Haemodynamic disorders Flashcards
Define Oedema.
where is the fluid from?
Abnormal increase in interstitial fluid
- this is when the fluid moves from the plasma to the interstitium
What three forces determine the movement of fluid between blood vessels and the interstitial space?
- Capillary hydrostatic pressure
venous obstruction
pushing out of the vessel - tissue hydrostatic pressure
pushing into the vessel - Plasma oncotic pressure
pulling in to the vessel
What are the four broad causes of oedema?
- Increased capillary hydrostatic pressure
congestive cardiac failure - Decreased capillary oncotic pressure (e.g. nephrotic syndrome)
- Inflammation
increased vascular permeability facilitates movement of fluid into the interstitium - Lymphatic Obstruction
ymphoedema - breast cancer treatment - damage the lymph vessels leading to build up of fluid
What is a common cause of pulmonary oedema?
Increased plasma hydrostatic pressure in the pulmonary capillary bed
Left Ventricular Failure – build up of pressure in left atrium leading to back pressure into the capillaries – this pushes water into the tissues
This is cardiogenic pulmonary oedema
What is non-cardiogenic pulmonary oedema?
Caused by increased permeability often seen in injecting drug users ARDS – Acute Respiratory Distress Syndrome Often caused by Sepsis, Shock and Trauma - can be chronic or acute - the main symptom is dyspnea which is shortness of breath
What are the four types of cerebral oedema?
Vasogenic – physical breakdown of the blood-brain barrier – commonly due to trauma or tumours
Interstitial – breakdown of the CSF-brain barrier – commonly due to obstruction of the flow of CSF (Obstructive Hydrocephalus)
Cytotoxic – derangement of the sodium-potassium pumps leads to a build up of intracellular sodium causing intracellular oedema (common with ischaemic strokes)
Osmotic – increase in plasma osmolality – commonly caused by Syndrome of inappropriate ADH secretion (SIADH) that is commonly caused by small cell lung cancer
VICO
What are the possible serious consequences of cerebral oedema?
Rise in intracranial pressure, which could cause brain herniation
- (squeezing of the brain across a structure
within the skull) and death
- confusion, nausea and vomiting
What are two common causes of generalised oedema?
Left Ventricular Failure dependent oedema (accumulated in areas affected by gravity)
Nephrotic Syndrome
fluid accumulates in all parts of the body
What is a consequence of oedema in a peripheral setting?
Impaired wound healing
- cellulitis
What are the three main factors affecting thrombus formation?
Hypercoagulability
Primary - Genetic Disorder
Secondary - Acquired
more likely to develop blood clots
Vessel Wall Injury
Physical Damage to Endothelium
exposes ECM and activated blood clotting cascade
- when the endothelium isn’t working properly it causes coagulants to be released
Stasis
-alteration to normal blood flow
platelets are exposed to the endothelium - more likely to form a clot
- might also change the dilution of blood clotting factors
What is cardiac thrombosis caused by and what is an important complication?
Stasis – e.g. atrial fibrillation
- Left Atrial Thrombosis is usually related to atrial fibrillation
- Left Ventricular Thrombosis is usually related to prior myocardial infarction
Complication – systemic embolisation
What is arterial thrombosis caused by?
Vessel wall injury
- Vessel wall injury is often caused by atherosclerotic plaques
What is venous thrombosis caused by and what is an important complication?
Stasis and Hypercoagulability happens in the deep veins - risk factors include age, obesity, malignancy, immobility Complication – pulmonary embolism
What are the four fates of a thrombus?
Propagation– thrombus accumulates fibrin and grows and takes up larger part of the vessel
Embolisation– thrombus dislodges and moves somewhere else
Dissolution– thrombus is destroyed by fibrinolytics
maybe through a drug
Organisation and Recanalisation–
thrombus becomes fibrotic and is remodelled, lumen appears again allowing blood flow
Where do most arterial thromboemboli originate?
Carotid arteries
- causes stroke in cerebral arteries
Define haematoma
A localised mass of extravasated blood that is relatively or completely confined within an organ or tissue
What are the three classes of haemorrhage based on size?
Petechiae = 1-2mm Purpura = >3mm Ecchymoses = 1-2cm
What is shock ?
characterised by?
- occurs when the tissue perfusion is inefficient to meet metabolism standards
Prolonged hypotension causes circulatory collapse leading to ischaemia of
multiple organs
Hypotension
What two equations are used to evaluate the effects of changes in various vascular factors?
MAP = CO x SVR
cardiac output x systemic vascular resistance
CO = HR x SV
heart rate x stroke volume
What are the five types of shock?
