2 - Haemodynamic disorders Flashcards
What is oedema?
Abnormal increase in fluid in the interstitial space.
What are the causes of oedema?
Raised hydrostatic pressure,
Reduced osmotic pressure,
Disruption to the capillary bed
What are the 2 different types of oedema?
Localized (e.g. pulmonary oedema, cerebral oedema)
Generalized (affects subcutaneous tissues and serous cavities).
What is pulmonary oedema?
Causes and consequences
WHAT - The result of raised pulmonary capillary hydrostatic pressure due to pulmonary venous congestion.
CAUSE - left ventricular failure.
CONSEQUENCES - breathlessness and susceptibility to pneumonia.
What is cerebral oedema?
Where does it normally occur?
What pressure is raised?
WHAT - The result of breakdown of the normal capillary barrier.
WHERE - occurs in brain tissue surrounding lesions such as cerebral contusions, haemorrhages, infarcts, and tumours.
Cerebral oedema contributes to a rise in intracranial pressure which can be fatal.
What is generalised oedema?
WHAT - Generalized oedema causes pitting peripheral oedema, pleural effusions and ascites.
The pathogenesis of generalized oedema is complex and multifactorial.
A key factor is thought to be activation of the renin-angiotensinaldosterone system which stimulates renal sodium retention.
What are the 3 common causes of generalised oedema?
Left ventricular failure,
Hepatic failure
Nephrotic syndrome.
What is thrombosis?
Pathological clot formation in a blood vessel.
What is thrombosis caused by?
Caused by abnormal activation of the haemostatic system.
What are the 3 broad factors that predispose to thrombosis? What are they known as?
- changes in the vessel wall
- changes in blood flow
- changes in blood coagulability
(Virchow’s triad)
Where can thrombi form?
arteries
veins
heart
What is venous thrombosis related to?
Where do they commonly form?
Related to stasis of blood and an increase in blood coagulability.
Commonly form in deep leg veins (deep venous thrombosis).
What is arterial thrombosis related to?
Related to changes in the vessel wall due to unstable atherosclerotic plaques.
What is cardiac thrombosis related to?
Related to stasis of blood in a cardiac chamber, most commonly the left atrium in association with atrial fibrillation or the left ventricle in association with a myocardial infarct.
What can thrombi do?
- Completely resolve
- Undergo organisation and recanalisation, in which case they may remain clinically silent.
When do thrombi become significant?
If they occlude a vessel or embolize.
What is an embolism?
An embolus is a detached mass within the circulatory system that is carried in the blood to a site distant from its point of origin.
What may happen to emboli in small vessels?
They can lodge in small vessels and block them off
What does thromboemboli mean?
Most emboli are fragment of dislodged thrombus
What may Venous thromboemboli do?
Travel via the heart into the pulmonary arteries causing pulmonary embolism.
What may Arterial thromboemboli do?
May impact in…
- cerebral arteries (causing stroke)
- the mesenteric arteries (causing small bowel infarction) - lower limbs (causing acute lower limb ischaemia)
What are the 3 rare types of emboli?
Fat emboli,
Septic emboli,
Amniotic fluid emboli
What is a Pulmonary embolism?
Occlusion of a pulmonary artery by embolic thrombus.
Very common and often underdiagnosed.
What do Emboli lodging in a major pulmonary artery cause?
Instant death
