Acute Lung Injury and Acute Respiratory Distress Syndrome in Foals

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are characterized by acute, uncontrolled interstitial and alveolar inflammation secondary to a pulmonary or systemic insult. Endothelial and epithelial damage increases alveolo-capillary permeability leading to protein-rich alveolar edema. Clinical manifestations include severe hypoxemia minimally responsive to oxygen therapy, decreased total lung compliance, and increased airway resistance. Foals present with acute onset of severe respiratory distress. In most cases the initial insult can be attributed to an underlying bacterial, or rarely, viral pneumonia. Laboratory findings include severe hypoxemia, hypo- or hypercapnia, leukocytosis, and hyperfibrinogenemia. Radiographic findings vary from heavy interstitial to coalescing alveolar patterns. Treatment consists of intranasal oxygen supplementation, anti-inflammatories, and antimicrobials if underlying bacterial infection is suspected. Based on limited available reports in foals, prognosis is guarded, but even severe cases can survive and return to athletic function.