Emergency Transfusion

In many situations, there is urgent need for blood before completion of compatibility testing (ABO-Rh, antibody screen, and crossmatch) (see Chapter 63 ). For those situations that do not allow time for complete testing, an abbreviated format for testing can be used. The preferred order for the selection of partially crossmatched blood is as follows.

Type-Specific, Partially Crossmatched Blood

When using uncrossmatched blood, it is best to obtain at least an ABO-Rh typing and an immediate-phase crossmatch. This incomplete crossmatch is accomplished by adding the patient's serum to donor RBCs at room temperature, centrifuging it, and then reading it for macroscopic agglutination. This takes 1 to 5 minutes and eliminates serious hemolytic reactions resulting from errors that may occur in ABO typing. Only a few unexpected antibodies outside the ABO systems are detected, such as those directed against antigens in the MN, P, and Lewis systems, most of which are not clinically significant.

Type-Specific, Uncrossmatched Blood

For proper use of type-specific blood, the ABO-Rh type must be determined during the patient's hospitalization. Blood types from historical records, relatives, ambulance drivers, and other hospitals are frequently inaccurate. For those who have never been exposed to foreign RBCs, most ABO type-specific transfusions are successful. Caution should be used for patients who have previously received transfusions or have had pregnancies. In my experience in the military, type-specific uncrossmatched blood was frequently used in emergencies with no serious consequence. In the civilian setting, using 1 year's experience with 56 patients, uncrossmatched, type-specific blood for emergency transfusion produced no adverse effects, even though complete serologic testing had not been performed.^[45] These investigators concluded that although the use of uncrossmatched blood is usually safe, the potential for serious reaction still exists, and they cautioned against its indiscriminate use. About 1 in 1000 patients has an unexpected antibody detected in crossmatch. For those who have previously been exposed to RBC antigens, transfusion of the ABO-Rh type-specific, uncrossmatched blood may be more hazardous. For every 100 of these individuals, 1 has an antibody detected by the crossmatch.

Type O Rh-Negative (Universal Donor), Uncrossmatched Blood

Type O blood lacks the A and B antigens and consequently cannot be hemolyzed by anti-A or anti-B antibodies in the recipient's blood (see Table 47-2 and Table 47-3 ). Because of this, people with type O blood have been called universal donors, and their blood can be used in emergency transfusions when typing or crossmatching is not available. However, some type O donors produce high titers of hemolytic IgG, IgM, anti-A, and anti-B antibodies. High titers of these hemolysins in donor units are capable of causing destruction of A or B RBCs of a non-type O recipient. Type O Rh-negative, uncrossmatched PRBCs should be used in preference to type O Rh-negative whole blood because packed erythrocytes have smaller volumes of plasma and are almost free of hemolytic anti-A and anti-B antibodies. If type O Rh-negative whole blood is to be used, the blood bank must supply type O blood that is free of hemolytic anti-A and anti-B antibodies.

During emergency transfusion of more than two units of type O Rh-negative, uncrossmatched whole blood, the patient probably cannot be switched to his or her blood type (A, B, or AB) once the blood bank determines the correct blood type. Switching could cause major intravascular hemolysis of donor RBCs by increasing titers of transfused anti-A and anti-B. Continued use of O Rh-negative whole blood results only in minor hemolysis of recipient RBCs, with hyperbilirubinemia as the only complication. The patient must not be transfused with his or her correct blood type until the blood bank determines that the transfused anti-A and anti-B has decreased to levels that permit safe transfusion of type-specific blood.

Specific Recommended Protocol

In view of the aforementioned considerations, the following steps are recommended for patients who are hypovolemic and require blood transfusion:

1. Infuse crystalloids or colloids.
2. Draw a blood sample for typing and crossmatching.
3. If crossmatched blood is not ready to give, use type-specific or type O Rh-negative cells or type O Rh-positive cells for males or postmenopausal females without a history of transfusions; type-specific, partially crossmatched blood; or type-specific, crossmatched blood.