- Clinical science
Transfusion of whole blood and fractionated blood components is a widespread method for managing numerous conditions. Packed RBCs are the most commonly transfused products and are primarily used for the treatment of acute or chronic blood loss. The rationale behind RBC transfusion is not simply to improve the Hb level, but rather to maintain organ perfusion and tissue oxygenation. The decision to transfuse RBCs therefore depends on the Hb level, the patient's hemodynamic status, and comorbidities (e.g., cardiovascular disease). Fresh frozen plasma (FFP) and cryoprecipitate, platelet transfusions, and clotting factor transfusions are also available.
Pretransfusion testing must be performed to prevent the transfusion of incompatible RBCs and subsequent immune hemolytic reactions. The testing involves blood typing of the recipient blood (ABO and Rhesus group), antibody screening of the recipient blood, and compatibility testing (crossmatching recipient plasma and donor RBCs). The most common transfusion reactions are minor allergic reactions (urticaria) and nonhemolytic febrile reactions. However, some transfusion reactions, such as the acute hemolytic transfusion reaction, may be life-threatening and require immediate supportive care. If transfusion reactions do occur, immediate cessation of the transfusion is essential.
| Incidence ||ABO antigen on RBCs||Antibodies in plasma||Packed RBC compatibility|
|Blood type O||∼ 45%||No antigens||A and B antibodies||O|
|Blood type A||∼ 40%||A antigen||B antibodies||A, O|
|Blood type B||∼10%||B antigen||A antibodies||B,O|
|Blood type AB||∼ 5%||A and B antigens||No A or B antibodies||AB, A, B, O|
|Rhesus negative||∼ 15%||-||Rhesus (Rh) antibodies after previous sensitization||Rh negative|
|Rhesus positive||∼ 85%||-||No Rh antibodies||Rh positive, Rh negative|
Recipient's plasma sample
- Usually EDTA tube
- Obtained within 3 days prior to testing in hospital inpatients, or patients with a history of transfusion or a history of pregnancy in the previous 3 months, or uncertain history of either
- Proper identification of the patient and labeling of the sample is vital.
- The person drawing the blood must identify the patient.
- The sample must be labeled properly and match the information of the requisition for the blood bank.
- Most blood banks require two separate samples to avoid possible mistakes.
Compatibility testing must be performed before an RBC unit can be released from the blood bank for transfusion!
- Emergency transfusions
Whole blood transfusions
- Content: donor blood or recipient (autologous) blood
- Rarely used except for massive transfusions for significant blood loss
- Elective autologous blood transfusion for elective surgery
Fractionated blood components
Content: red blood cells
- Leukoreduction; : filtration of blood cells to remove leukocytes; (FDA guidelines: < 5x106 leukocytes/unit) to reduce the risk of nonhemolytic febrile transfusion reactions and prevent transmission of CMV, HTLV-I/II, and EBV via leukocytes
- Irradiation: exposure to radiation to inactivate lymphocytes; leukodepleted RBC concentrates are used in immunosuppressed patients to prevent graft-versus-host disease
- Situational factors must be evaluated to assess the need for transfusion.
The indication for transfusion is not solely dependent on the Hb value, but rather on a combination of clinical findings and pre-existing conditions!
- Transfusion thresholds
|Transfusion recommendation (American Association of Blood Banks)|
|Clinical situation||Hb threshold||Transfusion|
| ||≤ 6 g/dL|| |
| ||< 7–8 g/dL|| |
- Effect: 1 unit of packed RBCs increases Hb value approx. 1.0 g/dL
- Complications: Chronic transfusions can lead to hemochromatosis.
Jehovah's Witnesses who do not want to accept blood transfusions should be asked to provide documentary evidence (e.g., advance directive card refusing blood). However, in life-threatening situations in which the patient cannot be consulted, or there is uncertainty concerning the documentation, it is advisable not to withhold blood!
- Content: plasma; all cellular components have been removed from the transfusion product
ABO compatibility must be considered.
- According to current guidelines, the Rhesus factor does not have to be considered.
- Lowering the risk of transmitting infections
|A||Rh+ or Rh-||A or AB|
|B||Rh+ or Rh-||B or AB|
|0||Rh+ or Rh-||0,A,B or AB|
|AB||Rh+ or Rh-||AB|
- Thrombocytopenia to prevent spontaneous bleeding
- Massive blood loss
- Effect: One platelet transfusion increases the platelet count by approx. 20–40/nL.
- Content: clotting factors (fibrinogen, factor VIII, factor XIII), vWF, and fibronectin
- Indications: similar to FFP; preferable if large transfusion volumes are undesirable
- Content: specific clotting factors that have been pooled from multiple donors
- Indications: specific clotting factor deficiencies, life-threatening bleeds, warfarin overdose
- Effect: increases the effects of heparin
- Inhibitor of coagulation, which is synthesized in the liver → inhibition of thrombin, Xa, IXa, XIa, and XIIa
Clerical errors are the most common cause of transfusion reactions!
|Acute hemolytic transfusion reaction|| || |
|Nonhemolytic febrile transfusion reaction|| || || |
|Minor allergic reactions|| || |
|Anaphylaxis|| || || |
|Transfusion-related acute lung injury (TRALI)|| || |
|Post-transfusion purpura|| || |
|Delayed hemolytic transfusion reaction|| || |
If fever develops in a patient receiving a transfusion, repeat donor and patient blood typing and crossmatching to rule out an incompatibility reaction!
Transfusion-associated circulatory overload (TACO):
- Definition: fluid overload that can occur with transfusion of blood products . Occurs during or within 6 hours of transfusion.
- Symptoms of hypervolemia: shortness of breath, S3 gallop, jugular venous distention, hypertension
- Chest x-ray shows diffuse bilateral infiltrates as a sign of pulmonary edema
- Treatment: diuretics to correct volume status, oxygen supplementation, assisted ventilation
- Hypocalcemia: Formation of complexes with the added citrate; occurs with whole blood transfusions, platelet transfusions, or FFP
- Sepsis if blood products are contaminated with bacteria