The consequences of premedication with buprenorphine, butorphanol ortramadol on anaesthesia safety induced with IV alphaxalone

Anaestheticsand analgesics have to be co-administered in order to allow for potentially painful interventions to be carried out. However, such
co-administration may exercerbate side effects. There are no published data on cardiorespiratory effects of analgesics in combination with anaesthetics in marmosets (Callithrix jacchus). We investigated clinical and physiological effectsof intravenous alphaxalone in combination with analgesic premedication with buprenorphine, butorphanol or tramadol.
Material and methods Aprospective, blinded, crossover study in nine marmosets was designed (four male, five female, mean body weight 391g, mean age 3.70 years) and Ethics approval by the Animal Experiments Committee (DEC) of the Biomedical Primate Research Centre (BPRC, Rijswijk, The Netherlands) was obtained prior to the commencement ofthe study. All marmosets originated from and were housed at the BPRC. The marmosetswere socially housed indoors with a same-sex buddy.One hour priorto anaesthetic induction with intravenous alphaxalone (16mg kg-1), the marmosets were premedicated with subcutaneous meloxicam, intramuscular atropine and one of the following intramuscular
analgesics: buprenorphine (20 ug kg-1). butorphanol (0.20 mg kg -1) or tramadol (1.5 mg kg -1). During anaesthesia, the following physiological
parameters were recorded every 5 minutes: respiratory frequency, pulse rate, rectal temperature, haemoglobin oxygen saturation, and arterial blood pressure. Judged were palpebral reflex, withdrawal reflex and muscle tone. Qualitative scores for induction and recoverywere allocated and adverse events recorded. Duration of induction, immobilisation and recovery were recorded. Results Weobserved of an unexpectedly high incidence ofapnoea inthe buprenorphine group (8out of9 marmosets). Oneapnoea even lasted for 63 minutes. Significantly lessadverse effects were observedinthe butorphanol group(2out of9 animals). No suchadverse effectswere observed inthe tramadol group. Similarly, intravenous alphaxalone without intramuscularanalgesicsshowed no cardiorespiratoryabnormalities. Therewere no significant differenceswhen comparing the baselinephysiologic parameters (excluding the apnoeic animals) between the protocols. Discussion and conclusions Optimisation (refinement)
of anaesthetic protocols and appropriate analgesia means implementation of the 3R's. In view of the severe respiratory complications encoun tered, we advise caution when considering pre-anaesthetic use of buprenorphine at the dose used in this study in combination with intravenous alphaxalone in marmosets. The combination of tramadol followed by intravenous alphaxalone instead can be considered safe, reliableand applicable for general anaesthesia in marmosets. Testing for analgesic efficiencywas not part of this study.