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 Emergency Red Blood Cell Usage


IMPORTANT: The ordering physician must sign an emergency release waiver if the urgency of the situation requires the release of un-crossmatched (group O) RBC units from the Blood Bank.

ABO 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 un-crossmatched RBCs. As soon as the patient's ABO/Rh is established, the patient will be converted to type specific crossmatched RBCs.

The Rh system

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.

Forming Anti- D

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.

O Negative Selectivity

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.

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