77 BLOOD PRODUCTS
# 78 BLOOD PRODUCTS
Transfusion questions in MRCS Part A cluster around three themes: blood group compatibility, which component to give for which problem, and recognising the transfusion reactions.
👩⚕️ Three anchors: FFP lasts 24 h once thawed (1 year frozen); UK transfusion recipients can NEVER donate (vCJD); citrate in stored blood binds calcium → hypocalcaemia in massive transfusion.
Detailed notes
Blood groups — ABO and Rh
ABO antigens are carbohydrates on the red cell surface. Naturally occurring IgM antibodies form against whichever antigens you do NOT possess — so ABO incompatibility is immediate and catastrophic because the antibody is already circulating before the transfusion starts.
| Group | RBC antigen | Plasma antibody | Frequency (UK) | Notes |
|---|---|---|---|---|
| A | A | Anti-B | ~42% | |
| B | B | Anti-A | ~10% | |
| AB | A and B | None | ~3% | Universal plasma donor; universal RBC recipient |
| O | None | Anti-A and anti-B | ~45% | Universal RBC donor; universal plasma recipient |
Note the inversion: O is universal RBC donor but universal plasma recipient; AB is the opposite. This catches candidates out constantly.
Rh (Rhesus) is a separate protein antigen system; RhD is the clinically dominant one. RhD-negative patients have no pre-formed anti-D — they develop it after sensitisation (transfusion or pregnancy), and the consequences appear on the second exposure.
➡ RhD-negative women of childbearing age must receive RhD-negative red cells.
➡ Anti-D immunoglobulin is given to RhD-negative mothers at 28 weeks and again postpartum (within 72 hours) if the baby is RhD-positive, plus after any sensitising event (miscarriage, bleeding, amniocentesis).
Cross-matching: group & save vs crossmatch
- Group & save (G&S): ABO + RhD typed, antibody screen done; no blood reserved. Used when transfusion is unlikely (e.g. lap chole).
- Crossmatch: patient serum mixed with donor cells; units reserved. Used when transfusion is likely.
- Emergency: O RhD-negative (~5 min); switch to group-specific then full crossmatch when available.
👩⚕️ A stable elective patient needs G&S, not a crossmatch — a classic SBA trap.
Blood components
Whole blood is rarely used; donations are separated into components.
#### Packed red cells
Stored at 4°C for up to 35 days. One unit ↑ Hb by ~10 g/L. Restrictive threshold Hb <70 (or <80 in cardiac disease) — TRICC trial. Must be ABO + RhD compatible; transfused over 2–4 h per unit.
#### Platelets
Stored at 22°C with agitation; shelf life 5–7 days. One adult dose pooled from 4 donors ↑ count by ~25–50 × 10⁹/L. Thresholds: <10 prophylactic; <20 in sepsis; <50 pre-op or active bleeding; <100 before CNS/eye surgery. RhD-negative platelets for RhD-negative females of childbearing age.
#### Fresh frozen plasma (FFP)
Contains all clotting factors at normal concentrations. Dose 15 mL/kg (≈4 units). Indications: DIC with bleeding, massive transfusion, TTP (plasma exchange). NOT first-line for warfarin reversal — PCC is faster. ABO-compatible required; no crossmatch needed. Use within 24 h of thawing.
#### Cryoprecipitate
Slow-thawed FFP. Rich in fibrinogen, vWF, factor VIII, factor XIII, fibronectin. Give if fibrinogen <1.5 g/L (or <2 in obstetric haemorrhage). Cryo = the fibrinogen one.
#### Prothrombin complex concentrate (PCC) — Beriplex / Octaplex
Contains factors II, VII, IX, X ("1972", the vitamin K dependent factors). First-line for major warfarin bleeding (with IV vitamin K) — works in minutes, no volume load. Also used in DOAC bleeding.
#### Also worth knowing
- Human albumin solution — large-volume paracentesis, hepatorenal syndrome.
- Anti-D immunoglobulin — see Rh section above.
