The mnemonic FAT BAT is useful to help recall the common causes of pulmonary embolism. These emboli sources are fat, air, thrombus, bacteria, amniotic fluid and tumor.
Fat emboli can occur from fracture of long bones, and are also associated with liposuction. A common exam question involves immobilized trauma patients developing fat embolisms.
Air can travel through the circulatory system and when in an artery, may directly stop blood flow to an area fed by the artery. Common causes of air emboli include surgery, trauma, scuba diving and being on a ventilator.
Pulmonary embolism most commonly occurs from thrombus formation which embolizes. A classic example of this is a DVT of the leg embolizing into the pulmonary arteries.
A cause of bacterial embolism is when an area of the body becomes infected with bacteria, resulting in the formation of pus. These may become dangerous if dislodged from their original location. Like other emboli, a septic embolism may be fatal.
Though rare and not completely understood, amniotic fluid can lead to pulmonary embolism. When amniotic fluid enters the mother's blood stream via the placental bed of the uterus and trigger an allergic reaction. This reaction then results in cardiorespiratory collapse.
Embolism can also occur from tumors that have broken off and made their way into the bloodstream.
Patients who are hypercoagulable are at increased risk for thrombus formation, which can then embolize into pulmonary flow.
Central venous lines can increase risk of pulmonary embolism. This is because as the line is changed (to prevent infection), clots may be released and can embolize from the catheter into pulmonary vasculature.
Patients who are immobile are at risk for thrombus formation and DVT. This can then embolize into the lungs.
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