Plasma Exchange as a Treatment for Hyperbilirubinemia in 2 Foals with Neonatal Isoerythrolysis

B ilirubin can cross the blood-brain barrier, especially when plasma concentrations are high and in neonates. Bilirubin is toxic and can lead to irreversible brain damage, signs of neurologic disease, and coma, which is called “kernicterus.” The most important cause of clinical icterus in equine neonates is neonatal isoerythrolysis (NI), an alloimmune disease characterized by immune-mediated hemolytic anemia and, consequently hyperbilirubinemia and hypoxia. Prognosis generally is guarded to good, but when NI leads to kernicterus, chances for survival are low. Treatment of NI consists of supportive care and blood transfusions, but none of these lower plasma bilirubin concentration. In human medicine, therapeutic plasma exchange has been successfully used in cases of hyperbilirubinemia. This case report describes 2 foals that were examined because of severe anemia and hyperbilirubinemia because of NI. Despite treatment, bilirubin concentrations continued to rise in the first 48 hours. Because of the risk of the development of kernicterus, plasma exchange treatment was performed with a commercial plasmapheresis device. Both foals had an immediate decrease (44 and 57%) in plasma bilirubin concentration and fully recovered.