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Basics ⬇

Outline

BASICS

Overview!!navigator!!

  • EIPH is defined as the presence of blood in the airways after exercise
  • Pathophysiology unknown. Current speculation—exercising horses have high cardiac outputs and vascular pressures. Repeated bouts of venous hypertension during strenuous exercise cause intrapulmonary vein wall remodeling and collagen accumulation, venous occlusion, and pulmonary capillary hypertension in the caudodorsal regions of the lung. Subjected to high pressures, there is capillary stress failure and bleeding into the interstitial and alveolar spaces. Blood in the interstitium or alveoli elicits an inflammatory reaction that contributes to bronchointerstitial fibrosis and arterial neovascularization, which may also be a source of hemorrhage during subsequent exercise
  • Worldwide distribution

Signalment!!navigator!!

  • Most commonly described in horses that run at high speed
  • Reported frequency based on postexercise endoscopy—>80% in racing Thoroughbreds, 87% in Standardbreds, 62% in racing Quarter Horses
  • Other breeds could be affected—associated with exercise
  • Occurs with onset of strenuous exercise and training, thus from 2 years of age
  • Males, geldings, and females are equally affected

Signs!!navigator!!

  • Commonly, no external clinical signs
  • Rarely, epistaxis can occur during or after exercise (0.1–9%)
  • Performance could be impaired

Causes and Risk Factors!!navigator!!

  • Strenuous exercise
  • Less commonly, underlying parenchymal disease

Diagnosis ⬆ ⬇

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DIAGNOSIS

Differential Diagnosis!!navigator!!

  • Epistaxis—ethmoid hematoma, guttural pouch mycosis, trauma, coagulopathy
  • Airway blood—pulmonary abscess, pneumonia, foreign body, neoplasia

CBC/Biochemistry/Urinalysis!!navigator!!

Usually, no significant abnormalities.

Other Laboratory Tests!!navigator!!

Tracheal wash or bronchoalveolar lavage fluid cytology (high sensitivity and specificity)—presence of red blood cells and macrophages with intracytoplasmic hemosiderin (hemosiderophages). Provides information on severity and duration of EIPH.

Imaging!!navigator!!

  • Thoracic ultrasonography—comet tail artifacts caudodorsally (high sensitivity, low specificity)
  • Thoracic radiography—increased homogeneous parenchymal density in caudodorsal lung fields (low sensitivity)

Other Diagnostic Procedures!!navigator!!

Tracheal endoscopy 30–120 min after strenuous exercise. Severity is assessed with a 0–4 scoring system. Repeated endoscopies increase sensitivity.

Pathologic Findings!!navigator!!

Gross

  • Characteristic patchy to multifocal, symmetric, blue-brown staining of the parenchyma in the caudodorsal regions of the caudal lung lobe
  • Foci of subpleural scarring with enhanced subpleural vasculature

Histopathologic

  • Remodeling of small pulmonary veins characterized by accumulation of adventitial collagen
  • Bronchiolitis
  • Hemosiderophages in the alveolar lumen and interstitial spaces
  • Fibrosis of interlobular septa, pleura, and around vessels and bronchioles

Treatment ⬆ ⬇

TREATMENT

  • No known treatment
  • Rest (30 days to 1 year) may help parenchymal repair
  • Reduce the intensity of athletic activity if exercise is continued

Medications ⬆ ⬇

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MEDICATIONS

Drug(s) of Choice!!navigator!!

  • Furosemide (0.5–1 mg/kg IV) 4 h before strenuous exercise. There is high-quality evidence that furosemide decreases the severity and incidence of EIPH
  • Other treatments (aminocaproic acid, bronchodilators, corticosteroids, NSAIDs, pentoxifylline, nasal strip)—low-quality evidence that EIPH severity is affected
  • Treat lower airway disease if present—see chapter Inflammatory airway diseases—IAD in performance horses (mild and moderate equine asthma)

Contraindications/Possible Interactions!!navigator!!

Chronic furosemide administration, especially if the horse is dehydrated, may predispose to electrolyte disorders. The use of furosemide is prohibited by many racing jurisdictions.

Follow-up ⬆ ⬇

Outline

FOLLOW-UP

Patient Monitoring!!navigator!!

  • Repeat endoscopy after subsequent strenuous activities provides information on the frequency and severity of the condition
  • If severe bleeding, repeat examination in 24–48 h to make sure bleeding has stopped; may indicate intercurrent disease

Prevention/Avoidance!!navigator!!

Administration of furosemide during training helps to reduce incidence and severity of EIPH episodes.

Possible Complications!!navigator!!

The link between EIPH and sudden death has yet to be clarified.

Expected Course and Prognosis!!navigator!!

  • There is evidence that EIPH is a progressive pathology and that affected horses have shorter racing careers
  • Resolution of lung pathology especially with continued strenuous exercise is unlikely

Miscellaneous ⬆ ⬇

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MISCELLANEOUS

Abbreviations!!navigator!!

  • EIPH = exercise-induced pulmonary hemorrhage
  • NSAID = nonsteroidal anti-inflammatory drug

Suggested Reading ⬆ ⬇

Hinchcliff KW, Couetil LL, Knight PK, et al. Exercise induced pulmonary hemorrhage in horses: American College of Veterinary Internal Medicine consensus statement. J Vet Intern Med 2015;29:743–758.

Author(s) ⬆

Author: Francesco Ferrucci

Consulting Editors: Mathilde Leclère and Daniel Jean

Acknowledgment: The author and editors acknowledge the prior contribution of John R. Pascoe.