Blood Transfusions and Coagulation/Thrombolysis

Question 1

What is the difference between blood grouping vs. crossmatching?

Answer 1

Blood Grouping = determining red cell antigens in blood of donor and recipient – look for agglutination (clumping of cells in the presence of an antibody) – we use this to determine the red cell compatability between donor and patient

Cross-matching – mix donor and recipient blood outside of the body – indicates that the donor blood is incompatable for the patient- it ensures that there was no error in ABO grouping of donor or recipient – and it also ensures that recipient has no naturally occurring or immune antibodies active against donors cells.

Question 2

Describe how the blood is grouped into A, B or O type

Answer 2

A type - has ‘A’ antigens on the surface

B type - has ‘B’ antigens on the surface

AB type - has ‘A and B’ antigens on the surface

and O type- does not have antigens on its surface

Question 3

What is the Rhesus system for classifying blood type?

Answer 3

They are either negative or positive for the rhesus antigen (most often rhesus antigen ‘D’) - these are also found on the surface of RBCs

Question 4

If you are blood type ‘A negative’ what antibodies do you possess?

Answer 4

you have

• ‘B’ antibodies

Question 5

If you are blood type ‘AB positive’ what antibodies do you posess?

Answer 5

• you do not posses any antibodies against blood

Question 6

If you are blood type “O negative” what antibodies do you produce?

Answer 6

• ‘A’ antibodies
• ‘B’ antibodies
• *this is the universal donor - will not produce a reaction in anyone*

Question 7

Why do we have antibodies against other blood types?

Answer 7

we encounter small amounts of Type A or B in food/bacteria

Question 8

Do rhesus negative blood types have antibodies against it?

Answer 8

NO - neither Rh positive, nor negative blood types have antibodies against this

UNLESS

unless you come across it somehow during life (like a mother with an infant) - you don’t expect to come across it under normal conditions

Question 9

Do we donate whole blood in blood transfusions?

Answer 9

NO we filter out the red cells from plasma and platelets - really we just want the red cells and plasma, we don’t want the WBC because that leads to immune garbage

Question 10

Why might the O negative blood type NOT be considered a universal donor?

Answer 10

Because the sample would also contain the antiA or antiB antibodies. We try to filter them out of the blood, but ultimately it depends on the titres

Question 11

Why might a mother reject her fetus based on blood type? Why is there no risk of this in the first pregnancy?

Answer 11

If the mother is rh negative and the fetus is positive, she creates antibodies against this …. with the next pregnancy she has the antibodies, baby could be born with jaundice and face anaemic death

Question 12

What is an autologous transfusion?

Answer 12

Donate your own blood weeks before a surgery - therefore there is no risk aassociated with blood borne viruses like AIDS

Question 13

What is haemostasis?

Answer 13

the maintanence of blood in a fluid/clot free state

Haemostasis induces a rapid formation of a localized haemostatic plug at the site of vascular injury - this is a well regulated process

Question 14

What is a Thrombos?

Answer 14

it is the inappropriate activation of the normal haemostatic process (blood clot formation) within the vascular system

• it has the potential to block the blood flow to the vital areas

Question 15

What does a Thrombus contain?

Answer 15

it consists of fibrin, red blood cells, and platelets

Question 16

What do you call a thrombus that breaks loose and travels to organs?

Answer 16

an Embolus

Question 17

If an embolus moves to the heart, what occurs?

Answer 17

an

Acute Myocardial Infarction (AMI= heart attack)

Question 18

what occurs if the embolus moves to your brain?

Answer 18

Thrombotic stroke or Transient ischemic attach (TIA)

Question 19

What if the embolus moves to your legs?

Answer 19

peripheral arterial disease - causes claudication

Question 20

In the venous system, what happens if an embolus moves to your legs, or your lungs?

Answer 20

In the venous system of legs = DVT

in the venous lungs = pulmonary embolism

Question 21

How do we treat an arterial thrombus vs. a venous thrombosis?

Answer 21

arterial = platelet inhibitors

venous = anti-coagulents

*though it’s not as if only platelets are at play in arteries and only coagulents are effecting the veins- it’s a matter of which is more dominantly effecting. You can remmber which is which by remembring that platelets are more likely to be activated by the sheer strain and quick movement of the blood in the arteries as opposed to the relatively relaxed venous system

Question 22

What is Virchow’s Triad?

