Hemodynamic disorders. Arterial hyperemia. Venous congestion - systemic and organ-specific
Normal homeostatic control of fluid in the body ensures a balance between the intra, and extracellular compartments of fluid (about 40% and 20% of body mass respectively). Where this is disrupted, we can see some of the following conditions.
Edema
- Swelling
- Excessive accumulation of free fluid in the interstitial tissue spaces/serous cavities
- Free fluid in the peritoneal cavity is known as ascites
- Free fluid in pleural cavity is hydrothorax or pleural effusion
- While hydropericardium is fluid in the pericardium
- Etiology
- Increased hydrostatic pressure (impaired venous return)
- Reduced plasma oncotic pressure (reduction in proteins in plasma due to loss or issue regarding synthesis)
- Lymphatic obstruction
- Sodium retention
- Inflammation (increased vascular permeability)
- Types classified by characteristics
- Pitting (low protein content in fluid)
- Product of vascular condition generally
- Non-pitting (high protein content in fluid)
- Product of lymphatics generally
- Types classified by location
- Localised
- Generalised
- Fluid
- Fluids are classified as Transudates or Exudates
- Exudate is fluid that leads out of the capillaries due to inflammation
- Transudate is fluid pushed through capillary due to high hydrostatic pressure (inflammation not required)
Arterial hyperemia
- Defined as increased blood in the arterial system
- Produced by increased inflow and vasodilation leading to engorgement with oxygenated blood
- Happens normally in physiological processes
- E.g. exercise, blushing
- And pathological
- In infection
- Inflammatory process
- Increase in temperature and redness
- Is an active process
Congestion
- There are three types:
- Local
- Systemic
- Or Generalised
- Congestion is, simply put, the backing up of blood
- Passive process
- Below we will consider some examples of local and systemic congestion
Local
Obstruction of one part of the body, leading to build up of venous blood:
- Mesenteric venous occlusion
- Gross: Dark purple, thick walls, oedematous and haemorrhagic
- Torsion of testis/Ovaries
Systemic
This is the engorgement of systemic veins. It commonly leads to a pitting oedema, and can be acute or chronic. In chronic cases we see chronic hypoxia potentially resulting in fibrosis.
Systemic congestion is the product of Left or Right sided heart failure, we’ll look at both, and the implications of acute vs chronic congestions.
Left sided heart failure
- Acute
- Result of acute failure of left ventricle, often a product of MI or Coronary Artery disease
- As the left ventricle fails we see the build up of blood in the pulmonary veins and capillaries
- This buildup leads to pulmonary oedema and acute congestion of lung as the additional hydrostatic pressure forces fluid into the lungs