Continuing the hemodynamic disorders , now we will learn about edema, hemorrhage, shock and atherosclerosis .

Edema

This disorder is characterized by excessive accumulation of fluid in the interstitium or in body cavities .
 

Edema can be inflammatory (exudate - high protein content as a result of increased vascular permeability) or noninflammatory (transudate - low protein content due to preservation of vascular permeability) .
 

The main factors for the edema to occur are :
1 - increase in hydrostatic pressure which leads to an increase of outflow of fluid from the capillary to the interstitium; from the moment in which the capacity of the lymph vessels to return excess fluid to the bloodstream is exceeded , we development of edema.
2 - reduction in oncotic pressure: when these proteins thar regulate the pressure decrease, there is an increase in the permeability , causing edema .
3 - lymphatic obstruction will cause an increase in permeability .
4 - retention of Na and H2O in consequence of changes in Na / K pump
5 - increase in vascular permeability by inflammatory events .
 

Hemorrhage
 

When the blood extravasate to the external environment or cavities  because of a vessel rupture, it's called hemorrhage.

Hemorrhage can occur due to trauma , atherosclerosis , cancer etc.

Morphologically , there is formation of petechiae , purpura , ecchymosis and hematoma.

Consequences as hypovolemia , local ischemia , and death can occur .

Atherosclerosis

It is caused, mainly, by LDL that clings in the intima of the blood vessel and forms crystals. Thereafter , the crystals are recognized as antigens and macrophages try to remove it , but they fail to digest and die , releasing lysosomal enzymes that recruit inflammatory cells , decreasing the lumen of the vessels and increasing blood pressure .

Shock

It is an acute and rapid circulatory changes that usually leads to death .

It is characterized by failure of the circulatory system to maintain adequate blood flow to the microcirculation with subsequent inadequate perfusion of vital organs causing hypoxia . Therefore, the shock causes systemic hypoperfusion by reducing cardiac output (CO ) and circulating blood volume .

There are five types of shock : 2 of macrocirculation and 3 of the microcirculation , respectively :
1 - Cardiogenic - changes in the myocardium that prevent the heart to adequately pump blood ( eg myocardial infarct , left heart failure )
2 - hypovolemic - decrease of body fluids , decrease venous return and CO ( eg, hemorrhage , dehydration burn )
3 - Septic - bacterias, mainly Gram negative , release endotoxins that promote vasodilation , decreasing venous return and cardiac output
4 - Anaphylactic - in allergic responses marked where there is increased release of vasodilator ( histamine ) that decreases venous return and cardiac output
5 - Neurogenic - vasomotor response with vasodilation , decreasing venous return and cardiac output ( eg, epidural )

The shock has three stages :
1 - Initial - perfusion is maintained and there is activation of compensatory mechanisms reflexes
2 - Progressive - tissue hypoperfusion and beginning circulatory imbalances
3 - Irreversible - starts after cellular injury so severe that even if the hemodynamics defects are corrected , survival is not possible.