- Tranexamic acid (TXA) — not a blood product, but always paired in stems. Give within 3 h of trauma (CRASH-2) or PPH (WOMAN).
| Component | Key contents | One-line indication |
|---|---|---|
| Packed RBC | Red cells | Anaemia / haemorrhage (Hb <70) |
| Platelets | Platelets | Thrombocytopenia with bleeding or pre-procedure |
| FFP | All clotting factors | DIC, massive transfusion (15 mL/kg) |
| Cryoprecipitate | Fibrinogen, vWF, VIII, XIII | Fibrinogen <1.5 g/L |
| PCC | II, VII, IX, X | Major warfarin bleeding |
Transfusion reactions
The highest-yield section. Examiners test pattern recognition: feature → reaction → action.
| Reaction | Timing | Mechanism | Key features | Action |
|---|---|---|---|---|
| Acute haemolytic | Minutes | ABO incompatibility (usually ID error) | Fever, hypotension, loin/back pain, dark urine (haemoglobinuria), DIC | STOP, IV fluids, send unit + bloods back to lab, check patient ID |
| Febrile non-haemolytic | 30 min – 2 h | Recipient antibodies to donor leukocytes/cytokines | Isolated fever, rigors, no haemodynamic change | Slow/stop, paracetamol, exclude haemolysis; commonest reaction |
| Allergic / urticarial | Minutes | Antibodies to donor plasma proteins | Urticaria, itch | Slow, antihistamine |
| Anaphylaxis | Minutes | IgA deficiency with anti-IgA antibodies | Hypotension, bronchospasm, angioedema | STOP, adrenaline; future products must be IgA-deficient/washed |
| TACO | Within 6 h | Volume overload | Pulmonary oedema, hypertension, raised JVP; elderly/cardiac | Slow, diuretics, oxygen |
| TRALI | Within 6 h | Donor anti-HLA/anti-neutrophil antibodies → non-cardiogenic pulmonary oedema | ARDS picture, hypotension, normal JVP | STOP, supportive (often ITU); inform blood service |
| Delayed haemolytic | 5–10 days | Anamnestic response to minor antigen (e.g. Kidd, Duffy) | Falling Hb, jaundice, positive DAT | Supportive; future antigen-negative units |
| TA-GVHD | 1–4 weeks | Donor lymphocytes attack recipient | Fever, rash, diarrhoea, pancytopenia; near-100% mortal | Prevent: irradiate blood for immunocompromised, Hodgkin's, intrauterine, neonates |
| Infection | Variable | Viral (HIV, HBV, HCV, HEV), bacterial, vCJD | Per-pathogen | Screening + leucodepletion; UK recipients excluded from donating |
👩⚕️ TACO vs TRALI is a classic SBA. Both cause pulmonary oedema within 6 hours. TACO = hypertension, raised JVP, responds to diuretics (the patient is wet). TRALI = hypotension, normal JVP, does not respond to diuretics (the lungs are leaking, the patient is not overloaded).
👩⚕️ If the stem mentions loin/back pain during transfusion, it is acute haemolytic until proven otherwise. Stop the transfusion immediately and recheck the patient ID against the unit — ABO incompatibility is almost always a clerical error.
Massive transfusion
Defined as >10 units RBC in 24 h, >50% blood volume in 4 h, or 4 units in 1 h with ongoing bleeding.
Activate the major haemorrhage protocol:
- Empirical 1:1:1 RBC : FFP : platelets (PROPPR trial), pending lab results.
- TXA 1 g IV within 3 h (CRASH-2).
- Cryoprecipitate if fibrinogen <1.5 g/L (or <2 in obstetrics).
- Keep warm; correct calcium; monitor potassium.
Complications — hypothermia, hypocalcaemia (citrate, SBA classic), hyperkalaemia (K⁺ leak from stored cells), hypomagnesaemia, dilutional coagulopathy, acidosis then alkalosis (citrate → bicarbonate).
Special situations
- Jehovah's Witnesses: refuse RBC, platelets, FFP, whole blood. Cell salvage, EPO, IV iron and TXA are usually acceptable — clarify and document individually. An adult with capacity has an absolute right to refuse.
- Paediatric transfusion: RBC and FFP at 10–15 mL/kg.
- Irradiated blood: Hodgkin's, post-HSCT, intrauterine, neonates, fludarabine — prevents TA-GVHD.
- CMV-negative blood: intrauterine, neonatal, pregnancy.
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A clean diagram showing the ABO compatibility matrix — donor groups (rows) vs recipient groups (columns), with red cells on one half and plasma/FFP on the other, highlighting that O is universal donor for RBC while AB is universal donor for plasma.
Purpose:
The donor/recipient inversion between red cells and plasma is the single most common ABO trap in MRCS Part A. A visual matrix locks it in far better than prose.
