Chapter 4: Embolism Flashcards
What is an embolus?
An embolus is a detached intravascular solid, liquid, or gaseous mass that is carried by the blood from its point of origin to a distant site, where it often causes tissue dysfunction or infarction
The vast majority of emboli derive from a dislodged thrombus. How is this called?
Thromboembolism
True/false: emboli that are very common: are composed of fat droplets, bubbles of air or nitrogen, atherosclerotic debris (cholesterol emboli), tumor fragments, bits of bone marrow, or amniotic fluid
False, these are less common
What are the primary consequence of systemic and pulmonary embolization?
The primary consequence of systemic embolization is ischemic necrosis (infarction) of downstream tissues, whereas embolization in the pulmonary circulation leads to hypoxia, hypotension, and right-sided heart failure.
True/false: Pulmonary emboli (PE) originate from deep venous thromboses and are responsible for the most common form of thromboembolic disease
True
What are the possible locations for pulmonary emboli (PE)?
Depending on size, a PE can occlude the main pulmonary artery, lodge at the bifurcation of the right and left pulmonary arteries (saddle embolus), or pass into the smaller, branching arterioles
True/false: small PE are often silent, not felt by the patient
True! With time, they undergo organization and become incorporated into the vascular wall; in some cases, organization of thromboemboli leaves behind bridging fibrous webs.
Does a large embolus that blocks a major pulmonary artery cause sudden death?
Yes
Fill in: Embolic obstruction of medium-sized arteries and subsequent rupture of downstream capillaries rendered anoxic can cause pulmonary hemorrhage/infarction
hemorrhage
(Such emboli do not usually cause pulmonary infarction because the area also receives blood through an intact bronchial circulation (dual circulation))
Fill in: Embolism to small end-arteriolar pulmonary branches usually causes hemorrhage/infarction
infarction
Multiple emboli occurring through time can cause …
pulmonary hypertension and right ventricular failure (cor pulmonale).
Most systemic emboli (80%) arise from intracardiac mural thrombi; two-thirds of these are associated with left ventricular infarcts and another 25% with dilated left atria (e.g., secondary to mitral valve disease). Where do the remainder originate from?
(please don’t learn this, just understand the concept)
Aortic aneurysms, thrombi overlying ulcerated atherosclerotic plaques, fragmented valvular vegetations, or the venous system (paradoxical emboli); 10% to 15% of systemic emboli are of unknown origin.
Do most venous emboli lodge in the lung?
Yeah
Do most arterial/systemic emboli lodge in the heart?
No, they can travel virtually anywhere
What are the most common sites of an arterial/systemic thromboembolism? And which are less common?
Common arteriolar embolization sites include the lower extremities (75%) and central nervous system (10%); intestines, kidneys, and spleen are less common targets
True/false: arterial/systemic embolism often leads to ischemia
False, the consequences of embolization depend on the caliber of the occluded vessel, the collateral supply, and the affected tissue’s vulnerability to anoxia; arterial emboli often lodge in end arteries and cause infarction.
How does a fat embolism arise?
Soft tissue crush injury or rupture of marrow vascular sinusoids (eg, due to a long bone fracture) release microscopic fat globules into the circulation
True/false: In 90% of the individuals with fat and marrow embolism, clinical findings are shown
False, only 10% show clinical findings
I don’t know if you really need to know this, but if you want to look at a fat embolism please see fig 4.16
Okki
What clinical symptoms can occur as a cause of fat embolism? (for illustration)
pulmonary insufficiency, neurologic symptoms, anemia, thrombocytopenia and a diffuse petechial rash (that might be fatal)
Explain the pathogenesis of fat emboli
just read this 1-2x
The pathogenesis of fat emboli syndrome involves both mechanical obstruction and biochemical injury. Fat microemboli occlude pulmonary and cerebral microvasculature, both directly and by triggering platelet aggregation. This deleterious effect is exacerbated by fatty acid release from lipid globules, which causes local toxic endothelial injury. Platelet activation and granulocyte recruitment (with free radical, protease, and eicosanoid release) complete the vascular assault.
What is amniotic fluid embolism?
Amniotic fluid embolism is an uncommon, grave compli- cation of labor and the immediate postpartum period occurring in 1 in 40,000 deliveries
Is amniotic fluid embolism fatal?
Yes in 80%! (making it the most common cause of maternal death)
and also 85% of the survivors suffer from permanent neurologic deficit! (not important but interesting)
How is the onset of amniotic fluid embolism characterized?
by sudden severe dyspnea, cyanosis, and hypotensive shock, followed by seizures and coma.
What is the underlying cause of amniotic fluid embolism?
The underlying cause is the entry of amniotic fluid (and its contents) into the maternal circulation via tears in the placental membranes and/or uterine vein rupture. Histologic analysis shows squamous cells shed from fetal skin, lanugo hair, fat from vernix caseosa, and mucin derived from the fetal respiratory or gastrointestinal tracts in the maternal pulmonary microcirculation
What is an air embolism?
Gas bubbles within the circulation can coalesce and obstruct vascular flow and cause distal ischemic injury. Thus, a small volume of air trapped in a coronary artery during bypass surgery or introduced into the cerebral arterial circulation by neurosurgery performed in an upright “sitting position” can occlude flow, with dire consequences.
Do small venous gas emboli cause harm?
No
A particular form of gas embolism called decompression sickness is caused by sudden changes in atmospheric pressure. Which jobs/activities are at risk for this decompression sickness?
Scuba divers, underwater construction workers, and persons in unpressurized aircraft who undergo rapid ascent
Explain how a diver that ascends too rapidly can form a gas emboli?
When air is breathed at high pressure (e.g., during a deep sea dive), increased amounts of gas (particularly nitrogen) become dissolved in the blood and tissues. If the diver then ascends (depressurizes) too rapidly, the nitrogen expands in the tissues and bubbles out of solution in the blood to form gas emboli
Do these air emboli cause hemorrhage?
No, they cause tissue ischemia
