Session 13

Disorders of Coagulation and Blood Transfusion

B.M.C. Randika WimalasiriLecturer (Prob.)

Department of MLSFaculty of Health Sciences

The Open University of Sri Lanka

Blood

• Must be kept in a fluid medium to facilitate transport of oxygen to tissues and carbon dioxide from tissues to the lungs.

• Also take all the nutrients from the gastrointestinal tract for distribution and to excrete by kidney as nitrogenous waste material.

• Trauma- blood must coagulate and seal off the leak within the vascular system to save the individual from bleeding to death.

Blood

• A series of proteins form the coagulation system that helps to form plugs to stop bleeding occurring.

• The clots formed must be removed in time to restore blood to vital organs.

• This is performed by proteins that comprise the fibrinolytic system.

• An anticoagulant system is also present to keep the blood in fluid state and to stop unnecessary clot formation within the vessels.

Blood

• Importance of blood is in fluid medium – to facilitate the smooth delivery of oxygen and

nutrients to peripheral tissues

– to remove carbon dioxide and nitrogenous waste material.

• Able to form small solid masses to block off leaks in the blood vessels which can otherwise cause exsanguination or bleeding to death.

Normal coagulation pathway

• A series of proteins – serine proteases form the normal coagulation pathway.

• These proteins are identified by roman numbers and have a total of 13 such factors.

• Please note that there are no coagulation factor numbers IV and VI.

Normal coagulation pathway

• These coagulation factor enzymes digest one another in a sequential fashion to finally cleave fibrinogen to form small fibrin monomers which form the main building blocks of the definitive clot.

Names of the coagulation factors

• I Fibrinogen• II Prothrombin• III Tissue factor• V Labile factor• VII Proconvertin• VIII Anti Haemophilic factor• IX Christmas factor• X Stuart-Prower factor• XI Plasma thromboplastin antecedent• XII Hageman (contact) factor• XIII Fibrin-stabilizing factor

Normal coagulation pathway

• Classified into 3 pathways.

1. Extrinsic pathway

2. Intrinsic pathway

3. Common pathway

Normal coagulation pathway

• Within the body the extrinsic pathway is the pathway that is usually activated.

• At times of injury to the vascular endothelial cells, tissue factor which is present in the subendothelial space is secreted into the vessel lumen.

• With the exposure of tissue factor, factor VII is cleaved to an active form.

• This initiates the coagulation process.

Normal coagulation pathway

• The tissue factor and activated factor VII complex directly activates the intrinsic pathway and a concerted effort is made to convert fibrinogen molecules to fibrin.

• Fibrin is a filamentous protein which forms a mesh which traps red cells and platelets, thus forming an initial clot.

• This clot is stabilized by factor XIII.

Normal coagulation pathway

• Though these coagulation pathways have been described as such, there is a concerted effort to form a clot and stem the bleeding.

• There are numerous inter connected pathways that activate each other proteins to establish a faster and more stable clot.

Inherited bleeding disorders

• First to be discovered amongst inherited diseases.

• Most common are von Willebrand’s disease and Haemophilia.

• In inherited bleeding disorders, usually a single coagulation factor or protein that is deficient, unlike in acquired bleeding disorders where more than one coagulation factor or protein is deficient.

Von Willebrand’s disease

• Commonest hereditary coagulation abnormality among human beings.

• Von Willebrand’s factor is a large protein multimer (A molecular aggregate held together by noncovalent bonds) produced by endothelial cells and platelets.

Von Willebrand’s disease

• Inherited as autosomal dominant as well as autosomal recessive.

• Commonest presentation is with menorrhagia(excessive menstruation).

• Patients with severe von Willebrand’s disease have low levels of factor VIII and may have more severe bleeding than usual.

Haemophilia

• Mainly 2 types depending on the type of the coagulation factor deficient. – Deficiency of factor VIII - haemophilia A – Deficiency of factor IX - haemophilia B

• Both haemophilias are inherited in a sex linkedand the gene for the coagulation factors VIII and IX are carried on the X chromosome.