Suggested source:
TeachMeSurgery / Wikimedia Commons (search "ABO compatibility chart").
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[Image: MCQs banner]
Test yourself
Which of the following statements is correct regarding fresh frozen plasma (FFP)?
- ((FFP must be used within 24 hours once thawed::☑️ Correct; once thawed clotting factor activity declines rapidly. Frozen shelf life is 1 year.))
- ((FFP is leuco-depleted::Red cell products are leukodepleted; FFP is not routinely leukodepleted.))
- ((Cross-matching must be done before giving FFP::ABO compatibility is required, but no crossmatch — FFP contains plasma antibodies, not red cells.))
- ((Urticaria is not a common reaction to FFP::Allergic/urticarial reactions are in fact among the commonest FFP reactions.))
👩⚕️ FFP is ABO-matched but never crossmatched — a frequent SBA trap.
According to UK NICE guidelines, what is the rule for people who have received a blood transfusion regarding future blood donation?
- ((Can donate once viral markers are negative::Incorrect — vCJD has no validated screening test.))
- ((Can donate within 6 weeks::Incorrect — this rule is permanent, not temporary.))
- ((Can donate within 12 weeks::Incorrect — exclusion is lifelong.))
- ((Can never donate::☑️ Permanent exclusion to prevent transmission of variant Creutzfeldt-Jakob disease (vCJD).))
👩⚕️ UK transfusion recipients are permanently excluded from donating — the only such lifelong exclusion in routine practice.
A patient receives a massive blood transfusion. She subsequently has hypocalcaemia. What is the cause for this?
- ((Citrate toxicity::☑️ Stored blood contains citrate as anticoagulant; in large volumes it binds ionised calcium.))
- ((Dilutional effect::Dilution alone does not explain acute symptomatic hypocalcaemia.))
- ((Hypothermia::A separate complication of massive transfusion; doesn't cause hypocalcaemia directly.))
- ((Hyperkalaemia::A separate complication from red cell leak — independent of calcium.))
👩⚕️ Citrate binds calcium AND is metabolised to bicarbonate — hypocalcaemia and metabolic alkalosis both follow.
A 68-year-old man on warfarin for AF presents with a large intracerebral haemorrhage. INR is 4.2. What is the most appropriate first-line reversal?
- ((Prothrombin complex concentrate (PCC) plus IV vitamin K::☑️ PCC reverses warfarin within minutes by replacing factors II, VII, IX, X.))
- ((Fresh frozen plasma::Slower, large volume load, and less complete factor replacement — not first-line for major bleeding.))
- ((Platelets::Warfarin does not affect platelet number or function.))
- ((Cryoprecipitate::Replaces fibrinogen, not vitamin K-dependent factors.))
👩⚕️ For major warfarin bleeding: PCC + IV vitamin K. FFP is the wrong answer in MRCS-land.
Twenty minutes into a red cell transfusion, a patient becomes hypotensive, febrile, and complains of severe loin pain with dark urine. What is the most likely diagnosis?
- ((Acute haemolytic reaction::☑️ ABO incompatibility — usually a clerical/ID error. Stop transfusion, return unit, recheck identity.))
- ((Febrile non-haemolytic reaction::Causes isolated fever/rigors without hypotension or loin pain.))
- ((TRALI::Presents with pulmonary oedema and hypoxia, not loin pain or haemoglobinuria.))
- ((Anaphylaxis::Presents with bronchospasm, urticaria, angioedema — not loin pain.))
👩⚕️ Loin/back pain + dark urine during transfusion = acute haemolytic until proven otherwise.
A 78-year-old with heart failure receives 3 units of red cells over 4 hours. He develops dyspnoea, raised JVP and bilateral basal crackles. BP is 175/95. What is the diagnosis?
- ((TACO (transfusion-associated circulatory overload)::☑️ Volume overload — hypertension, raised JVP, pulmonary oedema. Treat with oxygen and diuretics.))
- ((TRALI::Causes hypotension with normal JVP — not hypertension.))
- ((Acute haemolytic reaction::Loin pain and haemoglobinuria, not isolated pulmonary oedema.))
- ((Anaphylaxis::Bronchospasm and urticaria, not raised JVP.))
👩⚕️ TACO = wet patient, high JVP, high BP, responds to diuretics. TRALI = leaky lungs, normal JVP, low BP, no response to diuretics.
