Haemodynamic disorders Flashcards
Oedema: recall the aetiological classification of oedema, and explain the possible consequences of oedema at different sites Thrombosis, embolism and infarction: define thrombosis, embolism and infarction; recall the causes and possible consequences of each Haemorrhage: list causes and possible consequences of haemorrhage Shock: define shock and identify possible causes and mechanisms
What is odema?
An abnormal increase in interstitial fluid. Fluid that bathes tissues and surrounds cells.
Hydrostatic pressure pushing the fluid out is greater than the osmotic pressure pulling it in.
What are the three forces involved in oedema?
Capillary hydrostatic pressure pushing fluid out.
Plasma oncotic pressure pulling fluid in.
TISSUE hydrostatic pressure pushing fluid INTO vessels.
What is the definition of aetiology?
Causes of a disease.
What are the aetiologies of oedema? (x5)
Increased capillary hydrostatic pressure: occurs when impaired venous return or increased venous pressure e.g. in heart failure.
Salt and H2O retention: tissues retain H2O – this is usually because of high salt intake. Indicated by high hydrostatic pressure.
Reduced plasma oncotic pressure: malnutrition and reduced albumin in blood.
Inflammation: could be caused by sepsis or localised cellulitis (infection deep in skin). Inflammation results in increased blood vessel wall permeability which facilitates movement of fluid into interstitium.
Lymphatic obstruction: leads to accumulation in interstitial space. Maybe from lymphatic vessel damage.
What is oedema called when lymphatic obstruction is the cause?
Lymphoedema.
What are the two types of oedema?
Generalised and Localised.
What is generalised oedema? How can it be identified? What is that oedema called?
Widespread accumulation of fluid in subcutaneous tissues and serious cavities (pleural, pericardial or peritoneal).
In subcutaneous tissue, lower limbs can be seen to be particularly affected because gravity effects more greatly. When pressed = produces an indentation –> called generalised PITTED oedema.
What is generalised oedema commonly caused by? (x4) Explain what happens in heart failure.
Heart failure (specifically Left Ventricular Failure) = systemic blood accumulation. Blood stops pumping do blood accumulates in areas affected by gravity = dependent oedema. Inflammation e.g. sepsis Venous hypertension (means increased hydrostatic pressure and lesser ability of venous return). Lymphatic obstruction.
What is localised oedema?
Oedema that affects specific areas. Not systemic.
Commonly pulmonary and cerebral oedema.
What are the two causes of pulmonary oedema?
Usually from left heart failure - causes increased pressure in left atrium which causes back pressure in pulmonary capillaries = Increased hydrostatic pressure in the pulmonary capillary bed.
So fluid pushed out and accumulates in the interstitial space and eventually into the aveolar spaces.
OR, can be caused by increased permeability from sepsis or shock.
What are the consequences of pulmonary oedema? (x3)
Dyspnoea (breathlessness).
Worse when lying flat!
Fluid in alveoli predisposes to bacterial infection in the lungs e.g. pneumonia.
What are the four types of cerebral oedema?
Vasogenic cerebral oedema – physical breakdown of blood-brain barrier caused by trauma or tumours which release factors that break down the barrier.
OR Cytotoxic cerebral oedema – derangement of the Na+/K+ pump increases sodium concentration inside cells which encourages water take-up by such cells –> swelling.
OR Osmotic – reduced osmotic osmolality (less solutes in the blood).
OR Interstitial – caused by rupture of CSF-brain barrier. CSF = cerebrospinal fluid.
What are the consequences of cerebral oedema? (x4)
Increased intracranial pressure (pressure in skull).
Leads to brain herniation.
Confusion, vomiting.
What is thrombosis?
Abnormal blood clot formation in the circulatory system.
What are the three causes?
Vessel wall damage.
Stasis (alteration to blood flow).
Hypercoagulability (abnormality in blood coagulation – more likely to form blood clots)
What happens in vessel wall damage that causes thrombosis? (x2)
Damage to endothelium exposes ECM and activates blood clotting cascade.
OR, Endothelium isn’t working properly.
What happens stasis that causes thrombosis? (x2)
Loss of normal flow means platelets are exposed to endothelium (they would usually found in centre of the vessel not near endothelium) so MORE LIKELY to form a clot.
Stasis can change the dilution of blood clotting factors.
What happens in hypercoagulability to cause thrombosis? (x2)
Genetic disorder – primary cause.
Acquired cause e.g. obesity or oral contraceptive which are RISK FACTORS – secondary cause.
