Definition / Overview
Transfusion medicine encompasses the clinical indication, selection, administration, and monitoring of blood components (BCs), as well as the recognition and management of transfusion reactions and the conduct of massive transfusion. Safe transfusion practice integrates pre-transfusion testing, product modification, vigilance during administration, and informed consent - each of which is a potential exam viva focus.
Australian practice is governed by the National Blood Authority's patient blood management (PBM) framework, which emphasises optimising haematopoiesis, minimising surgical blood loss, and restricting transfusion to those with a genuine clinical need before reaching for a blood product.
Blood Products: Types, Indications, and Key Features
Packed Red Blood Cells (pRBCs)
- Standard indication: symptomatic anaemia or haemoglobin below a threshold in a patient who cannot compensate physiologically.
- Restrictive trigger: $\text{Hb} < 70\,\text{g/L}$ in haemodynamically stable patients without active cardiac disease (evidence from multiple RCTs supports non-inferiority of restrictive versus liberal strategies).
- Liberal trigger: $\text{Hb} < 80\,\text{g/L}$ in patients with symptomatic coronary artery disease, post-cardiac surgery, or patients with acute MI - Australian guidelines support a slightly higher threshold in this group.
- Each unit raises Hb by approximately $10\,\text{g/L}$ in a 70 kg adult.
- Administered via a $\geq 18\,\text{gauge}$ IV cannula through a standard $170\text{-}260\,\mu\text{m}$ filter; maximum infusion time 4 hours per unit; only normal saline may co-infuse in the same line.
- Storage lesion: older units accumulate extracellular potassium - clinically relevant in neonates, patients with renal failure, and large-volume rapid transfusion.
Fresh Frozen Plasma (FFP)
- Contains all coagulation factors and von Willebrand factor (vWF).
- Indicated for: active bleeding with multiple coagulation factor deficiency (DIC, massive transfusion dilutional coagulopathy), urgent warfarin reversal when prothrombin complex concentrate (PCC) is unavailable, thrombotic thrombocytopenic purpura (plasma exchange).
- Dose: typically $15\,\text{mg/kg}$; must be ABO-compatible but does not require crossmatch.
- Not appropriate for simple volume expansion or isolated factor deficiency where a specific product exists.
Platelets
- Prophylactic threshold: $10 \times 10^9/\text{L}$ in stable patients; $20 \times 10^9/\text{L}$ if febrile or with minor procedure; $50 \times 10^9/\text{L}$ for most surgical procedures; $100 \times 10^9/\text{L}$ for neurosurgery or posterior segment eye surgery.
- Therapeutic: any platelet count with active bleeding attributable to thrombocytopenia or platelet dysfunction.
- Stored at room temperature ($20\text{-}24°\text{C}$) - hence highest bacterial contamination risk among blood products.
- Do not require crossmatch; ABO/RhD compatibility preferred where possible.
Cryoprecipitate
- Rich in fibrinogen, factor VIII, vWF, factor XIII, and fibronectin.
- Primary indication: hypofibrinogenaemia ($\text{fibrinogen} < 1.5\,\text{g/L}$) in the context of active bleeding; also used in DIC and massive transfusion.
- Each unit raises fibrinogen by approximately $7\text{-}8\,\text{mg/dL}$; typically ordered in pools of 5-10 units.
- Not a first-line agent for haemophilia A or vWD - specific factor concentrates are preferred.
Albumin
- Available as 4% (iso-oncotic) and 20% (hyperoncotic) solutions.
- Indicated as a volume expander in large-volume paracentesis, spontaneous bacterial peritonitis, hepatorenal syndrome, and selected hypoalbuminaemia states.
- Does not transmit infectious pathogens as it undergoes pasteurisation.
Pre-transfusion Testing and Product Modifications
Type and Screen / Crossmatch
- Type and screen: determines ABO/RhD group and screens recipient serum for unexpected alloantibodies - valid for 72 hours in hospitalised patients with recent transfusion history.
- Serological crossmatch: tests recipient serum against a specific donor unit - required for patients with known alloantibodies.
