Let’s start by looking at a very broad approach and some important DEFINITIONS.
Broad Approach and Definitions:
Following the scheme in your lectures, haemodynamic disorders can be divided into TWO main pathophysiological aspects.
- Disorders of Circulation Click on each term to see the DEFINITION.
HYPERAEMIA – When vessels of the microcirculation contain more blood than normal
- Active hyperaemia – Blood flow is increased (this is an active process, where arteriolar dilation leads to increased blood flow)
- Passive hyperaemia = Congestion (See below)
CONGESTION – This is synonymous with PASSIVE HYPERAEMIA. Congestion is a passive process in which there is reduced outflow of blood from a tissue.
OEDEMA – An excessive extravascular accumulation of fluid, within the interstitial tissues.
Oedema fluid may be transudative or exudative. Refer to the mindmap for more explanation.
Note: Fluid accumulations within body cavities are named according to the site, eg. Hydrothorax or pleural effusion (within pleural cavity).
HAEMORRHAGE – The extravasation of blood into the extravascular space.
Haemorrhage can be traumatic or spontaneous, the latter usually due to vessel or coagulation abnormalities.
SHOCK – A state of inadequate perfusion of cells and tissues, leading to reversible hypoxic injury and, if severe or prolonged enough, to irreversible cell and organ injury and death
There are several types of shock:
- Hypovolemic shock – Due to markedly reduced volume eg. haemorrhage, severe burns, vomiting & diarrhea.
- Cardiogenic shock – Due to pump failure.
- Distributive shock – Due to generalised vasodilatation eg. septic shock, anaphylactic shock, neurogenic shock.
- Thromboembolic Disease
THROMBOSIS – The process in which a thrombus is formed.
THROMBUS – An intravascular mass formed during life from the constituents of blood.
Virchow’s triad – A series of 3 abnormalities which leads to thrombosis
- Endothelial injury
- Abnormal blood flow (stasis or turbulence)
- Hypercoagulability of blood
EMBOLUS – A detached intravascular solid, liquid or gaseous mass that is carried by the blood to a site distant from its point of origin.
The process is called EMBOLISM.
Note: Emboli can be solid, liquid or gaseous, or even infective. The video mindmap highlights some examples.
INFARCTION – Necrosis due to Ischaemia (usually due to the occlusion of an artery; sometimes occlusion of venous drainage)
The mindmaps below will help you to pull back and see the BIG PICTURE.
MINDMAP: The BIG PICTURE Haemdynamic Disorders Part 1 :
Haemodynamic Disorders Part 2: Thrombosis, Haemorrhage and Shock