaking of minor invasive procedures such as blood collection from the femoral vein, tuberculin testing, routine veterinary interventions such as minor surgical procedures or wound care, radiography, and ultrasonography. Methods Animals, housing, and care Ten (5 male and 5 female) healthy adult common marmosets (Callithrix jacchus), age 3.2 1.4 years and mean bodyweight of 364 27 g all originated from the Biomedical Primate Research Centre (BPRC, Rijswijk, The Netherlands). All monkeys received a complete physical, haematological, and biochemical examination before the study started. Only animals with all values within the normal range were included. They remained under intensive veterinary supervision during the entire study period. Animals were housed with a same-sex buddy in spacious cages (150 75 185 cm) enriched with branches and toys, in compliance with the new EU directive 63/2010. The animals were fed commercial m (...truncated)