Merck Manual

Please confirm that you are a health care professional

honeypot link

Nonthrombotic Pulmonary Embolism


Victor F. Tapson

, MD, Cedars-Sinai Medical Center

Last review/revision Jun 2021 | Modified Sep 2022
View Patient Education

Nonthrombotic sources of pulmonary embolism include air, fat, amniotic fluid, infected material, foreign bodies, and tumors.

Pulmonary embolism (PE) can arise from nonthrombotic sources. PE caused by nonthrombotic sources results in clinical syndromes that differ from those caused by thrombotic PE Pulmonary Embolism (PE) Pulmonary embolism (PE) is the occlusion of pulmonary arteries by thrombi that originate elsewhere, typically in the large veins of the legs or pelvis. Risk factors for pulmonary embolism are... read more Pulmonary Embolism (PE) . Diagnosis is usually based in part or completely on clinical criteria, including, in particular, the patient's risk. Treatment includes supportive measures.

Air 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

  • Surgery

  • Blunt trauma

  • Defective or uncapped venous catheters

  • Errors occurring during insertion or removal of central venous catheters

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

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.

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

Amniotic fluid 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

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

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

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

Cement embolism may develop after certain procedures such as vertebroplasty

Drugs Mentioned In This Article

Drug Name Select Trade
Sclerosol, STERITALC
View Patient Education
NOTE: This is the Professional Version. CONSUMERS: View Consumer Version
quiz link

Test your knowledge

Take a Quiz!