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Summary Pathology Chapter 4
Summary Chapter 4: Hemodynamic Disorders, Thromboembolism, and Shock Robbins Basic Pathology 10th edition
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Chapter 4: Hemodynamic Disorders, Thromboembolism, and Shock- Hemostasis: the process of blood clotting that prevents excessive bleeding after blood-
vessel damage
Inadequate hemostasis may result in hemorrhage, which can compromise regional tissue
perfusion and, if massive and rapid, may lead to hypotension, shock, and death
Hyperemia and Congestion
- Hyperemia is an active process resulting from arteriolar dilation and increased blood
inflow, as occurs at sites of inflammation or in exercising skeletal muscle
- Congestion is a passive process resulting from impaired outflow of venous blood from a
tissue. Eg. Cardiac failure or as a consequence of an isolated venous obstruction
Edema
- Edema: the accumulation of fluid in tissues resulting from a net movement of water into
extravascular spaces
- Extravascular fluid can also collect in body cavities, for example effusions in the pleural
cavity (hydrothorax), the pericardial cavity (hydropericardium), or the peritoneal cavity
(hydroperitoneum, or ascites)
- Anasarca is severe, generalized edema marked by profound swelling of subcutaneous
tissues and accumulation of fluid in body cavities
- Normally, the outflow of fluid produced by hydrostatic pressure at the arteriolar end of
the microcirculation is nearly balanced by inflow at the venular end owing to slightly
elevated osmotic pressure; hence there is only a small net outflow of fluid into the
interstitial space, which is drained by lymphatic vessels
Increased hydrostatic pressure or diminished colloid osmotic pressure causes an
increase in movement of water into the interstitium. Excess edema fluid is removed by
lymphatic drainage and is returned to the bloodstream by way of the thoracic duct
The edema fluid that accumulates in the setting of increased hydrostatic pressure or
reduced intravascular colloid typically is a protein-poor transudate. Because of increased
vascular permeability, inflammatory edema fluid is a protein-rich exudate.
- Edema is characterized by showing clearing and separation of the extracellular matrix
elements
Increased Hydrostatic Pressure
- Increases in hydrostatic pressure (blood pressure of the heart) are mainly caused by
disorders that impair venous return
- Heart failure: the failing heart cannot increase its
cardiac output in response to the compensatory
increases in blood volume. Instead, a viscious
cycle of fluid retention, increased venous
hydrostatic pressures, and worsening edema
ensues
Reduced Plasma Osmotic Pressure
, - Reduction of plasma albumin concentrations leads to decreased colloid osmotic pressure
of the blood and loss of fluid from the circulation
- Nephrotic syndrome is the most important cause of albumin loss from the blood. In
diseases that are characterized by nephrotic syndrome, the glomerular capillaries
become leaky, leading to the loss of albumin (and other plasma proteins) in the urine
and the development of generalized edema
Low albumin levels lead in a stepwise fashion to edema, reduced intravascular volume,
renal hypoperfusion, and secondary hyperaldosteronism
Lymphatic Obstruction
- Edema may result from lymphatic obstruction (caused by an inflammatory or neoplastic
condition) that compromises resorption of fluid from interstitial spaces
- One relatively common setting for this clinical entity is in women with breast cancer who
undergo axillary lymph node resection and/or irradiation, both of which can disrupt and
obstruct lymphatic drainage, resulting in severe lymphedema of the arm
Sodium and Water Retention
- Excessive retention of salt can lead to edema by increasing hydrostatic pressure and
reducing plasma osmotic pressure.
- Reasons to get edema (more fluid out):
1) Increased hydrostatic pressure (eg. heart failure)
2) Increased vascular permeability (eg. inflammation)
3) Decreased colloid osmotic pressure resulting from reduced plasma albumin
Decreased synthesis (eg. liver disease, protein malnutrition)
Increased loss (eg. nephrotic syndrome)
4) Lymphatic obstructions
Latrogenic: caused by doctors. Eg. Breastcancer: lymph nodes are removed but
lymph’s swell
Tumor
5) Sodium retention (eg. renal failure)
- Pitting edema → When you press the swollen skin, it stays like that for a moment.
- In the lungs edema can be very dangerous → pulmonary edema (too much fluid in the
vessels and lungs itself)
Consequences and risks of edema (in most cases risks are then limited) in the body:
(Edema interfer with the normal function of an organ)
Lungs
Brain: edema will stop the blood from entering the brain (the surrounding
(skull) are unyielding)
In the larynx: block the airway
Hemorrhage
- Hemorrhage, defined as the extravasation of blood from vessels, is most often the result
of damage to blood vessels or defective clot formation (loss of fluid, proteins, cells and
blood; bleedings):
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