Effects of medetomidine-midazolam, midazolambutorphanol, or acepromazine-butorphanol as premedicants for mask induction of anesthesia with sevoflurane in dogs.
OBJECTIVE
To characterize the effects of medetomidine-midazolam, midazolam-butorphanol, or acepromazine-butorphanol as premedicants for mask induction of anesthesia with sevoflurane in dogs.


METHODS
10 healthy Beagles.


METHODS
The following premedicants were administered intramuscularly: medetomidine-midazolam (20 microg/kg and 0.3 mg/kg, respectively), midazolam-butorphanol (0.1 and 0.2 mg/kg, respectively), and acepromazine-butorphanol (0.05 and 0.2 mg/kg, respectively). Saline (0.9% NaCI) 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 midazolam-butorphanol 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.


CONCLUSIONS
In dogs use of premedicants provides a smoother and better quality mask induction with sevoflurane.
Laboratory of Veterinary Surgery, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Japan.
Tatsushi
T
Mutoh
Ryohei
R
Nishimura
Nobuo
N
Sasaki
D000701:Analgesics, Opioid / Q000494:pharmacology; D018685:Anesthetics, Inhalation / Q000494:pharmacology*; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002077:Butorphanol / Q000494:pharmacology; D002302:Cardiac Output / Q000187:drug effects; D018592:Cross-Over Studies; D004285:Dogs / Q000378:metabolism*; D004359:Drug Therapy, Combination; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006993:Hypnotics and Sedatives / Q000494:pharmacology; D008297:Male; D008397:Masks / Q000662:veterinary; D020926:Medetomidine / Q000494:pharmacology; D008738:Methyl Ethers / Q000494:pharmacology*; D008874:Midazolam / Q000494:pharmacology; D011229:Preanesthetic Medication / Q000379:methods / Q000662:veterinary*; D012119:Respiration / Q000187:drug effects; D000077149:Sevoflurane
D000701:Analgesics, Opioid; D018685:Anesthetics, Inhalation; D006993:Hypnotics and Sedatives; D008738:Methyl Ethers; D000077149:Sevoflurane; D020926:Medetomidine; D002077:Butorphanol; D008874:Midazolam