Equis ISSN 2398-2977

Anesthesia: inhalational

Contributor(s): Matthew Gurney, Rachel McMeeking, Graham Munroe

Introduction

  • There are two options for maintenance of equine anesthesia; inhalational anesthesia or total intravenous anesthesia (TIVA)   Anesthesia: intravenous (IV)  .
  • Inhalational maintenance requires an anesthetic breathing system   Anesthesia: circuits - overview   a source of oxygen and a suitable volatile agent.
  • Minimum Alveolar Concentration (MAC %) is the minimum concentration of volatile agent within the alveoli which prevents 50% of patients reacting with purposeful movement in response to a painful stimulus (skin incision). MAC is used to compare potency. The higher the MAC the less potent the drug. There are several factors which may affect MAC such as age, pregnancy and hypotension.
  • The onset of action of an inhalational agent depends on its solubility in the blood. An agent of low solubility such as sevoflurane   Sevoflurane   will have a more rapid onset than halothane   Halothane  .
  • Inhalational agents may be used for induction but this method is generally only used for foals.
  • Inhalational anesthesia is preferred over intravenous anesthesia    Anesthesia: intravenous (IV)  for horses that are anesthetized for longer than 45 min. 
  • The administration of an inhalational agent requires a gas source, eg oxygen, a source of anesthetic agent, an anesthetic machine and a breathing system.

Aims of inhalational anesthesia

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Inhalational agents

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Toxicity of inhaled agents

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Monitoring of anesthetics

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Recovery

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Further Reading

Publications

Refereed papers
  • Recent references fromPubMed.
  • Valverde A  et al(2010)Comparison of cardiovascular function and quality of recovery in isoflurane-anaesthetised horses administered a constant rate infusion of lidocaine or lidocaine and medetomidine during elective surgery. Equine Vet J42 (3), 192-199.
  • Johnston G M, Eastment J K, Taylor P M & Wood J L N (2004) Is isoflurane safer than halothane in equine anesthesia? Results from a prospective multicenter randomised controlled trial. Equine Vet J36(1), 64-71PubMed.
  • Raisis A L et al(2000)A comparison of the hemodynamic effects of isoflurane and halothane anesthesia in horses. Equine Vet J30, 318-326PubMed.
  • Matthews N S, Hartsfield S M, Mercer D, Beleau M H & MacKenthun A (1998)Recovery from sevoflurane anesthesia in horses: comparison to isoflurane and effect of postmedication with xylazine. Vet Surg27(5), 480-485PubMed.
  • Bunsen D B (1990)Use of halothane and isoflurane in the horse. Vet Clin North Am6(3), 529-542PubMed.
  • Eicker S W & Cuvelliez S (1990)Equipment for inhalation anesthesia. Vet Clin North Am6(3), 543-549PubMed.
  • Steffey E P, Kelly A B & Woliner M J (1978)Time-related responses of spontaneously breathing laterally recumbent horses to prolonged anesthesia with halothane. Am J Vet Res48(6), 952-957PubMed.

Other sources of information

  • Taylor P M & Clarke K W (2005)Handbook of Equine Anesthesia. 3rd edn. W B Saunders, London, UK.
  • Johnston G M (2004)Findings from the CEPEF epidemiological studies into equine perioperative complications. AAEP Proceedings Vol 50. pp 281-286.
  • Thurmon J C, Tranquilli W J, Benson G J (1996)Lumb & Jones' Veterinary Anesthesia.3rd edn. Williams & Wilkins.
  • Steffey E P (1990)Inhalational Anesthesia.In: Current Pract Equine Surg. Eds. White N W & Moore J N. J B Lippincott Company, Philadelphia, USA. pp 77-83.
  • Hall L W & Clarke K W (1983)Veterinary Anesthesia.8th edn. Bailliere Tindall, London, UK.


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