Pathology: Haemodynamic disorders Flashcards
What is the overall distribution of intracellular and extracellular water like in the body?
2/3 intracellular and 1/3 extracellular
What is the distribution of extracellular fluid like?
80% in the interstitium and 20% in the plasma
What is oedema?
Accumulation of excess interstitial fluid
How does oedema occur?
Increased microvascular permeability: inflammation/toxins/anaphylaxis
Increased intravascular hydrostatic pressure: portal/ pulmonary hypotension, localised venous obstruction, fluid overload
Decreased intravascular osmotic pressure: decreased albumin production or increased loss
Decreased lymphatic drainage: Lymphatic obstruction
What are the two coagulation cascade pathways, what is their end product?
Intrinsic and extrinsic
Both cause activation of factor X and accumulation of proteolytic enzymes that initiate fibrin formation
Where does the intrinsic coagulation pathway take place?
Triggered by the effects of abnormal surfaces on components normally found in the blood
Where does the extrinsic pathway usually take place?
Occurs outside the blood vessel when shed blood contacts tissue debris
Thromboplastin plays a major role
What cause haemorrhage?
Loss of integrity of the endothelium/blood vessels: Due to trauma, erosion by inflammation, vascular fragility, toxins
Decrease in platelet numbers or abnormal platelets
Deficiencies in coagulation factors (inherited or acquired)
What is Ehlers-danlos syndrome?
Inherited vascular fragility as apposed to acquired via vitamin C deficiency
What is thrombocytopenia?
Decreased platelet numbers
What is thrombocytopathy?
Abnormal platelet function
Name an inherited and acquired coagulation factor defect
I: Von Willebrand
A: Warfarin or severe liver disease
What are petechiae (one petechia)?
Pinpoint 1-2mm haemorrhage
What are ecchymoses (one ecchymosis)?
haemorrhage up to 2-3cm
What is a haematoma?
Haemorrhage in a focal confined space
What is a haemoperitoneum?
Blood in the peritoneal cavity
What is a thrombosis ?
An inappropriate formation of a clot of fibrin and/or fibrin
On the wall of vessel/ heart: mural thrombus
Free in the lumen: thromboembolus
What causes a thrombosis?
Endothelial injury: Infectious agents/ IV injections
Alterations in blood flow: local stasis, cardiac disease, hypovolaemia
Hypercoaguability: Inflammation, increased platelet activity, increased clotting factor activation, antithrombin 3 deficiency
What is an embolus?
A piece of free floating material in the blood
Where do thromboemboli tend to lodge?
Venous: in the pulmonary circulation
Arterial: At vascular bifurcations
What causes disseminated intravascular coagulation (DIC)?
Diffuse vascular damage, systemic infections
What is the mechanism of DIC?
Excess thrombin –> Platelet aggregation and fibrin formation –> widespread microvascular clots –> consumption of the coagulation factors –> widespread haemorrhages
What is hyperaemia?
Increased blood flow, which causes active engorgement of vascular beds as inflow increases and outflow is te same or decreased
What causes hyperaemia?
Physiologic: Heat, postprandial
Pathological: Inflammation
What is congestion?
Passive engorgement of the vascular beds as outflow decreases and inflow is either normal or increased
What causes congestion?
Acute: Heart failure, anaesthesia, euthanasia
Chronic: Obstruction, heart failure, pulmonary disease
What is an infarction?
An area of ischemic necrosis caused by occlusion of either the arterial supply or venous drainage
What is shock?
Circulatory dyshomeostasis, associated with the loss of circulating blood volume, decreased cardiac output and inappropriate peripheral perfusion
What is the mechanism of shock?
Hypotension –> decreased tissue perfusion –> cellular hypoxia –> shift to anaerobic metabolism –> cellular degeneration –> Cell death
What is cardiogenic shock?
Failure of the heart to adequately pump blood
What is hypovolaemic shock?
Decrease in the circulating blood volume caused by blood or fluid loss
What are the types of maldistribution shock:
- Anaphylactic shock
- Neurogenic shock
- Septic shock
- Generalised type 1 hypersensitivity
- Trauma to the nervous system eg. electrocution, fear
- Peripheral vasodilation caused by components of bacteria (endotoxin) or fungi that induce release of excessive amounts of vascular inflammatory mediators
