Trusted medical expertise in seconds.

Access 1,000+ clinical and preclinical articles. Find answers fast with the high-powered search feature and clinical tools.

Try free for 5 days
Evidence-based content, created and peer-reviewed by physicians. Read the disclaimer.


Last updated: June 16, 2021

Summarytoggle arrow icon

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.

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 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!


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
    • E.g., prothrombin complex concentrate
  • Indications: specific clotting factor deficiencies, life-threatening bleeds, warfarin overdose

Antithrombin III (AT III)

  • Indication:
  • Effect: increases the effects of heparin
  • Inhibitor of coagulation, which is synthesized in the liver → inhibition of thrombin, Xa, IXa, XIa, and XIIa


Immunologic reactions

Overview of the most common immunologic transfusion reactions
Frequency Pathophysiology Time of onset Clinical features Treatment
Acute hemolytic transfusion reaction
  • 1 in 70,000 transfusions [13]
  • Rapid onset during transfusion (because of preformed antibodies) or up to 24 hours after the transfusion
Nonhemolytic febrile transfusion reaction [15]
  • 3% of transfusions
  • When blood products have been in storage for long periods of time cytokines may leak from donor WBCs and cause a mild immunologic reaction in the recipient.
  • Preformed recipient antibodies cause lysis of the few remaining leukocytes within donor blood products, resulting in an inflammatory reaction.
  • Quick onset in 1–6 hours after transfusion (since cytokines are preformed)
Minor allergic reactions
  • 3% of transfusions
  • Onset during or shortly after transfusion
  • 1 in 50,000 transfusions
  • WIthin 3 hours after the transfusion
Transfusion-related acute lung injury (TRALI)
  • 1 in 500–100,000 transfusions [16]
  • Two mechanisms:
    • Sequestration and priming of neutrophils in the pulmonary endothelium due to the recipient's comorbidities (prior to transfusion) [17]
    • Soluble factors (antibodies, certain lipids) in the donor blood lead to activation of the recipient's granulocytes release of the proinflammatory mediators → increase of vascular permeability → plasma transudation into pulmonary interstitium non-cardiogenic pulmonary edema [18]
  • Most commonly occurs following transfusion of FFP or platelets
  • Onset during or within 6 hours of transfusion
  • Discontinue transfusion and contact blood bank .
  • Supportive management
    • Maintain sufficient ventilation/oxygen supply.
    • Control hemodynamic parameters.
    • Use anti-inflammatory therapy with IV steroids (only in specific circumstances)
Post-transfusion purpura
  • 1 in 50,000–100,000 transfusions [19]
  • Occurs primarily in women with a history of multiple pregnancies
  • Onset in 5–10 days after transfusion
Delayed hemolytic transfusion reaction
  • 1 in 800–11,000 transfusions [13]
  • Most commonly asymptomatic
  • Mild fever
  • Jaundice
  • Anemia
  • No acute therapy required (self-limiting)
  • Antibody testing to prevent future reactions

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

Nonimmunologic reactions

  1. Blood Groups and Red Cell Antigens. Chapter 5, The ABO blood group. Updated: January 1, 2005. Accessed: February 14, 2018.
  2. Agabegi SS, Agabegi ED. Step-Up To Medicine. Wolters Kluwer Health ; 2015
  3. Le T, Bhushan V, Sochat M, Petersen M, Micevic G, Kallianos K. First Aid for the USMLE Step 1 2014. McGraw-Hill Medical ; 2014
  4. Jenkins B, McInnis M, Lewis C. Step-Up to USMLE Step 2 CK. Lippincott Williams & Wilkins ; 2015
  5. Carson JL, Kleinman S. Indications and hemoglobin thresholds for red blood cell transfusion in the adult. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. updated: November 14, 2016. Accessed: February 19, 2017.
  6. Kaplan LJ, Maerz LL. Transfusion and Autotransfusion. Transfusion and Autotransfusion. New York, NY: WebMD. Updated: January 27, 2015. Accessed: February 19, 2017.
  7. Carson JL, Grossman BJ, Kleinman S et al. Red Blood Cell Transfusion: A Clinical Practice Guideline From the AABB. Ann Intern Med. 2012; 157 (1): p.49-58. doi: 10.7326/0003-4819-157-1-201206190-00429 . | Open in Read by QxMD
  8. Kaufman RM, Djulbegovic B, Gernsheimer T. Platelet Transfusion: A Clinical Practice Guideline From the AABB. Ann Intern Med. 2015; 162 (3): p.205-213. doi: 10.7326/M14-1589 . | Open in Read by QxMD
  9. Ferreira J, DeLosSantos M. The Clinical Use of Prothrombin Complex Concentrate. J Emerg Med. 2013; 44 (6): p.1201-1210. doi: 10.1016/j.jemermed.2012.12.022 . | Open in Read by QxMD
  10. 2012 Clinical Practice Guide on Red Blood Cell Transfusion.
  11. Harewood J, Ramsey A, Master SR. Hemolytic Transfusion Reaction. StatPearls. 2020 .
  12. Silvergleid AJ. Hemolytic transfusion reactions. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. updated: March 27, 2017. Accessed: March 30, 2017.
  13. Transfusion medicine. Transfusion reaction. Febrile Nonhemolytic Transfusion Reaction (FNHTR). Updated: November 16, 2017. Accessed: February 20, 2018.
  14. Toy P, Lowell C. TRALI – Definition, mechanisms, incidence and clinical relevance. Best Practice & Research Clinical Anaesthesiology. 2007; 21 (2): p.183-193. doi: 10.1016/j.bpa.2007.01.003 . | Open in Read by QxMD
  15. Bux J, Sachs UJ. The pathogenesis of transfusion-related acute lung injury (TRALI).. Br J Haematol. 2007; 136 (6): p.788-99. doi: 10.1111/j.1365-2141.2007.06492.x . | Open in Read by QxMD
  16. Bux J. Transfusion-related acute lung injury (TRALI): a serious adverse event of blood transfusion. Vox Sang. 2005 . doi: 10.1111/j.1423-0410.2005.00648.x . | Open in Read by QxMD
  17. Rafei H, Yunus R, Nassereddine S. Post-Transfusion Purpura: A Case Report of an Underdiagnosed Phenomenon. Cureus. 2017 . doi: 10.7759/cureus.1207 . | Open in Read by QxMD
  18. Silvergleid AJ. Immunologic blood transfusion reactions. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate.§ionRank=1&anchor=H18#H18.Last updated: May 7, 2014. Accessed: February 19, 2017.
  19. Complications of Transfusion. Updated: July 1, 2014. Accessed: February 19, 2017.
  20. Hoffbrand V, Moss PAH. Essential Haematology. John Wiley & Sons ; 2011
  21. Uhl L. Pretransfusion testing for red blood cell transfusion. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. updated: January 5, 2016. Accessed: February 19, 2017.
  22. Le T, Bhushan V. First Aid for the USMLE Step 1 2015. McGraw-Hill Education ; 2014
  23. Blood Types. Updated: February 19, 2017. Accessed: February 19, 2017.
  24. Blood typing. Updated: November 2, 2016. Accessed: February 19, 2017.
  25. Carson JL, Guyatt G, Heddle NM, et al.. Clinical Practice Guidelines From the AABB: Red Blood Cell Transfusion Thresholds and Storage. JAMA. 2016; 316 (19): p.2025. doi: 10.1001/jama.2016.9185 . | Open in Read by QxMD