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hemodynamic disorders 2

Terms

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Definition of HEMORRHAGE

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bleeding; a discharge of blood from the vascular compartment to the exterior of the body or to non-vascular body spaces
Hemothorax
hemorrhage into the pleural cavity
Hemopericardium
hemorrhage into the pericardial space
Hemoperitoneum
bleeding into the peritoneal cavity
Hemarthrosis
bleeding into a joint space
Hematoma
hemorrhage into the soft tissues (painful in a muscle bruise but fatal if in brain)
Purpura
diffuse superficial hemorrhages in the skin-- as large as 1 cm in diameter.
Ecchymosis
a larger superficial hemorrhage than a purpura.
ex: a black eye
Petechia
a pinpoint hemorrhage, usually in the skin or conjunctiva. represents the rupture of a capillary or arteriole.
Hyperemia
Excess amount of blood in an organ.
Active hyperemia
An increased supply of blood to an organ, usually as a physiologic response to increased functional demand.

-neurogenic and hormonal influences play a role
-occurs in association with inflammation
-heart/skeletal muscles during exercise
Passive hyperemia
engorgement of an organ with venous blood.
Describe passive hyperemia of the LUNG.
chronic failure of left ventricle --> chronic passive congestion of lungs --> increased pressure in alveolar capillares --> vessels become engorged with blood....
1)microhemorrhages release erythrocytes into the alveolar spaces- mac's become "heart failure cells"
2)increased hydrostatic pressure results in pulmonary edema
3) fibrosis stimulates; fibrosis + iron = "brown induration"
4)pulmonary hypertension: increased capillary pressure is transmitted to the pulmonary arterial system.
Describe passive hyperemia of the LIVER.
Central veins of hepatic lobule become dilated and the increased venous pressure is transferred to the sinusoids, where it leads to dilatation of the sinusoids with blood.

curious reticulated appearance = Nutmeg liver
Passive hyperemia in the SPLEEN.
Increased pressure in liver --> higher pressure in portal vein --> higher pressure in splenic vein --> congestion of spleen.

Spleen becomes enlarged and tense.
Normal weight: 150 g, fibrocongestive splenomegaly: 250-750 g
Ascites
accumulation of fluid in the peritoneal spaces (abdomen).
Define thrombosis.
The formation of a thrombus within a vascular lumen, defined as an aggregate of coagulated blood containing platelets, fibrin, and entrapped cellular elements
Define a thrombus.
An aggregate of coagulated blood containing platelets, fibrin, adn entrapped cellular elements. Should be distinguished from a blood clot.
What is the most common cause of thrombosis in the ARTERIAL system?
atherosclerosis
The pathogenesis of arteiral thrombosis involves 3 principal factors:

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1) damage to the endothelium (disturbs the anticoagulant properties oft eh vessel wall)
2) alterations in the flow of blood
3) increased coaguability of the blood
Lines of Zahn
An arterial thrombus inititally is attached to the vessel wall and is soft and dark red. It has fine, alternating bands of yellowish platelets and fibrin , called Lines of Zahn.
The outcomes of an arterial thrombus (PATHOLOGY)
1) Lysis- due to potent thrombolytic activity of the blood.
2) an increasae in size (propagation)
3) Organization: eventual invasion of CT elements
4) Canalization: new lumina, lined by endothelial cells, form in an organized thrombus.
Define an infarct.
Ischemic necrosis of a tissue (due to an arterial thrombus).
Define mural thrombosis.
Thrombi attached to the endocardium of a cardiac chamber.
Disorders where mural thrombosis occurs:

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1) Myocardial infarction (cavity of left ventricle)
2) Atrial Fibrillation (left atrium)
3) Cardiomyopathy
4) Endocarditis
What is the major complication of thrombi at any location in the heart?

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embolization - detachment of fragments and their transport to distant sites where they lodge and occlude arterial vessels.
Thrombophlebitis
Inaccurate term.

venous thrombosis caused by an inflammatory or infectious process that had injured the vein.
Phlebothrombosis
a more accurate term -- no evidence of inflammation.

(venous thrombosis)
What is the most accurate term for thrombosis of the deep venous system of the legs?
Deep Venous Thrombosis
Conditions that favor deep venous thrombosis (pathogenesis)
1) stasis
2) injury (trauma, surgery, childbirth)
3)hypercoagulability (oral contraceptives, late prgenancy, cancer)
4) advanced age
4) sickle cell disease
Outcomes of venous thrombi (pathology):
1) lysis
2) Organization: small venous thrombi are incorporated into hte wall of the vessel while large venous thrombi may undergo canalization.
3) proapgation
4) embolization -- pulmonary emboli.
Where do deep venous thrombi usually occur?
>90% in deep veins of legs.
~10% in veins of pelvis.
Define embolism.
The passage through the venous or arterial circulations of any material capable of lodging in blood vessel and thereby obstructing the lumen.

