Peri-operative body temperatures in isoflurane-anaesthetized rabbits following ketamine–midazolam or ketamine–medetomidine


Nicola J Grint, Division of Veterinary Anaesthesia, University of Liverpool, Leahurst, Neston, Wirral CH64 7TE, UK. E-mail:


Objective  To investigate alterations in peri-operative body temperatures and oesophageal-skin temperatures in isoflurane-anaesthetized rabbits following either ketamine–midazolam or ketamine–medetomidine induction of anaesthesia.

Animal population  Fifty client-owned rabbits, (25 male, 25 female) of different breeds anaesthetized for elective neutering (age range: 3–42 months; mass range: 1.15–4.3 kg).

Study design  Randomized, blinded clinical study.

Methods  Pre-anaesthetic rectal temperature was measured. A 24 SWG catheter was placed in a marginal ear vein after local anaesthesia. Ketamine (15 mg kg−1) with medetomidine (0.25 mg kg−1) (group KMT) or with midazolam (3 mg kg−1) (group KMZ) was injected intramuscularly (IM). Following endotracheal intubation anaesthesia was maintained with isoflurane in oxygen. Carprofen (3 mg kg−1) and glucose saline (5 mL kg−1 hour−1) were administered through the intravenous catheter. Room temperature and humidity, skin temperature (from tip of pinna) and oesophageal temperature were measured during anaesthesia. Ovariohysterectomy or castration was performed. Rectal temperature was taken when isoflurane was discontinued (time zero) and 30, 60 and 120 minutes thereafter. Atipamezole (0.5 mg kg−1) was administered IM to rabbits in group KMT at zero plus 30 minutes. Mass, averaged room temperature and duration of anaesthesia data were compared using a two-tailed t-test. Age, averaged room humidity, rectal temperature decrease, oesophageal temperature decrease and oesophageal–skin difference data were compared using a Kruskal–Wallis test. p < 0.05 was considered significant.

Results  The averaged oesophageal–skin temperature difference was significantly greater in group KMT [median 9.85 °C (range 6.42–13.85 °C)] than in group KMZ [4.38 °C (2.83–10.43 °C)]. Rectal temperature decreased over the anaesthetic period was not significantly different between the two groups; however, oesophageal temperature decrease was significantly less in group KMT [1.1 °C (−0.1–+2.7 °C)] than in group KMZ [1.4 °C (0.6–3.1 °C)].

Conclusions  Oesophageal–skin temperature difference is larger in rabbits anaesthetized with ketamine–medetomidine combination than ketamine–midazolam.

Clinical relevance  The oesophageal temperature in rabbits anaesthetized with ketamine–medetomidine and isoflurane decreases significantly less than in animals anaesthetized with ketamine–midazolam and isoflurane, during anaesthesia.