A trauma patient receives 12 units of red cells within 4 hours. Which complication is the patient most at risk of?
- ((Hypocalcaemia from citrate toxicity::☑️ Citrate in stored blood binds ionised calcium when transfused in large volumes.))
- ((Hyperphosphataemia::Not a recognised complication of massive transfusion.))
- ((Metabolic acidosis from citrate::Citrate is metabolised to bicarbonate — causes alkalosis, not acidosis.))
- ((Hypokalaemia::Stored blood leaks potassium; massive transfusion causes hyperkalaemia.))
👩⚕️ The four classic biochemical hits of massive transfusion: low Ca, low Mg, high K, low temp.
Which blood component is first-line for a patient with fibrinogen of 1.0 g/L during postpartum haemorrhage?
- ((Cryoprecipitate::☑️ Concentrated source of fibrinogen, vWF, factors VIII and XIII — used when fibrinogen <2 g/L in obstetric bleeding.))
- ((FFP::Contains fibrinogen but at much lower concentration than cryoprecipitate.))
- ((PCC::Contains factors II, VII, IX, X — no fibrinogen.))
- ((Platelets::Address thrombocytopenia, not hypofibrinogenaemia.))
👩⚕️ Cryo = the fibrinogen one. PCC = the warfarin one. FFP = the everything-else one.
A patient develops hypoxia and bilateral pulmonary infiltrates 2 hours into a transfusion. JVP is not raised and BP is 80/50. What is the most likely diagnosis?
- ((TRALI::☑️ Donor anti-HLA antibodies trigger non-cardiogenic pulmonary oedema; hypotension with normal JVP.))
- ((TACO::Causes hypertension and raised JVP — opposite haemodynamic picture.))
- ((Acute haemolytic reaction::Causes loin pain and haemoglobinuria, not pulmonary infiltrates.))
- ((Anaphylaxis::Bronchospasm and urticaria, not bilateral infiltrates.))
👩⚕️ TRALI is the leading cause of transfusion-related mortality in the UK.
Which patient group must receive irradiated blood products?
- ((Patients with Hodgkin lymphoma::☑️ Cellular immunosuppression risks TA-GVHD; irradiation inactivates donor lymphocytes.))
- ((Patients with sickle cell disease::Require phenotypically matched red cells, not routinely irradiated.))
- ((Pregnant women::Require CMV-negative blood, not routinely irradiated.))
- ((Patients with iron deficiency anaemia::Standard transfusion only — no irradiation indicated.))
👩⚕️ Irradiate for: Hodgkin's, intrauterine transfusion, neonates, post-HSCT, fludarabine therapy.
Revision summary
➡ ABO: O = universal RBC donor; AB = universal recipient (and universal plasma donor).
➡ RhD-negative women of childbearing age must receive RhD-negative red cells. Anti-D at 28 weeks and postpartum.
➡ Group & save for low transfusion risk; crossmatch when transfusion likely; O-neg in emergencies.
➡ 1 unit RBC ↑ Hb by ~10 g/L. Transfuse if Hb <70 (or <80 with cardiac disease).
➡ 1 ATD platelets ↑ count by ~25–50. Pool of 4 donors.
➡ FFP = all clotting factors, 15 mL/kg, ABO-matched but no crossmatch, 24 h once thawed.
➡ Cryoprecipitate = fibrinogen (+ vWF, VIII, XIII). Give if fibrinogen <1.5 (<2 in obstetrics).
➡ PCC = II, VII, IX, X. First-line for major warfarin bleeding (with IV vitamin K) — not FFP.
➡ Acute haemolytic: minutes, loin pain, haemoglobinuria, ABO ID error — STOP and recheck identity.
➡ TACO vs TRALI: both <6 h with pulmonary oedema. TACO = high JVP, hypertensive, diuretics work. TRALI = normal JVP, hypotensive, supportive only.
➡ Anaphylaxis in transfusion → suspect IgA deficiency.
➡ TA-GVHD → irradiate blood for the immunocompromised.
➡ Massive transfusion: 1:1:1 RBC:FFP:platelets, TXA within 3 h, watch for low Ca, low Mg, high K, hypothermia, acidosis.
➡ UK transfusion recipients can never donate — vCJD risk.
➡ Jehovah's Witnesses: cell salvage, EPO, iron, TXA usually acceptable; clarify and document.