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Basics ⬇

Outline

Basics

Definition!!navigator!!

  • Sporadic, progressive, respiratory failure associated with pulmonary edema.
  • Acute onset, cyanosis, pulmonary hypertension without cardiac disease

Pathophysiology!!navigator!!

  • A variety of insults that directly or indirectly injure the lung.
  • Inflammation, leading to permeability–pulmonary edema, and clinical respiratory failure.
  • Immunosuppressive disorders associated with acute respiratory distress syndrome/interstitial lung disease in foals.
  • Causal disease may progress to multiple organ dysfunction

Systems Affected!!navigator!!

  • Primarily respiratory.
  • Renal, hepatic, and cardiovascular systems and clotting cascades

Genetics!!navigator!!

Not established.

Incidence/Prevalence!!navigator!!

Not established.

Geographic Distribution!!navigator!!

N/A

Signalment!!navigator!!

Foals 1–8 months of age.

Signs!!navigator!!

  • Acute or peracute depression, lethargy, fever, labored breathing, tachypnea, nostril flaring, increased abdominal and intercostal effort with cyanosis.
  • Nasal discharge and cough—frequent

Causes!!navigator!!

  • Foals with subclinical respiratory disease.
  • Heat stress.
  • Erythromycin use in hot weather.
  • Viral and bacterial pneumonia

Risk Factors!!navigator!!

  • Antimicrobial or other drug use.
  • Heat stress, inhaled irritant gases, and pneumotoxicants.
  • Immunosuppression

Diagnosis ⬆ ⬇

Outline

DIAGNOSIS

Differential Diagnosis!!navigator!!

  • Viral pneumonia—equine influenza, viral arteritis, herpesviruses, paramyxovirus, and adenovirus.
  • Bacterial pneumonia.
  • Upper airway dysfunction.
  • Ingestion, inhalation, or exposure to xenobiotics

CBC/Biochemistry/Urinalysis!!navigator!!

Common abnormalities—neutrophilic leukocytosis, elevated fibrinogen.

Other Laboratory Tests!!navigator!!

  • Arterial blood gas—hypoxemia, hypercapnia, and respiratory acidosis.
  • Blood samples; dehydration, disseminated intravascular coagulation, and injury to other organs

Imaging!!navigator!!

Thoracic Radiography

  • Lesions described include diffuse bronchointerstitial, coalescing interstitial to nodular, diffuse alveolar to coalescing alveolar infiltrates.
  • Pulmonary abscess

Transthoracic Ultrasonography

Consolidation, abscesses, in some foals.

Other Diagnostic Procedures!!navigator!!

  • Culture and cytologic evaluation of transtracheal wash, bronchoalveolar fluid, or blood may provide valuable information.
  • Transthoracic lung biopsy may be useful diagnostically (except when bleeding or abscesses are evident)

Treatment ⬆ ⬇

Outline

TREATMENT

Aims!!navigator!!

  • Improve oxygenation.
  • Reduce body temperature (in hyperthermic foals).
  • Reduce lung edema and inflammation.
  • Antimicrobial therapy

Appropriate Health Care!!navigator!!

Reduce body temperature of foals.

Nursing Care!!navigator!!

  • Nasal oxygen insufflation (2–5 L/min) (nasal or transtracheal catheter).
  • Cold water enemas to reduce body temperature.
  • IV fluids to lower core temperature (balanced electrolyte solution).
  • Pulmonary edema may necessitate diuretics

Client Education!!navigator!!

  • Education aimed at prevention.
  • Observe mares and foals on daily basis.
  • Possibility of hyperthermia when treating foals with erythromycin

Medications ⬆ ⬇

Outline

MEDICATIONS

Drug(s) of Choice!!navigator!!

  • Drugs to address hypoxemia, hypercapnia, inflammation, and hyperthermia.
  • Modulation of pulmonary inflammation.
  • Appropriate antimicrobial therapy.
  • Use of corticosteroids in foals is controversial; limited use of short-acting corticosteroids (e.g. dexamethasone sodium phosphate 0.05–0.1 mg/kg IV, prednisolone sodium succinate 0.5–1 mg/kg IV) provide short-duration reduction of pulmonary inflammation.
  • NSAIDs (e.g. flunixin meglumine 0.25 mg/kg every 8 h) may lower body temperature and reduce discomfort associated with respiratory disease

Contraindications!!navigator!!

Discontinue any medications (especially erythromycin/rifampin (rifampicin)) that could produce significant interactions when used concurrently.

Follow-up ⬆ ⬇

Outline

FOLLOW-UP

Patient Monitoring!!navigator!!

  • Arterial blood gases are the most sensitive indicator of progress.
  • Repeated thoracic radiography is useful to evaluate lungs

Prevention/Avoidance!!navigator!!

Avoid exposing foals with respiratory disease, and those being treated with macrolide antibiotics, to direct sun on hot days. This may necessitate indoor confinement.

Possible Complications!!navigator!!

N/A

Expected Course and Prognosis!!navigator!!

  • The mortality rate is high with or without intensive therapeutic intervention.
  • Long-term outcomes vary; however, full recovery has occurred in a few cases

Miscellaneous ⬆ ⬇

Outline

MISCELLANEOUS

Age-Related Factors!!navigator!!

Can occur at all ages; however, foals 1–8 months of age are more commonly reported.

Zoonotic Potential!!navigator!!

N/A

Synonyms!!navigator!!

  • Bronchointerstitial pneumonia.
  • Interstitial pneumonia.
  • Respiratory distress

Abbreviations!!navigator!!

NSAID = nonsteroidal anti-inflammatory drug

Suggested Reading ⬆ ⬇

Dunkel B, Dolente B, Boston RC. Acute lung injury/acute respiratory distress syndrome in 15 foals. Equine Vet J 2005;37:435–440.

Peek SF, Landolt G, Karasin AI, et al. Acute respiratory distress syndrome and fatal interstitial pneumonia associated with equine influenza in a neonatal foal. J Vet Intern Med 2004;18:132–134.

Wilkins PA, Seahorn T. Acute respiratory distress syndrome. Vet Clin North Am Equine Pract 2004;20:253–273.

Author(s) ⬆

Authors: Jeffrey Lakritz and W. David Wilson

Consulting Editors: Daniel Jean and Mathilde Leclère