• Females are carriers of the gene and males are affected.

• Haemophilia patients present with bleeding into joints and muscles. This may be spontaneous or following minor trauma.

Acquired bleeding disorders

• Acquired bleeding disorders are commoner than inherited bleeding disorders.

• Inherited bleeding disorders- one major coagulation factor is deficient or defective

• Acquired bleeding disorders- more than one factor may be deficient or defective.

• The commonest causes of acquired bleeding disorders are due to– Deficient production of coagulation factors– Increase in consumption of coagulation factors– Impaired function of normal coagulation factors

Deficient production of coagulation factors

• Commonest occurs due to liver failure.

• As the liver the main organ of synthesis of the enzymatic proteins required for coagulation, liver failure results in low levels of coagulation protein production, leading to bleeding.

• In liver failure more than one coagulation factor is deficient.

Deficient production of coagulation factors- Vitamin K

• Deficiency leads to acquired bleeding disorder. • Essential for gamma carboxylation of the

coagulation factors II, VII, IX and X which is a post translational modification ( enzymatic modification of proteins during or after protein biosynthesis) of the basic protein molecule.

• In the absence of vitamin K, gamma carboxylation does not take place giving rise to the production of “Proteins produced in the absence of Vitamin K”.

Deficient production of coagulation factors- Vitamin K

• As vitamin K is fat soluble, requires the presence of bile salts in the duodenum for absorption.

• In patients with complete obstruction of the bile duct, fat soluble vitamins such as Vitamins A,D, K and E absorption is impaired.

• Coagulation factors that are mainly affected by vitamin K deficiency are factors II, VII, IX and X.

Increase in consumption of coagulation factors

• Also called consumptive coagulopathy.

• Classic example - disseminated intravascular coagulation.

• DIC occurs as a result of generalized vascular endothelial injury resulting in activation of platelets and coagulation factors simultaneously.

Increase in consumption of coagulation factors

• This activation uses up all the platelets and coagulation factors giving rise to micro thrombi within the systemic circulation.

• Plasminogen is utilized to break down these thrombi resulting in low levels of fibrinolytic proteins as well.

Fibrinolysis

Impaired function of normal coagulation factors

• In multiple myeloma - production of large amounts of paraproteins (a protein found in the blood only as a result of cancer or other disease), and interfere with normal fibrin polymerization giving rise to impaired function.

• These proteins may coat platelets and impair its function.

Thrombophilia

• Spontaneous or unprovoked clot formation within the vascular system.

• Occurs due to an imbalance between the clot promoting factors in the blood and the anti coagulant proteins.

• Occur due to inherited deficiencies of naturally occurring anticoagulant proteins or due to acquired conditions.

• Examples - protein C deficiency and protein S deficiency.

Coagulation Inhibitory Mechanisms

1. Antithrombin (+heparin or heparan sulphate)

2. Protein C anticoagulation pathway

3. Tissue factor pathway inhibitor

1 & 2 are of known clinical importance!

3 is important physiologically, but of uncertain clinical importance!

+

+

FVIII

FV

FVIIIi

FVi

Procoagulant

Protein Ca

(APC)

Protein C/EPCR

Protein S

Anticoagulant

ThrombomodulinFibrinFibrinogen

ProthrombinThrombin

FVa

FX FXa

FVIIIa

FIXa

Coagulation Regulation

by Activated Protein C & S

Thrombophilia

• Acquired causes are more common and are mainly after major surgery, immobilization, large areas of soft tissue trauma and certain malignancies. Systemic lupus erythematosus– Numerous antibodies produced against one’s own

tissue. – Rarely, antibodies may be formed against coagulation

proteins activating them and giving rise to a thrombophilic condition.

– This is called antiphospholipid syndrome as the antibodies are mainly against phospholipids dependent coagulation factors.

Thrombophilia

Anticoagulation

• Anti coagulants are agents that inhibit coagulation.

• Most widely used anticoagulant is Warfarin -coumarin derivative.

–Warfarin acts by inhibiting production of vitamin K dependent proteins. i.e. by impairing the synthesis of coagulation factors II, VII, IX and X.

