haemolysis Flashcards
what is haemolysis
premature destruction of red cells
2 types of haemolysis
compensated
uncompensated
what is compensated haemolysis
increased red cell destruction
WITH
increased red cell production
HB is MAINTAINED
what is uncompensated haemolysis
haemolysis
no increase in RBC production
LOW Hb
physiological consequences of haemolysis
erythroid hyperplasia (increased RBC production from bone marrow - reticulocytosis) excess RBC breakdown products (eg bilirubin)
2 sites of haemolysis
extravascular (more common)
intravascular
what is extravascular haemolysis
RBCs are engulfed by spleen and liver
what is intravascular haemolysis
red cells destroyed within circulation
breakdown products found in extravascular
NORMAL products in excess (from porphyrin ring)
unconjugated bilirubin
urobilinogenuria
breakdown products found in intravascular
ABNORMAL products Hb in blood not in red cells: in circulation in urine (PINK then turns BLACK on standing) methaemalbuminaemia haemosiderinuria
what are causes of intravascular haemolysis
ABO incompatible blood transfusion (red cells attacked and broken down)
G6PD deficiency
severe falciparum malaria (blackwater fever)
paroxysmal
leaky heart valve (MAHA - red cell fragmentation)
burns
how does G6PD deficiency cause intravascular haemolytic anaemia
G6PD - required for glycolysis
produces ATP, NADH (NADH produces NADPH)
all required for membrane
oxidative stress -no protection of RBC - HAEMOLYSIS
causes of extravascular haemolysis
immune haemolysis (warm, cold, alloimmune)
hereditary spherocytosis
haemoglobinopathy (eg thalassaemia, sickle cell)
signs showing haemolysis
jaundice dark urine gall stones leg ulcers (poor blood flow) hepatosplenomegaly
investigations for haemolytic anaemia
FBC and blood film reticulocyte count (increased) unconjugated bilirubin serum haptoglobin urinary urobilogen direct antiglobulin test chromium labelling
blood film in haemolysis
polychromasia macrocytosis (increased MCV) spherocytes (membrane damage) red cell fragments (mechanical damage) Heinz bodies (oxidative damage) sickle cells
reticulocyte count wil be increased/decreased in haemolysis
increased
what type of haemolysis has increased unconjugated bilirubin, haptoglobins and urobilinogen
extravascular
what are haptoglobins
proteins produced by liver
binds to free Hb in circulation
haptoglobins in haemolysis
low - being used up faster
if nomal, EXCLUDES haemolytic anaemia
what is direct antiglobulin test
coombs test
shows agglutination of red cells if positive (confirms immune cause)
what is chromium labelling
measures RBC lifespan
identifies breakdown site
2 types of immune haemolysis
autoimmune
alloimmune
what is autoimmune
autoimmune antibodies attacking RBCs causing extravascular haemolysis
how is autoimmune haemolytic anaemia classified and what are the corresponding responsible antibodies
warm (IgG) - 37 degrees
cold (IgM) - <4 degrees
causes of warm autoimmune haemolysis
idiopathic SLE CLL penicillins infections
causes of cold autoimmune haemolysis
idiopathic
infections (EBV, mycoplasma)
CLL
what is alloimmune haemolysis
triggered by:
incompatible transfusion reaction
rhesus in newborns
antibody involved in immediate incompatible transfusion
IgM
antibody involved in delayed incompatible transfusion
IgG
