Medetomidine/midazolam/ketamine anaesthesia in ferrets: effects on cardiorespiratory parameters and evaluation of plasma drug concentrations

Objective To evaluate the cardiorespiratory effects and plasma concentrations of medetomidine-midazolam-ketamine (MMK) combinations administered by intramuscular (IM) or subcutaneous (SC) injection in sable ferrets (Mustela putorius furo). Study design Prospective randomized experimental study. Animals Eighteen adult ferrets: weight median 1.19 (range 0.81-1.60) kg. Methods Animals were allocated to one of three groups: group IM07 received 20 mu g kg(-1) medetomidine, 0.5 mg kg(-1) midazolam and 7 mg kg(-1) ketamine IM; group IM10 20 mu g kg(-1) medetomidine, 0.5 mg kg(-1) midazolam and 10 mg kg(-1) ketamine IM; and group SC10 20 mu g kg(-1) medetomidine, 0.5 mg kg(-1) midazolam and 10 mg kg(-1) ketamine SC. Following instrumentation, cardiorespiratory parameters and plasma drug concentrations were measured every 5 minutes (T5-T30) for 30 minutes Ferrets were then euthanased. Data were analysed using ANOVA for repeated measures. p < 0.05 was considered significant. Results Results are mean +/- SD. Induction of anaesthesia (minutes) in IM07 and IM10 [2 (1)] was significantly faster than in SC10 [5 (2)]. All groups demonstrated the following: results given as groups IM07, IM10 and SC10 respectively. Mean arterial blood pressures (mmHg) were initially high [186 (13); 174 (33) and 174 (9) at T5] but decreased steadily. Pulse rates were initially 202 (20), 213 (17) and 207 (33) beats minute(-1), decreasing with time. PaO2 (mmHg) was low [54.0 (8), 47.7 (10) and 38.5 (1)] at T5, although in groups IM07 and IM10 it increased over time. Plasma concentrations of all drugs were highest at T5 (36, 794 and 8264 nmol L-1 for medetomidine, midazolam and ketamine, respectively) and decreased thereafter: for both midazolam and ketamine, concentrations in IM07 and IM10 were higher than SC10. Conclusions and clinical relevance MMK combinations containing either 7 or 10 mg kg(-1) ketamine and given IM are suitable combinations for anaesthetising ferrets, although the observed degree of hypoxaemia indicates that oxygen administration is vital.