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22nd July 2024

Blood transfusion

Red blood cell transfusion

Guidelines do not give a fixed Hb level for transfusion and advise using clinical judgement. It is generally suggested to transfuse if Hb <70 g/L, and to target 70-90 g/L post-transfusion. For those with cardiac disease, a higher threshold is used, Hb <80 g/L, with a target of 80-100 g/L. These targets do not apply in cases of significant bleeding, symptomatic anaemia, acute coronary syndrome (ACS) or transfusion-dependent anaemia.

The blood grouping system commonly refers to ABO and rhesus D antigens, however there are other clinically significant antigens present. Patients will have antibodies against antigens missing from their own RBCs and it is important to ensure compatible blood is given – otherwise there is risk of a haemolytic reaction.

Alternatives to blood transfusion

It is generally recommended to use alternative methods to optimise patients instead of transfusing where possible. This includes iron replacement, which can be IV in an acute setting or oral in the community, and intraoperative cell salvage and tranexamic acid, which should be considered in all patients expected to have high blood loss.

Transfusion reactions
Acute haemolytic reaction A life-threatening reaction caused by ABO incompatibility or other mismatched antigens. Presents early in the transfusion with fever, chills, back/flank pain, hypotension, DIC (bleeding or oozing from lines) or haemoglobinuria.

Management: stop transfusion, IV fluids to aim for urine output > 100 ml/hour, confirm patient identity and the name on the blood product. A full set of bloods, including a group and save, Coombs test and haemolysis screen, should be sent.
Anaphylaxis Angioedema, bronchospasm/wheeze, cyanosis, hypotension, flushing, and urticaria.

Management: stop transfusion, treat anaphylaxis (adrenaline, consider antihistamine and hydrocortisone, and supportive measures as required, including airway).
Bacterial infection Can be caused by a blood product contaminated with a microorganism. Clinical features include fever >39ºC (or increase >2ºC following transfusion), rigors, tachycardia and hypotension – often occurring at least 30 minutes after the transfusion has been completed.

Management: stop transfusion, then manage as sepsis, including sending cultures. Blood bank needs to be informed and the blood bag sent to microbiology for culture.
Transfusion-related acute lung injury (TRALI) Acute lung injury or acute respiratory distress syndrome (ARDS) within 6 hours of transfusion. Symptoms often occur within the first hours of transfusion: hypoxia, hypotension and pulmonary infiltrates on CXR.

Management: stop transfusion, otherwise mostly supportive – oxygen supplementation, consideration of NIV. Early ITU discussions are needed, as patients may need mechanical ventilation ± circulatory support. Must be reported to the blood bank for recall of donors for HLA (human leukocyte antigens) antibody testing.
Transfusion-associated circulatory overload (TACO) Fluid overload within 12 hours of last transfusion (secondary to transfusion). Presents with dyspnoea, hypoxia, elevated jugular venous pressure (JVP) and bibasal crepitations. Often hypertensive – can help differentiate from TRALI.

Management: slow or stop transfusion depending on severity and indication for the transfusion. Supplemental oxygen and a diuretic can be given if required.
Non-haemolytic febrile reaction A diagnosis of exclusion – first rule out other reactions. Fever and shivering, often within 1 hour of start of transfusion, but with no other systemic features.

Management: slow or stop transfusion, give antipyretics.
Allergic reaction A common reaction associated with itching and urticaria.

Management: slow or stop transfusion, give antihistamines (e.g. chlorphenamine).
Transfusion-associated graft-versus-host disease (ta-GVHD) Often fatal. Can develop 4-30 days post-transfusion. Due to proliferation of T-lymphocytes from the donor’s blood, which attack host HLA-expressing cells. Presents with fever, pancytopenia, erythroderma, deranged LFTs and diarrhoea.

Risk factors:

  • Immunosuppression – primary e.g. severe combined immunodeficiency (SCID), Hodgkin lymphoma (even after remission), patients undergoing stem cell transplant (SCT), chemotherapy regimens including fludarabine (generally for haematological malignancies)
  • Foetuses and neonates
  • Partial HLA matching of donor and recipient

Gamma irradiation of blood products inactivates T cells, thus reducing the risk of ta-GVHD; patients who are defined as high risk need irradiated blood. Treatment is often ineffective and includes stem cell transplantation (limited time to find a suitable donor) and immunosuppression with steroids, IVIg or cyclosporin.

Platelet transfusion

Usual thresholds for transfusion in non-bleeding patients are platelets <10 x10⁹/L or <20 x10⁹/L in the context of sepsis. In bleeding patients, this threshold is increased to <30 x10⁹/L or higher for severe bleeding or high-risk sites, e.g. CNS bleeding. The peak increment can be measured 10-60 minutes post transfusion, and then reduces over the next 72 hours, with the expected increase to be around 30 x10⁹/L per pool of platelets transfused.

Complications include all of the transfusion reactions associated with blood transfusions (Table 4), however the most common reactions with platelet transfusion include infection (platelets are stored at room temperature so bacteria can divide rapidly) and alloimmunisation (production of anti-HLA antibodies against the donor platelets, leading to no significant increment in platelet count).

References

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Complete Guide to Paediatric Surgery ST3 Application and Recruitment in United Kingdom (2026)

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