ANTENATAL SELECTION OF DONORS FOR EXCHANGE TRANSFUSION IN ERYTHROBLASTOSIS

Open Access
Publisher Website
Google Scholar
Abstract
Two varieties of antibodies, agglutinins and blocking antibodies, are formed as a result of Rh sensitization. Blocking antibodies (glutinins) consist of smaller molecules, can pass the placental barrier and can "coat" the erythrocytes of the infant in utero. Clumping of the coated cells only occurs in the presence of conglutinin, which is absent from the infant''s plasma at and shortly after birth. Before an effective conglutinin concn. is reached in the infant''s plasma there is no intravascular clumping or icterus gravis. Hemolysis however can occur. If the mother''s blood contains mostly glutinins, then either an anemic child or a hydropic stillborn can be expected. When the mother''s blood contains mostly agglutinins these, because of their size, do not gain entrance to the child''s circulation until delivery, when the uterine contractions can force them into the fetal circulation. The infant appears normal at first, but within few hours or days, due to intravesical clumping, icterus gravis develops. Simple transfusions of Rh-neg. blood will only help in infants who have hemolytic anemia uncomplicated by clumping. Where clumping is likely the infant''s sensitized Rh-pos. cells must be replaced with inagglutinable Rh-neg. cells. This re- placement must be carried out as soon after birth as possible to avoid irreparable tissue damage. Therefore whenever feasible the compatible donors should be selected before birth. This is possible in the majority of cases. In urgent cases when compatible donors are not at hand Rh-neg. O blood neutralized with Witebsky''s A and B substance can be used to start the replacement transfusion.