Cardiovascular and respiratory effects of acetylpromazine and xylazine on halothane-anesthetized horses.
Abstract: Circulatory and respiratory effects of intravenously administered acetylpromazine (0.033 and 0.067 mg/kg) and xylazine (0.5 and 1.0 mg/kg) were studied in drug cross-over fashion in eight laterally recumbent horses anesthetized only with halothane (1.06%, end-tidal) in O2. Both doses of acetylpromazine caused a significant and sustained elevation in cardiac output via a rise in stroke volume. Xylazine produced an initial significant fall in cardiac output followed by a return to control levels. Halothane anesthesia did not prevent xylazine-related atrioventricular conduction block. All treatments caused a similar significant fall in arterial blood pressure (acetylpromazine, total peripheral resistance-related; xylazine, cardiac output-related). PaCO2 significantly increased after all treatments. PaCO2 decreased significantly only following xylazine treatment. One horse (not included in the tabulation) developed ventricular fibrillation and died 15 min after receiving its first injection (0.5 mg/kg) of xylazine.
Publication Date: 1985-09-01 PubMed ID: 3932674DOI: 10.1111/j.1365-2885.1985.tb00959.xGoogle Scholar: Lookup
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- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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The research explores the impact of two drugs, acetylpromazine and xylazine, on horses anesthetized with halothane. It was found that both drugs lead to significant changes in cardiac output and arterial blood pressure, with one horse experiencing fatal ventricular fibrillation following an injection of xylazine.
Research Context and Methodology
- The study investigated the cardiovascular and respiratory effects of acetylpromazine and xylazine on eight horses anesthetized with halothane.
- The drugs were administered intravenously in different doses to the laterally recumbent (lying on their side) horses.
- The crossover design of the study meant that the same horses were used to observe the effects of both drugs, reducing the potential for variations in individual responses.
Effects of Acetylpromazine
- The administration of acetylpromazine led to a significant and sustained increase in cardiac output, largely due to an increase in stroke volume, which is the amount of blood pumped by the left ventricle of the heart in one contraction.
- The decline in arterial blood pressure after treatment with acetylpromazine was found to be related to a decrease in total peripheral resistance, which refers to the resistance to blood flow in the circulatory system.
Effects of Xylazine
- Xylazine administration resulted in an initial significant decrease in cardiac output, which then normalized to control levels.
- Contrary to acetylpromazine, the drop in arterial blood pressure after xylazine administration was linked to a decrease in cardiac output.
- Atrioventricular block, a type of heart block in which the conduction between the atria and ventricles of the heart is impaired, was observed in horses treated with halothane and xylazine.
- Increased levels of PaCO2, the partial pressure of carbon dioxide, were observed after both acetylpromazine and xylazine treatments, although a significant decrease was noted only after xylazine treatment.
Adverse Effects
- One horse in the study developed ventricular fibrillation and died 15 minutes after receiving a half milligram per kilogram dose of xylazine, highlighting a potential lethal risk associated with the drug.
Conclusion
- The study concludes that both acetylpromazine and xylazine cause significant changes in cardiac output and arterial blood pressure in halothane-anesthetized horses.
Cite This Article
APA
Steffey EP, Kelly AB, Farver TB, Woliner MJ.
(1985).
Cardiovascular and respiratory effects of acetylpromazine and xylazine on halothane-anesthetized horses.
J Vet Pharmacol Ther, 8(3), 290-302.
https://doi.org/10.1111/j.1365-2885.1985.tb00959.x Publication
Researcher Affiliations
MeSH Terms
- Acepromazine / pharmacology
- Anesthesia, General / veterinary
- Animals
- Blood Pressure / drug effects
- Carbon Dioxide / metabolism
- Cardiac Output / drug effects
- Halothane
- Heart Rate / drug effects
- Hemodynamics / drug effects
- Horses / physiology
- Respiration / drug effects
- Thiazines / pharmacology
- Time Factors
- Vascular Resistance / drug effects
- Xylazine / pharmacology
Citations
This article has been cited 3 times.- Joo YS, Lee HJ, Choi JS, Sung KW. Acepromazine inhibits hERG potassium ion channels expressed in human embryonic kidney 293 cells. Korean J Physiol Pharmacol 2017 Jan;21(1):75-82.
- Brosnan RJ. Inhaled anesthetics in horses. Vet Clin North Am Equine Pract 2013 Apr;29(1):69-87.
- Shokrollahi S, Mohammadi R, Sarrafzadeh-Rezaei F, Jalilzadeh-Amin G, Hashemi-Asl SM. Clinical and echocardiographic evaluations of sedative and cardiovascular effects of combination of xylazine-acepromazine versus xylazine-pregabalin in horses. Vet Res Forum 2024;15(6):291-296.
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