Conditions · Hematology and oncology
Transfusion reactions !
Transfusion reactions are unwanted responses to donated blood, from mild fever or hives to life-threatening haemolysis, lung injury or fluid overload.
Updated 2026-11-01
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In immunology
Why it happens
- Blood groups, transfusion and transfusion reactions
- The red cell life cycle and the spleen
- Innate and adaptive immunity: overview
What it is
Adverse events that occur during or after the transfusion of blood components. They range from mild febrile or allergic reactions to acute haemolysis, transfusion-related acute lung injury (TRALI), circulatory overload (TACO), anaphylaxis and bacterial contamination.
Who gets it
Mild febrile and allergic reactions are the most frequent; acute haemolytic reactions are rare and are usually due to clerical or identification errors. In Colombia and Latin America, national haemovigilance programmes and voluntary unpaid donation are promoted to make transfusion safer.
Causes
- ABO-incompatible red cells destroyed by the recipient's preformed antibodies (acute haemolytic reaction)
- Cytokines and recipient antibodies against donor white cells (febrile non-haemolytic reaction)
- Recipient antibodies against donor plasma proteins; IgA-deficient recipients with anti-IgA antibodies (allergic reaction, anaphylaxis)
- Donor anti-leukocyte antibodies activating neutrophils in the recipient's lungs (TRALI)
- Volume given faster than the heart can handle (TACO)
- Minor-antigen antibodies boosted after a previous exposure (delayed haemolytic reaction)
- Bacterial contamination, most often of platelets stored at room temperature
Risk factors
- Patient or sample identification errors at the bedside or in the laboratory
- Previous transfusions or pregnancies (alloimmunisation)
- Heart failure, kidney failure, older age or infants (TACO)
- Rapid transfusion of several units
- IgA deficiency
Pathophysiology
In an acute haemolytic reaction, anti-A or anti-B antibodies bind donor red cells and activate complement, causing intravascular haemolysis, release of free haemoglobin, cytokine storm, hypotension, disseminated intravascular coagulation and acute kidney injury. Delayed reactions cause milder extravascular haemolysis in the spleen days later. TRALI is a non-cardiogenic pulmonary oedema caused by activated neutrophils in the lung capillaries, while TACO is a hydrostatic (cardiogenic) oedema from volume overload.
Classification
- Acute (within 24 hours): haemolytic, febrile non-haemolytic, allergic and anaphylactic, TRALI, TACO, septic (bacterial)
- Delayed (days to weeks): delayed haemolytic, post-transfusion purpura, transfusion-associated graft-versus-host disease, iron overload
- Infectious: transmission of viruses, bacteria or parasites (rare with screening)
Symptoms and signs
- Fever and chills during or soon after the transfusion
- Hives, itching and flushing (allergic reaction)
- Back or flank pain, pain at the infusion site and a sense of doom (acute haemolysis)
- Dark or red urine (haemoglobinuria)
- Shortness of breath, low oxygen and crackles (TRALI or TACO)
- Hypotension, tachycardia or high blood pressure with distended neck veins (TACO)
- Jaundice and an unexpected fall in haemoglobin days later (delayed haemolysis)
Diagnosis
- Clinical
- Any new symptom during a transfusion is treated as a possible reaction: the transfusion is stopped, vital signs are checked and the patient's identity is compared with the unit label and request.
- Tests
- Repeat blood group and crossmatch, direct antiglobulin (Coombs) test, haemoglobin, haemolysis markers (LDH, bilirubin, haptoglobin), urinalysis for haemoglobin, creatinine, coagulation tests for DIC, and blood cultures of the patient and the unit when sepsis is suspected. BNP helps separate TACO from TRALI.
- Imaging
- Chest X-ray shows bilateral infiltrates in TRALI and TACO; echocardiography helps judge volume status and heart function.
Differential diagnosis
- Fever from the underlying illness or an unrelated infection
- Anaphylaxis to a drug given at the same time
- Cardiogenic pulmonary oedema or ARDS from another cause
- Autoimmune haemolytic anaemia
- Haemolysis from G6PD deficiency or mechanical damage
Goal of treatment
Stop the exposure immediately, support breathing and circulation, protect the kidneys, identify the type of reaction and report it to the blood bank and haemovigilance system.
Treatment
- Acute
- Stop the transfusion at once, keep the venous line open with saline, check the bedside identification and return the unit and tubing to the blood bank.
- Acute
- Acute haemolysis: intravenous fluids to keep urine output high, vasopressors for shock and management of DIC; dialysis if kidney failure develops.
- Medical
- Antipyretics for febrile reactions and antihistamines for mild allergy; epinephrine, oxygen and airway support for anaphylaxis.
- Acute
- TRALI: oxygen and ventilatory support, with diuretics avoided. TACO: upright position, oxygen and loop diuretics.
- Follow-up
- Nursing priority: vital signs before, at the start (first 15 minutes) and during the transfusion, with close observation for early signs; two-person identity check before every unit.
Complications
- Shock and disseminated intravascular coagulation
- Acute kidney injury from haemoglobin deposition and hypotension
- Acute respiratory failure
- Death, mainly from ABO incompatibility, TRALI, TACO or sepsis
- Alloimmunisation that makes future crossmatching difficult
Prognosis
Febrile and mild allergic reactions resolve quickly. Acute haemolytic reactions, TRALI and TACO can be fatal, but most patients recover with early recognition and support; TRALI usually improves within a few days.
Prevention
- Strict patient identification and two-person bedside checks
- ABO and Rh typing and crossmatching before transfusion
- Transfusing only when indicated and at a rate suited to the patient
- Leukoreduced, washed or irradiated components for selected patients
- Donor screening and haemovigilance reporting
Test yourself
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What is the most common cause of an acute haemolytic transfusion reaction?
ABO incompatibility, usually from a clerical or patient-identification error.
What is the first action when a transfusion reaction is suspected?
Stop the transfusion immediately and keep the IV line open with normal saline.
How do TRALI and TACO differ?
TRALI is non-cardiogenic lung oedema from donor antibodies, with normal or low pressures; TACO is volume overload with hypertension, raised BNP and response to diuretics.
Which recipients are at risk of anaphylaxis to plasma-containing products?
IgA-deficient patients with anti-IgA antibodies.
Which test confirms immune-mediated haemolysis after a transfusion?
A positive direct antiglobulin (Coombs) test.
Related conditions
- Anaphylaxis
- Acute respiratory distress syndrome (ARDS)
- Acute kidney injury
- Heart failure
- Sepsis and septic shock
Educational information, not medical advice. For any symptom, see a health professional.
Sources: Hemolytic transfusion reaction (MedlinePlus (U.S. National Library of Medicine), 2024); Blood safety and availability (World Health Organization, 2025).
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