| Abstract: |
Background: An embolism occurs when an embolus migrates from one part of the body (through circulation) and causes a blockage (occlusion) of a blood vessel in another part of the body. The term was coined in 1848 by Rudolph Carl Virchow. This is in contrast with a thrombus, or clot, which forms at the blockage point within a blood vessel and is not carried from somewhere else. However, if a thrombus breaks loose from its location and travels to another location, it is then said to be an embolus and having caused an embolism. Embolization is a procedure to occlude blood vessels by purposely introducing emboli. Air embolism is a blockage of the main artery of the lung or one of its branches by a substance that has travelled from elsewhere in the body through the bloodstream (embolism). Usually this is due to embolism of a thrombus (blood clot) from the deep veins in the legs, a process termed venous thromboembolism. A small proportion is due to the embolization of air, fat or amniotic fluid. The obstruction of the blood flow through the lungs and the resultant pressure on the right ventricle of the heart leads to the symptoms and signs of PE. The risk of PE is increased in various situations, such as cancer and prolonged bed rest. Fat embolism is the occlusion of small blood vessels of the microcirculation by fat globules. It is encountered most often in patients suffering from severe traumatic injuries to fat laden tissues, such as fractures of long bones containing fatty marrow, or extensive damage to subcutaneous fat deposits e.g. liposuction. Increased pressure within the marrow cavity causes rupture of small venules and fat globules enter the circulation. Another theory is based on physiochemical changes in the circulating blood lipids. Amniotic fluid embolism syndrome (also called anaphylactoid syndrome of pregnancy) is a catastrophic condition that occurs during pregnancy or shortly after delivery. Although first reported in 1926, it was not widely recognized until 1941 when an autopsy series of eight women who had died from sudden shock during labor reported squamous cells and mucin of fetal origin in the maternal pulmonary vasculature. Fetal squamous cells have also been described in the vascular beds of the maternal kidneys, liver, spleen, pancreas, and brain. Amniotic fluid embolism syndrome is reviewed here. The management of critically ill obstetric patients is discussed separately, including those with venous thromboembolism. The first recorded case of air embolism in the medical literature is that occurring in a French Locksmith in 1918. Sporadic reports followed this, and air embolism as a complication during anaesthesia was not common until the use of controlled respiration (for neurosurgery in sitting position). Increase in incidence was secondary to the introduction of muscle relaxants and the low venous pressure which followed their use in the upright position. The true, and much larger incidence of air embolism has been revealed in prospective studies, and by the use of the Doppler ultrasound device. The pathophysiology of fat embolism syndrome has not yet been definitively characterized. A mechanical theory holds that fat embolism results from physical obstruction of the pulmonary and systemic vasculature with embolized fat. Increased intramedullary pressure after injury forces marrow into injured venous sinusoids, from which the fat travels to the lung and occludes pulmonary capillaries. Fat emboli can cause cor pulmonale if adequate compensatory pulmonary vasodilation does not occur.Objectives: The aim of the study is to discuss different types of embolism particularly air, fat, and amniotic fluid embolism which are of great importance as a complication in anaesthetic practice.
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