- Computer (electronic) crossmatch: acceptable for patients with no history of clinically significant alloantibodies and two concordant ABO typings on record.
- Plasma and platelets do not require crossmatch.
Blood Product Modifications
| Modification | Method | Indication |
|---|---|---|
| Leucoreduction | Prestorage filtration to $< 5 \times 10^6$ WBC/unit | All patients (standard in Australia); reduces febrile reactions, CMV risk, HLA alloimmunisation |
| Irradiation | Gamma/X-ray irradiation to inactivate donor T lymphocytes | Prevention of transfusion-associated GVHD in immunocompromised recipients (haematological malignancy, stem cell transplant, congenital immunodeficiency, neonates) |
| CMV-seronegative | Donor testing for CMV | Immunocompromised, CMV-seronegative patients; prestorage leucoreduced products are considered equivalent risk-reduction in most settings |
| Washed products | Removal of plasma proteins by washing | IgA deficiency with anti-IgA antibodies; recurrent severe allergic reactions |
| Pathogen reduction | UV-light inactivation of pathogens | Currently approved for platelets and plasma only; not yet widespread |
Emergency Release Blood
When life-threatening haemorrhage precludes waiting for crossmatch: - pRBCs: group O RhD-negative (universal donor) - switch to group-specific or crossmatched as soon as possible to preserve O-negative stock. - Plasma: group AB or group A plasma (universal donor plasma).
Transfusion Reactions: Recognition and Management
Approach to a Suspected Transfusion Reaction
- Stop the transfusion immediately - maintain IV access with normal saline.
- Check patient identity against the blood product label at the bedside - exclude clerical/identification error.
- Notify the blood bank; retain the implicated unit and all tubing for return.
- Send: repeat group and screen, direct antiglobulin test (DAT), FBC, UEC, coagulation, LDH, bilirubin, free haemoglobin (plasma and urine), blood cultures.
- Document time of onset, symptoms, and vital signs.
Classification and Management of Acute Reactions
| Reaction | Onset | Key Features | Immediate Action |
|---|---|---|---|
| Acute haemolytic (ABO incompatibility) | Minutes | Fever (rapid onset), rigors, back/loin pain, hypotension, haemoglobinuria, DIC | STOP; supportive care; IV fluids; target urine output $\geq 100\,\text{mL/h}$; alkalinise urine (NaHCO₃ to urinary $\text{pH} \geq 7.5$); treat DIC |
| Febrile non-haemolytic | 1-6 h | Fever, chills - no haemolysis | SLOW or STOP; paracetamol; exclude haemolytic cause |
| Allergic/urticarial | During | Urticaria, pruritus | SLOW or STOP; chlorphenamine 10 mg IV/IM; restart if mild and resolving |
| Anaphylaxis | Minutes | Bronchospasm, hypotension, angioedema | STOP; adrenaline 0.5 mg IM; airway/oxygen; IVF; check IgA deficiency |
| Bacterial contamination | Minutes | Rapid high fever, rigors, profound hypotension | STOP; blood cultures; broad-spectrum antibiotics immediately |
| TACO | During or shortly after | Dyspnoea, hypertension, pulmonary oedema, elevated BNP | SLOW or STOP; oxygen; furosemide; upright positioning |
| TRALI | Within 6 h | Dyspnoea, hypoxia, bilateral pulmonary infiltrates WITHOUT volume overload, possible fever | STOP; supportive oxygen; ICU if severe - anti-HLA/antineutrophil donor antibodies implicated |
Distinguishing TACO from TRALI
A critical clinical distinction:
| Feature | TACO | TRALI |
|---|---|---|
| Blood pressure | Elevated (systolic hypertension common) | Normal or low |
| JVP/CVP | Elevated | Normal or low |
| BNP/NT-proBNP | Markedly elevated | Minimally elevated |
| Chest X-ray | Bilateral alveolar infiltrates + cardiomegaly | Bilateral infiltrates, normal heart size |
| Response to diuretics | Improves | No benefit |
| Mechanism | Volume overload | Immune-mediated endothelial injury (donor antibodies → recipient neutrophil activation) |
Delayed Transfusion Reactions
- Delayed haemolytic reaction: 3-10 days post-transfusion; anamnestic antibody response to donor RBC antigens (e.g. Kidd, Duffy); falling Hb and Hct, positive DAT; treat as per acute haemolytic reaction if severe.
