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Chapter 3
Disorders of Vascular Flow
Yiran Ni M.D
[email protected]
INTRODUCTION
• The health of cells and organs critically
depends on an unbroken circulation to
deliver oxygen and nutrients and to remove
wastes.
• However, the well-being of tissues also
requires normal fluid balance; abnormalities
in vascular permeability or hemostasis can
result in injury even in the setting of an
intact blood supply.
This chapter will describe major disturbances
involving hemodynamics and the maintenance
of blood flow, including:
1. edema
2. hyperemia and congestion
3. hemorrhage
4. thrombosis
5. embolism
6. infarction
7. shock.
Normal fluid homeostasis encompasses
maintenance of vessel wall integrity as well as
intravascular pressure and osmolarity within
certain physiologic ranges.
Changes in vascular volume, pressure, or
protein content, or alterations in endothelial
function, all affect the net movement of water
across the vascular wall.
Defination:1.edema
• Such water extravasation into the interstitial
spaces is called edema and has different
manifestations depending on its location.
• In the lower extremities, edema mainly
causes swelling.
• in the lungs, edema causes water to fill
alveoli, leading to difficulty in breathing.
Defination:2. thrombosis
3. embolism 4. infarction
• Normal fluid homeostasis also means
maintaining blood as a liquid until such
time as injury necessitates clot formation.
• Clotting at inappropriate sites (thrombosis)
or migration of clots (embolism) obstructs
blood flow to tissues and leads to cell death
(infarction).
Defination: 5. hemorrhage
6. shock
• Conversely, inability to clot after vascular
injury results in hemorrhage.
• local bleeding can compromise regional
tissue perfusion, while more extensive
hemorrhage can result in hypotension
(shock) and death.
Edema
What do you
find?
What do you
find?
Edema!
Defination
• Approximately 60% of lean body weight is
water, two-thirds of which is intracellular
and the remainder is in extracellular
compartments, mostly as interstitial fluid;
only 5% of total body water is in blood
plasma.
• The term edema signifies increased fluid in
the interstitial tissue spaces.
Defination
• Fluid collections in different body cavities
are variously designated hydrothorax,
hydropericardium, or hydroperitoneum (the
last is more commonly called ascites).
Anasarca is a severe and generalized edema
with profound subcutaneous tissue swelling.
movement of fluid
There are several pathophysiologic
categories of edema:
1. Increased Hydrostatic Pressure
2. Reduced Plasma Osmotic Pressure
(Hypoproteinemia)
3. Lymphatic Obstruction
4. Sodium Retention
5. Inflammation
Increased Hydrostatic Pressure
• Localized increases in intravascular
pressure can result from impaired venous
return: deep venous thrombosis, pregancy
• Generalized increases in venous pressure,
with resultant systemic edema, occur most
commonly in congestive heart failure
Increased Hydrostatic Pressure
Impaired venous return
Congestive heart failure
Constrictive pericarditis
Ascites (liver cirrhosis)
Venous obstruction or compression
Thrombosis
External pressure (e.g., mass)
Lower extremity inactivity with prolonged dependency
Arteriolar dilation
Heat
Neurohumoral dysregulation
What else
do you find?
movement of fluid
Reduced Plasma Osmotic Pressure
• Reduced plasma osmotic pressure can result from
excessive loss or reduced synthesis of albumin, the
serum protein most responsible for maintaining
colloid osmotic pressure
Reduced Plasma Osmotic Pressure (Hypoproteinemia)
Protein-losing glomerulopathies (nephrotic syndrome)
Liver cirrhosis (ascites)
Malnutrition
Protein-losing gastroenteropathy
Lymphatic Obstruction
Lymphatic Obstruction
Inflammatory
Neoplastic
Postsurgical
Postirradiation
movement of fluid
Filariasis
or
elephantiasis
orange peel
• In breast carcinoma
infiltration and
obstruction of superficial
lymphatics can also cause
edema of the overlying
skin, the so-called orange
peel appearance.
• Such a finely pitted
surface results from an
accentuation of
depressions in the skin at
the site of hair follicles.
