Meconium aspiration syndrome in foals.

Meconium— refers to the dark, sticky feces foals first pass, and its basically a composition of gastrointestinal secretions such as bile, pancreatic enzymes and mucous, desquamated cells, lanugo, vernix caseosa, water, amniotic fluid and other cellular debris. When a foal becomes hypoxic in utero, a vicious cycle can ensue. Hypoxemia can stimulate gastrointestinal peristalsis that passes meconium in utero. It can also trigger the foal to reflexively gasp for air and aspirate meconium and amniotic fluid into its lungs.When aspirated, meconium is toxic due to the damaging effect on surfactant and lung tissue. Meconium occludes the airways, from the upper airway to the alveoli creating a valve-like effect such that during inspiration air may be able to pass through a partial obstruction and fill the deeper portion of the lungs and in the expiratory phase, air can become trapped behind the meconium obstruction and accumulate to the point where it ruptures lung tissue, causing a pneumothorax. more