The Pathophysiology of Congestion and Oedema Flashcards
Darcy’s Law
Flow = Pressure gradient/Resistance
Congestion
Relative excess of blood in vessels of tissue or organ, which is a passive process
Examples of congestion
- Local acute congestion-
- Local chronic congestion
- Generalised acute congestion
Local acute congestion
Deep vein thrombosis
Local chronic congestion
Hepatic cirrhosis
Generalised acute congestion
Congestive heart failure
Consequences of DVT (6)
Local acute congestion Decrease pressure gradient Decreased outflow Decreased flow No O2- Ischaemia and infarction Blood backed up in veins, venules and and capillaries
Consequences of Hepatic Cirrhosis
Intervening fibrosis Loss of normal architecture Portal blood flow blocked Increased portal venous pressure Collateral circulation Anastomosis with systemic circulation
Where do DVTs normally originate and what can cause them (4)
Pelvis
Pelvic malignancy, pregnancy (bilateral), Abscess
What is the appearance of the liver during local chronic congestion and what causes it
Fatty
Low levels of O2
Hepatic cells change to fatty cells as they have the least metabolic requirement and eventually die off
Consequences of hepatic cirrhosis (local chronic congestion)
Oesophageal varices
Caput medusae
What causes congestive heart failure
Heart is unable to clear blood from left and right ventricles due to ischaemia or valve problems
Consequences of congestive heart failure
Decreased CO
Decreased GFR
Activation of renin-angiotensin-aldosterone system
water retention in body
Left heart failure
Pulmonary oedema in lungs
Blood damns back into lungs
Clinical presentation of left heart failue
Crepitations and Tachycardia
Right heart failure
Central venous congestion in liver
Blood damns back into systemic circulation
When blood damns back into systemic circulation what does that result in
Increased JVP pressure
hepatomegaly
Peripheral Oedema
What causes oedema in the pulmonary circulation and peripheral circulation
Because the heart is too weak to pump the blood it accumulates and the pressure caused by the backflow causes fluid it seep out leading to oedema
Which hepatocyte receives the best oxygen supply and why? Periportal or pericentral;
Periportal
Close proximation with hepatic arterioles and receives the most oxygenated blood
Arterial side balance of pressure
Capillary hydrostatic pressure is greater than = filtration
Venous side balance of pressure
Capillary oncotic pressure is greater than hydrostatic pressure = reabsorption
Three components that affect net flux and filtration
- Hydrostatic pressure
- Oncotic pressure
- Permeability characteristics and area of endothelium
What does disturbance of starling forces lead to
Oedema
Starling’s Hypothesis
States that the fluid movement due to filtration across the wall of a capillary is dependent on the balance between the hydrostatic pressure gradient and the oncotic pressure
4 Starling Forces
hydrostatic pressure in the capillary (Pc)
hydrostatic pressure in the interstitium (Pi)
oncotic pressure in the capillary (pc )
oncotic pressure in the interstitium (pi )
What is oedema
Accumulation of abnormal amounts of fluid in the extravascular compartment
Transudate is caused by
alterations in the haemodynamic forced and is a sign of cardiac failure or hypoproteinemia
Exudate is caused by
the inflammatory process due to an increase in vascular permeability Tumour Allergy Inflammation High protein/albumin in cells
What are the events that occur in left ventricular failure (4)
Increase in left arterial pressure- back flow to pulmonary veins, capillaries and arteries
Increase in pulmonary vascular pressure
Increase in pulmonary blood volume
Increase in hydrostatic pressure leads to increase filtration and pulmonary oedema
What occurs in the lungs during left ventricular failure (3)
Perivascular and interstitial transudate
Progressive oedematous widening of alveolar septa
Accumulation of oedema fluid in alveolar spaces
Pathophysiology of peripheral oedema
Right heart failure
Retained blood and back flow in systemic veins
Increase in pressure- transudate
Blockage of the lymphatic drainage leads to
Lymphoedema
Primary cause for abnormal renal function
Acute tubular damage
Secondary cause for abnormal renal fucntion
Heart failure reduced GFR
Consequences of abnormal renal function (3)
Increased salt and water retention
Increased intravascular fluid volume
Oedema
Causes of low protein oedema (3)
Hypoalbuminemia:
- Nephrotic syndrome
- hepatic cirrhosis
- Malnutrition
What can cause permeability oedema
Burns
Acute inflammation such as pneumonia
What are the consequences of permeability oedema
Damage to endothelial lining leads to pores in the membrane which allow proteins and larger molecules to leak out reducing the oncotic pressure
