An exchange transfusion is the serial withdrawal and injection of small amounts of blood through a central vein-usually umbilical until the required volume has been exchanged. It is performed to correct anemia in infants severely affected with erythroblastosis and hydrops or to prevent or correct hyperbilirubinemia that might lead to neurologic sequelae. Double volume exchange transfusion lowers the bilirubin level in the plasma to about one-half the pre-exchange level. Bilirubin is removed from the extra-vascular space because extravascular bilirubin will equilibrate and bind to the albumin in the exchanged blood. The infant's antibodies are washed out, and red cells that are partially hemolyzed or antibody coated are washed out. Exchange transfusion is instituted if evaluation og bilirubin and albumin levels indicate a significant risk of bilirubin toxicity.