Equis ISSN 2398-2977
Anesthesia: monitoring - cardiac output and blood pressure
Contributor(s): Dennis R Gieser, Matthew Gurney, Craig Johnson, G Mark Johnston, Vetstream Ltd
- Measurement of arterial blood pressure is an important monitoring tool in equine anesthesia.
- Arterial blood pressure should be maintained above 60-70 mmHg to reduce the risk of developing anesthetic related myopathies/neuropathies Anesthesia: peri-operative complications - post-operative myopathy .
- Measurement of cardiac output is technically difficult and the equipment is expensive. It is currently limited to a research tool at present in the veterinary field.
- Arterial blood pressure does not equate to cardiac output, but can give a good indication of cardiovascular performance.
- Arterial blood pressure = cardiac output x systemic vascular resistance.
- In general, raised blood pressure is associated with increased cardiac output, increased peripheral resistance or a lighter anesthesia. Under anesthesia a sudden increase in mean arterial pressure often precedes movement.
- In most cases, hypotension Anesthesia: peri-operative complications - hypotension is associated with decreased cardiac output as a result of myocardial depression, eg due to anesthesia being too deep, endotoxic shock or acidosis.
- All inhalational anesthetic agents cause a dose dependent hypotension.
- Hypotension may also be associated with arrhythmias, eg bradycardia Heart: sinus bradycardia , sinus arrest Heart: sinus block , atrioventricular block Heart: atrioventricular block - 1st degree Heart: atrioventricular block - 2nd degree , or ventricular tachycardia Heart: ventricular tachycardia , or reduced venous return (due to positioning of the horse, hypovolemia or abdominal distension).
- Some premedicant drugs Anesthesia: premedication - overview can cause hypotension.
- Measurement of arterial blood pressure Cardiovascular: blood pressure monitoring can be by either direct or indirect methods.
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Further Reading
Publications
Refereed papers
- Recent references fromPubMedandVetMedResource.
- Menzies-Gow N J (2008)Effects of sedation with acepromazine on echocardiographic measurements in eight healthy thoroughbred horses. Vet Rec163(1), 21-25PubMed.
- Barr E D, Clegg P D, Senior J M & Singer E R (2005)Destructive lesions of the proximal sesamoid bones as a complication of dorsal metatarsal artery catheterization in three horses. Vet Surg34(2), 159-166PubMed.
- Trim C M (1998)Monitoring during anesthesia - techniques and interpretation. Equine Vet Educ10(4), 207-218VetMedResource.
- Jones J L (1996)Invasive monitoring techniques in anesthetized animals. Vet Med326VetMedResource.
- Jones J L (1996)Non-invasive monitoring techniques in anesthetized animals. Vet Med337VetMedResource.
- Keegan R D, Greene S A (1994)Equine anesthesia; blood pressure and monitoring - a review. Equine Pract16(7), 26.
- Riebold T W (1990)Monitoring Equine Anesthesia. Vet Clin North Am Equine Pract6(3), 607-624PubMed.
- Young S (1989)Monitoring the anesthetized horse. Equine Vet Educ1, 45-49.
Other sources of information
- Taylor P M & Clarke K W (2005)Handbook of Equine Anesthesia. 3rd edn. W B Saunders, London, UK.
- Hubbell J A E (1991)Monitoring. In: Equine Anesthesia Monitoring & Emergency Therapy. Eds: Muir W W & Hubbell J A E. Mosby. pp 153-179. ISBN: 0-8016-3576-4.
- McDonell W N & Dyson D H (1990)Monitoring the anesthetized horse.In: Current Practice of Equine surgery.Eds N A White & J N Moore. Lippincott. pp 87-93. ISBN: 0-397-50937-5.