Lecture 5 - Haemostasis and Thrombosis Flashcards
what is haemostasis?
bodys response to stop bleeding and loss of blood
what is successful haemostasis dependent on?
vessel wall
platelets
coagulation system
fibrinolytic system
how do blood vessels contribute to haemostasis?
constrict to reduce blood loss
how do platelets contribute to haemostasis?
adhere to damaged vessel wall and each other
form platelet plug
how does coagulation contribute to haemostasis?
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
which factors does thrombin positively feedback on?
factors V, VIII and XI
what are four thrombin inhibitors?
antithrombin III
alpha 1 anti trypsin
alpha 2 macroglobulin
protein c/s
what deficiencies can cause thrombophilia and thrombosis?
antithrombin III
protein c/s
what is fibrinolysis?
breakdown of fibrin by plasmin
how is fibrinolytic therapy used?
streptokinase which activates plasminogen
drastic treatment used in serious situations eg coronary artery occlusion or thrombus cutting off limb circulation
what is thrombosis?
formation of solid mass of blood within the circulatory system during life
what is virchows triad contributing to thrombosis?
changes in blood flow
changes in vessel wall
changes in blood components
what are the qualities of arterial thrombi?
pale
granular
lines of zahn
lower cell content
what are the qualities of venous thrombi?
deep red
soft
gelatinous
higher cell content
what are the effects of arterial thrombosis?
ischaemia
infarction
depends on site and collateral circulation
what are the effects of venous thrombosis?
congestion
oedema
ischaemia
infarction
what are the possible outcomes of thrombosis?
lysis propagation organisation recanalisation embolism
what is lysis?
complete dissolution of thrombus
fibrinolytic system active, blood flow reestablished
most likely when thrombus is small
what is propagation?
progressive spread of thrombus
distally in arteries
proximally in veins
what is organisation?
reparative process with ingrowth of fibroblasts and capillaries
lumen remains obstructed
what is recanalisation?
blood flow reestablished but usually incompletely
one or more channels formed through organising thrombus
what is embolism?
part of thrombus breaks off, travels through bloodstream and lodges at distant site
what are the types of emboli?
thromboemboli air amniotic fluid nitrogen medical equipment tumour cells
how many emboli are thromboemboli?
90%
describe thromboembolisms from systemic veins
pass to lungs as wont get stuck in large veins near heart
next vessels small enough for it to get stuck are in lungs
describe thromboembolisms from heart
pass via aorta to renal, mesenteric and other arteries
describe thromboembolisms from atheromatous carotid arteries
go to brain - stroke
describe thromboembolisms from atheromatous abdominal aorta
goes to arteries of legs
describe the types of pulmonary embolism
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
what 7 things can cause deep vein thrombosis?
immobility postop pregnancy and post partum oral contraceptives severe burns cardiac failure disseminated cancer
how is dvt treated?
intravenous heparin - anticoagulant and cofactor for antithrombin IIIoral warfarin - interferes with synthesis of vit k dependent clotting factors, slow effect
what can cause fat embolism?
fractures of long bones
lacerations of adipose tissue
what are signs of a fat embolism?
rash
shortness of breath
confusion
what can cause cerebral embolism?
atrial fibrillation causes stasis which causes a thrombus
if in left heart, can go to brain and cause stroke or tia
what is an iatrogenic embolism?
medical treatment eg air embolism from injection
what is a nitrogen embolism?
nitrogen bubbles form in blood with rapid decompression
what is disseminated intravascular coagulation?
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
what are triggers of dic?
infection
trauma
liver disease
obstetric complications
what is haemophilia?
type a and type b
x linked recessive so more common in males
due to nonsense point mutation
what is the deficiency in haemophilia a?
factor VIII
what is the deficiency in haemophilia b?
factor IX
what happens in haemophilia?
haemorrhage into major joints, synovial hypertrophy, pain
muscle bleeding causes pressure and necrosis of nerves
can haemorrhage into retro
peritoneum and urinary tract
how is haemophilia treated?
self administered factor replacement therapy
what is thrombocytopenia?
platelet count is way below reference range
usually accompanied by bone marrow dysfunction eg leukaemia, anaemia
what causes thrombocytopenia?
failure of platelet producion
increase in platelet destruction
sequestering of platelets (can cause dic)
