Nonthrombotic Pulmonary Embolism

Air embolism is caused by introduction of large amounts of air into systemic veins or into the right side of the heart, which then move to the pulmonary arterial system. Pulmonary outflow tract obstruction may occur, which can be rapidly fatal.

Causes include

Treatment includes placement of the patient in the left lateral decubitus position, preferably in the Trendelenburg position (ie, head lower than the feet), to trap air in the apex of the right ventricle and thus prevent brain embolism and main pulmonary artery outflow obstruction. Supportive measures are also needed.

Rapid decompression after underwater diving may cause microbubble formation in the pulmonary circulation, a different problem, which results in endothelial damage, hypoxemia, and diffuse infiltrates (see Arterial Gas Embolism Arterial Gas Embolism Arterial gas embolism is a potentially catastrophic event that occurs when gas bubbles enter or form in the arterial vasculature and occlude blood flow, causing organ ischemia. Arterial gas... read more ).

Fat embolism is caused by introduction of fat or bone marrow particles into the systemic venous system and then into pulmonary arteries. Causes include fractures of long bones, orthopedic procedures, microvascular occlusion or necrosis of bone marrow in patients with sickle cell crisis, and, rarely, toxic modification of native or parenteral serum lipids. Certain procedures such as liposuction, particularly with fat grafting, place patients at risk.

Fat embolism causes a pulmonary syndrome similar to acute respiratory distress syndrome Acute Hypoxemic Respiratory Failure (AHRF, ARDS) Acute hypoxemic respiratory failure is defined as severe hypoxemia (PaO2 (See also Overview of Mechanical Ventilation.) Airspace filling in acute hypoxemic respiratory failure (AHRF) may result... read more (ARDS), with severe hypoxemia of rapid onset often accompanied by neurologic changes and a petechial rash.

Early splinting of fractures of long bones and operative rather than external fixation are thought to help prevent fat embolism.

Amniotic fluid embolism is a rare syndrome caused by introduction of amniotic fluid into the maternal venous and then pulmonary arterial system. The syndrome occurs around the time of labor (amniotic fluid embolism Amniotic Fluid Embolism Amniotic fluid embolism is a clinical syndrome of hypoxia, hypotension, and coagulopathy that results from entry of fetal antigens into the maternal circulation. Amniotic fluid embolism is a... read more ) or, even less often, during prepartum uterine manipulations.

Patients can have cardiac and respiratory distress due to anaphylaxis, vasoconstriction causing acute severe pulmonary hypertension, and direct pulmonary microvascular toxicity with hypoxemia and pulmonary infiltrates.

Septic embolism occurs when infected material embolizes to the lung. Causes include IV drug use, right-sided infective endocarditis Infective Endocarditis Infective endocarditis is infection of the endocardium, usually with bacteria (commonly, streptococci or staphylococci) or fungi. It may cause fever, heart murmurs, petechiae, anemia, embolic... read more , and septic thrombophlebitis.

Septic embolism causes symptoms and signs of pneumonia (eg, fever, cough, sputum production, pleuritic chest pain, dyspnea, tachypnea, and tachycardia) or sepsis (eg, fever, hypotension, oliguria, tachypnea, tachycardia, and confusion). Initially, nodular opacities appear on the chest x-ray; the appearance may progress to peripheral infiltrates, and emboli may cavitate (particularly emboli caused by Staphylococcus aureus).

Treatment includes that of the underlying infection.

Foreign body embolism caused by introduction of particulate matter into the pulmonary arterial system, usually by IV injection of inorganic substances, such as talc by heroin users or elemental mercury by patients with mental disorders.

Focal pulmonary infiltrates may result.

Tumor embolism is a rare complication of cancer (usually adenocarcinoma) in which neoplastic cells from an organ enter the systemic venous and pulmonary arterial system, where they lodge, proliferate, and obstruct flow. Benign metastasizing leiomyoma may also embolize to the lung.

Patients typically present with dyspnea and pleuritic chest pain and signs of cor pulmonale that develop over weeks to months.

The diagnosis may be suggested by micronodules or diffuse pulmonary infiltrates on chest x-ray or CT scan, but these findings are neither very sensitive nor specific. The diagnosis can be confirmed by biopsy or occasionally by cytologic aspiration and histologic study of pulmonary capillary blood.

Cement embolism may develop after certain procedures such as vertebroplasty