MoD Haemostatis And Thrombosis Flashcards Preview

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Flashcards in MoD Haemostatis And Thrombosis Deck (20)
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1
Q

What can blood vessels do to limit blood loss?

A

Constrict

Occurs in arteries, veins and capillaries

2
Q

What is the role of platelets?

What do they form?

A

Adhere to damaged vessel wall

Adhere to each other

Platelet plug

3
Q

Describe the platelet release reaction?

A

ATP –> ADP

ADP, thromboxane A2 causes platelet aggregation

5HT, platelet factor 3 also released

PF3 important in coagulation

Platelets coalesce after aggregation

4
Q

What happens in the coagulation cascade?

A

Prothrombin is converted to thrombin

Thrombin cleaves fibrinogen to fibrin

5
Q

Why is tight regulation of the coagulation cascade required?

What is it a balance of?

A

1ml of blood can generate enough thrombin to convert all of the fibrinogen in the body to fibrin

Procoagulant and anticoagulant forces

6
Q

Name four thrombin inhibitors

A

Anti thrombin 2

Alpha 1 antitrypsin
Alpha 2 macroglobulin

Protein C and S - inherited deficiency

7
Q

What is fibrinolysis?

What happens to plasminogen?

What are the two drugs used in fibrinolytic therapy?

A

Breakdown of fibrin

Cleaved to plasmin using plasminogen activators

Streptokinase
tPA

8
Q

Define thrombosis

A

The formation of a solid mass of blood within the circulatory system during life

9
Q

Why does thrombosis occur?

Virchow’s triad

A

Abnormalities of vessel wall - atheroma, injury, inflammation

Abnormalities of the blood flow - stagnation or turbulence

Abnormalities of blood constituents - smoking, post partum, post op

10
Q

What is the difference in appearance of arterial and venous thrombi?

A

Arterial - pale, granular, lines of Zahn, lower cell content

Venous - deep red, soft, gelatinous, higher cell content

11
Q

What are the outcomes of thrombosis?

A

Lysis - complete dissolution of thrombus, fibrinolytic system active, blow flow re-established - most likely when thrombi small

Propagation - spread of thrombosis - distally in arteries, proximally in veins

Organisation - reparative process with in growth of fibroblasts and capillaries. Lumen remains obstructed

Recanalisation - blow flow re-established but usually incompletely. One or more channels formed through organising thrombus

Embolism - part of thrombus breaks off, travels in blood stream and lodges at distal site

12
Q

What are the effect of thrombosis on arterial and venous?

A

Arterial - infarction or Ischaemia

Venous - congestion, oedema, Ischaemia, infarction (rare)

13
Q

Define embolism

A

The blockage of a blood vessel by a solid, liquid or gas at a site distant from its origin

90% of emboli are thrombo emboli

14
Q

What are the types of embolism?

A

Thrombo-emboli

Air
Nitrogen - divers get 'the bends'
Amniotic fluid
Medical equipment 
Tumour cells
15
Q

What happens to thrombo-embolis from

Systemic veins
Heart
Carotid arteries
Atheromatous abdominal aorta

A

Systemic veins –> Pulmonary emboli

Heart - aorta to the renal, mesenteric and other arteries

Carotid arteries –> brain (Stroke)

Abdominal aorta –> arteries of the legs

16
Q

How can a DVT be prevented?

A

High risk patients identified and offered prophylaxis

Heparin subcutaneously
Leg compression stocking during surgery

17
Q

What are the risk factors for DVT?

A
Immobility
Post op
Pregnancy
Oral contraceptives - oestrogen effects coagulation
Severe burns
Cardiac failure
Disseminated cancer
18
Q

How are DVT treated?

A

IV heparin

Oral warafarin

Stop thrombus getting bigger, don’t dissolve thrombus

19
Q

What is a pulmonary embolism?

What reduction is blood flow is classed as a massive PE?

What happens in a major PE?

What happens in a minor PE?

What do recurrent PEs lead to?

A

Bit of thrombus that has passed to the lungs where it has got stuck

Massive PE >60% reduction in blood flow, rapidly fatal

Major PE - medium sized vessels blocked, shortness of breath, coughs blood stained sputum

Minor PE - small peripheral pulmonary arteries blocked. Asymptomatic or minor SOB

Hypertension

20
Q

What does successful Haemostasis depend on?

A

Vessel wall

Platelets

Coagulation system

Fibrinolytic system