Haemodynamic disorders, thrombosis and shock Flashcards
What is meant by microcirculation?
The exchange of fluid, nutrients and waste products between blood and cells taht takes place through the interstitium and microcirculation.
What is the interstitium?
Space between cells. Composed of structural, adhesive and absorptive components
Describe the fluid distribution in the body
Body= 80% water (2/3 intracellular. 1/3 extracellular)
extracellular= 80% in the interstitium and 20% in plasma
What helps control distribution of fluid nutrients and waste between blood/ interstitium and cells?
- Physical barriers
- Pressure
- Concentration gradients
What is the definition of oedema?
Accumulation of excess interstitial fluid
What are the mechanisms of oedema?
- Increased microvascular permeability
- incrased intravascular hydrostatic pressure
- decreased intravascular osmotic pressure
- decreased lymphatic drainage
What are the causes of increased microvascular permeability?
- Inflammation
- Toxins
- Anaphylaxis
- Clotting abnormalities
What are the causes of increased intravascular hydrostatic pressure
- Portal hypertension
- Pulmonary hypertension
- Localised hypertension
- Localised venous obstruction
- Fluid overload
- Hyperaemia
What are the causes of decreased intravascular osmotic pressure?
- Decreased albumin production
- Increased albumin loss
- Water intoxication
What are the causes of decreased lymphatic drainage?
- Lymphatic obstruction/ compression
- Lymphagitis
- Lyphatic aplasia/ hypoplasia
What is the definition of haemostasis?
Arrest of bleeding.
- The physiologic response to vascular damage, mechanism to seal an injured vessel
- Interactions between endothelium, platelets and coagulation factors
What are the three stages of haemostasis?
1) formation of platelet plug (primary haemostasis)
2) formation of fibrin network (secondary haemostasis)
3) Removal of platelet/ fibrin plug (fibrinolysis) (thrombus retraction)
Explain the extrinsic coagulation pathway
Occurs outside the blood vessel wall when shed blood contacts tissue debris. Involves THROMBOPLASTIN.
Explain the intrinsic coagulation pathway
Triggered by presence of abnormal surfaces on components normally present in the blood (all the coagulation factors). Finishes with activation of Factor X.
What is the other name for Factor 3 in the coag cascade?
Tissue factor/ Thromboplastin
What is Factor VII in the coag cascade?
Proconvertin
Which factor is at the terminus of the extrinsic and intrinsic pathways of the coag cascade?
Factor X
What is the end product of the coag cascade?
Fibrin
What is the name for too low concentration of platelets?
Thrombocytopenia
thrombocytopathy= name for abnormal platelet function
What is Petechia?
Pinpoint haemorrhage (1-2mm)
What is ecchymosis?
Haemorrhage of up to 2-3cm
What does the thrombosis Virchow triad include?
Endothelial injury
Abnormal blood flow
Hypercoagulability
Thrombosis in the centre
What is an embolus?
A piece of free floating foreign material within the blood e.g. fat, cartilage, thrombus fragment
What is a thromboembolus?
Embolus derived from fragments of a thrombus
Where do venous thromboemboli typically lodge?
Pulmonary circulation
Where do arterial thromboemboli normally lodge?
Sites of vascular bifurcation.
What does disseminated intravascular coagulation (DIC) mean?
Serious manifestation of abnormal coagulation, severe dyshomeostasis caused by the generation of excess thrombin.
Various causes e.g. diffuse vascular damage or systemic infections
What is the mechanism for DIC?
Excess thrombin- platelet aggregation and fibrin formation- widespread microvascular clots- consumption of coagulation factors- widespread haemorrhages
Describe hyperaemia
Increased blood flow- active engorgement of vascular beds
-increased inflow via arteriolar dilation
-outflow remains normal or is decreased.
-causes: heat (skin_ postprandial (GI)
pathologic cause= inflammation
Describe congestion
- Decreased blood flow, passive engorgement of vascular beds with a decrease outflow and normal or increased inflow.
- Causes: acute-heart failure/ euthanasia. Chronic- obstruction of venous outflow, heart failure, pulmonary disease
What are the causes of decreased tissue perfusion?
- Obstruction of a blood vessel
- Local vascular congestion
- Decreased cardiac output
What factors influence development of an infarct?
- nature of the vascular supply
- rate at which occlusion develops
- vulnerability to hypoxia (neurons/ myocardial cells vulnerable)
- oxygen content of the blood
What would an arterial obstruction lead to?
loss of blood downstream resulting in abrupt coagulative necrosis
What would venous obstruction lead to?
Reduction/ loss of venous return
List the events of shock
Hypotension- decreased tissue perfusion- cellular hypoxia- shift to anaerobic metabolism- cellular degeneration- cell death
What are the different types of shock?
1) cardiogenic: failure of heart to pump adequately
2) hypovolaemic: decreased circulating blood volume due to blood/ fluid loss
3) blood maldistribution: Anaphylactic (generalised type 1 hypersensitivity), neurogenic (trauma to NS), septic (peripheral vasodilation caused by components of bacteria/ fungi inducing release of vascular/ inflammatory mediators)
