Alterations in the arrhythmogenic dose of ...
|Title||Alterations in the arrhythmogenic dose of epinephrine after xylazine or medetomidine administration in isoflurane-anesthetized dogs|
|Author(s)||K. Lemke, W. Tranquilli, J. Thurmon, G. Benson, W. Olson|
|Journal||American Journal of Veterinary Research|
|Abstract||In a series of trials at least 3 days apart, 8 dogs (body weight, 12.5 to 21.5 kg) were assigned at random to each of 3 treatment groups not given glycopyrrolate (isoflurane-saline, IS; isoflurane-xylazine, IX; isoflurane-medetomidine, IM) that were not given glycopyrrolate and to each of 3 groups that were given glycopyrrolate (IGS, IGX, IGM). Dogs were anaesthetized with isoflurane (1.95% end-tidal concentration), and ventilation was controlled (PCO2, 35 to 40 mm of Hg end-tidal concentration). Glycopyrrolate was administered i.v. and i.m. at a dosage of 11 micro g/kg of body weight, each. Saline solution, xylazine (1.1 mg/kg, i.m.), or medetomidine (15 micro g/kg, i.m.) was administered 10 min after baseline ADE determination. Redetermination of the ADE at the same infusion rate was started 10 min after drug administration. Arrhythmogenic dose was determined by constant infusion of epinephrine at rates of 1.0, 2.5, and 5.0 micro g/kg min-1. The ADE was defined as the total dose of epinephrine that induced at least 4 ectopic ventricular depolarizations within 15 sec during a 3-min infusion, or within 1 min after the end of the infusion. Total dose was calculated as the product of infusion rate and time to arrhythmia. One-way ANOVA showed that differences in baseline and treatment ADE values among groups IS, IX, and IM were not significant. Differences for groups IGS, IGX and IGM could not be calculated because arrhythmias satisfying the ADE criteria were not observed at the maximum infusion rate of 5.0 micro g/kg min-1. It was concluded that in isoflurane-anaesthetized dogs, preanaesthetic dosages of xylazine or medetomidine do not enhance arrhythmogenicity, and that at the dosages given, there is no differences in the arrhythmogenic potential of either alpha 2adrenergic receptor agonist..|
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