Comparison of the effects of xylazine bolus versus medetomidine constant rate infusion on cardiopulmonary function and depth of anesthesia in horses anesthetized with isoflurane.
Abstract: To compare the effects of xylazine bolus versus medetomidine constant rate infusion (MCRI) on cardiopulmonary function and depth of anesthesia in dorsally recumbent, spontaneously breathing, isoflurane-anesthetized horses. Methods: Prospective, randomized crossover study. Methods: 10 healthy adult Standardbreds. Methods: Horses were premedicated with xylazine or medetomidine IV. Anesthesia was induced with diazepam and ketamine and maintained with isoflurane for 150 minutes. For the xylazine treatment, end-tidal isoflurane concentration was maintained at 1.7%, and xylazine (0.2 mg/kg [0.09 mg/lb], IV) was administered as a bolus at the end of anesthesia. For the MCRI treatment, end-tidal isoflurane concentration was maintained at 1.4%, and medetomidine (0.005 mg/kg/h [0.0023 mg/lb/h], IV) was infused throughout anesthesia. Physiologic data (ie, heart rate, respiratory rate, rectal temperature, bispectral index, and electromyographic values) were compared between treatments with xylazine bolus versus MCRI. Results: Heart rate was lower, but mean arterial blood pressure was higher from 20 to 40 minutes with MCRI treatment, compared with conventional treatment with xylazine. Respiratory rate and rectal temperature were greater with MCRI treatment. Bispectral index was lower with MCRI treatment from 80 to 150 minutes, and electromyographic values were lower with MCRI treatment from 30 to 150 minutes. Conclusions: In isoflurane-anesthetized horses, premedication with medetomidine followed by administration of medetomidine as a constant rate infusion resulted in decreased heart rate, higher arterial blood pressure from 20 through 40 minutes after induction of anesthesia, and better preserved body temperature, compared with conventional treatment with xylazine. Greater depth of anesthesia and muscle relaxation were seen with MCRI treatment, despite the lower isoflurane concentration.
Publication Date: 2012-04-05 PubMed ID: 22471829DOI: 10.2460/javma.240.8.991Google Scholar: Lookup
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- Journal Article
- Randomized Controlled Trial
- Research Support
- Non-U.S. Gov't
Summary
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The article investigates the effects of two drugs, xylazine and medetomidine, used on horses during anesthesia. The aim was to observe how these drugs impact the animal’s heart functioning and other physiological responses. The results indicated that the method of administration and choice of drug can significantly influence the heart rate, blood pressure, and overall anesthesia depth in horses.
Research Methodology
- This study was a randomized crossover trial involving 10 healthy adult Standardbreds.
- Each horse was premedicated with either xylazine or medetomidine, both of which were administered intravenously.
- Anesthesia was then induced using diazepam and ketamine and maintained with isoflurane for a period of 150 minutes.
- For the xylazine trial, the isoflurane concentration was kept at 1.7%, and xylazine was administered as a bolus at the end of the anesthesia period.
- On the other hand, for the medetomidine constant rate infusion (MCRI), the isoflurane concentration was held at 1.4% while medetomidine was infused continuously during anesthesia.
- Several physiological parameters, including heart and respiratory rates, rectal temperature, bispectral index (a measure of the depth of anesthesia), and electromyographic values (a measure of muscle activity), were monitored and compared between the two treatments.
Research Findings
- The MCRI treatment resulted in a lower heart rate, but higher mean arterial blood pressure between the 20th and 40th minutes following induction of anesthesia, compared to the xylazine treatment.
- The respiratory rate and body temperature were also found to be higher under the MCRI treatment.
- Moreover, the bispectral index values from the 80th to 150th minute were lower under the MCRI treatment, indicating a deeper level of anesthesia.
- Electromyographic values from the 30th to 150th minute, reflecting muscle relaxation were also found to be lower under the MCRI treatment.
Conclusions
- Administering medetomidine as a constant rate infusion before and during isoflurane anesthesia in horses resulted in several key changes compared to conventional xylazine treatment.
- These included decreased heart rate, higher arterial blood pressure (between 20 and 40 minutes after induction), better-preserved body temperature, and greater muscle relaxation.
- Furthermore, a greater depth of anesthesia was observed under MCRI treatment despite using a lower isoflurane concentration.
Cite This Article
APA
Creighton CM, Lemke KA, Lamont LA, Horney BS, Riley CB.
(2012).
Comparison of the effects of xylazine bolus versus medetomidine constant rate infusion on cardiopulmonary function and depth of anesthesia in horses anesthetized with isoflurane.
J Am Vet Med Assoc, 240(8), 991-997.
https://doi.org/10.2460/javma.240.8.991 Publication
Researcher Affiliations
- Departments of Companion Animals, Atlantic Veterinary College, Charlottetown, PE C1A 4P3, Canada. cate.creighton@adelaide.edu.au
MeSH Terms
- Adrenergic alpha-2 Receptor Agonists / administration & dosage
- Adrenergic alpha-2 Receptor Agonists / pharmacology
- Anesthesia, Inhalation / veterinary
- Anesthetics, Inhalation / administration & dosage
- Anesthetics, Inhalation / pharmacology
- Animals
- Blood Pressure / drug effects
- Drug Administration Schedule
- Female
- Heart Rate / drug effects
- Horses
- Isoflurane / administration & dosage
- Isoflurane / pharmacology
- Male
- Medetomidine / administration & dosage
- Medetomidine / pharmacology
- Xylazine / administration & dosage
- Xylazine / pharmacology
Citations
This article has been cited 5 times.- Cunneen A, Pratt S, Perkins N, McEwen M, Truchetti G, Rainger J, Farry T, Kidd L, Goodwin W. Total Intravenous Anaesthesia with Ketamine, Medetomidine and Midazolam as Part of a Balanced Anaesthesia Technique in Horses Undergoing Castration.. Vet Sci 2021 Jul 26;8(8).
- Wiederkehr A, Barbarossa A, Ringer SK, Jörger FB, Bryner M, Bettschart-Wolfensberger R. Clinical Randomized Comparison of Medetomidine and Xylazine for Isoflurane Balanced Anesthesia in Horses.. Front Vet Sci 2021;8:603695.
- Tokushige H, Okano A, Arima D, Ito H, Kambayashi Y, Minamijima Y, Ohta M. Clinical effects of constant rate infusions of medetomidine-propofol combined with sevoflurane anesthesia in Thoroughbred racehorses undergoing arthroscopic surgery.. Acta Vet Scand 2018 Nov 5;60(1):71.
- Tokushige H, Kushiro A, Okano A, Maeda T, Ito H, Wakuno A, Nagata SI, Ohta M. Clinical evaluation of constant rate infusion of alfaxalone-medetomidine combined with sevoflurane anesthesia in Thoroughbred racehorses undergoing arthroscopic surgery.. Acta Vet Scand 2018 Sep 4;60(1):50.
- Mizobe F, Wakuno A, Okada J, Otsuka T, Ishikawa Y, Kurimoto S. Clinical usefulness of intravenous constant rate infusion of fentanyl and medetomidine under sevoflurane anesthesia in Thoroughbred racehorses undergoing internal fixation surgery.. J Equine Sci 2017;28(4):143-147.
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