Flashcards in Cell Pathology 2 Deck (58):
What is oedema?
Abnormal increase in interstitial fluid
What maintains interstitial fluid balance?
1. Hydrostatic pressure (determined by BP)
2. Osmotic pressure (maintained by solutes in blood and interstitial fluid)
Give 5 causes of oedema?
1. Increased hydrostatic pressure.
2. Salt & H2O retention
3. Reduced plasma osmotic pressure
4. Lymphatic obstruction
What is generalised oedema?
Widespread fluid accumulation in subcutaneous tissues and serous cavities
Name 1 factor for generalised oedema?
What is seen in the skin of patients with generalised oedema?
List the causes of generalised oedema.
1. LV failure
2. Nephrotic syndrome (kidney damage)
3. Hepatic failure
What causes pulmonary oedema?
Raised hydrostatic pressure in the pulmonary capillary bed.
What is the most common cause of pulmonary oedema?
How can LV failure cause pulmonary oedema?
1. Inadequate removal of blood from pulmonary circulation.
2. Pressure builds up in pulmonary circulation.
3. Fluid accumulates in alveolar interstitium. Eventually moves into alveolar space - poor gas exchange.
What is the main symptom of pulmonary oedema?
Breathlessness (dyspnoea), usually worse when lying flat (orthopnoea).
Why is one more susceptible to pneumonia if they have pulmonary oedema?
Fluid in the alveolar space predisposes the lungs to bacterial infection.
What causes cerebral oedema?
1. Disruption of blood flow to cerebral capillaries
2. Causes pressure buildup in blood vessels.
Where is cerebral oedema seen?
In brain tissue surrounding lesions
Give 4 lesions in the brain
Contusion, haemorrhages, infarcts (stroke) and tumours.
Increase in fluid in the brain causes what.
1. Increased inter cranial pressure.
2. High ICP increases risk of herniation and death.
How should cerebral oedema be treated?
1. Raise the head (allows gravity to drain fluid).
2. Infuse isotonic fluids (replenish lost fluid from blood)
3. Infuse steroids and osmotic diuretics (Eg mannitol) - gets fluid back into blood
4. Surgical decompression
What is a thrombosis?
Abnormal blood clot formation in the circulation
What are the 3 factors that cause thromboses?
1. Blood stasis
2. Vessel wall injury
What are the main factors in venous thrombosis?
Stasis and hyper coagulability.
Why do most venous thromboses occur in deep leg veins?
1. Blood may be hyper coagulable.
2. Venous BP is much lower than arterial BP.
3. Therefore blood may stop flowing, especially in legs (as working against gravity).
4. In periods of non-movement, thromboses may occur (as muscle contraction in legs are major factor for pushing blood back upto heart).
What is the main cause of arterial thromboses?
Atherosclerotic plaque, which causes vessel wall injury.
What is the most important potential complication of a VT.
How can an Arterial thrombosis cause ischaemia or Infarction?
Arterial wall narrows (stenosis), because thrombus blocks the wall.
What causes cardiac thrombosis?
Stasis of blood.
Stasis is caused by cardiac fibrillation - irregular depolarisation and contraction means blood isn't moved (as efficiently) - so blood remains static
Left atrial thrombosis is usually related to...?
Left ventricular thrombosis is usually related to....?
Prior myocardial infarction.
What is the most important potential complication of cardiac thrombosis?
What is an embolus?
1. Detached mass within blood.
2. Carried to distant site from point of origin.
3. Most emboli are dislodged thrombus - thromboembolism.
Give rare types of emboli.
Fat, air, amniotic fluid, tumour.
Why are emboli dangerous?
They can lodge in vessels and block them off.
What is a venous thromboembolism?
An embolus (usually DVT) lodging itself in an artery.
What is the most serious consequence of a pulmonary thromboembolism.
Embolism to lung which blocks off pulmonary artery - instant death.
How can a pulmonary thromboembolism cause instant death?
1. No blood flow through lungs.
2. Puts immense pressure on right side of the heart
What are the symptoms of pulmonary embolism?
1. Difficulty breathing
2. Chest pain on inspiration
What are the clinical signs of pulmonary embolism?
1. Low blood oxygen saturation and cyanosis
2. Rapid breathing
3. Rapid heart rate
2. Very low BP
3. Sudden death
People with emboli in medium sized arteries present with?
Emboli in small arteries cause subtle symptoms of..?
Breathlessness, chest pain and dizziness.
Where do arterial thromboembolism originate from?
Heart or carotid arteries.
What may arterial thromboembolism cause?
Cerebral arteries - stroke
Mesentric arteries - bowel infarction
Lower limbs - acute lower limb ischaemia
What is an infarction?
Tissue necrosis due to ischaemia (lack of blood reaching tissue leads to tissue death)
What causes an infarction.
Usually caused by occlusion of an artery (sometimes veins) due to an embolus.
How do infarcts heal?
Usually they heal by repair. However, there is loss of functional tissue as dead tissue replaced by scar tissue.
What artery do MI almost always involve?
Left anterior descending coronary artery.
Cerebral infarction is usually confined to one hemisphere. T or F?
How is small bowel infarction caused?
Thromboembolus to bowel via superior mesenteric artery.
What can hypovolaemic hypotension (caused by loss of blood to gut) lead to.
Hypovolaemic shock and sepsis because gut flora can invade into blood.
What is haemorrhage?
Leakage (extravasation) of blood due to rupture.
What causes a haemorrhage?
2. Intrinsic disease of blood vessel - leads to weakening of wall
Major blood vessel rupture can lead to acute haemorrhage. What are the associated risks.
1. Hypovolaemia (decreased blood volume)
Small vessel ruptures can also be fatal. Eg, where?
Eg brainstem haemorrhage.
What is shock?
Generalised tissue perfusion failure (aka blood not sufficiently providing oxygen/nutrients to tissues)
What is shock caused by?
1. Pump failure
2. Peripheral circulation failure (e.g. hypovolaemia, sepsis, anaphylaxis)
What can circulatory collapse lead to?
Ischaemia of multiple organs.
What are the most vulnerable organs to shock?
Why can shock lead to multiple organ failure?
It has a positive feedback mechanism - condition gets worse once in shock.
Need rapid treatment.
What are the complications arising from shock?
1. Multiple organ failure.
2. Ischaemic tissue - lactic acidosis
3. Acute tubular necrosis