Equis ISSN 2398-2977

Anesthesia: induction - overview

Contributor(s): Dennis R Gieser, Craig Johnson, Mark Senior

Introduction

  • Induction is usually by administration of an intravenous agent, as safe restraint of an animal for gaseous induction would be impossible in most cases. One possible exception could be an ill foal, where the rapid recovery from, for example, isoflurane   Isoflurane  and the relative safety of restraint may make this a favorable option.
  • The aim of induction is a safe, smooth descent into unconsciousness with minimum movement by the horse.
  • The insertion of an intravenous catheter   Intravenous catheterization  into the jugular vein will make administration of an intravenous drug easier and safer, even in a restless patient.

Sites for induction

Clinic or purpose-built induction box

  • Padded walls (up to at least 2 m high) and floor with some method of restraining the horse are the essentials.
  • Other design features will depend on the availability of separate rooms for surgery and for recovery   Anesthesia: recovery - overview  .

Indoor arena/school

  • Usually a good choice, because the ground is soft and even and there should be no sharp objects, plenty of space and environmental effects are reduced.
  • A disadvantage can be the dustiness of many indoor arenas which the horse's eyes will need to be protected. Will make a poor surgical environment.

Stable

  • As well as removing protruding objects such as mangers etc, from the area, hazards such as walls which do not reach high enough or gaps under stable doors must also be noted and dealt with.
  • Clean straw bedding (left long enough for any dust to settle) is usually the best choice.
  • The horse should be stood against a wall with its hindquarters in a corner for induction. The side to be operated on should be closest to the wall and only two handlers should be present, because of the confined space.

Ensure that the stable is strong enough for a horse to recover from anesthetic in it.

Outdoors

  • A sheltered area, protected from the prevailing wind and shaded from bright sunlight in summer should be sought.
  • A layer of straw on the ground should help to insulate the patient from the cold and a clean blanket may be used to cover the animal during the surgery.
  • Care should be taken to clear the surrounding area of any sharp or hard objects and any noise should be kept to a minimum.
  • A strong, secure halter and soft, thick, cotton lead rope will help the handler to control the horse more effectively. Extra handlers are also of use, as they may be able to help control the place where the horse lands and which side it lands on. For example, turning the horse's head to the left just before it begins to go down will encourage the horse into right lateral recumbency.

Print-off the Owner factsheet All about anesthesia  All about anaesthesia  to give to your clients.

Intravenous agents

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Gaseous agents

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Further Reading

Publications

Refereed papers
  • Muir W W (1998)Anesthesia and pain management in horses. Equine Vet Educ10(6), 335-340.
  • Benson G J & Thurmon J C (1990)Intravenous anesthesia. Vet Clin North Am6(3), 519-525PubMed.
  • Brunson D B (1990)Use of halothane and isoflurane in the horse. Vet Clin North Am6(3), 529-540PubMed.

Other sources of information

  • Pascoe P J (1990)Induction and Recovery techniques. In: Current Practice of Equine Surgery. Eds: N A White & J N Moore. J B Lippincott Company, Philadelphia. pp 64-69.
  • Trim C M (1990)Intravenous Anesthesia: Induction and Maintenance. In: Current Practice of Equine Surgery. Eds: N A White & J N Moore. J B Lippincott Company, Philadelphia. pp 69-77.
  • Steffey E P (1990)Inhalation Anesthesia. In: Current Practice of Equine Surgery. Eds: N A White & J N Moore. J B Lippincott Company, Philadelphia. pp 77-83.
  • Brander G C, Pugh G M & Bywater R J (1982)Veterinary Applied Pharmacology and Therapeutics .4th edn. Bailliere Tindall, London, UK.
  • Hall L W & Clarke K W (1983)Veterinary Anesthesia.8th edn. Bailliere Tindall, London, UK.


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