EMBOLISM

Embolism Dedinition The process of impaction of an insoluble solid, liquid or gaseous mass (embolus) in a narrow vessel transported to it through the blood stream.

Classification I- According to the consistency 1) Solid : a. detached thrombi and vegetations (commonest cause) b. tumor fragments . c. atherosclerotic debris (cholesterol emboli) d. parasitic emboli

a. nitrogen bubles (Caisson disease) b. Air 2) Liquid : a. fat droplets b. amniotic fluid 3) Gas : a. nitrogen bubles (Caisson disease) b. Air

II- According to the site of origin : 1) Venous emboli 2) Arterial emboli III- According to sepsis : 1) Septic emboli (containing microrganims) 2) Aseptic emboli (sterile)

Effect of emboli depends upon 1) Nature of embolus (septic or aseptic) 2) State of collateral circulation in the affected organ 3) Size of embolus

So * aseptic embolus produces transient ischemia if the collateral circulation is good and infarction when poor. * septic embolus produces pyemic abscess at the site of its impaction.

Venous emboli Sources 1- 90-95% of cases arise from thrombi in large deep veins of leg : femoral, popliteal and iliac veins (after prolonged bed rest) 2- Rarely from pelvic veins , IVC or others(after labour or pelvic operation)

Fate Effects of pulmonary embolism Venous emboli drain through progressively larger channels >>> right heart >>> to be lodged in the pulmonary circulation. Effects of pulmonary embolism Big embolus >>> occludes the pulmonary artery or one of its main branches >>>

to acute right sided heart failure . 2) Medium sized embolus Death occurs in seconds to minutes due to acute right sided heart failure . 2) Medium sized embolus * if the lung is healthy >>> no effect as the lung has double blood supply . * in CVC of lung >>> pulmonary infarction . 3) Small sized embolus >>> no effect .

Special types Saddle embolus large embolus impacted at the bifurcation of main pulmonary artery. Paradoxical embolus venous embolus that enters the right side of heart and passes through interatrial or interventricular septal defects to enter the arterial systemic circulation.

Arterial emboli Sources Intracardiac mural thrombi (commonest) Mural thrombi in aortic aneurysm Atherosclerotic plaques in aorta Fragmentation of vegetations

Fate Arterial emboli follow a shorter pathway (because the vessels are progressively decreasing in diameter) Finally , they lodge in a vessel having a smaller diam. than their own >>> infarction of the organ supplied.

Fat embolism Rare and is caused by : Burns Fractures of shafts of long bones (fatty marrow) Burns Soft tissue trauma and inflammation of fatty tissue . The fat globules enter through the ruptured veins and produce pulmonary or systemic embolism

Amniotic fluid embolism refers to the presence in mother’s blood vessels of amniotic fluid (containing scales from fetal skin , lanugo hair and fat from vernix caseosa)

It occurs in old multiparous patients who have a had difficult delivery>>>strong uterine contractions >>> uteroplacental , fetal membranes and uterine or cervical tear with lacerations >>> amniotic fluid is pushed to the maternal circulation through an opened vein >>> fatal pulmonary embolism to the mother .

Air embolism Small amount of air < 50 c.c. is harmless. But if more >>> cardiac contraction and acute heart failure. Injury to large neck veins . Air is sucked by the negative pressure in the thorax. Faulty technique in doing artificial pneumothorax and in blood transfusion.

3. Caisson’s disease (decompression sickness) it occurs in individuals exposed to sudden lowering of atmospheric pressure : e.g. : deep sea divers or individuals in unpressurised aircrafts.

Deep sea divers, their blood gases (N2 , O2 and CO2) dissolve in their blood under high pressure . When they ascend quickly to the surface (low atmospheric pressure), these dissolved gases become undissolved and form small bubbles within the circulation . O2 and CO2 are redissolved , but N2 is less soluble and persists as small bubbles in blood .

These bubbles are trapped in the circulation GAS EMBOLI >>> blocking of circulation and hypoxic injury to the cells . This condition is corrected and treated by placing the individual in a compression chamber where barometric pressure is raised >>> dissolution of N2 gas bubbles , then slow decompression of the individual .

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