[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [General pathology](https://durgical.com/en/general-pathology/) › [Red cells and bleeding disorders](https://durgical.com/en/general-pathology/areas/red-cells/) › Complications of transfusion

# Complications of transfusion

- Topic

Transfusion is safe but not risk-free: fever, allergy, destroyed donor cells, lung injury, fluid overload and, rarely, infection.

Updated Nov 12, 2026

## Key points

- Acute haemolytic reaction: fever, chills, back pain, hypotension, haemoglobinuria; may progress to DIC, shock and renal failure.
- Delayed haemolytic reaction: days later, positive direct Coombs test, falling haemoglobin.
- Anaphylaxis in IgA deficiency: IgG anti-IgA antibodies in the recipient.
- TRALI: within hours, hypoxaemia and bilateral infiltrates without heart failure; donor anti-HLA or anti-neutrophil antibodies, often from multiparous women.
- Infectious risks: bacteria (platelets), HIV, hepatitis B and C (very rare with nucleic acid testing), West Nile virus, Trypanosoma cruzi, Babesia, malaria.

## What it is

The most frequent transfusion reaction is the febrile nonhemolytic reaction, from cytokines and antibodies against donor leukocytes. Allergic reactions range from hives (IgE against donor plasma proteins) to anaphylaxis in IgA-deficient recipients with anti-IgA antibodies. Acute haemolytic reactions, usually ABO mismatch from identification errors, are caused by preformed IgM that fixes complement; delayed reactions come from IgG to antigens met before (Rh, Kell, Kidd). Transfusion-related acute lung injury (TRALI) is a two-hit neutrophil injury of the lung. Infections are rare, bacterial contamination being commonest in platelets stored at room temperature.

## Step by step

- TRALI first hit: an illness (surgery, sepsis) primes neutrophils and makes them stick in lung capillaries.
- TRALI second hit: donor antibodies or lipids in the plasma activate the primed neutrophils.
- Neutrophils release proteases and oxidants: capillary leak and diffuse alveolar damage.
- Haemolytic reaction: recipient IgM binds ABO antigens on donor cells and activates complement.
- Complement and cytokines cause fever, hypotension and DIC; free haemoglobin injures kidneys.

## Transfusion reactions

| Reaction | Mechanism | Timing | Key features |
| --- | --- | --- | --- |
| Febrile nonhaemolytic | Cytokines; antibodies to donor leukocytes | During or within hours | Fever and chills, self-limited |
| Allergic and anaphylactic | IgE to plasma proteins; anti-IgA in IgA deficiency | Minutes | Hives; or shock and bronchospasm |
| [Acute haemolytic](https://durgical.com/en/conditions/transfusion-reactions/) | Preformed IgM (ABO), complement | Minutes to hours | Fever, back pain, haemoglobinuria, DIC, renal failure |
| Delayed haemolytic | IgG from previous sensitization (Rh, Kell, Kidd) | Days to weeks | Falling haemoglobin, positive Coombs, jaundice |
| [TRALI](https://durgical.com/en/conditions/acute-respiratory-distress-syndrome/) | Donor antibodies activating primed neutrophils | Within hours | Hypoxaemia, bilateral infiltrates, no volume overload |
| Transfusion-transmitted infection | Contaminated unit | Hours (bacteria) to months (viruses, parasites) | Sepsis after platelets; viral or parasitic disease later |

## Clinical notes

- Bedside identity checks prevent most ABO-mismatched transfusions.
- Chagas disease screening of donors matters in Colombia and Latin America.
- Transfusion-associated circulatory overload mimics TRALI but with heart failure and volume excess.

## Memory aid

Fever, hives, haemolysis, the lungs and the bugs: five things to watch every time blood runs.

## Test yourself

Think of the answer, then tap the question to see it.

## What usually causes an acute haemolytic transfusion reaction?

An ABO-incompatible unit given after an identification error; preformed IgM fixes complement on donor cells.

## Which recipients are at risk of anaphylaxis to plasma-containing products?

People with IgA deficiency who have antibodies against IgA.

## Why are platelet units the most likely to carry bacterial contamination?

Platelets are stored at room temperature, which allows skin bacteria introduced at collection to grow.

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## Elsewhere in DurgiPedia

- [Transfusion reactions](https://durgical.com/en/immunology/transfusion-reactions/)
- [ABO and Rh blood groups, hemolytic disease of the newborn](https://durgical.com/en/immunology/abo-and-rh-blood-groups-hemolytic-disease-of-the-newborn/)
- [Blood groups, transfusion and transfusion reactions](https://durgical.com/en/physiology/blood-groups-transfusion-and-transfusion-reactions/)
- [Blood transfusion: bedside checks, monitoring and reactions](https://durgical.com/en/nursing/blood-transfusion-bedside-checks-monitoring-and-reactions/)

## Connections

## Related 4

- [Diffuse alveolar damage (ARDS)](https://durgical.com/en/general-pathology/diffuse-alveolar-damage/)
- [Immunohaemolytic anaemia](https://durgical.com/en/general-pathology/immunohaemolytic-anaemia/)
- [Hemorrhage: petechiae, purpura, ecchymosis, hematoma, and what blood loss does](https://durgical.com/en/general-pathology/hemorrhage-petechiae-purpura-ecchymosis-hematoma-and-what-blood-loss-does/)
- [Disseminated intravascular coagulation: how consumption causes both clots and bleeding](https://durgical.com/en/general-pathology/disseminated-intravascular-coagulation-how-consumption-causes-both-clots-and-ble/)

## Related conditions 6

- [Transfusion reactions](https://durgical.com/en/conditions/transfusion-reactions/)
- [Acute respiratory distress syndrome (ARDS)](https://durgical.com/en/conditions/acute-respiratory-distress-syndrome/)
- [Graft-versus-host disease](https://durgical.com/en/conditions/graft-versus-host-disease/)
- [Viral hepatitis](https://durgical.com/en/conditions/viral-hepatitis/)
- [HIV infection and AIDS](https://durgical.com/en/conditions/hiv-infection-and-aids/)
- [Chagas disease](https://durgical.com/en/conditions/chagas-disease/)

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Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.

Sources: [Hemolytic transfusion reaction: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/001303.htm) (MedlinePlus, US National Library of Medicine, 2026); [Blood Transfusion and Donation | MedlinePlus](https://medlineplus.gov/bloodtransfusionanddonation.html) (MedlinePlus, US National Library of Medicine, 2026).

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