Cardiovascular assessment in horses sedated with xylazine or amitraz

R.L Linardi,C.A.A Valadão,J.C Canola

doi:10.1590/s0102-09352008000200008

R.L Linardi, C.A.A Valadão + Show 1 more

Open Access

https://doi.org/10.1590/s0102-09352008000200008

Copy DOI

Abstract

Cardiovascular effects due to intravenous (IV) xylazine (1.0mg/kg) or amitraz (0.1 or 0.4mg/kg) were evaluated in horses. Left ventricular function indexes, heart rate (HR), and cardiac output (CO) were measured by echocardiography. Second degree atrioventricular (AV) block was detected by electrocardiography. Invasive arterial blood pressure (AP) was also evaluated. All parameters were measured immediately before and during 60 minutes after drug injection. HR, CO, and second degree AV block were different between xylazine and amitraz-0.4mg/kg groups. Xylazine induced initial hypertension 10 minutes after injection, and hypotension was observed 30 minutes after amitraz-0.4mg/kg administration. Except for the second degree AV block which occurred only at five minutes, there was no change in the echocardiographic measurements after administration of amitraz-0.1mg/kg. Thus, amitraz-0.4mg/kg and xylazine (1.0mg/kg) induced similar cardiovascular side effects, but long-lasting action of amitraz-0.4mg/kg in the cardiovascular system was observed.

Highlights

Cardiac ultrasound named echocardiography was first used in veterinary medicine by Pippers and Hamlin (1977)
No information was found in the literature regarding the dose of amitraz for horses when it is diluted in lipid vehicle; the higher dose of amitraz (0.4mg/kg) was obtained by alommetry extrapolation (Pachaly and Brito, 2001) using the known dose 0.1mg/kg of amitraz in dogs reported by Farias (2004)
It was demonstrated that this vehicle did not compromise the cardiovascular system and it did guarantee the fidelity of the actions of amitraz when it was IV administered in dogs (Farias, 2004)

Summary

Introduction

Cardiac ultrasound named echocardiography was first used in veterinary medicine by Pippers and Hamlin (1977). Echocardiography is able to determine cardiovascular effects drugs-induced and to establish the compromised degree of cardiac function, allowing inferring about the efficacy, safety, and viability of drugs and their possible procedure risks (Raisis et al, 2000; 2005). Adrenergic receptor alpha-2 agonists are considered excellent sedatives usually used in association to potency other drugs (England and Clarke, 1996); they can cause light to severe cardiovascular changes and compromise the systemic hemodynamic (Bonagura and Muir, 1991; Canola et al, 2002; Pereira, 2002). An initial and transitory hypertension xylazine-induced is described in the literature followed by mild and prolonged hypotension and bradicardia reflex (negative cronotropism) which are usually followed by a second degree atrioventricular block and a decrease of 30 to 50% in CO (Bonagura and Muir, 1991; England and Clarke, 1996; QueirózNeto et al, 2000; Canola et al, 2002; Pereira, 2002; Farias, 2004).

Objectives

Methods

Results

Conclusion