An embolus is a detached intravascular solid, liquid, or gaseous mass that is carried by the blood to a site distant from its point of origin.
Clinical features of pulmonary emboli can be divided into the following syndromes:(4)

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1) asymptomatic small pulmonary emboli
2) transient dyspnea and tachypnea (fast breathing) with no other symptoms.
3) pulmonary infarction with pleuritic chest pain, hemoptysis, and pleural effusion.
4) cardiovascular collapse w/ sudden death.
Define paradoxical embolism.
An embolism that arises in the venous circulation and bypasses the lungs by traveling through an incompletely closed foramen ovale, subsequentely entering the left side of the heart and blocking flow in systemic arteries.
Common sites (organs) of infarction from arterial emboli: (5)
1) brain: causes strokes
2) intestine: infarction of the small intestine--> acute abdomen --> immediate surgery
3) lower extremity: sudden pain, absence of pulses, cold limb.
4) kidney: usually small peripheral infarcts
5) heart: coronary artery embolism --> myocardial infarct; left ventricle (rare)

also: retina, spleen
What is the most common source of arterial emboli?
the heart- from mural thrombi or diseased valves.
What is air embolism?
air entering the venous circulation.

Quantities of 100mL or more can lead to sudden death.

air bubbles tend to coalesce and obstruct the flow of blood in the right side of the heart, the pulmonary circulation, and the brain.
Those exposed to high atmospheric pressure are subject to....
decompression sickness, a unique form of gas embolism.

Large amts. of inert gas are dissolved in the body fluids when they descend. When they ascend, the gas is released and exhaled. If the ascent is too fast, gas bubble form in the circulation and within the tissues.
Describe acute decompression sickness.
Aka the bends.

Temporary muscular and joint pain owing to small vessel obstruction in the tissues.
Define amniotic fluid embolism.
The entry of amniotic fluid containing fetal cells and debris into the maternal circulation through the open uterine and cervical veins.
Define fat embolism.
The release of emboli of fatty marrow into damaged blood vessels following severe trauma to fat-containing tissue, particularly accompanying bone fractures.
Fat embolism syndrome and its 3 clinical features!!


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A case of SEVERE fat embolism.

Respiratory failure, mental changes, thrombocytopenia (low platelet count), widespread petechiae.
Define infarct.

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an area of ischemic necrosis caused by occlusion of either the arterial supply or the venous drainage in a particular tissue.
Pale Infarcts.
Typical in the heart, kidneys, brain, and spleen.

soft, sharply delineated; Becomes light yellow 1-2 days after the initial hyperemia. Border is red, reflecting hemorrhage into the surrounding tissue. Exhibits uniform coagulative necrosis.
Red Infarcts.
Characterized by coagulative necrosis but distinguished by bleeding into the necrotic area from adjacent arteries and veins.

Occurs in organs with a dual blood supply (lungs) or those with an extensive collateral circulation (SI, brain).

Sharply circumscribed, firm, dark red to purple.

Acute inflammatory cells infiltrate the necrotic area --> cellular debris phagocytized --> granulation tissue --> scar.
Septic infarct.
results when the necrotic tissue of an infarct is seeded by pyogenic (pus) bacteria and becomes infected.

Pulmonary infarcts are COMMON bc the necrotic tissue has low resistance to inhaled bacteria.
Define edema.
The presence of excess fluid in th einterstitial spaces of the body and may be local or generalized.
Anasarca
Extreme generalized edema, with fluid accumulation in subcutaneous tissues, visceral organs, and body cavities.

Edematous fluid may accumulate in body spaces, like the pleural cavity, peritoneal cavity, and pericardial cavity.
What is the principal determinant of ECF volume
Total body sodium.
It is the major cation that determined hte osmolality of the ECF.
Regulation of renal sodium excretion is influenced by: (3)
1) atrial natriuretic factor
2) the renin-angiotensin system of the juxtaglomerular apparatus
3) activity of the SNS
Most common conditions in which generalized edema is found:
CHF, cirrhosis of liver, nephrotic syndrome, some cases of chronic renal insufficiency.
Define congestive heart failure.
A syndrome that occurs when the heart does not pump a volume of blood adequate to meet the needs of the body.
what does atrial natriuretic factor do?
stimulates sodium excretion.
Clinical features of CHF
Dyspnea, paroxysmal nocturnal dyspnea.

Distended jugular veins and pitting edema of the lower extremities.

Enlarged/tender liver.
Rales.
Nephrotic Syndrome
Caused by a large loss of protein to the urine.
Low conc of plasma proteins (albumin) --> edema --> blood volume decreases --> sodium retention by renin-angiotensin-aldosterone mechanism.

