Hemodynamic effects of atropine and glycopyrrolate ...
|Title||Hemodynamic effects of atropine and glycopyrrolate in isoflurane-xylazine-anesthetized dogs|
|Author(s)||K. Lemke, W. Tranquilli, J. Thurmon, G. Benson, W. Olson|
|Abstract||The purpose of this study was to evaluate and compare the haemodynamic changes caused by the administration of i.v. atropine or glycopyrrolate after i.v. xylazine in isoflurane-anaesthetized dogs. Six healthy Beagles (8.2 to 10.7 kg) were used in 2 trials separated by 7 days. Anaesthesia was induced and maintained with isoflurane in 100% oxygen with controlled ventilation. Once constant end-tidal isoflurane (1.8%) and arterial partial pressure of carbon dioxide (35 to 45 mm Hg) values were reached, baseline data were recorded and xylazine (0.5 mg/kg, i.v.) was given. In trial 1 atropine (0.1 mg/kg, i.v.) was given 5 min after xylazine, and in trial 2 glycopyrrolate (0.025, mg/kg, i.v.), was given 5 min after xylazine. Haemodynamic variables were recorded 3 min after xylazine and 3 min after anticholinergic administration. In trial 2, bilateral vagotomies were performed 10 min after glycopyrrolate, and haemodynamic variables were recorded 3 min later. Heart rate, cardiac index, and stroke index decreased; arterial pressure and systemic vascular resistance increased after xylazine. Heart rate, cardiac index, and rate pressure product increased after anticholinergic administration. Significant differences between atropine and glycopyrrolate were not observed in any of the haemodynamic parameters. Similarly, significant differences between glycopyrrolate and bilateral vagotomy were not observed. The authors conclude that i.v. atropine and glycopyrrolate have equivalent haemodynamic actions during the increased pressure phase after i.v. xylazine in isoflurane-anaesthetized dogs; that i.v. atropine and glycopyrrolate produce comparable increases in heart rate and that both may increase the risk of myocardial hypoxia associated with an increase in rate pressure product; and that vagal blockade produced by high-dose glycopyrrolate (0.025 mg/kg, i.v.) is similar to that produced by bilateral vagotomy..|
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