Emergency Red Blood Cell Usage

EmergencyRedBloodCellsABO compatibility of Red Blood Cells (RBC) is fundamental to safe transfusion. Although ABO group typing only requires 5-10 minutes to perform, in certain critical situations a patient may lose a significant amount of blood during this time. When clinical circumstances do not allow time for determination of the patient's ABO group, the safest course of action is to provide group O RBCs otherwise considered uncrossmatched RBCs. As soon as the patient's ABO/Rh is established, the patient will be converted to type specific crossmatched RBCs.

The Rh system is immunologically different than the ABO system. Unlike the ABO system, there are no naturally occurring (pre-formed) antibodies to the "D" antigen in the Rh system. Under normal circumstances, Rh negative (Rh-) individuals who have not been exposed to the Rh antigen will not make anti-D. Such individuals could be safely transfused with either Rh positive or Rh negative RBCs, particularly in an emergency situation.

An Rh- individual may make anti-D only if exposed to the D-antigen via transfusion with Rh+ blood or platelets, or if pregnant with an Rh+ fetus. The probability of forming anti-D after transfusion of Rh+ RBCs is about one-third. Note, however, that this immunologic response requires approximately 3 to 4 months to develop and the patient is NOT at immediate risk of hemolysis. Individuals who have formed anti-D must receive only Rh- RBCs.

Many hospitals in the United States have a limited supply of group O- RBCs. Whenever possible; group 0- RBCs should be used for females of childbearing potential (generally women < 55 years of age) to avoid the possibility of alloimmunization. In order to effectively maintain an adequate supply of O- RBCs for these and other patients who should or must receive only this type, it is common practice to transfuse Rh+ RBCs to Rh- males as well as females of non-childbearing potential who require urgent or continued RBC transfusions.

IMPORTANT: The ordering physician must sign a waiver if the urgency of the situation requires the release of uncrossmatched (group O) RBC units from the Blood Bank.

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