- Post-transfusion purpura: $5\text{-}7$ days post-transfusion; platelet-specific antibody (commonly anti-HPA-1a) destroys patient's own platelets as well as donor platelets - profound thrombocytopenia; treat with IV immunoglobulin.
- Transfusion-associated GVHD: 1-6 weeks; donor T lymphocytes engraft and attack host tissues (skin, gut, liver, marrow); near-uniformly fatal - prevention by irradiation is paramount.
- Iron overload: cumulative iron deposition (each pRBC unit $\approx 200\text{-}250\,\text{mg}$ iron); clinically significant after $\sim 20$ units; affects liver, endocrine glands, heart; treat with iron chelation (desferrioxamine or deferasirox).
Transfusion-Transmitted Infections
- All donations screened for HIV-1/2, HTLV-1/2, Hepatitis B and C, West Nile virus, Zika virus, syphilis, Trypanosoma cruzi, and bacterial contamination (platelets).
- Residual risk is very low: Hepatitis B $\approx 1$ in 1,000,000; HIV and Hepatitis C $< 1$ in 1,000,000.
- Window period remains the main vulnerability.
- Most common organisms in bacterial contamination: Yersinia enterocolitica (pRBCs) and Staphylococcus spp. (platelets).
Massive Transfusion Protocol (MTP)
Definition
Replacement of $> 10$ units of pRBCs within 24 hours, or $> 50\%$ of estimated total blood volume within 3 hours - thresholds vary by institution but the core concept is life-threatening haemorrhage requiring a coordinated multidisciplinary response.
Goals and Haemostatic Resuscitation
Modern MTP uses damage control resuscitation: - Balanced ratio transfusion: approximately 1:1:1 (pRBC: FFP: platelets) - avoids dilutional coagulopathy from crystalloid excess. - Early cryoprecipitate/fibrinogen concentrate if fibrinogen falls $< 1.5\,\text{g/L}$. - Minimise crystalloid - avoid saline-induced hyperchloraemic acidosis. - Tranexamic acid $1\,\text{g}$ IV over 10 minutes, then $1\,\text{g}$ over 8 hours - most effective within the first 3 hours of injury onset; benefit wanes and may be harmful if given $> 3$ hours post-injury.
Complications of Massive Transfusion
| Complication | Mechanism | Prevention/Treatment |
|---|---|---|
| Hypocalcaemia | Citrate preservative chelates ionised calcium | Monitor iCa²⁺; IV calcium gluconate or chloride via separate line |
| Hypothermia | Transfusing cold product ($4°\text{C}$) | In-line blood warmers; warm the patient |
| Hyperkalaemia | $\text{K}^+$ leaks from stored RBCs (worse with older units, irradiated units) | Use fresh units where possible; monitor ECG; insulin-dextrose, calcium, furosemide |
| Dilutional coagulopathy | Replacement without clotting factors | Balanced ratio transfusion; FFP; cryoprecipitate; point-of-care coagulation testing (TEG/ROTEM) to guide |
| Transfusion-related | TACO, TRALI, haemolytic reactions | Vigilance; appropriate product selection |
| Acidosis | Underlying shock + citrate metabolism | Correct perfusion; bicarbonate rarely needed if resuscitation adequate |
Laboratory Monitoring During MTP
- FBC, coagulation (PT, APTT, fibrinogen), UEC, iCa²⁺, ABG/lactate - at minimum every 30-60 minutes during active MTP.
- Point-of-care viscoelastic testing (TEG or ROTEM): increasingly used to guide targeted factor replacement and reduce empirical over-transfusion.
