• What are blood tranfusions ?
• A blood transfusion is the procedure where a person receives blood, or elements of blood usually through an intravenous infusion meaning through a vein.
• Steps and componets of blood :
• if you take blood and spin it in a centrifuge: the heaviest blood components move to the bottom, and the lightest ones move to the top.
• There are three distinct layers form:
• 1- the erythrocytes or red blood cells at the bottom,
• 2 the buffy coat--which contains platelets and immune cells in the middle,
• 3- plasma at the top.
• how are transfusions given?
• 1- in rare situations, like in traumatic injuries, someone might receive a whole blood transfusion,
• 2- , a person with anemia could just receive packed red blood cells,
• 3- a person with clotting factor deficiency could get fresh frozen plasma which contains the coagulation factors,
• 4- someone with platelet deficiency might receive platelets.
• ‫يعني على حسب الحاله شنو نعطيه‬
• How is blood given ?
• 1- most blood transfusions are *homologous transfusions* where the blood comes from an anonymous donor.
• 2- Sometimes the transfused blood is *autologous* , meaning the blood was taken out of the person at a prior time, like when they plan
to have surgery in the near future.
• How to make sure the blood doesn’t coagulate ?
• once the blood is taken, it’s mixed with sodium citrate which prevents the blood from coagulating, and then refrigerated or frozen for
storage, or separated into its components by centrifuge.
• Every person has a unique blood group based on two classification systems: the ABO system and the Rh system.
• mechanism of both systems :
• Both systems are based on the presence or absence of glycoproteins, which are proteins attached to a sugar molecule, found on the
surface of red blood cells.
• what could happen if the blood is cross contaminated with non compatible blood ?
• 1- if blood that has any of these glycoproteins is given to a person that has immune cells that have never seen those glycoproteins
before, then the glycoproteins can act as antigens.
• 2- the recipient’s immune system might mistake the donor blood as an invader and mount an immune response.
• 3- This is usually caused by recipient IgM antibodies that float around in the plasma.
• 4- These IgM antibodies can bind to multiple donor red blood cells, which can result in the red blood cells clumping together.
• 5- In addition, the IgM can activate complement proteins which form a membrane attack complex on the surface of the donor red blood
cell causing pores to form and allowing the red blood cell to lyse.
• 6- The IgM also activate other immune cells to cause a systemic immune response resulting in fever, hypotension, and rash.
*This is called a hemolytic transfusion reaction.*
• ABO system :
• the ABO system refers to the type of glycoproteins found on a person’s red blood cells; you can have either:
• 1- type A,
• 2- type B,
• 3- type A and B glycoproteins
• 4- neither, which is called type O blood.
• how are blood given according to ABO system ?
• As you know The immune system produces antibodies against the glycoproteins that you don’t have. So
• 1- People with type A blood have antibodies to type B blood,
• 2- people with type B blood have antibodies to type A blood.
• 3- People with blood type AB don’t have antibodies to type A or type B blood, so they can receive blood from any of the blood
types(also called universal recipients) —- However since their red blood cells have both type A and type B antigens, they can’t donate
blood to anyone except other AB blood type individuals.(selfish type )
• 4- , people with type O blood have antibodies to both A and B glycoproteins, so people with type O cannot receive type A, type B, or
type AB blood But since their red blood cells don’t have type A or type B antigens, they can donate blood to anyone( universal
donors )—- selfless type
Note : in an emergency setting because these
individuals don't have naturally occurring Rh
antibodies, since Rh antibodies require prior
exposure to Rh positive RBCs.So, for
someone who doesn’t have Rh antibodies, Rh
positive blood might be okay the first time, but
then they'll develop antibodies and you won't
be able to give them Rh positive blood in the
future.
• RH group :
• It gets its name from the animal in which the Rh protein was first described, the rhesus monkey.
• mechanism :
• Unlike the ABO system, people are either Rh positive, meaning they have the antigen on their red blood cells, or they are Rh negative,
meaning it’s absent.
• how are blood given according to RH system ?
• 1- People that are Rh positive can receive both Rh negative or Rh positive blood since they do not have antibodies against the Rh
glycoprotein.
2- But if an Rh negative person receives Rh positive blood, they could develop a hemolytic transfusion reaction. That's why we don't
usually give Rh positive blood to Rh negative patients.
• how does blood typing work ?
• To prevent hemolytic transfusion reactions, blood must be typed and crossmatched so During blood typing
• 1- serum with known anti-A antibodies and anti-B antibodies are mixed with a person’s red blood cells.
• 2-If an agglutination reaction occurs, that means that the blood being tested has that glycoprotein on the surface
• For example, if Anti-A serum is mixed with a person’s red blood cells and an agglutination reaction occurs, but does not when mixed
with anti-B serum, then that person has blood type A.
• The same procedure is also performed for people to determine a person’s Rh status. After the test, blood types are reported as the
ABO group and then either negative or positive depending on the Rh status.
• what are the possible types after combining RH and ABO grouping ?
• 1- A+,
• 2-A-,
• 3- B+,
• 4-B-,
• 5- AB+,
• 6- AB-,
• 7-O+,
• 8- O-.
• what is cross matching ?
• cross matching is a test to make sure a donor's blood is safe for a person to receive.
• mechanism ?
• 1- During this process the recipient’s serum gets mixed with the donor's blood to see if an agglutination reaction occurs.
• 2- If agglutination occurs, this means the recipient's blood contains antibodies against the donor's red blood cells, so that person
cannot receive that donor’s blood.
• 3- This is helpful just in case there are additional glycoproteins that are causing a reaction beyond the ones identified in the blood
typing.