• 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.

Blood group systems

ABO blood type system and Rhesus blood group system

ABO antigen on RBCs Antibodies in plasma Can receive RBCs from Can donate RBCs to Can receive FFP from Can donate FFP to
Blood type O ∼ 45% No antigens A and B antibodies O O, A, B, AB O, A, B, AB O
Blood type A ∼ 40% A antigen B antibodies A, O A, AB A, AB A, O
Blood type B ∼ 10% B antigen A antibodies B, O B, AB B, AB B, O
Blood type AB ∼ 5% A and B antigens No A or B antibodies AB, A, B, O AB AB AB, A, B, O
Rhesus negative ∼ 15% - Rhesus (Rh) antibodies after previous sensitization Rh negative Rh negative, Rh positive Rh negative, Rh positive Rh negative, Rh positive
Rhesus positive ∼ 85% - No Rh antibodies Rh positive, Rh negative Rh positive Rh negative, Rh positive Rh negative, Rh positive

Individuals with blood type O negative are “universal donors” of packed RBCs! Individuals with blood type AB positive are “universal recipients” for packed RBCs!

For fresh frozen plasma transfusions, individuals with blood type O are universal recipients (type O plasma contains A and B antibodies) and individuals with blood type AB are universal donors (AB plasma contains no A or B antibodies)!

The universal red cell donor has blood type O. The universal plasma donor has blood type AB.


Pretransfusion testing

Pretransfusion testing must be performed to prevent the transfusion of incompatible blood products and subsequent immune hemolytic transfusion reactions.

Compatibility testing must be performed before an RBC unit can be released from the blood bank for transfusion!


Transfusion products

Whole blood transfusions

  • Content: donor blood or recipient (autologous) blood
  • Indications
    • Rarely used except for massive transfusions for significant blood loss
    • Elective autologous blood transfusion for elective surgery

Fractionated blood components

Packed red blood cells (RBC)

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
  • Hospitalized patients (independent of clinical findings)
≤ 6 g/dL
  • Recommended
  • Hospitalized patients (hemodynamically stable)
    • Postoperative patients
    • ICU patients
    • Cardiovascular disease
    • Symptomatic anemia
< 7–8 g/dL
  • Recommended
  • Maintain Hb > 7–9 g/dL

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!

Fresh frozen plasma (FFP)

  • Content: plasma; all cellular components have been removed from the transfusion product
  • Indications
    • Warfarin overdose
    • Clotting factor deficiency (e.g., liver cirrhosis, DIC)
    • Substitution of plasma (in the case of massive transfusions)
  • ABO compatibility must be considered.
    • According to current guidelines, the Rhesus factor does not have to be considered.
  • Lowering the risk of transmitting infections
    • Inactivation of viruses
    • Quarantine: FFPs are cooled (-30°C) to minimize the risk of HIV and HCV transmission and only released if the donor repeatedly tests negative for HIV and HCV after a quarantine period of 4 months.
  • For compatibility of FFP transfusions see ABO blood type system and Rhesus blood group system.

Platelet transfusion


Clotting factors

  • Content: specific clotting factors that have been pooled from multiple donors
  • Indications: specific clotting factor deficiencies, life-threatening bleeds, warfarin overdose

Antithrombin III (AT III)

  • Indication:
    • In hereditary AT III deficiency to optimize thrombosis prophylaxis with heparin
    • In DIC if applicable
  • Effect: increases the effects of heparin
  • Inhibitor of coagulation, which is synthesized in the liver → inhibition of thrombin, Xa, IXa, XIa, and XIIa


Transfusion reactions

Clerical errors are the most common cause of transfusion reactions!

Immunologic reactions

Frequency Pathomechanism Clinical features Treatment
Acute hemolytic transfusion reaction
  • 1 in 250,000 transfusions
  • Immediate cessation of transfusion
  • Confirm diagnosis
    • Test patient's blood: direct Coombs test , plasma free hemoglobin > 25 mg/dL
    • Repeat typing and cross-matching of the transfusion product to identify and record causative blood products
  • Supportive care
Nonhemolytic febrile transfusion reaction
  • 3% of transfusions
  • After periods of long storage of blood products, cytokines may leak from donor RBCs and subsequently cause a mild immunologic reaction in the recipient.
  • In addition, preformed recipient antibodies lead to lysis of the few remaining leukocytes within donor RBC concentrates, resulting in an inflammatory reaction.
  • Onset during or within 1–6 hours after transfusion
  • Clinical features: fever, chills, malaise
Minor allergic reactions
  • 3% of transfusions
  • 1 in 50,000 transfusions
  • Anti-IgA IgG in recipients with IgA deficiency bind to IgA on the surface of donor RBCs and trigger mast cell degranulation.
  • Sudden onset during the transfusion
  • Shock, hypotension
Transfusion-related acute lung injury (TRALI)
  • < 0.08% of transfusions
  • Onset: during or within 6 hours of transfusion
  • Sudden onset
  • Symptoms and imaging results are generally the same as in ARDS: dyspnea, hypotonia, fever; chest x-ray showing diffuse infiltrates; in some cases, leukopenia
  • Hypotension (due to hypovolemia)
  • Discontinue transfusion; contact blood bank
  • Supportive management:
    • Maintain sufficient ventilation/oxygen supply
    • Control hemodynamic parameters
    • Anti-inflammatory therapy with IV steroids (only in specific circumstances)
  • Mortality rate generally below 20%
Post-transfusion purpura
  • Rare
  • Occurs primarily in women who have a history of multiple pregnancies
  • IVIG therapy or plasmapheresis
Delayed hemolytic transfusion reaction
  • Rare
  • No acute therapy required
  • Antibody testing to prevent future reactions

If fever develops in a patient receiving a transfusion, repeat donor and patient blood typing and crossmatching to rule out an incompatibility reaction!

Nonimmunologic reactions