Pthophysiology of Congestion and Oedema Flashcards
Define Congestion
Congestion is defined as the relative excess of blood in vessels of tissues and organs. Congestion is a passive process which allows blood to increase in its volume in tissue without any particular predisposing event and is a secondary phenomenon. It is not like actue inflammation where active hyperiamia vessels actively open up to allow more blood flow. It can happen acutely or can be chronic
What are examples of clinical pathologies of congestion?
Local acute congestions - Deep vein thrombosis
Local Chronic congestion - Heppatic cirrhosis
Generalised acute congestion - congestive cardiac failure
What is deep vein thrombosis?
Deep vein thrombosis is caused by a vein being blocked. This results in blood being backed up in the veins, venules and capillaries. The effect of that is the outflow of the blood through the proximal vessles is blocked which causes local acute congestion. The pressure gradient across the limb is therefore reduced and the flow across the system is reduced. Due to no blood flow there is no oxygenation and that leads to ischaemia or infarction.
What is Hepatic cirrhosis?
Hepatic cirrhosis results from serious liver damage, there is then regeneration of the liver which forms nodules of liver cells, hepatocytes with inervating fibrosis. There is then loss of normal architecture and altered hepatic blood flow. Portal blood flow is locked. This means that there is congestion of portable veins and branches, which leads to increased venous pressure and attempt to find collateral circulation. The result of this is that there is chronic congestion in the gut and there may be a heamorrhage risk.
What is congestive cardiac failure?
In this the heart is dysfunctional and unable to clear blood from right and left ventricles, the pump is ineffective, this may be seen in ischeamic heart disease and in valvular heart disease.
What is the pathophysiology of congestive cardiac failure?
In congestive cardiac failure the cardiac output is reduced becuase of that there is an effect in kidneys. The effect of changing renal blood flow is activation of hormone system called renin-angiotensin-aldosterone system.
What is the effect of the activation of hormone system called renign-angiotensin-aldosterone system?
The effect of this is it increases sodium and water retention in the body and increases the amount of fluid that is retained. This results in too much fluid in the vessels and there is fluid overload - more blood flow into the heart than you can get out.
What is the treatment of congestive cardiac failure?
The patients are treated with diuretics
What is the effect of congestive cardiac failure?
- Pulmonary Oedema
- Heart Failure alongside tachycardia
- Peripheral Oedema
Pulmonary Oedema - Effect of congestive cardiac failure
Since the heart cannot clear the blood from the ventricles there is back pressure and blood is dammed back to the veins. This results in the lungs in pulmonary oedema.
Heart failure - Effects of congestive cardiac failure
May see heart failure with lung damming back into the lungs and this is present in clinical signs of the lungs where you hear little crackles and you may also have a tachycardia as the heart is working harder as it tries to push the blood through.
Peripheral oedema - The effect of congestive cardiac failure
In the liver, when there is right heart failure the blood dams back into the systemic circulation and the first thing effected is the liver. Clinically you may see higher jugular venous pressure, you may feel hepatomegaly and you will see peripheral oedema which you are able to palpate.
What is normal microciruclation?
Normal microcirculation has a constant movement of fluid through the capillary beds. This is a process of dynamic equilibrium. Microcirculation of the cardiovascular is primarly driven by hydrostatic pressure from heart. The fluid is balanced by osmotic pressure and endothelial permeability. There is also filteration of the blood from capillary beds into the interstium (tissue fluid filled areas).
What is usually refrerred to as microcirculation?
Capillaries in the interstitium and the capillaries in the lymphatics are collectively referred to as the microcirculation.
How is osmotic pressure produced?
Osmotic pressure is produced by molecules in various tissue compartments and tissue fluids in and outside vessels.
How does filteration from the vessels occur?
- Through the arterial side of capillary the capillary hydrostatic pressure is 35mmHg and then when you come out of the venous side it is reduced to about 20mm of mercury. The pressure gradient across the capillary bed is about 20mm of mercury.
- Osmotic pressure/oncotic pressure it is 25 mmHg inside and outside the capillary.
Define Oedema
Oedema is the accumulation of abnormal amounts of fluid in the extravascular compartment. There will be an extracellular tissue compartment which has gotten aditional fluid and also arises in body cavities - pleural cavity and peritoneal cavity.
What is peripheral oedema?
Increased interstial fluid in the tissue
What is efffusion?
Fluid collection in body cavities.
What is oedema transudate?
Trasudate is the result of alterations in the heamodynamic forces across a capillary wall. It is seen in cardiac failure and fluid overload. Not much protein in transudate but there is a lot of water and electrolytes. It has a low specific gravity.
What is oedema exudate?
Oedema exudate is a result of change in permeability. It is result of tumour, inflammation and allergy. There is a higher protein content in exudate and cells. It also contains water and electrolytes but has a high a specific gravity.
What is the pathophysiology of pulmonary oedema?
Pulmonary oedema is a result in the changes of hydrostatic pressure, hence it is a transudate.
What is the pathophysiology of peripheral oedema?
Failure of the right ventricle, the right ventricle cannot be empties in systole. Blood is therefore retained in the atrium and it backs up in the systemic veins. There is therefore increased pressure in the capillaries, increased filteration and therefore oedema. There is also secondary portal venous congestion via liver.
How does congestive cardiac failure cause pulmonary and peripheral oedema?
In congestive cardiac failure, both the right and left ventricles fail symultaneously. Due to this you see effects of both pulmonary oedema and peripheral oedema at the same time. This is all due to change in hydrostatic pressure
