Red blood cells (Sources: Revision notes) Flashcards
What is the WHO definition of anaemia?
Women Hb < 120 g/l
Men Hb < 130
Severe anaemia Hb < 80
What are the common causes if anaemia in ICU?
Blood loss Blood sampling Impaired erythopoiesis secondary to critical illness Haemodilution Extracorporeal therapies B12/folate deficiency Iron deficiency Myelodysplastic syndromes Anaemia of chronic disease Coeliac disease /malabsorption Haemolysis Drugs
How should you investigate anaemia in ICU?
In many cases this won’t be required as cause will be obvious
Thorough examination and history - e.g. looking for occult bleeding, medications such as NSAIDs
MCV - macrocytosis is seen in B12/folate deficiency, chronic alcohol, haemolysis, myelodysplasia, hypothyroidism and liver disease
Blood film, B12/folate, ferritin and iron studies can all be difficult to interpret in ICU. Ferritin increases and iron decreases in acute illness
Raised LDH and reticulocyte count suggest haemolysis
Discuss RBC transfusion in the ICU patient in the absence of major haemorrhage
It’s not a benign intervention and is associated with increased risk of death, infection and rplonged length of ICU stay
The British Committee for the Standards in Haematology recommends
-transfusion threshold of <70 in the general ICU population
-consider blood conservation deivces for blood sampling
-routine use fo erythropoietin
What are the current recommendations for blood transfusion for ICU patients as per the British Committee for Standards in Haematology?
Hb < 70g/L in the general ICU pts
Consider use of blood conservation devices
Routine use of EPO and iron not recommended
Which study is the main basis for the UK ICU transfusion trigger?
The Transfusion Requirements in Critical Care study (TRICC study)
Describe the TRICC study
Multi-centre RCT
Compared liberal vs restrictuve blood transfusion protocol
Transfusion threshold of 100 vs 70
Significantly fewer transfusions in the restrictive arm
Trend towards decreased mortality
Study was underpowered and done before routine leukodepletion so may not be applicable to current practice
What is the transfusion threshold in septic patients?
Aim Hb > 70
TRISS study showed no difference in outcome between liberal and restrictive
Higher thresholds in ARISE/PROCESS/PROMISE don’t show any increased outcome
What is the transfusion threshold post elective cardiac surgery?
Aim Hb > 90
‘Liberal or restrictive transfusion after cardiac surgery’
What is the recommended transfusion strategy for upper GI bleeding?
Transfusion strategies for acute upper GI bleeding by Villanueva et al NEJM 2013
Improved overall survival for all cause GI bleeding using restrictive strategy (70) compared with liberal (90) In Child-Pugh A and B but not C
What are the recommended transfusion strategies in TBI, TBI with cerebral ischaemia, SAH, Ischaemic stroke, critical illnessa with stable chronic IHD, ACS according to BCSH guidelines?
TBI target range Hb 70-90 TBI with iscahemia > 90 SAH 80-100 Ischaemic stroke Hb >90 Critical illness with chronic stable IHD >70 ACS 80-90
Describe TACO - clinical features, risk factors, frequency, treatment
Transfusion associated cardiac overload
Clinical features - acute respiratory distress, tachycardia, hypertension, pulmonary oedema, positive fluid balance
Risk factors - Low albumin, renal impariment, pre-transfusion overload
Frequency - 1 in every 357 red cell units transfused
Treatment - supportive measures, diuretics
Describe TRALI
Transfusion-related acute lung injury
Clinical features - APO within 6 hours with PO2/FiO2 < 40 kPa, bilateral pulmonary infiltrates in absence of suspected left atrial hypertension
Risk factors - products donated by multiparous women, non-leukodepleted blood
Frequency - 1 in every 1271 transfusions
Treatment - supportive
What are the risk associated with blood transfusion?
Infection - bacterial, viral, prion Haemolytic reaction - ABO incompatability, minor incompatability Allergy Hypothermia Immune sensitization TRALI TACO
What are the common causes of haemolysis in ICU patients?
Mechanical destruction - RRT, ECMO, IABP, ventricular assist device
Sepsis - may be immune mediated with any infection - some specific infections associated with haemolysis are Clostridium perfringens, Bartonellosis and Malaria
Drug - induced: - may be immune mediated or direct effect of the drugs
Microangiopathic haemolysis e.g. DIC, thrombotic thrombocytopenic purpura, HUS
Red cell enzyme deficiency (congenital) e.g. Glucose-6-phosphate dehydrogenase deficiency, pyruvate kinase deficiency
Haemaglobinopathies (congential) e.g. sickle cell, thalasaemia
