Cell pathology 2- Haemodynamic disorders Flashcards
Classify the cause of oedema (5)
Increased Capillary Hydrostatic Pressure
E.g. venous obstruction, congestive cardiac failure
Decreases Plasma osmotic Pressure
Inflammation
Increased vascular permeability facilitates movement of fluid into the interstitium
Lymphatic Obstruction
MOST COMMON - lymphoedema - breast cancer treatment - damage the lymph vessels leading to build up of fluid
Filariasis can cause massive lymphatic obstruction
Salt/H20 Retention
Classify the causes(2) of generalised oedema and the consequences(2) in a periphral setting
Severe Generalised Oedema = Anasarca
It is the widespread accumulation of fluid in subcutaneous tissues and serous cavities
Common Causes:
Left Ventricular Failure - dependent oedema (accumulated in areas affected by gravity)
Nephrotic Syndrome - fluid accumulates in all parts of the body
Impaired wound healing
Patients with generalised oedema are more prone to getting cellulitis
How can heart failure cause 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
2 Causes of pulmonary oedema
Cause: Raised hydrostatic pressure in the pulmonary capillary bed
Most Common Cause of this: Left Ventricular Failure
Other causes= ARDS (Acute Respiratory Distress Syndrome)
Commonly seen in injecting drug users
Most Common causes of ARDS: Sepsis, Shock and Trauma
Can be chronic or acute
How does left ventricular failure cause oedema
Left ventricular failure causes increased pressure in the left atrium
This causes back pressure into the capillaries
This pushes water into the interstitial space
Fluid accumulates in the interstitial space and then spills over into the alveolar spaces.
Main symptom of pulmonary oedema
MAIN SYMPTOM: DYSPNOEA
Dyspnoea is worse when they lie flat because of the movement of fluid (this is called orthopnoea)
Fluid collection in alveolar spaces predisposes to bacterial infection in the lung (pneumonia)
What are the 4 types of cerebral oedema
Vasogenic - physical breakdown of blood-brain barrier
Causes: Trauma and Tumours (by releasing factors which break down barriers)
Cytotoxic - derangement of sodium-potassium membrane pump
Common in ischaemic strokes
Increase in sodium within cells encourages water to be taken up
Causes intracellular oedema
Osmotic - reduction in plasma osmolality
Cause: SIADH (Syndrome of Inappropriate ADH secretion)
SIADH is commonly caused by SMALL CELL LUNG CARCINOMA
ADH release –> more water reabsorbed –> decrease in plasma osmolality
Interstitial - breakdown of CSF-brain barrier
Cause: Obstructive Hydrocephalus (abnormal accumulation of cerebrospinal fluid in the brain - due to blockage in flow of CSF)
CSF (NOT blood plasma) moves into the interstitial space
What is thrombosis, what is the cause and what 3 factors predispose it
Abnormal blood clot formation in the circulatory system.
Caused by abnormal activation of the haemostatic system
3 factors (virchows triad)
Vessel wall injury
Changes in blood flow (stasis)
Changes in blood coagulability
Describe cardiac thrombosis
STASIS is the main way that thromboses form
Left Atrial Thrombosis is usually related to atrial fibrillation
Left Ventricular Thrombosis is usually related to prior myocardial infarction
MOST IMPORTANT COMPLICATION: Systemic Embolisation
Describe Arterial Thrombosis
Almost always related to vessel wall injury
Vessel wall injury is often caused by atherosclerotic plaques
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
Describe Venous Thrombosis
KEY FACTORS: Stasis and Hypercoagulability
Risk Factors: Age Obesity Malignancy Immobility Oral Contraceptive Pill
Most form in DEEP VEINS (DVT)
MOST IMPORTANT COMPLICATION: Pulmonary Embolism
What are the 4 fates of the thrombus
Propagation-
Thrombus gets BIGGER - accumulates more fibrin and takes up a larger portion of the vessel
Embolisation-
Dislodges and travels to distant site
Dissolution-
Thrombus is destroyed by fibrinolytics (can be endogenous or given as a drug)
Organisation and Recanalisation-
As a result of the thrombus, there is inflammation `
Thrombus becomes fibrotic and remodels
Lumen appears again allowing blood flow
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.
