• Clinical science

Nonthrombotic embolism

Abstract

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: a potentially life-threatening condition caused by the entry of fat cells, usually from bone marrow, into the circulatory system
  • Etiology
  • Pathophysiology
  • 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
        • Appears within 1–3 days; disappears within a week
  • 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
    • Since there are no specific diagnostic tests, the following clinical criteria are used to diagnose fat embolism.
Gurd's criteria
Major criteria Minor criteria

1 major + 4 minor criteria

confirms fat embolism

Petechial rash Fever

Hypoxia

Tachycardia
Neurological symptoms (see above) Anemia
Thrombocytopenia
Increased ESR
Renal dysfunction (anuria, oliguria, lipiduria)
Retinal changes (petechiae, fatty inclusions);
Fat globules in sputum
Schonfeld's criteria
Feature Score

Total score > 5 points

is diagnostic of fat embolism

Petechial rash 5
Bilateral infiltrates on chest x-ray 4
Hypoxia 3
Fever 1
Tachycardia 1
Tachypnea 1
Confusion 1
  • Treatment: supportive care in an intensive care unit
  • Prognosis: mortality rate ∼ 15%

References:[1][2][3][4][5]

Air embolism

  • Definition: potentially life-threatening condition caused by the entry of air into circulation, often during a surgical procedures
  • Etiology
Venous air embolism Arterial air embolism

Pathophysiology

  • Air enters the venous system → embolization to the right ventricle of the heart → right ventricular outflow block (air block) → circulatory collapse
  • Air enters the arterial system and gets lodged in arterioles/capillaries of end organs → ischemic damage
Clinical features
Diagnostics
  • Chest x-ray: air shadows (hyperlucency) in the pulmonary arteries and cardiac chambers
  • Chest CT: similar findings as on a chest x-ray; more sensitive
  • 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) In suspected arterial air embolism, the Trendelenburg position can worsen the cerebral edema caused by cerebral air embolism. The supine position is preferred in patients with suspected arterial air embolism.
    • Central venous line insertion and direct aspiration of air bubbles from the cardiac chambers
    • Chest compression (closed cardiac massage)
  • Prognosis: high mortality rate (≥ 30%)

References:[6][7][8][9]

Amniotic fluid embolism

References:[10][11][12][13]

Pulmonary cement embolism

  • Definition: respiratory insufficiency as a result of embolization of bone cement material or indirect systemic effects after bone cement implantation
  • Occurrence: after orthopedic procedures using bone cement material
  • Pathophysiology: direct mechanical embolization and thermal effects or an immunological-mediated release of vasoactive substances; often associated with fat embolism
  • Clinical features
  • Diagnostics: CT pulmonary angiogram for the detection of mechanical embolization
  • Treatment
    • Supportive (intensive care) measures, including mechanical ventilation and catecholamine therapy
    • If necessary, interventional or surgical removal of the embolic cement material