Red Cells 1 Flashcards
What is anaemia
Reduction in RBC or their Haemoglobin content
Aetiology of anaemia
- Blood loss
- Increased destruction
- Reduced production
- Defective production
4 important substances for RBC production
- Iron
- Vit B12
- Folic acid
- Erythropoietin
What happens to RBCs in hereditary sypherocytosis
- They become spherical
- Due to defects in 5 different structural proteins
- Ankyrin
- Alpha spectrin
- Beta spectrin
- Band 3
- Protein 4.2
Presentation of hereditary spherocytosis
- Anaemia
- Jaundice
- Splenomegaly
- Pigment gallstones
Rx of hereditary spherocytosis
- Folic acid
- Transfusion
- Splenectomy
Function of Glucose 6 Phosphate Dehydrogenase (G6PD)
Protects RBCs from oxidative damage
Commonesnt disease causing enzymopathy in the world
G6PD Deficiency
What happens to RBCs in G6PD deficiecy
- Cells are vulnerable to oxidative damage
- Protects against malaria (most common in malarial areas)
- RBCs look like “Bite and Blister cells”
How is G6PD deficiency passed on
- X-linked
- Affects males (female carriers)
Presentation of G6PD
-Neonatal jaundice
-Splenomegaly
-Pigment gallstones
-DRUG or broad bean or infection precipitated jaundice + anaemia
(Intravascular haemolysis + Haemoglobinuria)
Triggers of G6PD
-Infection
-Acute illness (DKA)
-Broad (Fava) Beans “favism”
-Drugs
Antimalrials (primaquine)
Antibacterials (nitrofurantoin)
Analgesics (aspirin)
-Sulphonamides and sulphones (Sulfasalazine)
Haemoglobin function
Gas exchange (O2 to tissues, CO2 to lungs)
Describe the Bohr effect
Haemoglobin’s oxygen binding affinity is inversely related to acidity + concentration of CO2
What has a great affinity for 2, HbF or HbA
HbF
What is normal adult haemoglobin composed of
- Haem molecule
- 2 alpha chains + 4 alpha genes
- 2 beta chains + 2 beta genes
What happens to haemoglobin in thalassaemia
Reduced or absent globin chain production
What happens to haemoglonbin in Sickle cell disease
Structurally abnormal globin chain
What is haemoglobin composed of in sickle cell disease
- Haem molecule
- 2 alpha chains
- 2 beta (sickle) chains
Pathogenesis of sickle cell disease
- HbS polymerises when deoxygenated
- Causing RBCs to deform, producing sickle cells
- They’re fragile and haemolyse + occlude small vessels
3 types of sickle cell crisis
- Vaso-occlusive “painful” crisis
- Aplastic crisis
- Sequestration crisis
Describe vaso-occlusive “painful” crisis
- Common, due to microvascualr occlusion
- Severe pain
- Occlusion can cause mesenteric ischaemia (mimicing an acute abdome)
- CNS infarction
- Avascular necrosis of femoral head + leg ucers
- Children <3y dactylitis (if hands + feet affected)
- Priaprism
Describe aplastic crisis
- Due to parvovirus B19
- With sudden reduction in bone marrow production (sep. RBCs)
- Usually self limitting , <2wks
- Transfusion may be needed
Describe sequestration crisis
- Mainly affects children as the spleen has not yet undergone atrophy
- Pooling of blood in spleen +/- liver
- Organomegaly
- Severe anaemia + shock
- Urgent transfusion required
Life expectancy in sickle cell disease
- Male early 40s
- Female Late 40s
(childhood + perinatal mortality contribute to this reduction)
Management of painful crisis
- Analgesia (severe = opiates)
- Hyrdation
- O2
- Consider antibiotics
Give analgesia within 30mins of presentation + avoid pethidine (demerol)
Presentation of a chest crisis
- Chest pain
- Fever
- Worsening hypoxia
- Infiltrates of CXR
Rx of a chest crisis
- Resp. support
- Antibiotics
- IV fluids
- Analgesia
- Transfusion
Management of sickle cell disease
Life long prophylaxis
- Vaccination
- Penicillin + malarial prophylaxis
- Folic acid
Acute events
- Hydration
- O2
- Prompt Rx of infection
- Analgesia (opiates, NSAIDS)
(possible bone marrow transplant)
Disease modifying drug for sickle cell disease
Hydroxycarbamide
