PLASMAPHERESIS
Plasmapheresis is an experimental procedure done in animals to demonstrate the importance of plasma proteins. Earlier, this was called Whipple’s experiment because it was established by George Hoyt Whipple.
PROCEDURE
Plasmapheresis is
demonstrated in dogs. Blood is removed completely from the body of the dog. Red
blood cells are separated from plasma and are washed in saline and reinfused
into the body of the same dog along with a physiological solution called Locke’s
solution. Due to sudden lack of proteins, the animal undergoes a state of
shock. If the animal is fed with diet containing sufficiently high quantity of
proteins, the normal level of plasma proteins is restored within seven days and
the
animal survives. The new plasma proteins are synthesized by the liver of
the dog. If the experiment is done in animals after removal
of liver, even if the
diet contains adequate quantity of proteins, the plasma proteins are not
produced. The
shock persists in the animal and leads
to death. Thus, the experiment ‘plasmapheresis’ is used to
demonstrate:
1. Importance of
plasma proteins for survival
2. Synthesis of plasma
proteins by the liver.
CLINICAL SIGNIFICANCE
OF PLASMAPHERESIS – THERAPEUTIC PLASMA EXCHANGE
Plasmapheresis is used
as a blood purification procedure for an effective temporary treatment of many
autobecause
immune diseases. It is also called therapeutic plasma exchange. In an autoimmune
disease, the immune system attacks the body’s own tissues through antibodies.
The antibodies that are proteins in nature circulate in the bloodstream
before attacking the target tissues. Plasmapheresis is used to remove these antibodies
from the blood.
Procedure
Venous blood is removed
from the patient and blood cells are separated from plasma by the equipment
called cell separator. This equipment works on the principle of a centrifuge.
An anticoagulant is used to prevent the clotting of blood when it is removed
from the body. After the separation of blood cells, the plasma is discarded. The
blood cells are returned to the bloodstream of the patient by mixing with a
substitute fluid (saline) and sterilized human albumin protein.
Uses of
Plasmapheresis
Though plasmapheresis is used to
remove antibodies from the blood, it cannot prevent the production
of
antibodies by the
immune system of the body. So, it can provide only a temporary benefit of
protecting the tissues from the antibodies. The patients must go for repeated sessions
of this treatment.
Plasmapheresis is an
effective temporary treatment
for the following
diseases:
1. Myasthenia gravis – autoimmune
disease causing muscle weakness (Chapter 17)
2. Thrombocytopenic purpura – bleeding
disorder 3. Paraproteinemic peripheral neuropathy – dysfunction
of peripheral nervous
system due to an abnormal
immunoglobulin called paraprotein.
4. Chronic
demyelinating polyneuropathy – neurological disorder characterized by
progressive weakness
and impaired sensory
function in the legs and arms due to the damage of myelin sheath in
peripheral nerves.
5. GuillainBarré syndrome
– autoimmune disease causing
weakness, abnormal sensations (like
tingling) in the limbs and paralysis.
6. LambertEaton myasthenic
syndrome – autoimmune disorder of the neuromuscular junction.
VARIATIONS IN PLASMA PROTEIN LEVEL
Level of plasma proteins
vary independently of one another. However, in several conditions, the quantity
of albumin and globulin
change in opposite direction. Elevation of all fractions of plasma proteins is
called
hyperproteinemia and
decrease in all fractions of plasma proteins is called hypoproteinemia.
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