Abstract
Objective—To characterize the effects of medetomidine- midazolam, midazolam-butorphanol, or acepromazine- butorphanol as premedicants for mask induction of anesthesia with sevoflurane in dogs.
Animals—10 healthy Beagles.
Procedure—The following premedicants were administered intramuscularly: medetomidine-midazolam (20 µg/kg and 0.3 mg/kg, respectively), midazolambutorphanol (0.1 and 0.2 mg/kg, respectively), and acepromazine-butorphanol (0.05 and 0.2 mg/kg, respectively). Saline (0.9% NaCl) solution (0.1 ml/kg) was administered intramuscularly as a control. Anesthesia was induced in each dog with sevoflurane in a 100% O2 at a flow rate of 4 L/min developed by a facemask. Vaporizer settings were increased by 0.8% at 15-second intervals until the value corresponding to 4.8% sevoflurane was achieved. Time to onset and cessation of involuntary movements, loss of the palpebral reflex, negative response to tail-clamp stimulation, and endotracheal intubation were recorded, and the cardiopulmonary variables were measured.
Results—Mask induction with sevoflurane in dogs that received each premedicant resulted in a shorter induction time and milder changes in heart rate, mean arterial blood pressure, cardiac output, and respiratory rate, compared with mask induction without premedicants. Treatment with medetomidine-midazolam resulted in a shorter and smoother induction, compared with acepromazine-butorphanol or midazolambutorphanol treatment, whereas the cardiovascular changes were greater. Cardiopulmonary variables of dogs during induction following treatment with acepromazine- butorphanol or midazolam-butorphanol were maintained close to the anesthetic maintenance values for sevoflurane, with the exception of mild hypotension that was observed in dogs following acepromazine-butorphanol treatment.
Conclusion and Clinical Relevance—In dogs use of premedicants provides a smoother and better quality mask induction with sevoflurane. (Am J Vet Res 2002;63:1022–1028)
