Pathology XIII: Embolism, Infarction, and Shock

Question 1

What is an embolus?

Answer 1

a plug of material that travels through the bloodstream and lodges in a vessel. most arise from thrombi.

Question 2

What are the unusual types of embolus?

Answer 2

air, gas, fat, bone marrow, cholesterol, amniotic fluid, tumors, bacterial vegetation

Question 3

Where do pulmonary emboli come from?

Answer 3

90-95% arise from DVTs above the knee level. may be multiple or single.
a few come from other sourcesm like the right heart mural thrombi, cardiac valve vegetations, or nonthrombotic sources

Question 4

What three factors affect the risk of embolization of a thrombus?

Answer 4

location, free floating tail, and acute change in pressure or increase in blood flow (that’s why people die suddenly on airplanes when they get up).

Question 5

What is a saddle embolus?

Answer 5

embolus that lodges at a pulmonary bifurcation. causes sudden death/severe pulmonary compromise.

Question 6

Why is pulmonary hemorrhage common with a large embolus, while infarction is rare?

Answer 6

collateral circulation. infarction with hemoptysis (expectoration of blood), pain, and pleural inflammation

Question 7

What are some sources of systemic emboli?

Answer 7

mural thrombi from right atrium/ventricle
aorta (aneurysms or atherosclerotic plaques)
paradoxical (due to septal defect that allows emboli from venous system to enter systemic circ)

Question 8

What happens with a systemic emboli?

Answer 8

emboli lodge at arterial bifurcations, in small arteries, or in arteries occluded by atherosclerotic plaque. this leads to infarction/gangrene.

Question 9

What sites are usually the most affected by systemic emboli (4)

Answer 9

brain
kidney
spleen
lower extremities

Question 10

What happens with an air embolus? How big to be significant? How does it get there?

Answer 10

need 100 cc to be significant
air gains access to circ via delivery, pneumothorax, lung injury, injury to neck veins, suicide, apheresis (platelet donation), or rapid decompression causing dissolved nitrogen to bubble out of soln (the bends)

Question 11

What happens with fat or bone marrow emboli? What kind of damage can they cause? What causes these emboli to occur?

Answer 11

may be incidental, but can cause CNS or pulmonary symptoms or sudden death.
caused by sever traumatic injuries to bone/adipose tissue

Question 12

What should I know about amniotic fluid emboli? What does it cause?

Answer 12

fetal squamous cells, hair, mucous, debris enters the maternal circulation. this can lead to shock and DIC.
this is very rare but has a very high mortality rate.

Question 13

How does bacterial vegetation lead to embolization?

Answer 13

mitral or aortic valve bacterial endocarditis can lead to embolization. the do not usually cause significant infarction but can cause septic absesses in the brian and kindeys. right sided endocarditis in IV drug users can cause pulmonary abscesses

Question 14

What is the source of cholesterol emboli? What is there clinical significance/

Answer 14

flakes of atherosclerotic plaques from aortic lesions

found in kidneys. usually of little clinical significance.

Question 15

What is ischemia?

Answer 15

insufficient blood supply that causes tissue dysfunction or damage but not overt death

Question 16

What is hypoxia?

Answer 16

decreased O2 delivery to the tissue

Question 17

What is an infarction?

Answer 17

an area of necrosis from ischemic or anoxic injury

Question 18

What are some causes of infarction? (3 big ones)

Answer 18

arterial occlusion, reduced blood flow, or impaired oxygen delivery

Question 19

What are the causes of arterial occlusion that might lead to infarction?

Answer 19

atherosclerosis, thrombosis, embolism, compression (tumor), torsion or twisitin of a pedicle compromising blood supply.

Question 20

What are some causes of reduced blood flow that might lead to infarction?

Answer 20

hypotension, shock, severe venous obstruction

Question 21

What are causes of impaired oxygen delivery that might lead to infarction?

Answer 21

resp. obstruction (drowning, aspiration, pulmonary edema), or interference with hemoglobin-oxygen dissociation (CO poisoning)

Question 22

What is an anemic infarction?

Answer 22

pale/white
arterial obstruction in solid organs with dense parenchyma that limits amount of hemorrhage that can seep into the necrotic area from adjacent capillary beds (heart, kidney)
(obstruction in organs with dense parenchyma that prevents hemorrhage by nearby capillaries)

Question 23

What is hemorrhagic infarction?

Answer 23

red
arterial obstruction in organs with dual circulations where the alternate pathway is insufficient to maintain viability but allows blood seepage into the infarct (lung, intestine).
may also be caused by venous occlusions?

Question 24

What is the morphology of infarction, grossly?

Answer 24

early on, it may be hard to detect. WITHIN 24 HRS, you may see pale appearance due to coagulative necrosis, or mixed pale in tissues with dual blood supply. late stage has wedge shaped (spleen, kidney) or irregular (heart) pale area with hyperemic border. may evenually heal with fibrosis.

Question 25

What do you see microscopically with infarction?

Answer 25

early: coagulative necrosis; fluid exudates
mid: hyperemia on infarct periphery or in infarct, depending on the tissue. acute inflammation.
late: removal of debris by phagocytes with chronic inflammatory response, granulation tissue, fibrosis.

Question 26

Why is intestinal infarct especially problematic?

Answer 26

secondary infection- may necessitate surgical removal

Question 27

What is special about infarctions in the brain?

Answer 27

lead to liquefactive necrosis, followed by invasion of glial cells and formation of a smooth walled cystic cavity

Question 28

What four factors most affect the severity of ischemic injury?

Answer 28

nature of vascular supply, rate of development of the occlusion (slower is better bc it gives time for collateral circ to develop), vulnerability to hypoxia (neurons, heart cells, renal tubular cells esp. vulnerable); O2 content of the blood- anemia, COPD, etc. may tip balance toward infarction

Question 29

What is shock?

Answer 29

systemic reduction in tissue perfusion resulting in multiple organ dysfunction. often due to loss of blood volume or pressure

Question 30

causes of shock (5 main types)

Answer 30

hypovolemic
cardiogenic
septic
neurogenic
anaphylactic

Question 31

What are some common causes of hypovolemic shock?

Answer 31

hemorrhage, burns, trauma, vomiting, diarrhea. involves rapid blood loss, either external or internal.

Question 32

What are some causes of cardiogenic shock?

Answer 32

REDUCED CARDIAC OUTPUT:

MI, pulmonary embolus, arrhytmia, pericardial tamponade, ruptured valve or ventricular wall.

Question 33

What are some causes of septic shock?

Answer 33

LPS from gram neg organisms activates monocytes, endothelial cells. There are many inflammatory mediators that cause vasodilation, myocardial dysfunction, and endothelial injury.

Question 34

What is neurogenic shock?”

Answer 34

generally not a big deal- sudden loss of vascular tone. anasthesia, spinal cord injury potential causes.

Question 35

What are causes of anaphylactic shock?

Answer 35

vasoactive mediators released in IgE mediated sensitivity.

Question 36

What are four ways the body tries to compensate for shock?

Answer 36

vasoconstriction to maintain pressure
redistribution to vital organs (cutaneous vasoconstriction)
tachycardia
renal fluid conservation/decr. urine output

Question 37

Which kinds of shock have the worst prognosis?

Answer 37

endotoxic and cardiogenic.