Review of hypoxaemia in anaesthetized horses: predisposing factors, consequences and management.
Abstract: To discuss how hypoxaemia might be harmful and why horses are particularly predisposed to developing it, to review the strategies that are used to manage hypoxaemia in anaesthetized horses, and to describe how successful these strategies are and the adverse effects associated with them. Methods: Google Scholar and PubMed, using the search terms horse, pony, exercise, anaesthesia, hypoxaemia, oxygen, mortality, morbidity and ventilation perfusion mismatch. Conclusions: Although there is no evidence that hypoxaemia is associated with increased morbidity and mortality in anaesthetized horses, most anaesthetists would agree that it is important to recognise and prevent or treat it. Favourable anatomical and physiological adaptations of a horse for exercise adversely affect gas exchange once the animal is recumbent. Hypoxaemia is recognised more frequently in horses than in other domestic species during general anaesthesia, although its incidence in healthy horses remains unreported. Management of hypoxaemia in anaesthetized horses is challenging and often unsuccessful. Positive pressure ventilation strategies to address alveolar atelectasis in humans have been modified for implementation in recumbent anaesthetized horses, but are often accompanied by unpredictable and unacceptable cardiopulmonary adverse effects, and some strategies are difficult or impossible to achieve in adult horses. Furthermore, anticipated beneficial effects of these techniques are inconsistent. Increasing the inspired fraction of oxygen during anaesthesia is often unsuccessful since much of the impairment in gas exchange is a direct result of shunt. Alternative approaches to the problem involve manipulation of pulmonary blood away from atelectatic regions of the lung to better ventilated areas. However, further work is essential, with particular focus on survival associated with general anaesthesia in horses, before any technique can be accepted into widespread clinical use.
Copyright © 2017 Association of Veterinary Anaesthetists and American College of Veterinary Anesthesia and Analgesia. Published by Elsevier Ltd. All rights reserved.
Publication Date: 2017-01-11 PubMed ID: 28385614DOI: 10.1016/j.vaa.2016.06.001Google Scholar: Lookup
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- Journal Article
- Review
Summary
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This research article discusses the challenges related to management of hypoxaemia, a condition characterized by low oxygen levels in the blood, in anaesthetized horses. The authors explore the factors that make horses particularly susceptible to this condition, review the techniques used to address it, and investigate the varying degrees of success and potential adverse effects associated with these management strategies.
Understanding Hypoxaemia
This part of the research discusses hypoxaemia, a condition that involves low oxygen content in the blood. Below are the key points:
- Horses tend to be particularly prone to developing hypoxaemia, especially when under general anesthesia.
- There is no proven direct link between hypoxaemia and increased mortality or morbidity in horses. However, most anaesthetists agree on the importance of recognizing and addressing this condition to prevent potential complications.
- The favourable anatomic and physiologic adaptations that make horses well-suited to exercise can adversely affect their gas exchange mechanisms when they are recumbent, promoting hypoxaemia.
Managing Hypoxaemia in Anaesthetized Horses
This research paper proceeds to discuss the complexities involved in managing hypoxaemia in anaesthetized horses. Here are the key insights:
- Techniques that employ positive pressure ventilation, originally designed for humans with alveolar atelectasis (collapsed lung), have been adapted for use in horses. These methods often lead to unpredictable cardiopulmonary side effects and may be impractical, if not impossible, to implement in adult horses.
- Attempts to increase the inspired fraction of oxygen during anaesthesia often fail to resolve hypoxaemia, largely because the disruption in gas exchange is driven by a condition known as shunting, where blood bypasses the lungs and therefore is not oxygenated.
- Alternative strategies involve manipulating pulmonary blood flow away from collapsed sections of the lung to areas with better ventilation.
Future Directions
The study concludes with a call for further research to:
- Advance understanding of the association between general anaesthesia and survival rates in horses.
- Determine the most effective and least harmful ways to treat hypoxaemia in anaesthetized horses, before these methods can be broadly implemented in a clinical setting.
Cite This Article
APA
Auckburally A, Nyman G.
(2017).
Review of hypoxaemia in anaesthetized horses: predisposing factors, consequences and management.
Vet Anaesth Analg, 44(3), 397-408.
https://doi.org/10.1016/j.vaa.2016.06.001 Publication
Researcher Affiliations
- Institute of Biodiversity, Animal Health and Comparative Medicine, School of Veterinary Medicine, University of Glasgow, Glasgow, UK. Electronic address: adam.auckburally@glasgow.ac.uk.
- Department of Clinical Sciences, Swedish University of Agricultural Sciences, Uppsala, Sweden.
MeSH Terms
- Anesthesia / veterinary
- Animals
- Causality
- Horse Diseases / etiology
- Horse Diseases / therapy
- Horses
- Humans
- Hypoxia / etiology
- Hypoxia / therapy
- Hypoxia / veterinary
- Oxygen / administration & dosage
- Patient Positioning / adverse effects
- Patient Positioning / veterinary
- Pulmonary Atelectasis
- Respiration
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