Effects of a medetomidine-midazolam-butorphanol combination on renal cortical, intestinal and muscle microvascular blood flow in isoflurane anaesthetized dogs: A laser Doppler study

Objective To obtain renal cortical, ileal, colonic and skeletal muscle microvascular blood flow measurements in dogs using the laser Doppler technique and to characterize the effects of medetomidine-midazolam-butorphanol combination on these flows. Study Design Prospective randomized experimental study. Animals Fourteen clinically normal beagles (two groups of seven), aged 1–4 years and weighing 13.2±1.8kg. Methods All dogs were anaesthetized with 1.7% end-tidal isoflurane in oxygen. In the treatment group, after instrumentation and when anaesthesia was considered stable, medetomidine (1mg m⁻² body surface area (BSA)) was administered intramuscularly (time 0). Midazolam (1mg kg⁻¹) and butorphanol (0.1mg kg⁻¹) were administered intravenously 20 minutes later. Atipamezole (2.5mg m⁻² BSA) was administered intramuscularly 60 minutes after medetomidine. In the control group, saline (0.5, 2.5 and 0.25mL) was administered at the corresponding times. Heart rate, systolic, diastolic and mean arterial pressures, body temperature, renal cortical, ileal, colonic and skeletal muscle microvascular blood flows were measured before time 0, and 5, 15, 25, 40, 60, 65, 70 and 90 minutes thereafter. Results Heart rate, ileal and skeletal muscle blood flows decreased in the treatment group, while no changes were observed in the control group. Conclusions Laser Doppler flowmetry allowed the measurement of microvascular blood flow in different organs. The medetomidine-midazolam-butorphanol combination decreases intestinal and skeletal muscle microvascular blood flows, while renal cortical blood flow is maintained. Clinical relevance Medetomidine-midazolam-butorphanol combination can be used to induce a short duration anaesthesia in dogs, but it will induce cardiovascular depression. This depression appears to be accompanied by a redistribution of blood flow.