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Cardiovascular System > Pathophysiology of Congestion and Oedema > Flashcards

Pathophysiology of Congestion and Oedema Flashcards

1
Q

Down what gradient does fluid in the body flow?

A

Down pressure gradient

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2
Q

What does Darcy’s Law state and what is the equation?

A

Q = change in pressure / resistance

Velocity of blood flow is in proportion to the pressure gradient in the direction of the flow

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3
Q

What is congestion?

A

Excess of blood in vessels of tissue or organ

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4
Q

Give an example of local acute congestion

A

Deep vein thrombosis

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5
Q

Give an example of local chronic congestion

A

Hepatic cirrhosis

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6
Q

Give an example of generalised acute congestion

A

Congestive heart failure

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7
Q

Describe the pathophysiology of DVT causing infarction and ischaemia?

A

Thrombus occludes vessel, causing blood to back up in the veins, venues and capillaries which decreases outflow of blood, pressure gradient and flow.

Decrease in flow leads to less O2 delivery -> ischaemia and infarction

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8
Q

What does hepatic cirrhosis result from?

A

Serious liver damage i.e. HBV, alcohol

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9
Q

What is the pathophysiology of hepatic cirrhosis?

A
  1. Serious liver damage
  2. Regenerating liver forms nodules of hepatocytes with intervening fibrosis
  3. This alters hepatic blood flow
  4. Can block vessels, so causes congestion in portal vein and branches
  5. Increased portal venous pressure
  6. Collateral circulation develops
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10
Q

What are some consequences of portal-system hypertension?

A

Blood is shunted to areas causing features like oesophageal varices and caput medusae

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11
Q

What is dangerous about oesophageal varices?

A

They only have a thin lining over them so can easily be ruptured, causing haemorrhage

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12
Q

What is congestive cardiac failure?

A

The heart is unable to clear blood from the right and left ventricles (the heart is an ineffective pump)

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13
Q

What is the pathophysiology of congestive cardiac failure?

A
  1. Decrease in cardiac output
  2. Decrease in renal glomerular filtration rate
  3. This causes the activation of the renin-angiotensin-aldosterone system
  4. This causes sodium and water retention
  5. Therefore increases the fluid in the body
  6. There is a fluid overload in the veins
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14
Q

What is the pathophysiology of pulmonary oedema caused by left ventricular failure?

A
  1. Increase in left atrial pressure
  2. Back up in pulmonary veins, capillaries and arteries
  3. Increase in vascular pressure
  4. Increase in pulmonary blood volume
  5. Increased hydrostatic pressure leads to increased filtration
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15
Q

What are the signs of central venous congestion?

A

Increased JVP
Hepatomegaly
Peripheral oedema

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16
Q

What causes central venous congestion?

A

Right heart failure - blood dams back into systemic circulation

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17
Q

What is the appearance of hepatic central venous congestion?

A 
Liver red brown & pale spotty appearance macroscopically:
Pericentral hepatocytes (red) - poor oxygenation
Periportal hepatocytes (pale) - better oxygenated due to close BV
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18
Q

Describe the normal microcirculation

A

Constant movement of fluid through capillary beds; process of dynamic equilibrium

19
Q

What are the mechanisms involved in microcirculation?

A 
Hydrostatic pressure (filtration to ISF) 
Osmotic pressure and endothelial permeability
Lymphatic system absorbing excess fluid from ISF
20
Q

What are the 3 components that affect net flux and filtration?

A

Hydrostatic pressure
Oncotic pressure
Permeability characteristics and area of endothelium

21
Q

What is the colloid (oncotic) pressure?

A

Osmotic pressure created by protein in the vessels, drawing fluid from the ISF
Pressure increases from arteries to veins

22
Q

What is the hydrostatic pressure?

A

It is the driving force for pushing fluid out of the vessels and into the ISF as the pressure is greater inside the vessel
Decreases from arteries to veins

23
Q

What can disturbances in the normal starling forces cause?

A

Oedema

24
Q

What is oedema?

A

Accumulation of abnormal amounts of fluid in the extravascular compartment - in ECF or body cavities

25
Q

Give example of increase fluid in ISF

A

Peripheral oedema

26
Q

Give example of increase fluid in body cavities

A

Effusions - pleural, pericardial, joints or ascites in abdominal cavity

27
Q

What is a transudate?

A

Altered haemodynamic forces across vessel wall - increased hydrostatic

28
Q

What is specific gravity and its relevance in transudates and exudates?

A

Ratio of the mass of a solution compared to the mass of an equal volume of water

Transudate: low SG as it was high conc. of water which is why fluid is pushed out

Exudate: high SG but increased permeability means fluid and protein lost

29
Q

What is an exudate?

A

Part of inflammatory process due to increase vascular permeability

30
Q

What are the causes of transudate fluid in oedema?

A

Cardiac failure: fluid back up -> increase hydrostatic pressure -> oedema
Low protein/albumin -> pushes fluid into ISF
Lots of H2O and electrolytes
Low specific gravity

31
Q

What are the causes of exudate fluid in oedema?

A

Tumour, inflammation, allergy
High protein/albumin
H2O and electrolytes
High specific gravity

Loss of fluid and protein

32
Q

What is the pathophysiology of left ventricular failure causing pulmonary oedema?

A
  1. Increase in atrial pressure causing back flow to veins
  2. Increase pulmonary vascular pressure
  3. Increase pul. blood volume
  4. Increase in hydrostatic pressure
  5. Increase filtration and pulmonary oedema

Forms transudate fluid due to increase hydrostatic pressure

33
Q

What is the effect of pulmonary oedema in the lungs?

A

Perivascular and interstitial transudate
Oedematous widening of alveolar septa
Fluid in alveolar spaces

34
Q

What is the pathophysiology of right heart failure causing peripheral oedema?

A
  1. Cannot empty RV in systole
  2. Blood retained in systemic veins
  3. Increasing pressure and filtration

Also occurs due to portal venous congestion in liver

35
Q

What happens in the body due to congestive heart failure?

A
  1. R and L ventricles fail

2. Pulmonary and peripheral oedema at same time

36
Q

What happens if the lymphatic vessels are blocked?

A

Lymphatic obstruction -> lymphoedema

37
Q

What does abnormal renal function result in?

A

Salt and H2O retention

38
Q

What causes abnormal renal function?

A

Secondary in HF: reduced renal blood flow

Primary: acute tubular damage i.e. hypotension

39
Q

How does abnormal blood flow result in oedema?

A
  1. Increase salt and H2O
  2. Increase in intravascular fluid volume
  3. Secondary increase in hydrostatic pressure
  4. Oedema
40
Q

How does low protein in vessels cause oedema?

A

Hypoalbumamia -> decreased oncotic pressure and increases filtration

Transudate

41
Q

How does hepatic cirrhosis cause oedema?

A

Diffuse nodules and fibrosis in liver means that the liver is not able to make enough protein -> decrease in oncotic pressure and increase in filtration

42
Q

How can endothelial permeability cause oedema?

A

Damage to lining increase number of pores in membrane allows protein and larger molecules to leak out as well as fluid

43
Q

What are 2 causes of permeability oedema?

A

Inflammation (pneumonia)

Burns

Cardiovascular System (37 decks)

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