Switching Rh(D) groups

Switching Rh(D) groups involves different considerations than does switching ABO groups. When switching the latter, we are concerned about regularly occurring ABO antibodies causing immediate intravascular hemolysis (IVH) and associated morbidity and mortality. When switching Rh(D) types, we are primarily concerned about the highly immunogenic D antigen stimulating anti-D in Rh(D) negative patients. Production of anti-D will not cause an immediate transfusion reaction. However, it would mean that the patient could never again receive Rh(D) positive red cells; and for women in the child-bearing years or younger, anti-D may cause hemolytic disease in offspring.

If Rh(D) positive blood is unavailable for Rh(D) positive patients

hotlink Rh(D)- negative RBC can be issued. There should be no problems for Rh(D) positive patients who lack irregular alloantibodies such as anti-c, etc.

If Rh(D) negative blood is unavailable for Rh(D) negative patients

This is the circumstance most likely to occur due to blood shortages of scarce Rh(D) negative donors (15 percent of Caucasians).

hotlink If possible, try to find Rh(D) negative RBC (e.g., from the blood center or other central supplier). This is especially important if the patient is a female within the child-bearing years or younger, for whom stimulation of anti-D could cause future hemolytic disease of the newborn (HDN) in offspring.

hotlink Transfusing Rh(D) negative blood is also important for all Rh(D) negative patients since, once anti-D is made, only Rh(D) negative RBC can be transfused. Research has shown that there is about a 70% chance that the Rh(D) negative patient will produce anti-D if Rh(D) positive RBC are transfused. Decisions as to when to switch to Rh(D) positive blood for these patients involve factors such as age, prognosis, and how critical the current blood shortage is.

hotlink For any patient, if bleeding is life-threatening, Rh(D) positive RBC can be issued with the permission of the laboratory medical director.

hotlink Depending on the clinical condition of patients, the director may sometimes elect to transfuse Rh(D) positive blood early on in order to conserve scarce Rh(D) negative RBC for patients who really need them, i.e., young Rh(D) negative females with a good prognosis.

Switching Rh(D) Groups