Transfusion and Anaemia in Critically Ill Adults (BSH 2012, bsh 2025)

Intro

 

Anaemia is associated with poorer outcomes during ITU stays, and during recovery post-ITU discharge

Up to 25% of ITU patients receive a transfusion, usually for multifactorial anaemia

20-30% of patient admitted to ITU have an Hb <90g/l

After 7 days, 80% of ITU patients have an Hb <90g/l

ITU accounts for 10% of annual blood use

NB. The BSH 2025 paper is a confirmation of the position taken by the ESICM 2020 guidelines, rather than a new guideline in its own right.

 

Pathophysiology

 

Global oxygen delivery (DO2) is a product of cardiac output and arterial O2 concentration

Tissue hypoxia can occur as the result of a problem at any stage in the oxygen cascade – airway, pulmonary, cardiac, vascular flow etc.

Anaemia reduces oxygen carrying capacity

When tissue DO2 falls, compensatory mechanisms increase oxygen extraction up to a point

Once compensation is overwhelmed, O2 transport becomes directly proportional to O2 supply and tissue hypoxia becomes much more likely to occur.

Healthy individuals can maintain O2 supply down to a Hb of 40-50g/l

 

Alternatives to Red Cell Transfusion

 

Reduce iatrogenic blood loss

  • Typically approx. 40ml blood loss per day from blood sampling

  • Use of small bolume bottles reduces blood loss without affecting assay quality.

 

Erythropoietin

  • Critically ill patients do not produce a physiological increase in Epo production

  • Epo is not licensed for critically ill patient with anaemia due to no difference in patient outcomes and a concern over increased VTE risk. Not recommended.

 

Iron Therapy

  • Evidence of absolute iron deficiency is absent in most ITU patients…

  • …But insufficient evidence to support use of routine iron supplementation. IRONMAN 2022 found IV iron to be safe but did not reduce transfusion or length of stay.

  • Typical Iron profile in ITU

    • Serum iron – decreased

    • Total Iron Binding Capacity – Decreased

    • Ferritin – Increased

    • Transferrin – Decreased

    • Soluble Transferrin – Normal

 

Adverse Effects of RBC Transfusion in Critical Care

 

TACO

  • Acute respiratory distress with pulmonary oedema, tachycardia, increased BP and a positive fluid balance after blood transfusion

TRALI

  • Onset of pulmonary oedema within 6 hours of blood transfusion, hypoxia and bilateral pulmonary infiltrates on CXR.

  • Results from anti-neutrophil antibodies (leukoagglutinins) present in the donor plasma

RBC Storage Duration

  • Red cell storage process depletes 2,3 DPG, impairing oxygen release

  • Also depletes nitric oxide and causes membrane changes with decreased deformability, which combined limit capillary transit.

  • However no evidence to support need for ‘fresher’ blood in ITU patients

 

Transfusion Triggers

 

General ITU Population

  • Transfusion threshold = 70g/l

  • TRICC Study 1999

    • Liberal <100g/l trigger v.s. Restrictive <70g/l trigger

    • Restrictive group received 54% fewer RBC units, and 33% no blood at all

    • No global difference in mortality

    • Patients <55 y.o. and those who were less ill (APACHE <20) had lower mortality with restrictive strategy. NNT = 13.

Ischaemic Heart Disease

  • Acute coronary syndrome – Transfusion threshold = Hb 90-100g/l.

  • Stable Angina – Hb >70g/l but transfusion >100g/l has uncertain benefit

Sepsis

  • Transfusion threshold = 70g/l

  • This is a change from the 2012 guidance, evidence in intervening years supports a restrictive threshold

 

Cardiac Surgery

  • Transfusion threshold = 75g/l

  • TRACS 2010 trial supports this restrictive threshold

Weaning from ventilation

  • Transfusion threshold = 70g/l

Specific scenarions without a specific recommendation

  • Acute neurological injury (a change from BSH 2012, which did make recommendations)

  • ECMO

  • Malignancy

  • Elderly adults