HAEMOLYSIS

Question 1

what is haemolysis

Answer 1

premature red cell destruction

ie shortened red cell survival

Question 2

why are red cells particularly susceptible to damage

Answer 2

they need to have a biconcave shape to transit the circulation successfully
they have limited metabolic reserve and rely exclusively on glucose metabolism for energy
can’t generate new proteins once in the circulation

Question 3

what is compensated haemolysis

Answer 3

increased red cell production is able to maintain Hb concentration despite increased red cell destruction

Question 4

what is decompensated haemolysis

Answer 4

increased rate of red cell destruction exceeds bone marrow capacity for red cell production causing Hb to fall

Question 5

what are some consequences of haemolysis

Answer 5

erythroid hyperplasia (increased bone marrow red cell production)
excess red cell breakdown products (eg bilirubin)

Question 6

how is haemolysis detected clinically

Answer 6

evidence of increased red cell production

evidence of increased breakdown products

Question 7

what is the bone marrow response to haemolysis

Answer 7

reticulocytosis

erythroid hyperplasia

Question 8

in which situations, other than haemolysis, might reticulocyte count be increased

Answer 8

bleeding

response to iron therapy in iron deficiency

Question 9

what is the difference between extravascular and intravascular haemolysis

Answer 9

extravascular occurs in the reticuloendothelial system (spleen and liver)
intravascular occurs within the circulation

Question 10

which type of haemolysis is more common

Answer 10

extravascular

Question 11

which sign, palpable on examination, might suggest extravascular haemolysis

Answer 11

hyperplasia at the site of destruction

splenomegaly +/- hepatomegaly

Question 12

what are signs of excess breakdown products in extravascular haemolysis

Answer 12

unconjugated bilirubinaemia 
- jaundice
- gall stones 
urobilinogenuria 
- dark urine

Question 13

extravascular haemolysis causes an excess of normal/abnormal breakdown products

Answer 13

normal breakdown products

Question 14

what are signs of intravascular haemolysis

Answer 14

haemoglobinaemia (free Hb in circulation)
methaemalbuminaemia (oxidised Hb bound to albumin)
haemoglobinuria (pink urine, turns black on standing)
haemosiderinuria (brown urine)

Question 15

intravascular haemolysis causes an excess of normal/abnormal breakdown products

Answer 15

abnormal breakdown products

Question 16

what are causes of intravascular haemolyiss

Answer 16

ABO incompatible blood transfusion
G6PD deficiency
severe falciparum malaria
PNH/PCH

Question 17

how to confirm haemolytic state (Ix)

Answer 17

FBC + blood film
reticulocyte count 
serum unconjugated bilirubin 
serum haptoglobin 
urinary urobilinogen

Question 18

what is the function of haptoglobin

Answer 18

bind free Hb in the plasma

Question 19

what does a low Haptoglobin level indicate

Answer 19

haemolysis

Question 20

how can a blood film help identify the cause of haemolysis

Answer 20

spherocytes suggest membrane damage
red cell fragments suggest mechanical damage
Heinz bodies suggest oxidative damage

Question 21

what is a coombs’ test used for

Answer 21

to detect the presence of antibodies in the plasma in suspected autoimmune haemolysis

Question 22

what are the possible sites of red cell defect leading to haemolysis

Answer 22

premature destruction of normal red cells (immune or mechanical)
abnormal cell membrane
abnormal red cell metabolism
abnormal Hb

Question 23

what is the difference between warm and cold autoimmune haemolysis

Answer 23

warm = IgG
cold = IgM

Question 24

what are possible causes of autoimmune haemolysis

Answer 24

idiopathic 
autoimmune disorders (SLE)
lymphoproliferative disorders 
drugs 
infections (EBV, malaria)

Question 25

what are causes of alloimmune haemolysis

Answer 25

haemolytic transfusion reaction

passive transfer of antibodies eg pregnancy

Question 26

what is the difference between immediate and delayed haemolytic transfusion reaction

Answer 26

immediate = IgM and is predominantly intravascular 
delayed = IgG and is predominantly extravascular

Question 27

what can cause mechanical red cell destruction

Answer 27

DIC
HUS (Ecoli 0157)
TTP
leaking heat valve 
infections eg malaria

Question 28

how do DIC and HUS cause mechanical damage to red cells

Answer 28

create turbulent flow

Question 29

what is microangiopathic haemolytic anaemia

Answer 29

red cell fragmentation as a result of mechanical (extrinsic) damage

Question 30

how do severe burn result in haemolysis

Answer 30

red cells are sheared as they pass though the damaged capillaries

Question 31

in what situation do microspherocytes occur

Answer 31

severe-burns related haemolysis

Question 32

what is Zieve’s syndrome associated with

Answer 32

haemolysis
alcoholic liver disease
hyperlipidaema

Question 33

what types of haemolysis are caused by membrane defects

Answer 33

liver disease (Zieve's syndrome)
vitamine E deficiency 
PNH

Question 34

what is the pathophysiology of hereditary spherocytosis

Answer 34

red cell membrane abnormalities cause reduced membrane deformability
increased transit time through spleen as unable to move through small blood vessels
prolonged exposure to oxidant environment in spleen causes extravascular red cell destruction

Question 35

what is G6PD needed for

Answer 35

G6PD is needed to regenerate NADPH, which in turn regenerate glutathione
glutathione is needed as a reducing agent to prevent oxidative damage

Question 36

what does deficiency of G6PD result in

Answer 36

inability to reduce oxidative agents therefore resulting in damage to the cell

Question 37

which Hb abnormality can cause haemolysis

Answer 37

sickle cells disease (HbS)

Question 38

why do bony deformities occur in beta thal major

Answer 38

marrow cavity expansion due to chronic erythroid hyperplasia