Transfusion and Anaemia in Critically Ill Adults (BSH 2013)
General ITU – Threshold <70, Target 70-90
Sepsis – early Target 90-100, later Target 70-90
Neuro – TBI Target 70-90, SAH Target 80-100, Stroke Target >90
IHD – Stable Target >90, ACS Target >80
- 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
- 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
- General ITU Population
o TRICC Study 1999
o Liberal <100g/l trigger v.s. Restrictive <70g/l trigger
o Restrictive group received 54% fewer RBC units, and 33% no blood at all
o No global difference in mortality
o Patients <55 y.o. and those who were less ill (APACHE <20) had lower mortality with restrictive strategy. NNT = 13.
- TRACS (cardiac surgery) and FOCUS (elective hip surgery) made the same conclusions
Alternatives to Red Cell Transfusion
Blood Sampling Techniques to reduce iatrogenic blood loss
- Typically approx.. 40ml blood loss per day
- Use of paediatric bottles reduces blood loss without affecting assay quality.
- 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
- Evidence of absolute iron deficiency is absent in most ITU patients
- Iron supplementation not recommended due to lack of randomized trials and concern over increased susceptibility to infection
- Typical Iron profile in ITU
o Serum iron – decreased
o Total Iron Binding Capacity – Decreased
o Ferritin – Increased
o Transferrin – Decreased
o Soluble Transferrin – Normal
Adverse Effects of RBC Transfusion in Critical Care
- Acute respiratory distress with pulmonary oedema, tachycardia, increased BP and a positive fluid balance after blood transfusion
- 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
Severe Sepsis Patients
Early hours of sepsis
- Low SVCO2% and high lactate indicative of tissue hypoxia
- Transfusion to Hb approx. 100g/l associated with improved survival, but in trials that had many intensive interventions being tested at once.
Later stages of sepsis
- As per TRICC trial, can use <70g/l as transfusion trigger
Neuro Critical Care
Difficult – increase Hct à increased oxygen carrying capacity, but also viscosity which may in itself reduces delivery to cerebral microvasculature.
Traumatic brain injury
- Target 70-90g/l, increased to >90g/l if cerebral ischaemia present
- Target 80-100g/l
- Target >90g/l
Ischaemic Heart Disease on ITU
Stable Angina – Hb >70g/l but transfusion >100g/l has uncertain benefit
ACS – Hb >80-90g/l