Thrombophilia

Anticoagulation

• Heparin also used as an anticoagulant.

–Heparin is a high molecular weight protein which functions by activating anti thrombin.

–Anti thrombin in turn inhibits thrombin, factors XII, XI, IX and X.

Blood transfusion

• Entails donation of whole blood or a component from one individual to another.

• With the discovery of the circulatory system, the blood groups and the ability to store blood for long periods of time helped to develop a more systematic transfusion service.

Blood transfusion

• The person who donates the blood is called the “donor” and the person who receives it is called the recipient.

• Is a life saving procedure.

• Require in many surgeries, transplantation and treatment with many cytotoxic drugs used for malignancy.

Blood groups

• Red cells carry antigens on their cell membranes which are classified as blood group antigens.

• More than 400 blood groups identified. • Most important and clinically significant blood

group systems are the ABO, and Rh systems. • Some blood groups systems such as the Kidd,

Kell and Duffy play an important role in pregnancy.

Blood groups

• Blood groups are genetically determined and code for small molecules on the surface of cells.

• These molecules found in body fluids such as sweat, saliva and semen as well.

• Useful in forensic medicine and legal practice.

Blood transfusions

• Purpose is to increase the oxygen capacity of the blood and the main indication is anaemia.

• To maximize the survival of donated red cells, the red cells of the donor are mixed with the plasma of the recipient to detect antibodies that may lyse the donated red cells.

• Transfusions involve matching antibodies of the recipient with the red cells of the donor.

• This procedure is called cross matching.

Blood components

• Whole blood is composed of many components. • Whole blood, separate into many components by

centrifugation.• Components has specific indications. E.g. for a

patient suffering with anaemia, a red cell concentration would suffice.

• The transfusion of whole blood causes unnecessary exposure of other antigens on white cells and transfusion reactions to certain proteins present in the plasma.

Blood components

• Platelet concentrate

• Platelet poor plasma

• Cryoprecipitate

• Factor concentrate

• Albumin

• Immunoglobulins

Activities

• Donation of blood

• Blood grouping and compatibility tests

• Screening blood samples for transfusion transmitted infections

• Preparation of blood products

• Storage of blood products

Blood Donation

Blood donor

• Healthy normal adult

• With normal haemoglobin content

• Free of infections that are likely to transmitted through blood

• One unit of blood can be donated every 4-6 months

• Blood donor is interviewed and examined by the medical officer

• His /her Hb is tested whether it is above the suitable level

A fingerstick is made to obtain a drop of

blood to test the hematocrit

The site for drawing blood is selected and disinfected

• The needle used to draw the blood from the vein is gently inserted.

• The needle is attached to plastic tubing to conduct the blood to the collection bag.

• Blood fills the collection bag by gravity in a few minutes. The sealed plastic collection bag contains a blood preservative

• The needle is removed and pressure is applied over the venipuncture site, then a bandage is placed for the next couple of hours.

• A unit of blood must be properly labelled and the label MUST be checked before use

Units are refrigerated until used. A storage refrigerator is shown here.

A crossmatch is being performed. A full crossmatch procedure takes about 45 min to complete and

cannot be shortened.

Crossmatching is performed if red cells are transfused

If compatible blood component is transfused to the patient

Blood components preparation

• Blood components are prepared by differntial centrifugatiom and freezing and thawing

• Blood components• Differential centrifugation

– Packed cells

– Buffy coat

– Platelet concentrate

– Fresh frozen plasma • Freezing & thawing

– Cryo precipitate

Blood is collected as whole blood, as shown below:

Blood can be stored as whole blood (with all of the plasma present) or, much more commonly, as packed red blood cells (PRBC's) in which about 70% of the

plasma has been removed. This is done by light centrifugation, as shown below:

The platelet rich plasma can then be expressed off, leaving

packed red blood cells (PRBC's) as shown here:

The plasma can be centrifuged heavily a second time to separate the platelet rich plasma, as shown below:

After centrifugation plasma is removed to the next pack leaving platelet concentrate

Blood components

Packed red cells

• First component made from immediate centrifugation of a whole blood unit.

