Haemolysis Flashcards
haemolysis definition
Premature red cell destruction
i.e. shortened red cell survival
what is compensated haemolysis
Increased red cell destruction compensated by increased red cell production
i.e. Hb Maintained
WHY ARE RED CELLS PARTICULARLY SUSCEPTIBLE TO DAMAGE?
1.They need to have a biconcave shape to transit the circulation successfully
2.They have limited metabolic reserve and rely exclusively on glucose metabolism for energy (no mitochondria)
3. Can’t generate new proteins once in the circulation (no nucleus)
what is haemolytic anaemia (decompensated haemolysis)
Increased rate of red cell destruction exceeding bone marrow capacity for red cell production
i.e. Hb Falls
consequences of haemolysis
Erythroid hyperplasia (increased bone marrow red cell production)
Excess red cell breakdown products eg bilirubin (clinical features differ by aetiology and site of red cell breakdown)
what is the bone marrow response to haemolysis
- reticulocytosis
- erythroid hyperplasia
extravascular haemolysis
Occursin the reticuloendothelial system (spleen and liver predominantly)
intravascular haemolysis
Red cells destroyed within the circulation
which is more common, extravascular or intravascular haemolysis
extravascular
intravascular haemolysis is potentially lifethreatening, true or false
true
intravascular haemolysis causes
- ABO incompatible blood transfusion
- G6PD deficiency
- severe falciparum malaria
- rare diseases - PNH, PCH
haemolysis investigations - confirming haemolytic state
- confirm haemolytic state
- FBC and blood film
- Reticulocyte count
- Serum unconjugated bilirubin
- Serum haptoglobins
- Urinary urobilinogen
haemolysis investigations
- confirm haemolytic state
- Identify cause
haemolysis investigations - blood film. what might we see?
Membrane damage (spherocytes)
Mechanical damage (red cell fragments)
Oxidative damage (Heinz bodies)
Others e.g.. HbS (sickle cells)
acquired causes of haemolysis
autoimmune haemolysis
alloimmune haemolysis
autoimmune haemolysis - warm or cold antibody
warm (Ig__)
cold (Ig__)
warm IgG
cold IgM
haemolytic disease of the newborn is an example of _____immune haemolysis
alloimmune
causes of acquired haemolysis - mechanical red cell destruction
Disseminated intravascular coagulation
Haemolytic uraemic syndrome (eg E. coli O157)
TTP
Leaking heart valve
Infections e.g. Malaria
causes of acquired haemolysis - membrane defects (All very rare)
Liver Disease (Zieve’s Syndrome)
Vitamin E deficiency
Paroxysmal Nocturnal Haemoglobinuria
genetic causes of haemolysis - abnormal red cell metabolism
failure to cope with oxidant stress (G6PD deficiency)
failure to generate ATP: metabolic processes fail
NB Even the metabolic pathways of normal cells if sufficiently stressed e.g.by dapsone or salazopyrin can get oxidative damage
genetic causes of haemolysis - abnormal haemoglobins
sickle cell disease (Hb S)
