Thrombosis Flashcards
define hemostasis
A physiological response to vessel injury .The process by which bleeding is arrested .
It has 3 major steps .
1.Vasoconstriction
2.Activation of platelets > adhere and aggregate
(formation of platelet plug at injury site) > temporary block
3.Activation of the coagulation cascade > fibrin thrombus formation > closure of site of injury
these processes seal the defect until tissues are repaired
Haemostasis - pathogenesis
- When blood comes in contact with tissue ,it activates coagulation cascade
- 13 coagulation factors constituting of fibrinogen (soluable plasma protein ) is cleaved into fibrin ,(a non - soluable plasma protein )
- fibrin proteins stick together to form a thrombus
*Fibrinolytic system ( a system that breaks down fibrin.
Plasminogen > plasmin > lysis > fibrin clot
What is the difference between thrombosis and clot
- A blood clot is a what forms in a test tube or in blood vessels after death .It is smooth and it does not adhere to the vessel wall
- A thrombus is a soild/semi-solid mass formed from the constituents of blood within the vascular system during life , it is adherent to vessel wall , it has a granular appearance
discuss the virchow’s triad
factors contributing to thrombosis
1. Endothelial injury caused by *trauma *inflammation *atheroma
- Abnormal blood flow
* Stasis(no flow)
* obstruction - Hypercoagulation
* dehydration
* post surgery
Types of thrombi
- Venous thrombi
> Phlebo - thrombosis : vein not inflamed
cause : stasis -heart failure ,shock ,bed rest ,postpartum , post surgery
usually ,involved deep calf veins
Clinically - pain ,pressure on dorsiflexion ,edema
> .Thrombo - phlebitis
-site of inflammation eg drip site with damage to vessel wall
site oflocal infection eg appendicitis
- Arterial thrombi : damage to wall eg atheroma , inflammation ,disturbance to flow eg stasis ( aneurysm and tumor )
- Cardiac thrombi :
Atria - mitral stenosis - stasis ,ventricles ,myocardial infarct ,myocarditis ,aneurysm
4.Capillary thombi :
disseminated intravascular coagulopathy
Outcomes of thrombus
- Dissolution
* Clots dissolves ,lumen returns to normal - Propagation : Along length of vessel
- Recanalization : Capillaries invade thrombus - re-establish blood flow ; may result in multiple small lumina
- Organization : Scar tissue ,lumen obliterated
- Embolism : To a distant site
Thrombo- embolic disease
Embolus -a mass of undisssolved material transported from one part of the vascular tree to another
Venous thrombo- embolic disease
*Extremely common cause of morbidity / mortality
*Post-operative ,bed -ridden ,aged patients
*Economic class air travel = no leg room
*
Deep vein thrombosis in lower limb embolises to
>pulmonary trunk
if it forms a saddle- embolus > usually fatal> but if it enters a segment of lung > sub- pleural infarct
- these thrombo - embolic do not travel through the lungs ,they never affect the systemic of the circulation
Other types if emboli except for venous emboli
- Arterial thrombo- emboli
- Atheromatous( a build up of materials that can adhere to arteries ) - thrombotic material admixed with varying amounts of atheromatous debris
- Air/ gas embolism
* Abortions
* head and neck and orthopedic surgery
* Sudden decompression(decompression sickness due to building up of N2) - diving
4.Amniotic fluid embolus
- fat embolism
- extensive trauma to skeleton - Tumor
7.Foreign bodies / parasites
What is hypoxia and give 4 types of it
Hypoxia is a deficiency of oxygen in the tissues
types
1.Ischaemic hypoxia : inadequate blood supply
- Hypoxix hypoxia = decreased o2 in the blood > due to respiratory failure
- Anaemic hypoxia : Too little hemoglobin to carry O2
- Toxic or histotoxic hypoxia
* Caused by cell injury blocking the uptake of O2 eg Cyanide poisoning
Ischemia and infarction
Ischaemia is a condition of inadequate blood supply to an area of the body .
* partial
*complete : localized area of ischaemic necrosis ie infarction
*Ischaemia an lead to >hypoxia = little O2 >anoxia = no o2 >reduced nutrition to cells > accumulation of waste
Types of ischaemia
- Generalized : cardiac failure> affects the whole body
- Localized ; Affects only part of the body
it can be complete or partial
> cause
In most cases it is due to failure of the arterial blood supply - thrombo- embolus , atheroma ,spasm ,external pressure
May also result from venous obstruction eg in the gut
Ischaemia
factors affecting the severity of ischaemia
- Blood supply : double blood supply organs are usually resistant to ishaemia eg liver / lungs
Collateral blood supply > brain ,lower limbs
End arteries > heart / kidney /spleen / distal cerebral arteries ,,impact of ischaemia is worse
- Rate of onset : too rapid o allow collateral to develop poor
- Degree of vascular occlusion : partial vs complete
- Nature of tissue eg brain vs connective tissue
- Anaemia > poorer outcome
- respiratory compromise > poorer outcome
Classification of infarcts
- Color
* Pale(anaemic) > kidney and spleen
* starts of by being haemorrhagic briefly but rapidly become pale due to density of the tissue which swells after infarction ,pushing out the blood within the infarcted area
- Hemorrhagic > lung/ gut
- Start off and remain hemorrhagic as the tissues are less dense
- Presence or absence of infection
- Bland = non-septic
- Septic = are initially infected or become so early in their development
