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5 embolism


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for Undergraduate medical students (MBBS)

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5 embolism

  2. 2. Def: 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.
  3. 3. Almost all emboli represent some part of a dislodged thrombus Unless specified embolism means Thromboembolism
  4. 4. Rare forms of emboli  droplets of fat  bubbles of air or nitrogen  Cholesterol emboli from AS debri  tumor fragments  bits of bone marrow, or even  foreign bodies such as bullets
  5. 5. Effect of embolus Occlusion Emboli lodge in vessels too small to permit further passage, resulting in partial or complete vascular occlusion
  6. 6. Consequences Infarction The potential consequence of such thromboembolic events is the ischemic necrosis of distal tissue, known as infarction
  7. 7. Clinical outcome Depends on: the site of origin & the site of lodgment The clinical outcomes are best understood from the standpoint of whether emboli lodge in the pulmonary or systemic circulations.
  8. 8. Saddle embolus Lerisch syndrome Paradoxical embolism
  9. 9. PULMONARY THROMBOEMBOLISM •Incidence of 20 to 25 per 100,000 hospitalized patients •In more than 95% of instances, venous emboli originate from deep leg vein thrombi •Depending on the size of the embolus, it may occlude the main pulmonary artery, impact across the bifurcation (saddle embolus), or pass out into the smaller, branching arterioles •in general, the patient who has had one pulmonary embolus is at high risk of having more. •Rarely, an embolus may pass through an interatrial or interventricular defect to gain access to the systemic circulation (paradoxical embolism)
  10. 10. • Most pulmonary emboli (60% to 80%) are clinically silent because they are small. With time, they undergo organization and are incorporated into the vascular wall in some cases, organization of the thromboembolus leaves behind a delicate, bridging fibrous web. • Sudden death, right heart failure (cor pulmonale). or cardiovascular collapse occurs when 60% or more of the pulmonary circulation is obstructed with emboli. • Embolic obstruction of medium-sized arteries may result in pulmonary hemorrhage but usually does not cause pulmonary infarction because of the dual blood flow into the area from the bronchial circulation. A similar embolus in the setting of left-sided cardiac failure (i.e., with sluggish bronchial artery flow), however, may result in a large infarct. • Embolic obstruction of small end-arteriolar pulmonary branches usually does result in associated infarction. • Multiple emboli over time may cause pulmonary hypertension with right heart failure. PULMONARY THROMBOEMBOLISM
  11. 11. Consequences of Pul.embolism • The morphologic consequences depend on the size of the embolic mass and the general state of the circulation • Large emboli - Sudden death often ensues - acute cor pulmonale (ECG-elecromechanical dissociation) • Smaller emboli – with good CVS – hemorrhages resorption & reconstitution of the preexisting architecture – with CVS compromise - 10% infarction
  12. 12. Here is large pulmonary thromboembolus seen in cross section of this lung. The typical source for such thromboemboli is from large veins in the legs and pelvis.
  13. 13. Figure 4-17 Large embolus derived from a lower extremity deep venous thrombosis and now impacted in a pulmonary artery branch
  14. 14. Pulmonary thromboembolus
  15. 15. Recent, small, roughly wedge-shaped hemorrhagic pulmonary infarct
  16. 16. Non thrombotic forms of pul.emboli • uncommon but potentially lethal • air (may be iatrogenic) • bone marrow (after trauma and bone marrow necrosis in sickle cell patients) • fat (trauma and surgery) • amniotic fluid (during parturition) and • foreign bodies (in I/V drug abusers)
  17. 17. SYSTEMIC THROMBOEMBOLISM • refers to emboli travelling within the arterial circulation • Common source: Mural thrombi in heart (80%) • Less common source: Aorta (AS, Aneurysm)
  18. 18. Mural thrombi
  19. 19. SYSTEMIC THROMBOEMBOLISM The major sites for arteriolar embolization • Lower extremities (75%) and • Brain (10%) • the intestines, kidneys, spleen, and upper extremities involved to a lesser extent
  20. 20. SYSTEMIC THROMBOEMBOLISM The consequences of systemic emboli depend on: the extent of collateral vascular supply in the affected tissue the tissue's vulnerability to ischemia and the caliber of the vessel occluded in general, arterial emboli cause infarction of tissues downstream of the obstructed vessel
  21. 21. Tissues supplied by end-arteries without significant collateral supplies will be the most susceptible. Obstruction of blood supply leads to ischemia which when prolonged leads to necrosis and atrophy. Where there is reperfusion after ischemic necrosis the tissues will show a hemorrhagic necrosis. Where there is infection by Clostridia (gram positive bacilli), gangrene sets in.
  22. 22. FAT EMBOLISM • Presence of microscopic fat globules in the circulation • Causes: # of long bones Soft tissue trauma Burns
  23. 23. FAT EMBOLISM Fat embolism syndrome is characterized by pulmonary insufficiency, neurologic symptoms, anemia, and Thrombocytopenia Symptoms: typically begin 1 to 3 days after injury, sudden onset of tachypnea, dyspnea, and tachycardia
  24. 24. FAT EMBOLISM Fat embolism syndrome: Pathogenesis mechanical obstruction and biochemical injury Fat globule platelet complexes Fat globule RBC complexes Release of FFA > toxic injury to endothelium > inflammation > further damage to the vessels
  25. 25. FAT EMBOLISM Demonstration of fat embolism in specimens: By means of frozen sections Routine processing dissolves fat
  26. 26. Figure 4-18 Bone marrow embolus in the pulmonary circulation. The cleared vacuoles represent marrow fat that is now impacted in a distal vessel along with the cellular hematopoietic precursors.
  27. 27. AIR EMBOLISM • Gas bubbles within the circulation can obstruct vascular flow • Entry of gas into circulation occurs during Obstetric procedures Chest wall injury
  28. 28. AIR EMBOLISM Dose: should be > 100ml to produce any clinical effect Bubbles act like physical obstructions and may coalesce to form frothy masses sufficiently large to occlude major vessels
  29. 29. AIR EMBOLISM Decompression sickness: Scuba and deep sea divers, underwater construction workers, and individuals in unpressurized aircraft Gas: Nitrogen Clinically: bends, chokes, ischemia, infarction Treatment: slow decompression Caisson disease: chronic form of decompression sickness
  30. 30. AMNIOTIC FLUID EMBOLISM Uncommon complication of laborUncommon complication of labor Has a mortality rate of 20% to 40% Clinically: sudden severe dyspnea, cyanosis, and hypotensive shock, followed by seizures and coma Pathogenesis: DIC The underlying cause: infusion of amniotic fluid or fetal tissue into the maternal circulation via a tear in the placental membranes or rupture of uterine veins The classic findings: the presence in the pulmonary microcirculation of squamous cells shed from fetal skin, lanugo hair, fat from vernix caseosa, and mucin derived from the fetal respiratory or gastrointestinal tract
  31. 31. E N D