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

Abstract

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 °C (T0) to 37.4 °C (T30), 37.1 °C (T40), 36.9 °C (T50) and 36.6 °C (T60), in MF group from 38.3 °C (T0) to 37.7 °C (T30), 37.5 °C (T40), 37.2 °C (T50) and 37.1 °C (T60) and in AF group from 37.7 °C (T0) to 37.3 °C (T40), 37.2 °C (T50) and 37.1 °C (T60). The T-Rec significantly decreased in F group from 38.0 °C (T0) to 37.4 °C (T40), 37.2 °C (T50) and 36.9 °C (T60), in MF group from 38.3 °C (T0) to 37.5 °C (T50) and 37.4 °C (T60) and in AF group from 38.2 °C (T0) to 37.6 °C (T40), 37.5 °C (T50) and 37.4 °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.