MoD Haemostatis And Thrombosis Flashcards Preview

Semester 2 > MoD Haemostatis And Thrombosis > Flashcards

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

What can blood vessels do to limit blood loss?

Constrict

Occurs in arteries, veins and capillaries

2

What is the role of platelets?

What do they form?

Adhere to damaged vessel wall

Adhere to each other

Platelet plug

3

Describe the platelet release reaction?

ATP --> ADP

ADP, thromboxane A2 causes platelet aggregation

5HT, platelet factor 3 also released

PF3 important in coagulation

Platelets coalesce after aggregation

4

What happens in the coagulation cascade?

Prothrombin is converted to thrombin

Thrombin cleaves fibrinogen to fibrin

5

Why is tight regulation of the coagulation cascade required?

What is it a balance of?

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

Procoagulant and anticoagulant forces

6

Name four thrombin inhibitors

Anti thrombin 2

Alpha 1 antitrypsin
Alpha 2 macroglobulin

Protein C and S - inherited deficiency

7

What is fibrinolysis?

What happens to plasminogen?

What are the two drugs used in fibrinolytic therapy?

Breakdown of fibrin

Cleaved to plasmin using plasminogen activators

Streptokinase
tPA

8

Define thrombosis

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

9

Why does thrombosis occur?

Virchow's triad

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

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

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

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

11

What are the outcomes of thrombosis?

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

What are the effect of thrombosis on arterial and venous?

Arterial - infarction or Ischaemia

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

13

Define embolism

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

What are the types of embolism?

Thrombo-emboli

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

15

What happens to thrombo-embolis from

Systemic veins
Heart
Carotid arteries
Atheromatous abdominal aorta

Systemic veins --> Pulmonary emboli

Heart - aorta to the renal, mesenteric and other arteries

Carotid arteries --> brain (Stroke)

Abdominal aorta --> arteries of the legs

16

How can a DVT be prevented?

High risk patients identified and offered prophylaxis

Heparin subcutaneously
Leg compression stocking during surgery

17

What are the risk factors for DVT?

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

18

How are DVT treated?

IV heparin

Oral warafarin

Stop thrombus getting bigger, don't dissolve thrombus

19

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?

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

What does successful Haemostasis depend on?

Vessel wall

Platelets

Coagulation system

Fibrinolytic system