Why do so few patients transfused with un-crossmatched red cells in an emergency experience a hemolytic transfusion reaction?

Hemolytic transfusion reactions seldom occur because the incidence of unexpected antibodies in random patients is relatively low, e.g., 3-5% is sometimes cited.

Being transfused with O Rh negative RBC is irrelvant if you have an unexpected antibody like anti-K or anti-c.

Incompatible red cells may "bleed out" but only if bleeding is brisk. Even then, a hemolytic

reaction may occur later once the patient’s antibody rebounds and destroys remaining antigen-positive donor red cells.

It’s true that some patients have only cold-reactive antibodies that will not react at body temperature. But this does not explain why warm-reactive red cell antibodies cause few reactions

Why do so few patients transfused with un-crossmatched red cells in an emergency experience a hemolytic transfusion reaction? Select the one best reason.
A . The incidence of unexpected red cell antibodies is relatively low.
B. They usually receive group O Rh negative red cells; a hemolytic transfusion reaction will never occur if O Rh-negative red cells are transfused.
C. They hemorrhage so severely that incompatible donor red cells "bleed out" before a reaction occurs.
D. Some patients have cold-reactive antibodies that will not react at body temperature.

View Answer

Answer: A