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.

• Definition: potentially life-threatening condition caused by the entry of fat cells, usually from bone marrow, into the circulatory system
• Etiology
  • Traumatic fat embolism (95% of cases)
    • Most commonly long bone fractures (e.g., femoral fracture)
    • Orthopedic surgeries
    • Bone marrow transplant
  • Non-traumatic fat embolism
    • Sickle cell crisis
    • Others: pancreatitis, osteomyelitis, parenteral lipid infusion
• 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%

References:^{[1][2][3][4][5]}

• Definition: : potentially life-threatening condition caused by the entry of air into circulation, often during a surgical procedure
• Etiology
  • Surgery; : neurosurgical procedures (highest risk) ; laparoscopic surgery
  • Trauma
  • Barotrauma: mechanical ventilation ; decompression sickness
  • Accidental injection of air (infusion-related errors); intentional injection of air (suicidal/homicidal intent)
  • Central venous catheter (insertion and removal)

• 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 maneuver)
  • 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]

• Definition: rare, but life-threatening condition caused by the entry of fetal cells and debris (from the amniotic fluid) into maternal circulation
• Risk factors
  • Maternal age > 30 years
  • Multiparity
  • Complicated labor (e.g., placenta previa/abruption, forceps delivery, eclampsia)
• Clinical features
  • AFE mostly occurs during labor.
  • Acute onset of
    • Respiratory collapse: hypoxia; , dyspnea, tachypnea, cough, cyanosis, basal crepitations, acute respiratory distress syndrome
    • Cardiovascular collapse: hypotension; , arrhythmias, cardiac arrest
    • Altered consciousness (drowsiness, seizures)
    • Features of disseminated intravascular coagulation
    • Multi-organ dysfunction
    • Fetal bradycardia (decelerations on cardiotocography)
• Diagnosis: mainly clinical
  • Arterial blood gas evaluation: features of respiratory acidosis
  • Complete blood count: anemia, thrombocytopenia
  • Coagulation studies: prolonged prothrombin time (PT)
• Treatment
  • Correction of hypoxia: high flow oxygen or intubation and mechanical ventilation
  • Correction of hypotension/shock: vasopressors (noradrenaline or dopamine)
  • Correction of anemia and coagulopathy: transfusion of platelet/fresh frozen plasma (FFP) and packed red blood cells
  • Emergency cesarean delivery
• Prognosis
  • High maternal mortality rate
  • Neurological deficits in surviving infants

References:^{[10][11][12][13]}

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13. Pulmonary Air Embolism. https://radiopaedia.org/articles/pulmonary-air-embolism. Updated: March 27, 2017. Accessed: March 27, 2017.