Anaemia Flashcards
Definition
Haemoglobin concentration falls below the defined level
Clinical consequence of insufficient O2 delivery
Causes
Low RBC count
Low HB content
Altered HB doesn’t carry sufficient oxygen
Symptoms
Lethargy - low supply of blood to tissues
Shortness of breath
Palpitations - pulsing blood in ears
Headache
Often non-specific
Worse if acute onset
Loss of blood over short amount of time like haemorrhage is anaemia due to hypovolemia and loss of HB
Signs
Pallor - pale conjunctivae
Tachypnoea
Tachycardia
Chronic anaemia
Loss of HB over months - can be relatively asymptomatic
Causes (5)
Bleeding over many months
Deficiency in necessary components: in iron, B12, folic acid - components needed to make DNA. deficiency from diet or reabsorption from gut - anaemia due to lack of synthesis of RBC
Haemolytic: increased RBC destruction, shortened RBC lifespan, RBC consumed at a faster rate than being produced - also cause of sickle cell where more RBC in bone marrow than normal known as compensation
Bone Marrow Dysfunction/Infiltration: e.g. aplastic anaemia
Poor O2 utilisation/carriage
Classification
Size of RBC
Acute or chronic
Underlying aetiology
Iron Deficiency
Most common type
Range of causes: bleeding, nutrition, increased requirements, bowel cancer, Pectacarcaration in oesophagus, Crohn’s disease (malabsorption), pregnancy
Ferritin binds iron in tis core - find in liver and bone marrow where it holds iron and releases it to be incorporated in red cells, iron is needed for enzymatic processes in body - test ferritin for iron deficiency
Diagnostic tests for iron
Serum ferritin: Storage form of iron, low = deficient
Serum iron: Labile so reflects recent intake of iron - not very useful
Serum transferrin: Carrier molecule for iron, goes up if iron deficient, picks up iron in gut and carries to tissues, if iron deficient then high transferrin to take more from gut to get to tissues
Percent transferrin saturation: sensitive measure of iron status, low means deficient
Causes of iron deficiency in UK
Bleeding: menstrual heavy periods (menorrhagia), Occult GI malignancy - loss of blood in stool (indicative of bowel cancer), GI peptic ulceration
Unlikely to be iron deficient from diet alone but vegans at higher risk, malabsorption from coeliac disease and Crohn’s
Increased requirements - from pregnancy
Size of RBC
Mean corpuscular volume - normally 80-100fL
Microcytic (small) - iron deficiency, inherited disorders of HB (thalassaemia)
Macrocytic (large) - B12 and folic acid deficiency, myelodysplasia
Normocytic (normal)
Blood film
Easy, quick, useful for haematinic deficiency, haemolysis, normal white cells
RBC last 100 days in the circulation
Features: Hypochromia, microcytosis, pencil cells, target cells
Reticulocyte count
Represents RBC production rate by marrow: low if bone marrow infiltrated, low during iron deficiencies, high in haemolysis, high in chronic bleeding, if in normal range when anaemic, bone marrow is not responding appropriately
Can be used to monitor progress of treatment
Measured by flow cytometry that counts cells with nucleic acids or using a specific statin and microscopy
History when anaemia suspected
GI symptoms: dyspepsia, change in bowel habit, weight loss
Menstrual history
Dietary history, travel (hookworm infestations cause iron deficiency), ethnic origin, family history
Megaloblastic anaemia
Macrocytic
Due to deficiency of vit B12, folate
Required for DNA
Large RBCs, sufficient precursors for cell growth, insufficient precursors for cell division
B12 deficiency
Dietary - strict vegans
Pernicious anaemia: autoimmune (parietal cell loss), deficiency of intrinsic factor (they can’t absorb B12)
Malabsorption: Post gastric/ surgery
Crohn’s disease
Folate deficiency
Dietary Malabsorption (Coeliac, Crohn's disease) Excess utilisation (Chronic haemolysis, pregnancy) Alcohol Drugs (phenytoin, methotrexate)
Anaemia of chronic disease
Most common form of anaemia in hospitalised patients
Common causes: Chronic inflammation, chronic infection (TB), Auto-immune conditions (rheumatoid arthritis), cancer
Poor utilisation of iron in body: iron is stuck in macrophages of the reticuloendothelial system and can’t be mobilised into the early erythroblasts
Dysregulation of iron homeostasis: decreased transferrin, increased hepcidin
Impaired proliferation of erythroid progenitors: blunted response to erythropoietin, iron is unavailable
Sickle cell anaemia
Point mutation in beta globin gene causing HbS
RBC turnover = 20 days
due to haemolysis
Sickle cell crisis: Triggered by low blood O2 level, vaso-occlusive, ischaemia, pain, necrosis and often organ damage
Management: analgesics, hydration, transfusion
Genetic, autosomal, recessive, sub-Saharan Africa, shortened life expectancy
Sickle cell anaemia mechanism
Mutated sickle haemoglobin
Forms long filamentous strands
Insoluble at low O2 tension
RBCs become inflexible + spiky - problem
Sickle cell trait = heterozygous for HbS and HbA, much lower risk of sickling and crisis
Resistant to malaria infection
Thalassaemia
Insufficient Hb production - due to altered Hb gene expression
Inherited autosomal recessive
Clinical features: enlarged spleen, liver and heart; bones may be misshapen
Ask about family history
Conduct a blood film
Bone Marrow infiltration
Leukaemia: non specific symptoms, bone marrow failure
Lymphoma: lymphadenopathy, weight loss
Myeloma: anaemia, hypercalcaemia, renal failure
Get bone marrow from iliac crest - aspirate film for morphology of cells, trephine biopsy for histological sections
Management of acute anaemia
Transfuse: Acute is more dangerous that chronic, guided by symptoms instead of Hb levels
Management of chronic anaemia
Treat underlying cause: iron supplementation, folic acid and B12
Erythropoietin in patients with kidney failure particularly of on haemodialysis
Long term transfusion causes: iron overload, allo-antibodies
Worldwide impact
Poor pregnancy outcome
Impaired physical and cognitive development
Increased risk of morbidity in children
Reduced work productivity
contributes to 20% of all maternal deaths
