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The Journal of veterinary medical science2000; 62(10); 1025-1032; doi: 10.1292/jvms.62.1025

Cardiovascular effects of medetomidine, detomidine and xylazine in horses.

Abstract: The cardiovascular effects of medetomidine, detomidine, and xylazine in horses were studied. Fifteen horses, whose right carotid arteries had previously been surgically raised to a subcutaneous position during general anesthesia were used. Five horses each were given the following 8 treatments: an intravenous injection of 4 doses of medetomidine (3, 5, 7.5, and 10 microg/kg), 3 doses of detomidine (10, 20, and 40 microg/kg), and one dose of xylazine (1 mg/kg). Heart rate decreased, but not statistically significant. Atrio-ventricular block was observed following all treatments and prolonged with detomidine. Cardiac index (CI) and stroke volume (SV) were decreased with all treatments. The CI decreased to about 50% of baseline values for 5 min after 7.5 and 10 microg/kg medetomidine and 1 mg/kg xylazine, for 20 min after 20 microg/kg detomidine, and for 50 min after 40 microg/kg detomidine. All treatments produced an initial hypertension within 2 min of drug administration followed by a significant decrease in arterial blood pressure (ABP) in horses administered 3 to 7.5 microg/kg medetomidine and 1 mg/kg xylazine. Hypertension was significantly prolonged in 20 and 40 microg/kg detomidine. The hypotensive phase was not observed in 10 microg/kg medetomidine or detomidine. The changes in ABP were associated with an increase in peripheral vascular resistance. Respiratory rate was decreased for 40 to 120 min in 5, 7.5, and 10 microg/kg medetomidine and detomidine. The partial pressure of arterial oxygen decreased significantly in 10 microg/kg medetomidine and detomidine, while the partial pressure of arterial carbon dioxide did not change significantly. Medetomidine induced dose-dependent cardiovascular depression similar to detomidine. The cardiovascular effects of medetomidine and xylazine were not as prolonged as that of detomidine.
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Publication Date: 2000-11-10 PubMed ID: 11073071DOI: 10.1292/jvms.62.1025Google Scholar: Lookup
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  • Comparative Study
  • Journal Article

Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

This research study investigates the cardiovascular effects of three sedative drugs—medetomidine, detomidine, and xylazine—on horses. The effects observed include an initial increase in blood pressure, followed by a significant decrease, along with a reduced heart and respiratory rate.

Study Procedures and Trial Drugs

  • The researchers conducted their study on fifteen horses whose right carotid arteries had been surgically altered for proper monitoring during general anesthesia.
  • Each of these horses was administered eight different treatments. These included four doses of medetomidine, three doses of detomidine, and a single dose of xylazine, each injected intravenously.

Observations and Findings

  • All the administered treatments led to a decrease in the heart rate of the horses, although this change was not statistically significant.
  • An Atrio-ventricular block, a delay or disruption in the electrical signals between the chambers of the heart, was observed in the horses following all treatments. This effect was prolonged when the drug administered was detomidine.
  • All treatments also caused decreases in the cardiac index and stroke volume, measures of heart functionality. The cardiac index decreased further after the administration of medetomidine and xylazine, and for multiple time intervals after detomidine was given.
  • In terms of blood pressure, all treatments induced an initial hypertension (spike in blood pressure) within two minutes of the drugs being administered. This was followed by a significant decrease in arterial blood pressure in the horses administered with medetomidine and xylazine. However, this hypertension phase prolonged significantly in horses administered higher doses of detomidine.
  • Correspondingly, an increase in peripheral vascular resistance was noted in relation to changes in blood pressure, suggesting that the treatments affected the blood flow resistance in the smaller and farther blood vessels.
  • The sedative drugs also reduced respiratory rates, and the duration of this effect varied with varying doses of medetomidine and detomidine.
  • The decrease in the partial pressure of arterial oxygen was observed to be significant in horses that received higher doses of medetomidine and detomidine. However, the partial pressure of arterial carbon dioxide remained largely unaffected.

Outcome and Conclusion

  • Overall, Medetomidine induced cardiovascular depression in a dose-dependent manner, showing similar effects to Detomidine. However, the cardiovascular effects of Medetomidine and Xylazine were not prolonged as much as Detomidine.
  • The study provides valuable insight into the cardiovascular effects of these three commonly used sedative drugs in horses, which is crucial for their safe and effective use in veterinary practice.

Cite This Article

APA
Yamashita K, Tsubakishita S, Futaok S, Ueda I, Hamaguchi H, Seno T, Katoh S, Izumisawa Y, Kotani T, Muir WW. (2000). Cardiovascular effects of medetomidine, detomidine and xylazine in horses. J Vet Med Sci, 62(10), 1025-1032. https://doi.org/10.1292/jvms.62.1025

Publication

The Journal of veterinary medical science
ISSN: 0916-7250
NlmUniqueID: 9105360
Country: Japan
Language: English
Volume: 62
Issue: 10
Pages: 1025-1032

Researcher Affiliations

Yamashita, K
  • Department of Veterinary Surgery I, School of Veterinary Medicine, Rakuno Gakuen University, Ebetsu, Hokkaido, Japan.
Tsubakishita, S
    Futaok, S
      Ueda, I
        Hamaguchi, H
          Seno, T
            Katoh, S
              Izumisawa, Y
                Kotani, T
                  Muir, W W

                    MeSH Terms

                    • Adrenergic alpha-Agonists / administration & dosage
                    • Adrenergic alpha-Agonists / pharmacology
                    • Analgesics / administration & dosage
                    • Analgesics / pharmacology
                    • Animals
                    • Blood Gas Analysis / veterinary
                    • Blood Pressure / drug effects
                    • Cardiovascular System / drug effects
                    • Dose-Response Relationship, Drug
                    • Heart Rate / drug effects
                    • Horses / physiology
                    • Imidazoles / administration & dosage
                    • Imidazoles / pharmacology
                    • Injections, Intravenous / veterinary
                    • Medetomidine / administration & dosage
                    • Medetomidine / pharmacology
                    • Receptors, Adrenergic, alpha / metabolism
                    • Respiration / drug effects
                    • Xylazine / administration & dosage
                    • Xylazine / pharmacology

                    Citations

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