Key Facts

Blood transfusion involves the intravenous administration of blood components to treat anaemia, bleeding, or coagulopathy. The UK blood service provides leucodepleted components as standard since 1999. Proper patient identification and documentation are the most critical safety steps.

Epidemiology

• ~2.5 million units of red cells issued per year in England
• Transfusion errors remain a significant patient safety issue: ~2,000 adverse events reported to SHOT annually
• Most common error: wrong blood in tube (WBIT) — incorrect patient sampling
• TACO is now the leading cause of transfusion-related mortality in the UK

Aetiology

Indications for transfusion:

• Acute haemorrhage: trauma, GI bleeding, obstetric haemorrhage
• Symptomatic anaemia refractory to medical therapy
• Bone marrow failure: chemotherapy-induced, aplastic anaemia, MDS
• Coagulopathy: DIC, liver failure, massive transfusion
• Thrombocytopenia with active bleeding or pre-procedure

Pathophysiology

• Red cell transfusion: restores oxygen-carrying capacity; stored RBCs undergo storage lesion (reduced 2,3-DPG, increased potassium)
• Platelet transfusion: provides functional platelets for haemostasis; shelf life only 5 days (bacterial contamination risk)
• FFP: contains all coagulation factors; used in DIC, massive transfusion, TTP (therapeutic plasma exchange)
• Cryoprecipitate: concentrated fibrinogen, factor VIII, von Willebrand factor, factor XIII — used when fibrinogen <1.5 g/L

Acute Transfusion Reactions

• Acute haemolytic reaction: ABO incompatibility — fever, rigors, back pain, hypotension, haemoglobinuria within minutes of starting transfusion
• Febrile non-haemolytic reaction: temperature rise ≥1°C — most common reaction; due to cytokines from leucocytes
• Allergic/urticarial reaction: urticaria, pruritus, flushing — usually mild; anaphylaxis rare
• Anaphylaxis: hypotension, bronchospasm, angioedema — often in IgA-deficient patients

Delayed Reactions

• Delayed haemolytic reaction: 1–14 days post-transfusion; falling Hb, jaundice, positive DAT
• TACO: dyspnoea, hypertension, raised JVP, pulmonary oedema — within 6 hours; BNP elevated
• TRALI: acute dyspnoea, bilateral infiltrates, hypoxia — within 6 hours; BNP normal; treat supportively

Red Flags

• Fever, rigors, or hypotension during transfusion — STOP transfusion immediately
• Dark urine (haemoglobinuria) suggesting haemolysis
• Dyspnoea or desaturation during/after transfusion
• Loin/back pain during transfusion

Bedside

• Observations: temperature, pulse, BP, SpO2 — at baseline, 15 min, and hourly during transfusion
• Fluid balance chart: monitor input/output to detect TACO
• Urinalysis: haemoglobinuria if haemolysis suspected

Bloods

• Group and screen: ABO and RhD typing, antibody screen
• Cross-match: serological or electronic (if no antibodies)
• FBC: pre- and post-transfusion Hb, platelet count
• Coagulation screen: PT, APTT, fibrinogen — pre-FFP/cryoprecipitate
• U&Es, LFTs: baseline
• If reaction: DAT, repeat group & screen, LDH, bilirubin, haptoglobin, blood cultures (from patient and unit), urinary haemoglobin

Imaging

• CXR: if TACO or TRALI suspected

Special Tests

• BNP/NT-proBNP: elevated in TACO, normal in TRALI
• IgA levels: if anaphylaxis — IgA deficiency
• SHOT reporting: all reactions must be reported

Non-pharmacological

• Patient identification: check identity band, prescription, and compatibility label against patient — requires two staff members
• Informed consent: document consent for transfusion
• Restrictive transfusion strategy (NICE NG24): transfuse single unit, reassess clinically, avoid Hb target >80 g/L unless ACS
• Alternatives: IV iron (ferric carboxymaltose 1000mg), erythropoietin, tranexamic acid 1g IV for bleeding (CRASH-2 trial)

Pharmacological

Pre-medication:

• Paracetamol 1g and chlorphenamine 10mg IV only if history of febrile/allergic reactions

If transfusion reaction:

• Stop transfusion, maintain IV access with 0.9% NaCl
• Mild allergic: chlorphenamine 10mg IV, restart cautiously
• Febrile non-haemolytic: paracetamol 1g, send investigation samples
• Anaphylaxis: IM adrenaline 0.5mg (1:1000), IV fluids, hydrocortisone 200mg IV
• TACO: sit upright, furosemide 40mg IV, oxygen, slow/stop transfusion
• Acute haemolysis: aggressive IV fluids to maintain urine output >1 ml/kg/hr, involve haematology urgently

Landmark trials:

• TRICC trial: restrictive (Hb 70) vs liberal (Hb 100) — restrictive non-inferior, possibly superior in ICU
• CRASH-2: tranexamic acid within 3 hours reduces mortality in bleeding trauma

Surgical/Interventional

• Cell salvage: intraoperative blood recovery — reduces allogeneic transfusion requirements
• Therapeutic plasma exchange: for TTP (daily until ADAMTS13 recovery)

Referral Criteria

• Haematology for massive transfusion, complex antibodies, refractory transfusion requirements
• Transfusion laboratory for all suspected reactions
• Blood bank for rare blood types and complex cross-matching

• Febrile non-haemolytic reactions: excellent prognosis, self-limiting
• Acute haemolytic reactions: mortality ~2–10% depending on volume transfused and speed of recognition
• TACO: mortality ~5–15%; higher in elderly and those with cardiac comorbidity
• TRALI: mortality ~5–10%; most recover within 48–72 hours with supportive care
• Transfusion-associated GvHD: >90% mortality — prevention (irradiation) is key
• Overall transfusion-related mortality in UK: approximately 1 in 250,000 units transfused

Blood Product Summary

Transfusion Thresholds (NICE NG24)