Effects of xylazine on ventilation in horses.
Abstract: The effects of 3 commonly used dosages (0.3, 0.5, and 1.1 mg/kg of body weight, IV) of xylazine on ventilatory function were evaluated in 6 Thoroughbred geldings. Altered respiratory patterns developed with all doses of xylazine, and horses had apneic periods lasting 7 to 70 seconds at the 1.1 mg/kg dosage. Respiratory rate, minute volume, and partial pressure of oxygen in arterial blood (PaO2) decreased significantly (P less than 0.001) with time after administration of xylazine, but significant differences were not detected among dosages. After an initial insignificant decrease at 1 minute after injection, tidal volume progressively increased and at 5 minutes after injection, tidal volume was significantly (P less than 0.01) greater than values obtained before injection. Partial pressure of carbon dioxide in arterial blood (PaCO2) was insignificantly increased. After administration of xylazine at a dosage of 1.1 mg/kg, the mean maximal decrease in PaO2 was 28.2 +/- 8.7 mm of Hg and 22.2 +/- 4.9 mm of Hg, measured with and without a respiratory mask, respectively. Similarly, the mean maximal increase in PaCO2 was 4.5 +/- 2.3 mm of Hg and 4.2 +/- 2.4 mm of Hg, measured with and without the respiratory mask, respectively. Significant interaction between use of mask and time was not detected, although the changes in PaO2 were slightly attenuated when horses were not masked. The temporal effects of xylazine on ventilatory function in horses should be considered in selecting a sedative when ventilation is inadequate or when pulmonary function testing is to be performed.
Publication Date: 1992-06-01 PubMed ID: 1626781
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- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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The study evaluates the impacts of different dosages of a drug named xylazine on the breathing function of Thoroughbred gelding horses. It discovered that all dosages caused changes to respiratory patterns, and also influenced other metrics like respiratory rate and oxygen levels, which dropped after the administration of the drug.
Investigation of Xylazine Effects on Horse Respiration
This research study examined the effects of xylazine, a commonly used drug, on the ventilation or breathing patterns in Thoroughbred gelding horses. The study was designed with three different doses of xylazine (0.3, 0.5, and 1.1 mg/kg of body weight, given intravenously) to determine how these amounts impact ventilatory function.
- Altered respiratory patterns were observed in horses with all doses of xylazine, including instances of apnea (periods where breathing stops temporarily) when the highest dose was administered.
- The study also found that the respiratory rate, as well as the level of oxygen present in arterial blood (PaO2), significantly decreased over time after xylazine was given.
- Interestingly, tidal volume—a measure of the air volume displaced during inhalation and exhalation—initially decreased but then showed a trend of progressive increase from 1 minute onwards after injection.
Analysis of Arterial Blood and Mask Use
Partial pressure of carbon dioxide present in arterial blood (PaCO2) reportedly increased, though not to a statistically significant degree.
- Utilising the highest dose of xylazine led to an average decrease in PaO2 of 28.2 +/- 8.7 mm of Hg with a mask and 22.2 +/- 4.9 mm of Hg without a mask. The slight difference in results between masked and unmasked situations may suggest that mask use could modulate the effects of xylazine on horse ventilatory function.
- Indeed, similar results were noticed with respect to the pressure of carbon dioxide (PaCO2), where a mean maximum increase was detected that was again higher with mask use.
- However, any interaction between mask use and time did not reach a level of statistical significance.
Implications for Veterinary Practice
The paper indicates that the chronotropic effects of xylazine on horses’ breathing function need to be carefully evaluated, particularly for horses with inadequate ventilation or in cases where pulmonary function testing is to be performed. The findings suggest that selection of a sedative should take into consideration the impact on the horse’s breathing patterns and overall respiratory function.
Cite This Article
APA
Lavoie JP, Pascoe JR, Kurpershoek CJ.
(1992).
Effects of xylazine on ventilation in horses.
Am J Vet Res, 53(6), 916-920.
Publication
Researcher Affiliations
- Department of Surgery, School of Veterinary Medicine, University of California, Davis 95616.
MeSH Terms
- Animals
- Carbon Dioxide / blood
- Dose-Response Relationship, Drug
- Heart Rate / drug effects
- Horses / physiology
- Male
- Oxygen / blood
- Respiration / drug effects
- Tidal Volume / drug effects
- Xylazine / pharmacology
Citations
This article has been cited 3 times.- Dixon CE, Bedenice D, Mazan MR. Comparison of Flowmetric Plethysmography and Forced Oscillatory Mechanics to Measure Airway Hyperresponsiveness in Horses.. Front Vet Sci 2020;7:511023.
- Dupras J, Vachon P, Cuvelliez S, Blais D. [Anesthesia of the New Zealand rabbit using the the combination of tiletamine-zolazepam and ketamine-midazolam with or without xylazine].. Can Vet J 2001 Jun;42(6):455-60.
- Singh S, Young SS, McDonell WN, O'Grady M. Modification of cardiopulmonary and intestinal motility effects of xylazine with glycopyrrolate in horses.. Can J Vet Res 1997 Apr;61(2):99-107.
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