Cardiogenic Hypovolaemic Anaphylactic Neurogenic Septic
CHANS
Describe each of the five types of shock and its causes and effects
Cardiogenic -impaired cardiac function,
- Causes include cardiac tamponade
fluid in the pericardium
- heart doesn’t work so lowered stroke volume leading to shock
Hypovolaemic– loss of blood volume,
- Causes include: trauma, haemorrhage
low volume - Low SV- Low MAP - Body tries to compensate with tachycardia
Anaphylactic– IgE mediated hypersensitivity,
- Causes vasodilation and increased permeability, Reduced SVR leads to Reducer MAP
- Neurogenic– injury to sympathetic pathways, Normally happens after trauma
- Widespread vasodilation and reduced SVR
- Septic– result of inflammatory response,
- Causes vasodilation.
- Reduced SVR leads to Reduced MAP
Define infarction.
Tissue necrosis due to unresolved ischaemia
What are the two types of infarction and how are they different?
Red – haemorrhagic – affects organs with a dual blood supply
- normally caused by venous blood supply
White – anaemic – affects solid organs that have one blood supply
How can the rates of development of the occlusion affect the infarction?
If the occlusion develops slowly then there may be enough time for collateral vessels to form
What are the two types of myocardial infarction?
Transmural – across the whole wall of the heart
- occurs when there is a complete blockage of the vessel and complete cessation of the blood supply
Subendocardial – some myocardial tissue -just the layer under the endocardium
Describe the process of atherosclerosis.
1) Endothelial damage
2) Macrophage infiltration and release of cytokines
3) Cytokines recruit LDLs
4) LDLs become oxidised and hence become pro-inflammatory and drive progression of plaque
5) Smooth muscle cells migrate from the tunica media to the lesion and deposit a collagen-rich matrix, which forms a protective fibrous cap
What are the two types of atherosclerotic plaque and how are they different?
Stable – thick fibrous cap – less likely to rupture
less inflammation
Unstable – thinner fibrous cap – more likely to rupture
more inflammation
what is generalised oedema?
Severe Generalised Oedema = Anasarca
- It is the widespread accumulation of fluid in subcutaneous tissues and serous cavities
-
what is the mechanism of heart failure causing oedema?
- Low Renal Blood Flow
- Release of Renin from kidneys
- Formation of angiotensin II
- Release of aldosterone from adrenal gland
- Absorption of sodium and water from kidneys Generalised oedema
what are the consequences of arterial thrombosis ?
- Stenosis = narrowing of the artery by the thrombus
- Stenosis causes ischaemia of the tissue supplied by the artery
• Occlusion = complete blockage of the artery by the thrombus
• Occlusion causes infarction of the tissue supplied by the artery
what is an embolism?
A detached intravascular solid, liquid or gaseous mass that is carried by the blood to a site distant from its point of origin.
where do venous thromboembolism originate from?
- Most originate in Deep Veins
- Most Significant Consequence - pulmonary (thromboembolism)
what are the consequences of a pulmonary embolism?
- Consequence depends on the size of the embolus and where it gets lodged.
- major pulmonary artery can cause instantaneous death
- lodged at the bifurcation of one pulmonary artery into two, it is called a saddle embolus
- medium arteries = breathlessness
- small arteries = non-specific symptoms
where do cardiac Thromboemboli start?
- Most originate on the LEFT SIDE OF THE HEART
- ## might lodge in the cerebral artery, mesenteric artery, lower limb artery
what is a Haemorrhage and what are the causes?
Extravasation of blood due to vessel rupture.
causes include trauma and intrinsic disease of the vessel
what does the rupture of a major vessel result in?
- Hypovolaemia
- Shock
- Death
what will a solid haematoma result in?
- can be fatal
- causing a rise in intracranial pressure and tonsillar herniation
what are factors influencing the development of the infarction?
- the nature of the blood supply
single blood supply (kidney and spleen) or double blood supply ( lung and liver) - the rate of development of occlusion
if the occlusion develops slowly there might be time for collateral vessels to form - vulnerability to hypoxia
different types of cells are vulnerable eg. neurones are very vulnerable - Oxygen content of the blood
patients who have anaemia and chronic heart failure will have reduced levels of oxygen in their blood - more prone to developing infarctions
what are other consequences of myocardial infarction?
- pericarditis
(inflammation of the pericardium) - Cardiac Rupture
what is cerebral infarction?
- Wedge shaped area in the right middle cerebral artery (MCA) area
- the MCA area is a common area to get affected by infarction
what is atherosclerosis?
- complex chronic disease underlying cause of most vascular disease
- accumulation of lipids and fibrous tissue associated with smooth
muscle proliferation - medium and large vessels are affected
- it develops from a fatty streak into plaque within the intima
