Blood Transfusion: ABO and Rh Blood Group System

Blood transfusion is a common and safe procedure where blood and/or blood products are transferred from the circulation of one person (known as a donor) to the circulation of another person (known as a recipient) or to the circulation of the patient himself (autologous transfusion) at a different time. It helps to replace blood loss following trauma, surgery, or hematologic illnesses, e.g., leukemia.


Various products have different indications as follows:
Whole blood that is preferred in acute transfusion where massive volume replacement is needed.

Packed red blood cells: used for routine transfusion.
Fresh frozen plasma: indicated for bleeding diathesis where all clotting factors are needed.
Platelets concentrate: administered for blood loss in the setting of thrombocytopenia.
Cryoprecipitate: made up of fibrinogen and factor VIII thus considered in the setting of hemophilia and von Willebrand disease.

Indications for a Blood Transfusion
Hemorrhage following accidental trauma, e.g., car crashes, fractures, war or 1.

ABO System of Blood Transfusion
Each red blood cell (RBC) in humans expresses ABO blood group antigens. These antigens are also expressed by other cells in the human body. The function of the ABO antigens is unknown, but they are clinically significant because they are extremely reactive.
The immune system forms antibodies against the ABO antigen which is absent on an individual's RBC. As seen in the accompanying table, an individual with Group A antigens will have anti-B antibodies, while an individual with Group B antigens will have anti-A antibodies. Serum of individuals with Group O has anti-A as well as anti-B.

Rh System of Blood Transfusion
The Rh or rhesus antigen is expressed only on the RBC membrane and helps to maintain its integrity. These antigens may carry the D-antigen (RhD) or C or c antigen (RhC or Rhc). An absence of the Rh antigen may lead to an alteration in the shape of the RBC with increased fragility, decreased lifespan on the RBC and mild hemolytic anemia.
In addition, there is an increased risk of transfusion reactions in these patients due to the production of Rh antigens which are highly reactive. Usually, IgG antibodies are formed against the Rh antigens and anti-D, anti-C and anti-c have all been associated with hemolytic disease of the newborn (HDN) and delayed hemolytic transfusion reactions.

Complications of Blood Transfusion
Complications of blood transfusion can be classified as acute and delayed. Each of these can be further classified as infectious and non-infectious.

Acute complications are defined as those occurring within minutes to up to twenty-four hours after a blood transfusion.
Delayed complications can occur within days, months or years following a blood transfusion.

Non-infectious complications
These are more likely compared to infectious complications as there have been fewer advances in preventing these. Some of these are discussed in more detail below.

Acute
Hemolytic reaction

Acute
Hemolytic reaction: Usually occurs within 24 hours of the transfusion and can be either due to immune or non-immune causes. Immune causes include ABO incompatibility, Rh incompatibility and are due to antibodies produced following sensitization during a previous pregnancy or transfusion.

Non-immune causes include improper storage, bacterial contamination,
infusing along with non-compatible medications or through small-bore intravenous tubes. It is clinically characterized by: Acute febrile non-hemolytic reaction: Is defined as an increase in body temperature by a minimum of 1.80 F over normal body temperature within 24 hours of a blood transfusion. It is a diagnosis of exclusion and is characterized by rigors, chills and severe discomfort. It is more commonly seen with platelet transfusions and the removal of white blood cells (leukoreduction) from donor blood which is associated with decreasing its incidence. Hepatic dysfunction within one to six weeks following a blood transfusion It is fatal in the majority of the affected patients. It can be prevented by irradiating the blood products to prevent the donor lymphocytes from proliferating.

Use of red cell transfusions
They are given for anemia -typically if hemoglobin is < 80 g/l. If the patient is not making any red cells they will need transfusion every 3 weeks. Over the long term, a problem becomes the accumulation of iron. The major concern is that the ABO system is matched.
Use of fresh frozen plasma This is generated by taking the plasma off a blood donation and freezing it until it is needed. It contains clotting factors and is often used for patients with blood clotting disorders. It has no value as a blood volume expander.