Interactions of morphine and isoflurane in horses.
Abstract: To quantitate dose- and time-related magnitudes of interactive effects of morphine (MOR) and isoflurane (ISO) in horses and to characterize pharmacokinetics of MOR in plasma and the ventilatory response to MOR during administration of ISO. Methods: 6 adult horses. Methods: Horses were anesthetized 3 times to determine the minimum alveolar concentration (MAC) of ISO in O2 and then to characterize the change in anesthetic requirement as defined by the alteration in ISO MAC following IV administration of saline (0.9% NaCl) solution and 2 doses of MOR (low dose, 0.25 mg/kg; high dose, 2.0 mg/kg). Arterial blood samples were obtained before and after MOR and analyzed. Results: Mean +/- SD baseline ISO MAC was 1.43 +/- 0.06%. The ISO MAC did not change with time after administration of saline solution. Effects of MOR on ISO MAC varied. Maximal change in MAC ranged from -20.2 to +28.3% and -18.9 to +56.2% after low and high doses of MOR, respectively. Typical half-life of MOR in plasma was 40 to 60 minutes and related to dose. Mean PaCO2 increased from 70 mm Hg before MOR to 88 to 102 mm Hg for 30 to 240 minutes after the high dose of MOR. Recovery from anesthesia after administration of the high dose of MOR was considered undesirable and dangerous. Conclusions: Our results do not support routine clinical use of MOR administered IV at dosages of 0.25 or 2.0 mg/kg as an adjuvant to anesthesia in horses administered ISO.
Publication Date: 2003-02-27 PubMed ID: 12602585DOI: 10.2460/ajvr.2003.64.166Google Scholar: Lookup
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- Clinical Trial
- Journal Article
- Randomized Controlled Trial
- Research Support
- Non-U.S. Gov't
Summary
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This research tests the effects of administering morphine, in combination with the anaesthetic isoflurane, on horses. The study found that morphine administration had differing effects and in some instances could be considered harmful, thus, it does not support the use of morphine as an adjunctive treatment to isoflurane anaesthesia in horses.
Experimental Setup
- The research was carried out on six adult horses each of which were anesthetized three times.
- The purpose of the initial anesthesia was to determine the minimum alveolar concentration (MAC) of isoflurane in oxygen, a critical measure of anesthetic potency.
- Subsequent administrations aimed to identify any changes in anesthetic requirements (as defined by changes in isoflurane MAC) following the IV administration of either a saline solution or two distinct doses of morphine.
- Arterial blood work was extracted and analyzed both prior to, and after, morphine administration.
Findings
- The study determined that the effect of morphine on isoflurane requirement was variable.
- The change in isoflurane MAC ranged from a decrease by 20.2% to an increase by 28.3% after a low dose of morphine, and a larger range of decrease by 18.9% to an increase by 56.2% after high dose.
- The detected half-life of morphine in plasma spanned 40 to 60 minutes and was found to be dose-dependent.
- Arterial carbon dioxide pressure (PaCO2) increased from 70 mm Hg before morphine administration to between 88 to 102 mm Hg for 30 to 240 minutes after the high morphine dose.
- The recovery period from anesthesia after the high morphine dose was assessed as potentially dangerous and undesirable.
Conclusion
- Given the findings, the research does not support clinical routine use of morphine in combination with isoflurane in horses.
- The data indicates that the administration of morphine intravenously at dosages of 0.25 or 2.0 mg/kg does not serve as a useful adjunct to isoflurane anaesthesia in horses, given the variability and potential negative consequences recorded.
Cite This Article
APA
Steffey EP, Eisele JH, Baggot JD.
(2003).
Interactions of morphine and isoflurane in horses.
Am J Vet Res, 64(2), 166-175.
https://doi.org/10.2460/ajvr.2003.64.166 Publication
Researcher Affiliations
- Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California, Davis, CA 95616, USA.
MeSH Terms
- Analgesics, Opioid / administration & dosage
- Analgesics, Opioid / adverse effects
- Analgesics, Opioid / pharmacokinetics
- Analgesics, Opioid / pharmacology
- Anesthesia / veterinary
- Anesthetics, Inhalation / administration & dosage
- Anesthetics, Inhalation / adverse effects
- Anesthetics, Inhalation / pharmacokinetics
- Anesthetics, Inhalation / pharmacology
- Animals
- Blood Pressure / drug effects
- Cross-Over Studies
- Dose-Response Relationship, Drug
- Drug Interactions
- Female
- Half-Life
- Heart Rate / drug effects
- Horses
- Isoflurane / administration & dosage
- Isoflurane / adverse effects
- Isoflurane / pharmacokinetics
- Isoflurane / pharmacology
- Male
- Morphine / administration & dosage
- Morphine / blood
- Morphine / pharmacokinetics
- Morphine / pharmacology
Citations
This article has been cited 9 times.- Brandly JE, Midon M, Douglas HF, Hopster K. Flow-controlled expiration reduces positive end-expiratory pressure requirement in dorsally recumbent, anesthetized horses.. Front Vet Sci 2023;10:1135452.
- Gozalo-Marcilla M, Ringer SK. Recovery after General Anaesthesia in Adult Horses: A Structured Summary of the Literature.. Animals (Basel) 2021 Jun 14;11(6).
- 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.
- Re M, Canfrán S, Largo C, Gómez de Segura IA. Effect of Lidocaine-Ketamine Infusions Combined with Morphine or Fentanyl in Sevoflurane-Anesthetized Pigs.. J Am Assoc Lab Anim Sci 2016;55(3):317-20.
- Conde Ruiz C, Cruz Benedetti IC, Guillebert I, Portier KG. Effect of Pre- and Postoperative Phenylbutazone and Morphine Administration on the Breathing Response to Skin Incision, Recovery Quality, Behavior, and Cardiorespiratory Variables in Horses Undergoing Fetlock Arthroscopy: A Pilot Study.. Front Vet Sci 2015;2:58.
- Carregaro AB, Freitas GC, Ribeiro MH, Xavier NV, Dória RG. Physiological and analgesic effects of continuous-rate infusion of morphine, butorphanol, tramadol or methadone in horses with lipopolysaccharide (LPS)-induced carpal synovitis.. BMC Vet Res 2014 Dec 21;10:966.
- Brosnan RJ. Inhaled anesthetics in horses.. Vet Clin North Am Equine Pract 2013 Apr;29(1):69-87.
- Chesnel MA, Aprea F, Clutton RE. Anesthetic management of a horse with traumatic pneumothorax.. Can Vet J 2012 Jun;53(6):648-52.
- Barter LS, Carstens EE, Jinks SL, Antognini JF. Rat dorsal horn nociceptive-specific neurons are more sensitive than wide dynamic range neurons to depression by immobilizing doses of volatile anesthetics: an effect partially reversed by the opioid receptor antagonist naloxone.. Anesth Analg 2009 Aug;109(2):641-7.
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