Sodium and Water Retention
Sodium Retention
Excessive salt intake with renal insufficiency
Increased tubular reabsorption of sodium
Renal hypoperfusion
Increased renin-angiotensin-aldosterone secretion
Inflammation
Inflammation
Acute inflammation
Chronic inflammation
Angiogenesis
• The edema fluid occurring with volume or pressure overload,
or under conditions of reduced plasma protein, is typically a
protein-poor transudate; it has a specific gravity less than
1.012.
• Conversely, because of the increased vascular permeability,
inflammatory edema is a protein-rich exudate with a specific
gravity that is usually greater than 1.020 .
Morphology
• Edema is most easily recognized grossly;
microscopically, edema fluid is reflected
primarily as a clearing and separation of the
extracellular matrix elements with subtle
cell swelling. Although any organ or tissue
in the body may be involved, edema is most
commonly encountered in subcutaneous
tissues, lungs, and brain.
Subcutaneous edema
• Subcutaneous edema may have different
distributions depending on the cause. It can be
diffuse, or it may be relatively more conspicuous at
the sites of highest hydrostatic pressures. In the
latter case, the edema distribution is typically
influenced by gravity and is termed dependent.
Edema of the dependent parts of the body (e.g.,
the legs when standing, the sacrum when
recumbent) is a prominent feature of congestive
heart failure, particularly of the right ventricle.
Morphology
• Edema as a result of renal dysfunction or
nephrotic syndrome is generally more severe than
cardiac edema and affects all parts of the body
equally. It may, however, initially manifest itself in
tissues with a loose connective tissue matrix, such as
the eyelids; thus, periorbital edema is a
characteristic finding in severe renal disease.
Morphology
• Finger pressure over substantially edematous
subcutaneous tissue displaces the interstitial fluid
and leaves a finger-shaped depression, so-called
pitting edema.
Heart failure
or renal
hypofunction?
Pulmonary edema
• It is a common clinical problem most typically seen
in the setting of left ventricular failure but also
occurring in renal failure, acute respiratory distress
syndrome, pulmonary infections, and
hypersensitivity reactions.
• The lungs are two to three times their normal
weight, and sectioning reveals frothy, blood-tinged
fluid representing a mixture of air, edema fluid, and
extravasated red blood cells.
Edema of the brain
• It may be localized (e.g., owing to abscess or
neoplasm) or may be generalized, as in encephalitis,
hypertensive crises, or obstruction to the brain's
venous outflow.
• Trauma may result in local or generalized edema
depending on the nature and extent of the injury.
• With generalized edema, the brain is grossly
swollen, with narrowed sulci and distended gyri,
showing signs of flattening against the unyielding
skull.
Clinical Correlation
• Effects of edema may range from merely annoying
to fatal.
• Subcutaneous tissue edema in cardiac or renal
failure is important primarily because it signals
underlying disease; however, when significant, it
can also impair wound healing or the clearance of
infection.
•
Clinical Correlation
• Pulmonary edema can cause death by interfering
with normal ventilatory function. Not only does
fluid collect in the alveolar septa around capillaries
and impede oxygen diffusion, but edema fluid in
the alveolar spaces also creates a favorable
environment for bacterial infection.
Clinical Correlation
• Brain edema is serious and can be rapidly fatal; if
severe, brain substance can herniate (extrude)
through, for example, the foramen magnum, or the
brain stem vascular supply can be compressed.
Either condition can injure the medullary centers
and cause death.
SUMMARY
• Edema is extravasation of fluid from vessels
into interstitial spaces;
• the fluid may be protein poor (transudate) or
may be protein rich (exudate).
SUMMARY
• Edema results from any of the following
conditions:
• Increased hydrostatic pressure, caused by a
reduction in venous return (as in heart failure)
• Decreased colloid osmotic pressure, caused by
reduced concentration of plasma albumin (due to
decreased synthesis, as in liver disease, or
increased loss, as in kidney disease)
SUMMARY
• Lymphatic obstruction that impairs interstitial fluid
clearance (as in scarring, tumors, or certain
infections)
• Primary renal sodium retention (in renal failure)
• Increased vascular permeability (in inflammation)