Blood Products and Coagulation

Published on 07/03/2015 by admin

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Chapter 54 Blood Products and Coagulation

George Kasotakis, MD , Hasan B. Alam, MD, FACS

1 What components of blood are available for transfusion?

Components available for transfusion include whole blood, packed red blood cells (PRBCs), fresh frozen plasma (FFP), platelets, factor concentrates, cryoprecipitate, and white cell preparations. Fresh whole blood is sometimes used by the military but is not typically available for civilian use.

2 What are PRBCs?

Red blood cells contain hemoglobin and serve as the primary oxygen-transporting agent to tissues. Red blood cells are obtained by centrifugation of whole blood to remove much of the plasma, or by apheresis (a procedure in which blood is drawn and separated into its components, with the unwanted ones being returned by transfusion to the donor). The resulting product is called PRBCs, because of its high hematocrit (65%-80%) concentration. The usual volume of 1 unit of PRBCs ranges between 225 and 350 mL, and its shelf life ranges from 21 to 42 days, depending on the type of anticoagulant-preservatives added. When transfused, 1 unit of PRBCs typically raises the hemoglobin by 1 mg/dL or the hematocrit by an average of three points.

3 What are the main red blood cell surface antigen systems?

An individual’s red cells may express A, B, both, or no surface antigens, which determine that individual’s blood type. Those who do not express an antigen will eventually develop antibodies against it. People carrying anti-A or anti-B antibodies cannot receive red blood cells with the corresponding surface antigens, or immunologic destruction of the transfused red cells may occur. Consequently, type O individuals are considered universal donors, whereas AB individuals may donate only to other AB recipients. Similar to the ABO system, a separate Rh surface antigen exists that may be either present (Rh+) or absent (Rh−) from the red cell plasma membrane. Individuals who are Rh negative will develop antibodies to the Rh factor when exposed to Rh+ blood. This is not a problem with the initial exposure, but hemolysis may occur with subsequent transfusions (Table 54-1).

Table 54-1 Compatible packed red blood cells donor-recipient combinations

4 What are blood typing, screening, and crossmatching?

Donor and recipient blood typing is a process that determines what ABO and Rh antigens are expressed on the red cell surface. Screening is a process that detects circulating antibodies to various other antigens that might interact with the donor blood components. Cross-matching involves directly mixing the recipient’s plasma with the donor’s red cells to ensure that hemolysis does not occur from undetected antibodies.

6 What is a febrile nonhemolytic reaction?

A febrile nonhemolytic reaction manifests as a mild to moderate temperature elevation (typically ≤ 2° F or < 1.1° C) during or shortly after a transfusion and in the absence of any other pyretic stimuli. Febrile reactions occur in fewer than 1% of all transfusions and are thought to arise from circulating molecules or cells either in the transfused product or generated by the recipient. Routine pretreatment with antihistamines and antipyretics may ameliorate symptoms. Patients having recurrent severe febrile reactions may benefit from leukocyte-reduced blood products.

7 What is a hemolytic reaction?

It is the immunologic destruction of the transfused cells due to incompatibility of the antigen on their surface with preexisting circulating antibodies in the recipient’s plasma. It may occur when as little as 10 mL of blood is infused and is associated with significant morbidity. Associated mortality may be as high as 35%. The most common cause of acute hemolytic reactions is transfusion of ABO- or Rh-incompatible blood, resulting from identification errors. Serologic incompatibility undetected during pretransfusion testing is much less common. Delayed hemolytic reactions can also occur in previously alloimmunized patients in whom antigens on the transfused product provoke anamnestic antibody production. This anamnestic response is usually most evident within 2 to 14 days after the transfusion.

8 What are the classic findings in a hemolytic transfusion reaction?

Fever (with or without chills), tachycardia, back or flank pain, chest pain, dyspnea, hypotension, and oliguria are frequently present. Disseminated intravascular coagulopathy (DIC) may become clinically evident in severe cases. Laboratory findings include hemoglobinuria and elevation of the indirect serum bilirubin and lactate dehydrogenase levels. The direct antiglobulin test is also positive.

9 How should a hemolytic transfusion reaction be managed?

When an acute hemolytic reaction is recognized, the transfusion must be stopped immediately. The blood bank should be notified and transfusion forms and labels rechecked. Postreaction blood samples need to be sent along with the remaining blood component. Treatment is supportive and includes administration of intravenous fluids, diuretics, inotropes, and close monitoring as needed. Delayed reactions are typically benign and require no treatment.

10 What are the infectious risks of transfusion?

The incidence of transmission of hepatitis C, human T-lymphotropic virus, and human immunodeficiency virus in the United States through a blood component transfusion is approximately 1:2,000,000 units transfused.

Hepatitis B is transmitted in 1:270,000 transfusions.

The risk of transfusion-related bacterial infections is much higher at 1:2000 units of platelets transfused (platelets carry a higher risk of contamination because they are stored at room temperature).

Transmission of other infectious agents (e.g., Babesia spp, variant Creutzfeldt-Jakob disease agent, West Nile virus) for which blood products are not routinely tested is possible, yet even rarer.

11 What is TRALI?

TRALI describes the acute onset of hypoxemia (within 6 hours) after a blood component transfusion and is the most common cause of transfusion-related death in the United States. In addition to hypoxemia, criteria for diagnosis include bilateral infiltrates on chest radiograph and exclusion of preexisting lung injury or circulatory overload. Postulated mechanisms include second-hit injuries to the lungs from lipid products in stored blood products, human neutrophil antibodies, and human leukocyte antigen antibodies. Treatment consists of aggressive pulmonary support, frequently requiring mechanical ventilation.

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