Emergency Red Blood Cell Usage
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 uncrossmatched RBCs. As soon as the patient's ABO/Rh is
established, the patient will be converted to type specific crossmatched
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.