Hemolytic Transfusion Reaction
An acute hemolytic transfusion reaction (AHTR) is a type of transfusion reaction that is associated with hemolysis. It occurs very soon after the transfusion often within 24 hrs post-transfusion. It can occur quickly upon transfusing a few milliliters, or up to 1-2 hours post-transfusion.
This is a medical emergency as it results from rapid destruction of the donor red blood cells by host antibodies (IgG, IgM). It is usually related to ABO blood group incompatibility - the most severe of which often involves group A red cells being given to a patient with group O type blood. Properdin then binds to complement C3 in the donor blood, facilitating the reaction through the alternate pathway cascade. The donor cells also become coated with IgG and are subsequently removed by macrophages in the reticuloendothelial system (RES). Jaundice and disseminated intravascular coagulation (DIC) may also occur. The most common cause is clerical error (i.e. the wrong unit of blood being given to the patient).
The major complication is that the hemoglobin, released by the destruction of red blood cells, may cause acute renal failure (also known as the "oliguric phase"). About 20 annual deaths in the US are due to AHTR.
Acute hemolytic reactions occur with transfusion of red blood cells, and occurs in about 0.016 percent of transfusions, with about 0.003 percent being fatal. This is due to destruction of donor erythrocytes by preformed recipient antibodies. Most often this occurs due to clerical errors or improper typing and crossmatching. Symptoms include fever, chills, chest pain, back pain, hemorrhage, increased heart rate, shortness of breath, and rapid drop in blood pressure. When suspected, transfusion should be stopped immediately, and blood sent for tests to evaluate for presence of hemolysis. Treatment is supportive. Kidney injury may occur due to the effects of the hemolytic reaction (pigment nephropathy).
Delayed hemolytic reactions occur more frequently (about 0.025 percent of transfusions) and are due to the same mechanism as in acute hemolytic reactions. However, the consequences are generally mild and a great proportion of patients may not have symptoms. However, evidence of hemolysis and falling hemoglobin levels may still occur. Treatment is generally not needed, but due to the presence of recipient antibodies, future compatibility may be affected.
Febrile nonhemolytic reactions are due to recipient antibodies to donor white blood cells, and occurs in about 7% of transfusions. This may occur after exposure from previous transfusions. Fever is generally short lived and is treated with antipyretics, and transfusions may be finished as long as an acute hemolytic reaction is excluded. This is a reason for the now-widespread use of leukoreduction - the filtration of donor white cells from red cell product units.
Much of the routine work of a blood bank involves testing blood from both donors and recipients to ensure that every individual recipient is given blood that is compatible and is as safe as possible. If a unit of incompatible blood is transfused between a donor and recipient, a severe acute hemolytic reaction with hemolysis (RBC destruction), renal failure and shock is likely to occur, and death is a possibility. Antibodies can be highly active and can attack RBCs and bind components of the complement system to cause massive hemolysis of the transfused blood.
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