• Used to increase the oxygen carrying capacity of patients with anaemia.

Platelet rich plasma

• Useful for transfusing those with thrombocytopenia and bleeding (eg. patients with Dengue fever).

• Also very useful in patients undergoing chemotherapy for various malignancies.

Blood components

White cells transfusions (Buffy coat)

• Rarely used now due to reactions to the white cell antigens and the risk of many transfusion transmitted infections.

• Used in patients with very low white cell counts and infections.

Blood components

Fresh Frozen Plasma• Used to replenish clotting factors in patients with

bleeding. • Can be stored for many months.

Cryoprecipitate• Formed from fresh frozen plasma. • Rich in factor VIII and fibrinogen. • Used liberally in treatment of haemophilia before the

advent of recombinant factor VIII.

Blood components

Albumin

• Is a small protein present in plasma.

• Important molecule within the plasma that maintains the colloid oncotic pressure within blood vessels.

• Useful in patients with liver failure who are unable to synthesize sufficient amounts of albumin.

Complications of blood transfusions

• Classified according to the time of onset.

Early complications 1. Haemolytic reactions - immediate – occur due to

mismatch of major blood groups. 1. E.g. group A person being transfused group B blood

2. Haemolytic reactions - delayed within a few days –occur due to incompatibility of a minor blood group.

Complications of blood transfusions

3. Reactions due to infected blood –seen with platelet transfusions as platelets stored at room temperature and facilitate growth of bacteria within the platelet pack.

4. Allergic reactions to WBCs, platelets & proteins

5. Pyrogenic reactions to plasma proteins, HLA antibodies

6. Circulatory overload – seen with chronic long standing anaemia who are given rapid transfusions. Also seen in elderly patients with heart disease.

Complications of blood transfusions

7. Air embolism –Uncommon complication seen with cannulation of veins prior to transfusion.

8. Thrombophlebitis –seen with inflammation of the vein to which the transfusion is given to.

9. Citrate toxicity –seen in those receiving large volumes of blood over a short period of time. – Citrate is added as an anticoagulant to keep the blood

in a fluid state when being stored. – Citrate enters the circulation in large amounts in those

who have multiple transfusions.

Complications of blood transfusions

10. Hyperkalemia ––With aging of red cells within the blood

pack during storage, some cells lyse releasing intra cellular potassium into the transfusion pack.

–With transfusion of blood closer to the expiry date, the recipient may have high levels of serum potassium following the transfusion.

Complications of blood transfusions

11. Clotting abnormalities –– All clotting factors have a finite life span. – Clotting factor that survives the shortest time is

factor VII for approximately 7 hours. – As the blood pack is kept refrigerated for

prolonged periods of time, the levels of coagulation proteins reduce progressively.

– Transfusion of large volumes of stored blood may give rise to deficiency of coagulation proteins and cause clotting abnormalities.

Late Complications of transfusion

Transmission of diseases1. Viral infections

– most dreaded complications of transfusion. – donated blood testing for transfusion transmitted

diseases. – Some infections are Hepatitis A, B, & C, Human

Immunodeficiency Virus 1 & 2 (HIV), Cytomegalovirus (CMV), Human T Lymph tropic virus HTLV I & II, West Nile virus

Late Complications of transfusion

2. Bacterial infections

– Many bacteria causing transfusion transmitted infections.

– Most common with platelet transfusions.

– Some of the bacteria that have been implicated are - Treponema pallidum causing syphilis, Brucella and Salmonella

Late Complications of transfusion

3. Parasitic infections

• Many parasitic infections caused by blood transfusions.

• Malaria, Babesiosis (malaria-like parasitic disease caused by infection with Babesia), chagas disease (caused by a trypanosome transmitted by bloodsucking bugs), Leishmaniasis.

Late Complications of transfusion

4. Prion diseases (also known as transmissible spongiform encephalopathies (TSE's) are a group of progressive neurodegenerative conditions)