Most emboli are fragments of dislodged thrombus (thromboemboli)
Note: Rarer types of embolic material: Fat Air Amniotic Fluid Tumour
Describe Arterial Thromboemboli
Most originate in CAROTID ARTERIES
Most likely to affect cerebral arteries - causing STROKE
Describe Cardiac Thromboemboli
Most originate on the LEFT SIDE OF THE HEART
May lodge in:
Cerebral Artery - STROKE
Mesenteric Artery - BOWEL INFARCTION
Lower Limb Artery - ACUTE LOWER LIMB ISCHAEMIA
Consequences of pulmonary embolism and what is the death rate
Emboli lodging in a major pulmonary artery can cause instantaneous death
If it gets lodged at the bifurcation of one pulmonary artery into two, it is called a saddle embolus
Emboli lodging in medium sized arteries present with breathlessness
Small emboli lodging in small arteries cause non-specific symptoms - e.g. dizziness, chest pain, breathlessness
30% of patients with PE die from it
Risk of death INCREASES with time taken to make the diagnosis
What is a haemorrhage and what causes them
Haemorrhage can be external or enclosed within a tissue
Haematoma = a localised mass of extravasated blood that is relatively or completely confined within an organ or tissue
CAUSES:
Trauma
Intrinsic disease of the vessel
What can occur when you have an acute haemorrhage in a major vessel
Hypovolaemia
Shock
Death
What does a haematoma cause
Formation of a solid haematoma within the cranial cavity can be FATAL by causing a RISE IN INTRACRANIAL PRESSURE and TONSILLAR HERNIATION
What is shock and how is it caused?
Generalised failure of tissue perfusion
Caused by a pump failure or peripheral circulation failure
How do patients with shock appear and what symptoms do they have?
Grey and feel clammy
Tachycardia and hypotension
What can untreated shock cause
Ischemia of heart, lungs, gut, and kidney
5 types of shock
Hypovolaemic
Most commonly due to LOSS OF VOLUME
Cardiogenic
Due to IMPAIRED CARDIAC FUNCTION
Septic
Result of INFLAMMATORY RESPONSE
Anaphylactic
Result of IgE MEDIATED HYPERSENSITIVITY
AP
Neurogenic
RARE
Normally happens after trauma
What is an infarction
Tissue necrosis due to ischaemia.
Most due to obstruction of an artery
Describe red infarctions
haemorrhagic - affects organs with a dual blood supply - generally caused by venous blood supply `
Describe white infarctions
anaemic - affects solid organs which have one blood supply
Factors influencing the development of infarctions
Nature of Blood Supply:
If there is an obstruction in the lung or liver, they can use other vessels to supply the tissue.
Kidney and spleen are more susceptible to infarction
Rate of Development of Occlusion:
If the occlusion develops slowly, there could be enough time for Collateral Vessels to form and provide an alternate blood supply
Vulnerability to Hypoxia
EXAMPLE: neurones are very susceptible to hypoxia, fibroblasts aren’t
Oxygen content of the blood
EXAMPLE: patients who have anaemia and chronic heart failure will have reduced levels of oxygen in their blood - more prone to developing infarctions
What are the twp types of myocardial infarction
Transmural Infarction
Entire wall is affected
Occurs when there has been complete blockage of a vessel and complete cessation of the blood supply
Subendocarial Infarction
Some myocardial tissue underneath the endocardium has been affected by infarction
Caused by drop in blood oxygen content or rapid drop in blood supply (e.g. due to blood loss)
What is Atherosclerosis
Complex chronic disease - underlying cause of most vascular diseases
Focal intimal accumulation of lipids and fibrous tissue associated with smooth muscle proliferation
Affects medium and large vessels
Develops from fatty streak into plaque within the intima
What is the Process of Atherosclerosis (7)
Endothelial damage
macrophages release cytokines
Cytokines recruit LDLs
LDLs become oxidised
Oxidised LDLs are pro-inflammatory and drive progression of plaque
Smooth muscle cells migrate from the tunica media to the lesion
Smooth muscle cells deposit a collagen rich matrix that forms a protective fibrous cap
Diseases caused by stable atherosclerotic plaques:
Stable angina
Chronic lower limb ischaemia
Diseases caused by thrombosis overlying an unstable atherosclerotic
Unstable angina
Myocardial infarction
Cerebral infarction
Acute lower limb infarction