Answer 22

thrombosis is caused by abnormalities in one or more of the following

1) quality of the vessel wall (endothelial cell injury?)
2) nature of the blood flow (stasis/tubulence)
3) composition of the blood (hypercoagulable or thrombophilia)

Question 23

What can cause arterial thrombosis?

Answer 23

a common cause of arterial thrombosis is atrial fibrillation - causes disturbed blood flow or

arterial thrombosis can follow a rupture of atheroma (antherothrombosis)

Question 24

How many plasma proteins are involved in the coagulation cascade?

Answer 24

11 plasma proteins in the cascade - most factors are protease enzymes (an enzyme that cleaves a protein at a specific residue)

Question 25

What are the alternative names for

Factor 1

Factor 2

Factor 3

of the coagulation cascade?

Answer 25

1= fibrinogen

2= prothrombin

3= tissue factor or throboblastin

Question 26

What are the first steps of the extrinsic coagulation cascade?

Answer 26

1. small amounts of tissue factor is realeased by damaged endothelial cells or exposed at the site of injury
2. TF activates factor VII in the plasma
3. TF enables the conversion of Factor VII to activated Factor VII (FVIIa)

Question 27

What is the first step of the instrinsic coagulation cascade?

Answer 27

contact with a synthetic or chaged surface causes the activation of a different coagulation factor (Factor XII) = activation converts it to FXIIa an active protease

Question 28

Where do the extrinsic and intrinsic coagulation cascades meet?

Answer 28

They meet when they activate Factor X - after that it is a common pathway

Question 29

What does the Final Common Pathway consist of in the coagulation cascade

Answer 29

it results in the conversion of the plasma preprotein, fibrinogen, to fibrin polymer or clot

Question 30

What factor feedsback and accelerates the conversion of Factor VII to it’s activated form?

Answer 30

Factor 10a feedsback and accelerates it’s formation

Question 31

Without calcium present, what reaction cannot take place?

Answer 31

Factor 10a cannot convert prothrombin to thrombin

Question 32

Thrombin has many roles in the coagulation cascade- name them all

Answer 32

1) thrombin (when in the presence of calcium) will convert fibrinogen to fibrin
2) it activates factor 13 allowing it to crosslink fibrin clots
3) activates Factor 5 and accelerates the action of Factor 10
4) Generates more factor 7 - positive feedback loop
5) it is also a potent activator of platelet aggregation

Question 33

What controls coagulation?

Answer 33

The activation of FXa by TF- FVIIa is almost immediately inhibited by tissue factor pathway inhibitor (TFPI) - which is a naturally occuring anticoag. protein that directly inactivates coagulation factor Xa and produces feedback inhibition of the factor VIIa/tissue factor catalytic complex

*ultimately it’s a ballance between Tissue factor and TFPI that determines whether coagulation will proceed

Question 34

What naturally occuring inhibitors are there for Factor X and Factor II?

Answer 34

• Anti-Thrombin III
• Heparin
• Thrombomodulin

Question 35

What factors are involved in the intrinsic pathway?

Answer 35

Factors XII, XI, IX, VIII, and X as well as prekallikrein, HK, calcium, and platelet phospholipids

Question 36

What cofactors are necessary for the proper function of the coagulation cascade?

Answer 36

• calcium and phospholipid for the tenase and prothrombinase complexes
• negatively charged phospholipids
• calcium mediates the binding of coagulation factors
• calcium - for the Vitamin K dependent coagulation factors

Question 37

Why is Vitamin K an essential component in coagulation?

Answer 37

Vitamin K acts as a catalyst for the maturation of coagulation cascade factors in formation

Question 38

What factors favor thrombosis?

Answer 38

• blood stasis allows accumulation of HMWK etc.
• the release of tissue factor- activates cascade
• exposed collagen- binds plasma and platelets adhere
• Thrombin - converts fibrinogen to polymeric fibrin

Question 39

What factors inhibit thrombosis?

Answer 39

• antithrombin
• PGI2 and NO

Question 40

What is the last step in the coagulation cascade?

Answer 40

• enzymatic cleavage of soluble plasma fibrinogen (Factor I to Factor Ia)

fibrin spontaneoulsy polymerizes and results in the formation of a permanent fibrous plug - and induces further platelet recruitement