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Home / Equine Research Bank / J Vet Emerg Crit Care (San Antonio) / The pathophysiology of uncontrolled hemorrhage in horses.
Journal of veterinary emergency and critical care (San Antonio, Tex. : 2001)2022; 32(S1); 63-71; doi: 10.1111/vec.13122

The pathophysiology of uncontrolled hemorrhage in horses.

Abstract: Hemorrhagic shock in horses may be classified in several ways. Hemorrhage may be considered internal versus external, controlled or uncontrolled, or described based on the severity of hypovolemic shock the patient is experiencing. Regardless of the cause, as the severity of hemorrhage worsens, homeostatic responses are stimulated to ameliorate the systemic and local effects of an oxygen debt. In mild to moderate cases of hemorrhage (<15% blood volume loss), physiological adaptations in the patient may not be clinically apparent. As hemorrhage worsens, often in the uncontrolled situation such as a vascular breach internally, the pathophysiological consequences are numerous. The patient mobilizes fluid and reserve blood volume, notably splenic stored and peripherally circulating erythrocytes, to preferentially supply oxygen to sensitive organs such as the brain and heart. When the global and local delivery of oxygen is insufficient to meet the metabolic needs of the tissues, a cascade of cellular, tissue, and organ dysfunction occurs. If left untreated, the patient dies of hemorrhagic anemic shock. Conclusions: An understanding of the pathophysiological consequences of hemorrhagic shock in horses and their clinical manifestations may help the practitioner understand the severity of blood volume loss, the need for referral, the need for transfusion, and potential outcome. In cases of severe acute uncontrolled hemorrhage, it is essential to recognize the clinical manifestations quickly to best treat the patient, which may include humane euthanasia. Conclusions: Uncontrolled hemorrhage may be defined as the development of a vascular breach and hemorrhage that cannot be controlled by interventional hemostasis methods such as external pressure, tourniquet, or ligation. Causes of uncontrolled hemorrhage in horses may be due to non-surgical trauma, surgical trauma, invasive diagnostic procedures including percutaneous organ biopsy, coagulopathy, hypertension, cardiovascular anomaly, vascular damage, neoplasia such as hemangiosarcoma, toxicity, or idiopathic in nature. When a critical volume of blood is lost, the respondent changes in heart rate, splenic blood mobilization, and microcirculatory control can no longer compensate for decreasing oxygen delivery to the tissues In spite of organ-specific microvascular responses (eg, myogenic responses, local mediator modulation of microvasculature, etc), all organs experience decreases in blood flow during severe hypovolemia Acute, fatal hemorrhagic shock is characterized by progressive metabolic acidosis, coagulopathy, and hypothermia, often termed the "triad of death," followed by circulatory collapse.
© Veterinary Emergency and Critical Care Society 2022.
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Publication Date: 2022-01-20 PubMed ID: 35044067DOI: 10.1111/vec.13122Google Scholar: Lookup
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Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

This study explores the physiological process and consequences of uncontrolled bleeding in horses. The research emphasizes the need to quickly recognize and adequately respond to this condition to improve the chances of survival, or regretfully, consider humane euthanasia in severe cases.

Explanation of Hemorrhagic Shock in Horses

  • The study starts by categorizing hemorrhagic shock in horses, meaning severe blood loss, based on several factors including whether it is internal versus external, controlled or uncontrolled, and the severity of the resultant hypovolemic shock, a condition characterized by decreased blood volume.
  • It explains that if a horse loses less than 15% of its total blood volume, the physiological adjustments might not be outwardly noticeable.

Pathophysiological Consequences of Severe Hemorrhage

  • However, if the bleeding worsens – an uncontrolled bleed, for example, due to internal vascular damage – the pathophysiological impacts are numerous.
  • The horse’s body tries to maintain oxygen delivery to critical organs like the brain and heart by mobilizing fluid and reserve blood volume, particularly stored blood from the spleen and circulating red blood cells.
  • When these adaptations fail to supply enough oxygen to meet tissue requirements, a cascade of cellular, tissue, and organ dysfunction begins. This can lead to fatal hemorrhagic anemic shock if not addressed.

Clinical Manifestations and Treatment

  • Understanding the pathophysiological implications of hemorrhagic shock and their clinical symptoms can be crucial in assessing the extent of blood volume loss, identifying the need for referral or transfusion, and informing on the potential outcome.
  • Timely recognition of severe acute uncontrolled hemorrhage is essential for effective treatment, which can unfortunately involve considering humane euthanasia in some circumstances.

Causes of Uncontrolled Hemorrhage

  • The research expands on the causes of uncontrolled bleeding in horses, outlining potential factors like non-surgical trauma, surgical trauma, invasive diagnostic procedures (like percutaneous organ biopsy), blood clotting disorders (coagulopathies), hypertension, cardiovascular anomaly, vascular damage, cancer (like hemangiosarcoma), toxicity, or idiopathic causes (unknown origins).
  • As hemorrhage intensifies and blood volume decreases, compensatory physiological responses such as increased heart rate, movement of splenic blood, and control of small blood vessels (microcirculation) can no longer maintain oxygen supply to tissues.
  • All organs experience decreased blood flow during severe blood loss, regardless of specific microvascular responses. Severe, fatal hemorrhagic shock is then characterized by a progression of metabolic acidosis (excess acid in body fluids), coagulopathy, and hypothermia, often referred to as the “triad of death,” followed by circulatory collapse.

Cite This Article

APA
Hurcombe SDA, Radcliffe RM, Cook VL, Divers TJ. (2022). The pathophysiology of uncontrolled hemorrhage in horses. J Vet Emerg Crit Care (San Antonio), 32(S1), 63-71. https://doi.org/10.1111/vec.13122

Publication

Journal of veterinary emergency and critical care (San Antonio, Tex. : 2001)
ISSN: 1476-4431
NlmUniqueID: 101152804
Country: United States
Language: English
Volume: 32
Issue: S1
Pages: 63-71

Researcher Affiliations

Hurcombe, Samuel D A
  • Emergency Surgery and Medicine, Cornell Ruffian Equine Specialists, Elmont, New York, USA.
Radcliffe, Rolfe M
  • Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, New York, USA.
Cook, Vanessa L
  • Department of Large Animal Clinical Sciences, Michigan State University, East Lansing, Michigan, USA.
Divers, Thomas J
  • Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, New York, USA.

MeSH Terms

  • Animals
  • Blood Coagulation Disorders / veterinary
  • Hemorrhage / etiology
  • Hemorrhage / therapy
  • Hemorrhage / veterinary
  • Horse Diseases / therapy
  • Horses
  • Hypovolemia / therapy
  • Hypovolemia / veterinary
  • Microcirculation
  • Shock, Hemorrhagic / therapy
  • Shock, Hemorrhagic / veterinary

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Citations

This article has been cited 1 times.
  1. Du J, Wang J, Xu T, Yao H, Yu L, Huang D. Hemostasis Strategies and Recent Advances in Nanomaterials for Hemostasis.. Molecules 2023 Jul 7;28(13).
    doi: 10.3390/molecules28135264pubmed: 37446923google scholar: lookup
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