Haemodynamic disorders Flashcards
Week 1
Haemodynamics
the movement of blood, the study of blood circulation
What does homeostasis require?
vessel wall integrity
osmolarity
maintenance of intravascular pressure
Hydrostatic pressure
pressure exerted by a fluid at equilibrium at a given point within the fluid
What does a high hydrostatic pressure do to fluid
drives it out of the vessel and into the tissues
What is colloid osmotic pressure
a form of osmotic pressure exerted by proteins (albumin)
What does high colloid osmotic pressure do to fluid
drives fluid into the vessel from the interstitial space
Hydrothorax
oedema in the thoracic cavity
Hydropericardium
oedema in the pericardial cavity
General causes of oedema
increased hydrostatic pressure decreased colloid osmotic pressure lymphatic obstruction sodium retention inflammation
example of oedema due to increased hydrostatic pressure
generalised heart failure
localised in limbs in DVT
example of oedema due to decreased colloid osmotic pressure
reduction in general plasma proteins (e.g. liver cirrhosis and malnutrition).
Anasarca
widespread swelling of the skin due to effusion of fluid into extracellular space
what conditions can cause anasarca
cirrhosis, renal failure, right-sided heart failure, severe malnutrition
example of oedema due to lymphatic obstruction
elephantiasis (lymph nodes blocked by parasitic worm)
malignancy
following surgery and radiation therapy
example of oedema due to sodium retention
excessive salt intake in renal insufficiency
increased renin-angiotensin-aldosterone system –> these increase hydrostatic pressure
3 phases of the circulatory haemostats process
1- haemorrhage (process of bleeding)
2- thrombosis (process of clotting)
3- fibrinolysis (process of close dissolution)
what is a haemorrhage?
the extravasation of blood due to rupture of blood vessel. can be internal or external.
what happens if you have above 20% blood loss
hypovolemic shock (severe fluid loss makes it impossible for heart to pump sufficient blood around the body, can lead to organ failure)
name 4 causes of haemorrhage
trauma
atherosclerosis
inflammation
erosion by tumour
name 3 types of bleeding into skin in size order
petechiae
purpura
ecchymosis
petechiae
minute haemorrhage (1-2 mm) of skin and mucosa occurs during thrombocytopenia, clotting factor deficiency or increased pressure in capillaries
purpura
small haemorrhage (3-5 mm) Usually due to trauma or vasculitis
ecchymosis
subcutaneous hepatoma. changes in colour from red –> blue-green –> yellow —> brown
what is a blood clot made up of
platelets, red blood cells, neutrophils, lymphocytes held together by fibrin
what 3 main factors can form a thrombus
endothelial injury, abnormal blood flow, hyper-coagulability
what are arterial thrombi usually made up of
platelets
why are arterial thrombi made up of platelets
blood is flowing under higher pressure. form around ruptured atherosclerotic plaques or damaged endothelium.
what is the name of the arterial thrombi that don’t occlude vessel
mural thrombi
occlusive thrombi
occludes vessel
what are venous thrombi rich in
fibrin
how is a venous thrombi formed
changes in blood flow (stasis due to immobility) –> activates coagulation system –> hyper coagulation –> fibrin driven response
what is an embolism?
solid, liquid or gaseous mass carried in the blood to a site distant from the point of origin, clinical significance is related to where they lodge rather than origin
what are nearly all emboli the result of
a dislodged thrombus (a thromboembolism)
what is are hyperaemia and congestion characterised by
a local increase of blood volume in a particular tissue
hyperaemia
increased blood flow in to a tissue in response to a change in the environment
2 types of hyperaemia
reactive –> local vasodilation in response to oxygen debt or accumulation of metabolic waste
active –> increased blood flow/vasodilation is response to a period of activation (e.g exercise)
congestion
reduced blood flow out caused by impaired venous return from the affected area (passive process)
what can cause congestion
physical obstruction of veins or failure of heart to pump blood away from affected area
what is circulatory shock
life-threatening medical condition that occurs due to the provision of inadequate substrates for cellular respiration
typical symptoms of shock
weak heart rate low blood pressure poor organ function confusion low urine output loss of consciousness
causes of shock
reduced cardiac output or ineffective circulation
types of shock
cariogenic shock hypovolemic shock septic shock neurogenic shock anaphylactic shock
cardiogenic shock
failure of the heart to pump sufficient blood due to myocardial damage (e.g. myocardial infarction, arrhythmia, pulmonary embolism with outflow obstruction)
hypovolemic shock
loss of blood plasma (e.g. haemorrhage or severe burns
septic shock
systemic infection, primary cause is bacteria (bacteria in the bloodstream).
sepsis vs septic shock
sepsis –> uncontrolled systemic reaction to the infection leading to life threatening organ dysfunction
septic shock –> subset of patients with sepsis in which particularly profound circulatory, cellular and metabolic abnormalities substantially increase mortality
infection –> bacteremia –> sepsis –> septic shock
neurogenic shock
caused by severe damage to the CNS. loss of systemic stimulation of blood vessels (via sympathetic adrenergic stimulation). leads to widespread vasodilation, pooling of blood in extremities and hypotension
anaphylactic shock
severe allergic reaction causes release of inflammatory mediators cytokines (triggers widespread vasodilation and hypo perfusion).
