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 from PubMed and VetMedResource.
- Menzies-Gow N J (2008) Effects of sedation with acepromazine on echocardiographic measurements in eight healthy thoroughbred horses. Vet Rec 163 (1), 21-25 PubMed.
- 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 Surg 34 (2), 159-166 PubMed.
- Trim C M (1998) Monitoring during anesthesia - techniques and interpretation. Equine Vet Educ 10 (4), 207-218 VetMedResource.
- Jones J L (1996) Invasive monitoring techniques in anesthetized animals. Vet Med, 326 VetMedResource.
- Jones J L (1996) Non-invasive monitoring techniques in anesthetized animals. Vet Med, 337 VetMedResource.
- Keegan R D, Greene S A (1994) Equine anesthesia; blood pressure and monitoring - a review. Equine Pract 16 (7), 26.
- Riebold T W (1990) Monitoring Equine Anesthesia. Vet Clin North Am Equine Pract 6 (3), 607-624 PubMed.
- Young S (1989) Monitoring the anesthetized horse. Equine Vet Educ 1, 45-49.
Other sources of information
- Taylor P M & Clarke K W (2005) Handbook of Equine Anesthesia. 3rd edn. W B Saunders, 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.