Flashcards in MoD Haemostatis And Thrombosis Deck (20):
What can blood vessels do to limit blood loss?
Occurs in arteries, veins and capillaries
What is the role of platelets?
What do they form?
Adhere to damaged vessel wall
Adhere to each other
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
What happens in the coagulation cascade?
Prothrombin is converted to thrombin
Thrombin cleaves fibrinogen to fibrin
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
Name four thrombin inhibitors
Anti thrombin 2
Alpha 1 antitrypsin
Alpha 2 macroglobulin
Protein C and S - inherited deficiency
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
The formation of a solid mass of blood within the circulatory system during life
Why does thrombosis occur?
Abnormalities of vessel wall - atheroma, injury, inflammation
Abnormalities of the blood flow - stagnation or turbulence
Abnormalities of blood constituents - smoking, post partum, post op
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
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
What are the effect of thrombosis on arterial and venous?
Arterial - infarction or Ischaemia
Venous - congestion, oedema, Ischaemia, infarction (rare)
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
What are the types of embolism?
Nitrogen - divers get 'the bends'
What happens to thrombo-embolis from
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
How can a DVT be prevented?
High risk patients identified and offered prophylaxis
Leg compression stocking during surgery
What are the risk factors for DVT?
Oral contraceptives - oestrogen effects coagulation
How are DVT treated?
Stop thrombus getting bigger, don't dissolve thrombus
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