Transfusion basics

Core concepts (what you’re trying to achieve)

• Transfusion is a treatment for inadequate oxygen delivery (anaemia/bleeding) or disordered clotting—not a routine “top up”.
• Always balance benefit vs risk: wrong blood, reactions, fluid overload, infection risk (rare), and immunological complications.
• Treat the patient, not just the Hb: consider bleeding rate, physiology, symptoms, and comorbidities (e.g. IHD).
• Use patient blood management: stop bleeding, optimise coagulation, minimise blood loss, and use restrictive thresholds where safe.

Key definitions (plain English)

• RBC (red cell) transfusion: increases oxygen-carrying capacity; one adult unit usually raises Hb by ~10 g/L (1 g/dL) in a non-bleeding adult.
• FFP (fresh frozen plasma): replaces multiple clotting factors; used for significant coagulopathy with bleeding or before urgent procedures when clotting is abnormal.
• Platelets: treat or prevent bleeding due to low platelets or platelet dysfunction (e.g. antiplatelet drugs in some scenarios).
• Cryoprecipitate: concentrated fibrinogen (plus factor VIII, vWF, factor XIII); used when fibrinogen is low, especially in major haemorrhage/obstetrics.
• Group & screen (G&S): determines ABO/RhD and checks for atypical antibodies; allows compatible blood to be issued.
• Crossmatch: confirms compatibility for a specific patient and unit; takes longer but safest when time allows.

When to transfuse RBCs (intro thresholds + clinical context)

• Stable, non-bleeding adult: consider transfusion if Hb <70 g/L; aim 70–90 g/L in many patients (local policy may vary).
• Acute coronary syndrome/symptomatic ischaemia: consider a higher threshold (often <80 g/L) and discuss early with senior/haematology if uncertain.
• Ongoing major bleeding: don’t wait for Hb—base decisions on physiology, blood loss, and major haemorrhage protocol (MHP).
• Symptoms/signs suggesting inadequate oxygen delivery: chest pain, ECG changes, hypotension unresponsive to volume, rising lactate, low mixed/central venous saturation, reduced urine output (interpret in context).
• Give one unit at a time in stable patients, then reassess clinically and with Hb (unless actively bleeding).

Product basics (what’s in the bag and common uses)

• RBCs: for anaemia/haemorrhage; check if special requirements apply (irradiated, CMV-negative, antigen-negative).
• FFP: typically in significant bleeding with prolonged PT/INR/aPTT or as part of MHP; not for simple volume expansion.
• Platelets: bleeding with thrombocytopenia or peri-procedural support; in major haemorrhage often targeted to keep platelets >50 x10^9/L (higher for neurosurgery/ocular surgery).
• Cryoprecipitate: for low fibrinogen (commonly target >1.5–2.0 g/L in major haemorrhage; obstetrics often aims higher—follow local guidance).
• Tranexamic acid (TXA) is not a blood product but is a key early adjunct in major bleeding (unless contraindicated).

ABO/RhD essentials (what you must know on day 1)

• ABO incompatibility is the most dangerous transfusion error—can cause rapid intravascular haemolysis, shock, DIC, and death.
• If group unknown and urgent: use O negative RBCs (especially females of childbearing potential) or O positive per local policy for males/post-menopausal females when O neg stock limited—confirm with your lab policy.
• Plasma compatibility differs: AB plasma is universal donor for plasma; group-specific plasma preferred when available.
• RhD: avoid giving RhD-positive blood to RhD-negative females of childbearing potential if possible; if unavoidable, involve haematology and consider anti-D prophylaxis as per policy.

Pre-transfusion checks (the ‘never events’ prevention bundle)

• Correct patient identification at sampling: ask patient to state full name and DOB (if possible); check wristband; label samples at the bedside immediately.
• Ensure the request form matches the patient and sample exactly; document indication and urgency.
• Before administration: check patient identity, compatibility label, unit number, blood group, expiry, and special requirements—ideally with a second trained checker or approved electronic system.
• Inspect the unit: leaks, clots, unusual colour; if abnormal, do not transfuse—return to blood bank.
• Baseline observations (pulse, BP, temp, SpO2) and ensure IV access is adequate; start slowly and stay nearby for the first 15 minutes.

How to give blood safely (practical steps)

• Use a blood giving set with filter; avoid adding drugs to blood lines.
• RBCs are usually infused over 1.5–3 hours per unit (faster if haemorrhaging; slower if at risk of fluid overload). Do not exceed local maximum hang time (commonly 4 hours).
• Warm blood only with an approved blood warmer when indicated (e.g. rapid transfusion, massive transfusion, cold agglutinins)—not with improvised methods.
• Monitor: repeat observations at 15 minutes, then at intervals per policy; watch for new fever, rash, dyspnoea, hypotension, back pain, or anxiety/“sense of doom”.
• Recheck Hb and coagulation after transfusion when clinically indicated (especially in bleeding/MHP).

Major haemorrhage (first-time scenario essentials)

• Recognise early: ongoing blood loss, falling BP, tachycardia, poor perfusion, rising lactate, increasing vasopressor requirement, surgical concern.
• Call for help early: senior anaesthetist, theatre team, blood bank; activate the Major Haemorrhage Protocol (MHP) per local pathway.
• Priorities: stop bleeding (surgery/IR), restore circulating volume, correct coagulopathy, maintain temperature, correct calcium, avoid acidosis.
• Send urgent bloods: FBC, coagulation (PT/INR, aPTT), fibrinogen, U&E, calcium, blood gas/lactate; consider viscoelastic testing (TEG/ROTEM) if available.
• Give TXA early if appropriate; maintain normothermia; give calcium (citrate in blood binds calcium—hypocalcaemia worsens hypotension/coagulopathy).
• Aim for balanced component therapy guided by labs/viscoelastic results and local MHP packs.

Transfusion reactions (what to do immediately)

• If reaction suspected: STOP transfusion, keep IV access with 0.9% saline, check patient and unit identity, call for senior help and inform the blood bank.
• Assess ABCDE; treat anaphylaxis immediately if suspected (airway support, IM adrenaline per guidelines, fluids, adjuncts).
• Send samples as per policy: repeat group & screen, haemolysis markers, DAT, cultures if sepsis suspected; return the unit and giving set to the lab.
• Common patterns: febrile reaction (fever/rigors), allergic reaction (urticaria), anaphylaxis (airway/breathing compromise), acute haemolysis (pain, hypotension, dark urine), TACO (fluid overload), TRALI (acute hypoxia with non-cardiogenic pulmonary oedema).
• Do not restart the transfusion until reviewed and advised by senior/haematology/blood bank.

Special requirements you must not miss

• Irradiated blood: required for certain immunocompromised patients (e.g. Hodgkin lymphoma, purine analogues, CAR-T/HSCT pathways) to prevent transfusion-associated graft-versus-host disease—check history and alerts.
• CMV-negative components: may be required for some high-risk groups (e.g. intrauterine/neonatal transfusion, some transplant settings)—follow local policy.
• Antigen-negative blood: patients with known antibodies need specifically matched units—this can take time; warn the lab early.
• Sickle cell disease: transfusion decisions are nuanced (simple vs exchange); involve haematology early and follow local protocols.