Edema appears preferentially in the soft CT, eyes, eyelids, and subcutaneous tissue.
Hyaline membranes
In cases of pulmonary edema caused by alveolar damage, cell debris, fibrin, and proteins forms films of proteinaceous material, called hyaline membranes, in the alveoli.
Cardiac tamponade
when pericardial fluid accumulates rapidly, pressure in the pericardial cavity rises to EXCEED the filling pressure of the heart --> decline in Q --> fatal.
Define shock.
A condition of profound hemodynamic and metabolic distutrbance characterized by failure of the circulatory system to maintain adequate perfusion of vital organs.
What are the main causes of cardiogenic shock?
myocardial infarction
myocarditis
cardia tamponade

depressed systolic cardiac function --> decreased cardiac output.
What causes internal fluid loss (hypovolemic shock)?
endotoxemia
burns
trauma
anaphylaxis

--> increased vascular permeability
what causes external fluid loss (hypovolemic shock)?
hemorrhage
diarrhea
dehydration (from excessive urine formation and perspiration)
Septic shock (endotoxic shock)
The vascular collapse that results from bacterial septicemia. Infection with gram-negative organisms is the most common cause.

Invading bacteria are responsible for the release of endotoxin when lysed = LPS = lipopolysaccharide. Endotoxin binds to LBP = LPS-binding-protein, after which the complex binds to a a CD14 receptor on the surface of monocytes/mac's. This causes these cells to secrete TNF-alpha, which mediates septic shock by causing endothelial cell injury.
What are the mechanisms by which TNF-alpha mediates septic shock? (4)
direct cytoxicity

enhance the adherence of PMN leukocytes

stimulate the release of IL-1, a cytokine that injures endothelial cells

promoting the expression of procoagulant tissue factor, leading to thrombosis and local ischemia.
Systemic Inflammatory Response syndrome
In patients who survive the acute manifestations of shock, multiple organ failure may result from a systemic inflammatory respons.

2 or more signs of systemic inflammation: fever, tachycardia, tachypnea, leukocytosis, leukopenia.
What is the most important cause of SIRS (systemic inflammatory response syndrome)?
Systemic release of cytokines, particularly TNF, IL-1, IL-6, and PAF.
What are the mechanisms of edema formation?
increased hydrostatic pressure
decreased oncotic pressure
lymphatic obstruction
sodium retention
Factors that influence the development of an infarct (4)
(1) the nature of the vascular supply;
(2) the rate of development of the occlusion;
(3) the vulnerability of a given tissue to hypoxia; and
(4) the blood oxygen content.
Disorders associated with edema - increased hydrostatic pressure.
arteriolar dilatation
increased venous pressure
hypovolemia
disorders associated with edema - decreased oncotic pressure.
hypoproteinemia
increased capillary permeability
lymphatic obstruction
Stages of shock (3)
1. An initial nonprogressive phase during which reflex compensatory mechanisms are activated and perfusion of vital organs is maintained

2. A progressive stage characterized by tissue hypoperfusion and onset of worsening circulatory and metabolic imbalances, including acidosis

3. An irreversible stage that sets in after the body has incurred cellular and tissue injury so severe that even if the hemodynamic defects are corrected, survival is not possible.
Effect of shock - heart
petechial hemorrhages (of epicardium and endocardium.
effect of shock - kidney
acute tubular necrosis, acute renal failure
effect of shock - lung
interstitial pneumonitis = SHOCK LUNG.
effect of shock - GI tract
diffuse GI hemorrhage, ischemic necrosis in the intestines.
effect of shock - liver
centrilubular congestion
effect of shock - pancrease
acute pancreatitis
effect of shock - adrenals
hemorrhagic necrosis of the entire gland in the Waterhouse-Friderichsen syndrome (asso. with meningococcal septicemia)
Characteristics of the coagulation pathways.
both pathways are required for normal hemostasis and there are positive feedback loops between the 2 pathways that amplify reactions to produce enough fibrin to form a life-saving plus.

Regardless of whether extrinsic or intrinsic pathway starts coagulation, completion of the project follows a common pathway.
Definition of vascular malformations.
Developmental cutaneous anomalies, present at birth, characterized by commensurate growth.

"false" hemangiomas; developmental abnormalities.

NO INVOLUTING PHASE.
Pathology of hemangiomas.
2 phases:
1. proliferative phase that mjya last 3-9 months
2. slow regression phase (involution phase) that may last several years. most of them spontaneously regress by age 10-12 years.

Can be superficial or deep, depending on the layers of the skin involved.
Clinical features of hemangiomas.
Most COMMON TUMOR OF INFANCY.

Present at birth, commonly affects hte skin, mucous membranes of the oral cavities and lips, or internal organs (liver).

No clinical consequences, but may present complications.

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