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Mechanisms of Disease > Lecture 5 - Haemostasis and Thrombosis > Flashcards

Lecture 5 - Haemostasis and Thrombosis Flashcards

1
Q

what is haemostasis?

A

bodys response to stop bleeding and loss of blood

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2
Q

what is successful haemostasis dependent on?

A

vessel wall
platelets
coagulation system
fibrinolytic system

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3
Q

how do blood vessels contribute to haemostasis?

A

constrict to reduce blood loss

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4
Q

how do platelets contribute to haemostasis?

A

adhere to damaged vessel wall and each other

form platelet plug

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5
Q

how does coagulation contribute to haemostasis?

A

cascade, series of inactive components become activated
1ml of blood can generate enough thrombin to convert all fibrinogen in the body to fibrin so tight regulation required
balance of procoagulant and anticoagulant forces

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6
Q

which factors does thrombin positively feedback on?

A

factors V, VIII and XI

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7
Q

what are four thrombin inhibitors?

A

antithrombin III
alpha 1 anti trypsin
alpha 2 macroglobulin
protein c/s

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8
Q

what deficiencies can cause thrombophilia and thrombosis?

A

antithrombin III

protein c/s

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9
Q

what is fibrinolysis?

A

breakdown of fibrin by plasmin

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10
Q

how is fibrinolytic therapy used?

A

streptokinase which activates plasminogen

drastic treatment used in serious situations eg coronary artery occlusion or thrombus cutting off limb circulation

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11
Q

what is thrombosis?

A

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

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12
Q

what is virchows triad contributing to thrombosis?

A

changes in blood flow
changes in vessel wall
changes in blood components

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13
Q

what are the qualities of arterial thrombi?

A

pale
granular
lines of zahn
lower cell content

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14
Q

what are the qualities of venous thrombi?

A

deep red
soft
gelatinous
higher cell content

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15
Q

what are the effects of arterial thrombosis?

A

ischaemia
infarction
depends on site and collateral circulation

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16
Q

what are the effects of venous thrombosis?

A

congestion
oedema
ischaemia
infarction

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17
Q

what are the possible outcomes of thrombosis?

A 
lysis
propagation
organisation
recanalisation
embolism
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18
Q

what is lysis?

A

complete dissolution of thrombus
fibrinolytic system active, blood flow reestablished
most likely when thrombus is small

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19
Q

what is propagation?

A

progressive spread of thrombus
distally in arteries
proximally in veins

20
Q

what is organisation?

A

reparative process with ingrowth of fibroblasts and capillaries
lumen remains obstructed

21
Q

what is recanalisation?

A

blood flow reestablished but usually incompletely

one or more channels formed through organising thrombus

22
Q

what is embolism?

A

part of thrombus breaks off, travels through bloodstream and lodges at distant site

23
Q

what are the types of emboli?

A 
thromboemboli
air
amniotic fluid
nitrogen
medical equipment
tumour cells
24
Q

how many emboli are thromboemboli?

A

90%

25
Q

describe thromboembolisms from systemic veins

A

pass to lungs as wont get stuck in large veins near heart

next vessels small enough for it to get stuck are in lungs

26
Q

describe thromboembolisms from heart

A

pass via aorta to renal, mesenteric and other arteries

27
Q

describe thromboembolisms from atheromatous carotid arteries

A

go to brain - stroke

28
Q

describe thromboembolisms from atheromatous abdominal aorta

A

goes to arteries of legs

29
Q

describe the types of pulmonary embolism

A

massive pe > 60% reduction in blood flow - rapidly fatal
major pe blocks medium sized vessels - shortness of breath, cough, blood stained sputum
minor pe blocks small peripheral pulmonary arteries - asymptomatic or minor shortness of breath
recurrent pe gives pulmonary hypertension

30
Q

what 7 things can cause deep vein thrombosis?

A 
immobility
postop
pregnancy and post partum
oral contraceptives
severe burns
cardiac failure
disseminated cancer
31
Q

how is dvt treated?

A

intravenous heparin - anticoagulant and cofactor for antithrombin IIIoral warfarin - interferes with synthesis of vit k dependent clotting factors, slow effect

32
Q

what can cause fat embolism?

A

fractures of long bones

lacerations of adipose tissue

33
Q

what are signs of a fat embolism?

A

rash
shortness of breath
confusion

34
Q

what can cause cerebral embolism?

A

atrial fibrillation causes stasis which causes a thrombus

if in left heart, can go to brain and cause stroke or tia

35
Q

what is an iatrogenic embolism?

A

medical treatment eg air embolism from injection

36
Q

what is a nitrogen embolism?

A

nitrogen bubbles form in blood with rapid decompression

37
Q

what is disseminated intravascular coagulation?

A

pathological activation of coagulation mechanisms in response to a variety of diseases
small clots form throughout the body disrupting normal coagulation by using up the clotting factors
abnormal bleeding occurs from skin

38
Q

what are triggers of dic?

A

infection
trauma
liver disease
obstetric complications

39
Q

what is haemophilia?

A

type a and type b
x linked recessive so more common in males
due to nonsense point mutation

40
Q

what is the deficiency in haemophilia a?

A

factor VIII

41
Q

what is the deficiency in haemophilia b?

A

factor IX

42
Q

what happens in haemophilia?

A

haemorrhage into major joints, synovial hypertrophy, pain
muscle bleeding causes pressure and necrosis of nerves
can haemorrhage into retro
peritoneum and urinary tract

43
Q

how is haemophilia treated?

A

self administered factor replacement therapy

44
Q

what is thrombocytopenia?

A

platelet count is way below reference range

usually accompanied by bone marrow dysfunction eg leukaemia, anaemia

45
Q

what causes thrombocytopenia?

A

failure of platelet producion
increase in platelet destruction
sequestering of platelets (can cause dic)

Mechanisms of Disease (11 decks)

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