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Perioperative blood transfusion and transfusion reactions
Blood is given by a restrictive threshold and by the patient's condition, in massive bleeding products are given in a balanced ratio with early tranexamic acid, and transfusion reactions are recognised — especially acute haemolysis, TRALI and TACO.
Why it matters in the exam
The exam asks for the haemoglobin threshold for transfusion in a stable patient and in a cardiac patient, what to do in massive bleeding (a 1:1:1 ratio, calcium, warming), when tranexamic acid is given, and how warfarin is reversed urgently. Case questions show a patient who develops breathlessness, fever or hypotension during a transfusion, and the candidate must tell TRALI from TACO, a haemolytic reaction from a simple febrile reaction, and allergy from anaphylaxis in IgA deficiency.
One unit of blood raises haemoglobin by about 1 g/dL in an adult. Massive bleeding creates a "lethal triad" — cold, acidosis and coagulopathy — and large transfusions also cause hypocalcaemia from citrate and hyperkalaemia. Under general anaesthesia an acute haemolytic reaction shows mainly as hypotension, red urine and diffuse bleeding, because the patient cannot complain.
Patient blood management starts before surgery: anaemia is diagnosed and treated (usually iron deficiency, sometimes with intravenous iron), anticoagulants are stopped on time, and during surgery careful surgical technique, tranexamic acid and cell salvage are used where suitable. A patient who refuses blood for religious reasons is entitled to an informed decision; the products and methods he accepts are discussed with him in advance.
Key points
- Restrictive threshold: 7 g/dL, and 8 g/dL in cardiac patients.
- Massive bleeding: 1:1:1, calcium, warming, tranexamic acid within 3 hours.
- Urgent warfarin reversal: PCC and vitamin K.
- TACO — overload and hypertension, diuretics; TRALI — hypotension and fever, support.
- Acute haemolytic reaction — stop, fluids, look for an identification error.
Summary table
| Issue | Rule | Exam point |
|---|---|---|
| Haemoglobin threshold | 7 g/dL in most stable patients; 8 g/dL in heart disease or cardiac and orthopaedic surgery | One unit raises it by about 1 g/dL |
| Massive bleeding | Blood, plasma and platelets in a 1:1:1 ratio; calcium; warming | Viscoelastic tests (TEG/ROTEM) to guide therapy |
| Tranexamic acid | 1 g within 3 hours of injury, then another 1 g over 8 hours | After 3 hours — no benefit and possibly harm |
| Urgent warfarin reversal | PCC (4-factor) with IV vitamin K | Plasma only if PCC is unavailable |
| TRALI versus TACO | TRALI within 6 hours, TACO within 12 hours; TRALI — non-cardiogenic oedema, fever, hypotension; TACO — overload, hypertension, high BNP | TACO — diuretics; TRALI — support only |
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Sources
- AABB International Guidelines: Red Blood Cell Transfusion Thresholds and Storage, 2023 — Restrictive thresholds
- European guideline on management of major bleeding and coagulopathy following trauma, 6th edition (2023) — Coagulation support and tranexamic acid
- Miller's Anesthesia, 9th edition (2020) — Patient Blood Management: Transfusion Therapy
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-02. The text may contain errors; when in doubt, check the source.