- Liaise directly with haematology and blood bank throughout.
Consent, Refusal, and Ethical Practice
Informed Consent for Transfusion
- Transfusion is a medical procedure requiring informed consent - this includes explanation of the indication, benefits, risks (infection, haemolytic reaction, TACO, TRALI, alloimmunisation), and alternatives (iron, erythropoietin, cell salvage, tranexamic acid).
- Consent should ideally be obtained electively before an anticipated transfusion (e.g. pre-operatively).
- Document consent in the medical record.
Refusal of Blood Products - Jehovah's Witnesses and Other Groups
- Adult patients with decision-making capacity have an absolute legal and ethical right to refuse any medical treatment, including blood transfusion, even if that refusal may result in death - this applies under common law (assault/battery if overridden) and is reinforced by Australian and New Zealand human rights frameworks.
- Assess capacity carefully using a structured approach - the patient must understand the information, retain it, weigh it, and communicate a decision.
- Document the refusal in detail, including the extent of the patient's understanding and the alternatives offered.
- Explore which specific products are acceptable - individual Jehovah's Witnesses have variable personal positions on fractions (albumin, clotting factors, erythropoietin) and cell salvage; do not assume blanket refusal of all products.
- An advance healthcare directive refusing transfusion is binding on clinicians if valid and applicable to the situation.
- Children: parental refusal does not automatically extend to children - in an immediately life-threatening situation, the child's best interests take precedence; obtain urgent legal advice and involve senior clinicians. Courts can and do authorise transfusion for children whose parents refuse.
Alternatives to Allogeneic Transfusion
- Preoperative optimisation: treat iron deficiency anaemia with oral or IV iron; erythropoietin in selected patients.
- Intraoperative cell salvage: collects shed blood for re-infusion; used in cardiac, vascular, orthopaedic surgery.
- Antifibrinolytics: tranexamic acid reduces surgical blood loss.
- Surgical haemostasis: meticulous technique, deliberate hypotension where appropriate.
Long-term Care and Special Populations
Chronically Transfused Patients
- Monitor for iron overload with serum ferritin and liver MRI ($T2^*$ sequence); initiate chelation therapy (deferasirox oral or desferrioxamine subcutaneous) when indicated.
- Screen for alloantibody formation - increasingly complex crossmatching with each subsequent transfusion episode.
- Patients with sickle cell disease and thalassaemia benefit from extended phenotype matching (at minimum Rh and Kell antigens) to reduce alloimmunisation risk.
Indigenous Australians and Health Equity
- Higher rates of haemoglobinopathies and nutritional anaemia in some Indigenous communities - increased likelihood of requiring transfusion or iron supplementation.
- Sickle cell disease is increasingly identified in Aboriginal and Torres Strait Islander people of diverse ancestry; alloimmunisation risk from transfusion is particularly relevant.
- Ensure culturally safe communication when discussing transfusion consent - use professional interpreters and community liaison where language or cultural barriers exist.
- Pre-hospital access to blood products and MTP capabilities may be limited in remote settings - advocate for appropriate resource allocation and retrieval pathways.
Key Exam Points
- Restrictive transfusion strategy (Hb trigger $< 70\,\text{g/L}$) is the default; raise threshold to $80\,\text{g/L}$ for acute coronary syndrome or symptomatic cardiac disease.
- First step in any transfusion reaction: stop the transfusion, maintain IV access with saline, check patient and product ID.
- TACO vs TRALI: blood pressure, BNP, and response to diuretics are the pivotal distinguishing features - TRALI is managed with supportive oxygen and does not respond to diuretics.
- Massive transfusion: early 1:1:1 ratio, tranexamic acid within 3 hours, treat the "lethal triad" of hypothermia, acidosis, and coagulopathy.
- Capacity to refuse transfusion is absolute in an adult - document carefully, explore product-specific preferences, and seek ethics or legal input early for complex cases.
- Irradiated products prevent TA-GVHD in immunocompromised patients - failure to prescribe irradiated products where indicated is a preventable, often fatal, error.