Hemolysis And Fragility Of Red Blood Cells Notes

Hemolysis And Fragility Of Red Blood Cells Definition

1. Hemolysis: Hemolysis is the destruction of formed elements. To define more specifically, it is the process, which involves the breakdown of RBC and liberation of hemoglobin.
2. Fragility: The susceptibility (to be affected) of RBC to hemolysis or tendency to break easily is called fragility (Fragile = easily broken).

Fragility is of two types:

1. Osmotic fragility which occurs due to exposure to hypotonic saline
2. Mechanical fragility which occurs due to mechanical trauma (wound or injury).

Read And Learn More: Medical Physiology Notes

Normally, old RBCs are destroyed in the reticuloendothelial system. Abnormal hemolysis is the process by which even younger RBCs are destroyed in large number by the presence of hemolytic agents or hemo- lysins.

Process Of Hemolysis

Normally, plasma and RBCs are in osmotic equilibrium. When the osmotic equilibrium is disturbed, the cells are affected. For example, when the RBCS cells are immersed in hypotonic saline the cells swell and rupture by bursting because of endosmosis. The hemoglobin is released from the ruptured RBCs.

Fragility Test

• The fragility test is a test that measures the resistance of erythrocytes in hypotonic saline solution. It is done by using sodium chloride solution at different concentrations from 1.2-0.2%. The solutions at different concentrations are taken in series of Cohn’s tubes.
• Then one drop of blood to be tested is added to each tube. The sodium chioride solution and the blood in each tube are mixed well and left undisturbed for sometime.
• The results can be analyzed by observing the tubes directly or by centrifuging the tubes after 15 minutes:

Direct observations:

1. If there is no hemolysis – the fluid in the tube appears turbid
2. If hemolysis is started the turbidity is reduced 3. If hemolysis is completed – fluid becomes clear.

Observations after centrifuging:

1. If there is no hemolysis – the cells sediment at the bottom with clear colorless fluid above
2. If hemolysis is started cell sedimentation is less and the fluid becomes slightly reddish because of the release of small amount of hemoglobin from few hemolyzed RBCs
3. If hemolysis is completed – the fluid becomes more reddish without any sedimentation due to release of more amount of hemoglobin from all the hemolyzed cells.

Index for Fragility: After twenty minutes

No hemolysis up to 0.6%

Onset of hemolysis = around

0.45% Completion of hemolysis around 0.35%

At 0.45%, only the older cells are destroyed because their membrane is fragile. So, these cells cannot withstand this hypotonicity. But, younger cells are not affected. At 0.35%, even the younger cells are destroyed.

Conditions When Hemolysis Occurs

1. Hemolytic jaundice
2. Antigen-antibody reactions
3. Poisoning by chemicals or toxins
4. While using an artificial kidney for hemodialysis or a heart-lung machine during cardiac surgery (rare occasions).

Hemolysins: Hemolysins or hemolytic agents are the substances, which cause the destruction of RBCs. The hemolysins are of two types:

1. Chemical substances
2. Substances of bacterial origin or substances found in body.

Chemical Substances

1. Alcohol
2. Benzene
3. Chloroform
4. Ether
5. Acids
6. Alkalis
7. Bile salts
8. Saponin
9. Chemical poisons like
   1. Arsenal preparations
   2. Carbolic acid
   3. Nitrobenzene
   4. Resin.

Substances Of Bacterial Origin Or Substances Found In Body

1. Toxic substances or toxins from bacteria
   1. Streptococcus
   2. Staphylococcus
   3. Tetanus bacillus, etc.
2. Venom of poisonous snakes like cobra
3. Hemolysins from normal tissues.