Influence of fentanyl, medetomidine-fentanyl or acepromazine-fentanyl premedication on oesophageal and rectal temperature in dogs under anaesthesia

Objective To compare changes in oesophageal (T-Oeso) and rectal (T-Rec) temperature in dogs during general anaesthesia and premedicated with fentanyl, medetomidine-fentanyl or acepromazine-fentanyl. Study design Prospective, randomized, blind clinical study. Animals A total of 120 healthy dogs, aged 2-10 years and weighing 5-20 kg. Methods Dogs were randomly allocated to one of three groups. Animals of F group were premedicated with fentanyl (0.01 mg kg(-1)), MF group with medetomidine (0.005 mg kg(-1)) and fentanyl (0.01 mg kg(-1)) and AF group with acepromazine (0.01 mg kg(-1)) and fentanyl (0.01 mg kg(-1)). Anaesthesia was induced with propofol and maintained with isoflurane in oxygen-air mixture. Fentanyl was administered continuously (0.01 mg kg(-1) hour(-1)). The T-Oeso, T-Rec and ambient temperatures were recorded after induction (T0) and subsequently at 10 minute intervals for 60 minutes (T10-T60). Data were analysed using anova or their non-parametric equivalents (p < 0.05). Results Median T-Oeso was significantly higher in MF group between T0-T20 compared with other groups. Median T-Oeso significantly decreased in F group from 38.0 degrees C (T0) to 37.4 degrees C (T30), 37.1 degrees C (T40), 36.9 degrees C (T50) and 36.6 degrees C (T60), in MF group from 38.3 degrees C (T0) to 37.7 degrees C (T30), 37.5 degrees C (T40), 37.2 degrees C (T50) and 37.1 degrees C (T60) and in AF group from 37.7 degrees C (T0) to 37.3 degrees C (T40), 37.2 degrees C (T50) and 37.1 degrees C (T60). The T-Rec significantly decreased in F group from 38.0 degrees C (T0) to 37.4 degrees C (T40), 37.2 degrees C (T50) and 36.9 degrees C (T60), in MF group from 38.3 degrees C (T0) to 37.5 degrees C (T50) and 37.4 degrees C (T60) and in AF group from 38.2 degrees C (T0) to 37.6 degrees C (T40), 37.5 degrees C (T50) and 37.4 degrees C (T60). Conclusions and clinical relevance Premedication with fentanyl, medetomidine-fentanyl or acepromazine-fentanyl in the doses used decreased the T-Oeso and T-Rec. The T-Oeso at the beginning of anaesthesia was higher after premedication with medetomidine-fentanyl. However, this difference was not clinically significant.