Acute haemolytic transfusion reaction

Overview

•Caused by ABO-incompatible blood - almost always human error (mislabelled sample, failed identity check)

•Preformed IgM anti-ABO antibodies → classical complement activation → intravascular haemolysis + macrophage cytokine release → fever, pain, shock

Presentation

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Classic exam triad: fever + pain (abdominal/chest/back) + hypotension during active transfusion. Pain is the discriminating feature - separates AHTR from febrile non-haemolytic reaction (fever only) and TACO (hypertension + pulmonary oedema).

•Fever and rigors - cytokine-mediated; rise ≥1.5°C

•Pain - abdominal, chest, back/flank, or infusion site; hallmark distinguishing feature

•Hypotension and tachycardia - cytokine-mediated vasodilation and shock

•Haemoglobinuria - dark red/brown urine; hallmark of intravascular haemolysis

•Feeling of apprehension - early symptom; patient reports 'something is wrong' before objective signs

•Oozing from wounds/puncture sites - indicates evolving DIC

•Symptoms can begin after as little as 5-10 mL of incompatible blood

Investigations

•Bedside identity check - most important immediate step; verify patient against blood unit label

•Direct antiglobulin test (DAT/direct Coombs) - detects antibodies/complement on red cells; typically positive in AHTR

•Repeat ABO typing and crossmatch - discrepancy confirms mismatch

•FBC - falling Hb confirms haemolysis

•LDH and unconjugated bilirubin - both rise with red cell destruction

•Urine dipstick - haemoglobinuria

•U&E and clotting screen - detect evolving AKI and DIC

Management

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Do NOT wait for results - stop the transfusion immediately and resuscitate. Investigations run in parallel.

🥇 First-line

•Stop transfusion immediately - keep IV access patent; return unit and giving set to blood bank

•IV 0.9% sodium chloride - maintain circulating volume and renal perfusion; target urine output ≥100 mL/hour

•Urinary catheterisation - monitor urine output and detect haemoglobinuria

•Notify blood bank urgently - repeat identity checks, withdraw associated components

🥈 Second-line

•Mannitol (forced diuresis) - if urine output inadequate despite adequate fluid resuscitation

•Vasopressors - distributive shock unresponsive to fluids

🥉 Third-line

•Renal replacement therapy - if established oliguric/anuric AKI

•FFP, cryoprecipitate, or platelets - if DIC develops

Complications

•AKI - free haemoglobin directly toxic to renal tubules; tubular obstruction and renal vasoconstriction

•DIC - complement/cytokine activation triggers coagulation cascade; thrombocytopaenia, elevated PT/APTT, low fibrinogen, wound oozing

•Distributive shock - massive cytokine-driven vasodilation; may require vasopressors and ITU

•Death - up to 10% mortality in severest reactions (e.g. group O receiving group A blood)