Week 4

Question 1

List four stimuli for platelet activation

Answer 1

Collagen
Thrombin
Thromboxane
ADP

Question 2

What does aPTT stand for?

Answer 2

activated Partial Thromboplastin Time

Question 3

What does aPTT mean clinically?

Answer 3

aPTT = the time for clot formation in citrated plasma after the addition of Ca2+, contact activator and phosphilipid to mimic the platelet membrane
I.e measures the function of the sample’s intrinsic pathway

Question 4

What test would you use to measure the extrinsic pathway function of your sample?

Answer 4

Prothrombin time (time for clot formation of plasma after addition of Ca2+ and tissue factor)

Question 5

What effect does giving low-dose aspirin therapy have, and avoid?

Answer 5

Inhibits platelet TXA2 formation, which inhibits aggregation of exposed platelets permanently
Cleared by liver, so largely avoid vasodilatory effects on blood vessels throughout the body

Question 6

Name two drugs that aim to reduce coagulation by activating plasmin

Answer 6

Streptokinase

Alteplase

Question 7

What are the three factors predisposing to thrombosis? Which is most important?

Answer 7

1. Endothelial injury (most important)
2. Abnormal haemodynamics e.g blood stasis or turbulence
3. Hypercoaguability of blood

Question 8

Name three things injured endothelial cells release that promotes thrombosis.

Answer 8

1. vWF (platelet adhesion)
2. Tissue factor (extrinsic pathway)
3. Plasminogen-activator inhibitors (suppress plasmin production and thence fibrinolysis)

Question 9

How does viral infection predipose to thrombosis?

Answer 9

Deposition of viral antigen-antibody complexes in BV walls > complement activation > membrane attack complex punches holes in endothelial cells, causing damage

Question 10

How does blood turbulence predispose to thrombosis (2 things)?

Answer 10

1. Creates counter currents of blood flow which create areas of blood stasis > thrombosis
2. Increases activity of intravascular procoagulant cellular and enzymatic reactions that lead to blood coagulation

Question 11

How does blood stasis predispose to thrombosis (3 things)?

Answer 11

1. Stagnant blood becomes viscous and hypercoaguable
2. Local endothelial cells may sustain hypoxic injury and release or express pro-coagulant molecules as a result
3. Retards removal of procoagulant molecules and arrival of anticoagulant molecules from circulating blood

Question 12

What does the presence of lines of Zahn signify?

Answer 12

That the thrombus was initially non-occlusive with continued blood flow over it

Question 13

What three things influence the shape, size and colour of thrombi?

Answer 13

Age
Location (rate of blood flow)
Septic or not

Question 14

Under what circumstances (specifically) might a pulmonary thromboembolus lodged in a medium sized artery cause pulmonary infarction?

Answer 14

Anything reducing O2 supply to the lung tissue itself so anemia, pneumonia, pre-exisiting fibrosis or oedema of lungs

Question 15

At whay systolic BP range would you start to see clinical consequences of hypertension?

Answer 15

> 160-180 mmHg

Question 16

What systolic BP value is considered hypotension? What about MAP?

Answer 16

Systolic < 80 mmHg

MAP < 60 mmHg

Question 17

What are the three major mechanisms of shock?

Answer 17

Hypovolemic
Cardiogenic
Distributive

Question 18

What are the four subsets of distributive shock?

Answer 18

Neurogenic
Anaphylactic
Heat stroke
Septic

Question 19

Define cardiac tamponade

Answer 19

The adverse consequences of rapid, excess fluid volume in the pericardial sac