• Clinical science

Nonthrombotic embolism


Embolisms of fat, air, and amniotic fluid are uncommon but potentially life-threatening events caused when these substances enter the circulatory system. Fat emboli mostly originate from the bone marrow in patients with long bone fractures. Air can enter the circulatory system during surgical procedures (mostly neurosurgery), while amniotic fluid emboli occur during delivery. The emboli usually lodge within the pulmonary arteries and cause right ventricular outflow obstruction and circulatory collapse. Clinical features of special embolisms typically include acute onset of hypoxia, hypotension, and neurological symptoms (altered consciousness, seizures, coma). The diagnostic sign of fat embolism is a petechial rash on the upper body (if present), while that of venous air embolism is a mill wheel cardiac murmur. Diagnosis of any type of special embolism is primarily clinical, with arterial blood gas evaluation, ECG, and chest x-ray providing additional evidence. Treatment is mainly supportive and includes oxygenation, mechanical ventilation, and administration of vasopressors, if necessary. Mortality rates of all types of special embolisms are high.

Fat embolism

  • Definition: potentially life-threatening condition caused by the entry of fat cells, usually from bone marrow, into the circulatory system
  • Etiology
  • Clinical features
    • Symptoms develop within 12 hours to 2 weeks of the inciting insult
    • Classic triad of
      1. Hypoxia (most common symptom): tachypnea, dyspnea, cyanosis, diffuse crackles in the chest
      2. Neurological symptoms: confusion, lethargy, seizures, focal neurological deficits, coma
      3. Petechial rash; (seen in up to 50% patients) : mainly seen in the axilla, chest wall, head, neck, conjunctiva, and buccal mucosa
  • Diagnosis: mainly clinical
    • Complete blood count: anemia, thrombocytopenia
    • Chest x-ray: mostly normal; bilateral infiltrates may be seen
    • Microscopic examination of urine and sputum: fat droplets may be seen
  • Treatment: supportive care in an intensive care unit
  • Prognosis: mortality rate ∼ 15%


Air embolism

  • Definition: : potentially life-threatening condition caused by the entry of air into circulation, often during a surgical procedure
  • Etiology
Venous air embolism Arterial air embolism
Clinical features
  • Chest x-ray: air shadows (hyperlucency) in the pulmonary arteries and cardiac chambers
  • Echocardiography: evidence of air in the (right) cardiac chambers
  • CT scan of the brain, abdomen, or pelvis may show ischemic changes in the affected organs.
  • Treatment
    • General measures
      • Compression of the suspected site of entry (airtight sealing)
      • Correction of hypoxia and hypotension
      • Initiate CPR, if necessary
    • Position change (venous air embolism): Trendelenburg (head down position) and left lateral decubitus (Durant's maneuver)
    • Central venous line insertion and direct aspiration of air bubbles from the cardiac chambers
  • Prognosis: high mortality rate (≥ 30%)


Amniotic fluid embolism