Haemolysis Flashcards
What is haemolysis?
Premature red cell destruction
What products of red cell breakdown are a) recycled? b) broken down?
a) iron and globin chains b) haem group (protoporphyrin)
The haem group is first broken down into what? And then into what? For this reason, the first sign of somebody who is haemolysing may be what?
Biliverdin / bilirubin / they become jaundiced
What are the two main consequences of haemolysis?
Erythroid hyperplasia (more red cell production in the bone marrow) and presence of excess red cell breakdown products
What is compensated haemolysis?
When there is increased red cell destruction which is compensated for by increased red cell production
What happens to Hb in compensated haemolysis? Do patients become anaemic?
It is normal / no
What is decompensated haemolysis?
Increased rate of red cell destruction exceeds the bone marrow capacity for red cell production
What happens to Hb in decompensated haemolysis? Do patients become anaemia?
It is low / yes
It is difficult to measure red cell survival directly. Therefore, we rely on detecting the consequences of haemolysis to determine the cause. What are these?
Increased red cell production and detection of breakdown products
What are the bone marrow’s two main responses to haemolysis?
Erythroid hyperplasia and reticulocytosis
Due to the presence of reticulocytes, when someone is haemolysing what will be seen on a blood film?
Large, polychromatic red cells (reticulocytes)
Is the presence of reticulocytes diagnostic of haemolysis?
No, because it can also be seen as a response to bleeding or iron therapy
How is erythroid hyperplasia actually visualised? Is this done often?
Bone marrow biopsy - no, only when you think the person is haemolysing because of a disorder that would show up on a biopsy
Where are red cells broken down in extravascular haemolysis?
They are taken up by the reticuloendothelial system, predominantly the liver and spleen
Where are red cells broken down in intravascular haemolysis?
Within the circulation
What effect does extravascular haemolysis have on the site of red cell destruction? Give examples?
It causes hyperplasia at the site of destruction - usually splenomegaly +/- hepatomegaly
In extravascular haemolysis, the protoporphyrin that forms the haem group gets broken down, leading to the release of what?
Unconjugated bilirubin in the blood / urobilinogen in the urine
In extravascular haemolysis, the release of unconjugated bilirubin into the blood leads to what clinical symptoms/signs?
Jaundice and gallstones
Describe the abnormality with the breakdown products in extravascular haemolysis?
They are normal breakdown products, just seen in excess
In intravascular red cell destruction, there is release of what into the circulation?
Free Hb (haemoglobinaemia) and Hb bound to albumin (methaemalbuminaemia)
In intravascular red cell destruction, there is release of what into the urine?
Hb (haemoglobinuria) and haemosiderin (haemosiderinuria)
How does the presence of Hb in the urine look?
Looks pink initially, but turns black when left to stand
What are some causes of intravascular red cell destruction?
ABO incompatibility, G6PD deficiency, severe falciparum malaria (Blackwater fever)
Describe the abnormality with the breakdown products which is seen in intravascular haemolysis?
Abnomal breakdown products are produced - these can be life threatening
