Transfusion and Anaemia in Critically Ill Adults (BSH 2012)
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
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.
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
Serum iron – decreased
Total Iron Binding Capacity – Decreased
Ferritin – Increased
Transferrin – Decreased
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 —> 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
Ischaemic Heart Disease on ITU
Stable Angina – Hb >70g/l but transfusion >100g/l has uncertain benefit
ACS – Hb >80-90g/l