Haemodynamic disorders Flashcards
what is oedema?
an abnormal increase in interstitial tissue
what 5 things can oedema be caused by?
- increased hydrostatic pressure
- salt and water retention
- reduced plasma osmotic pressure
- lymphatic obstruction
- inflammation
what does generalised oedema cause?
- left ventricular failure
- nephrotic syndrome
- hepatic failure
what causes generalised oedema?
low renal blood flow results in an increase in renin secretion which causes the transformation of angiotensinogen to angiotensin I
the precursor hormone angiotensin I is converted to the active hormone angiotensin II by angiotensin-converting enzyme (ACE), which promotes the secretion of aldosterone from the adrenal cortex, resulting in retention of sodium and water in the kidneys
what is pulmonary oedema caused by?
raised hydrostatic pressure in the pulmonary capillary bed most commonly due to left ventricular failure
what is the main symptom of pulmonary oedema?
breathlessness
what does fluid in the alveolar spaces increase the risk of?
bacterial infection = acquiring pneumonia
what is cerebral oedema usually caused by?
disruption to the cerebral capillaries that can be vasogenic, cytotoxic, osmotic or interstitial
what is the vasogenic cause of cerebral oedema?
breakdown of blood-brain barrier (e.g. due to trauma/tumours)
what is the cytotoxic cause of cerebral oedema?
abnormalities in sodium-potassium pump (e.g. due to ischaemic stroke)
what is the osmotic cause of cerebral oedema?
reduction in plasma osmolality (e.g. due to SIADH)
what is the interstitial cause of cerebral oedema?
breakdown of cerebrospinal fluid-brain barrier (e.g. due to obstructive hydrocephalus)
what is thrombosis?
abnormal blood clot formation in the circulatory system
what 3 things is thrombosis caused by?
- changes in the intimal surface of a blood vessel
- changes in blood constituents
- changes in pattern of blood flow
what is venous thrombosis?
thrombosis mainly occurring in deep leg veins (DVT) where stasis and hyper-coagulability are key factors
what is a potential complication of DVT?
pulmonary embolism
what is coronary artery thrombosis?
complete blockage of the artery by thrombus, possibly due to haemorrhage within an atherosclerotic plaque, which can cause MI
what is cardiac thrombosis?
abnormal cardiac contractibility where stasis is the key factor
what is an embolus?
a detached mass (usually fragments of dislodged thrombus but may be fat/air/tumour) within the circulatory system that is carried in the blood to a site far from its point of origin, where it can lodge in vessels and block them off = embolism
describe the formation of a venous thrombo-embolism
1) blood clot forms in veins, breaks free and travels to the heart
2) embolus travels through the heart and blocks blood vessel in the lung
3) emboli either:
- lodges in a major pulmonary artery causing instant death
- lodges in a medium sized artery causing breathlessness
- lodges in small arteries causing subtle symptoms of breathlessness, chest pain and dizziness
what is an infarct?
tissue necrosis due to ischaemia (normally becuase of the obstruction of an artery)
what is a red infarct?
mostly by venous occlusion
what is a white infarct?
arterial occlusion
how does an infarct heal?
by repair - structural integrity is maintained but there is permanent loss of tissue function
