Arterial gas embolism

Background

• Also known as "air embolism"
• May be fatal when air entry reaches 200-300 mL (pressure gradient of 5 mmHg across 14 ga catheter entrains air at 100 mL/sec)
• Dialysis related
  • Due to negative intrathoracic pressure from spontaneous breathing
• Scuba related
  • Results from pulmonary barotrauma (most common) and decompression sickness

Prevention

• Positive pressure mechanical ventilation reduces positive pressure gradient
• Trendelenburg for insertion/removal of IJV and subclav lines
• Reverse Trendelenburg for femoral

Clinical Features

• Asymptomatic
• Mild: dyspnea, cough
• Cardiogenic shock: hypotension, oliguria, altered mental status, chest pain
• Dialysis related
  • Acute dyspnea, chest tightness, LOC, cardiac arrest, arrhythmia
• Scuba related
  • Symptoms develop during ascent or immediately upon surfacing
  • Causes variety of stroke syndromes depending on part of brain affected
    • Immediate death, loss of consciousness, seizure, blindness, hemiplegia

Differential Diagnosis

Dialysis Complications

• Dialysis-associated hypotension
• Dialysis disequilibrium syndrome
• Air embolism
• Missed dialysis (pulmonary edema)

Diving Emergencies

• Barotrauma of descent
  • Otic barotrauma
  • Pulmonary barotrauma
  • Sinus barotrauma
  • Mask squeeze
  • Barodentalgia (trapped dental air causing squeeze)
• Barotrauma of ascent
  • Pulmonary barotrauma (pulmonary overpressurization syndrome)
  • Decompression sickness (DCS)
  • Arterial gas embolism
  • Alternobaric vertigo
  • Facial baroparesis (Bells Palsy)
• At depth injuries
  • Oxygen toxicity
  • Nitrogen narcosis
  • Hypothermia
  • Contaminated gas mixture (e.g. CO toxicity)
  • Caustic cocktail from rebreathing circuit

Evaluation

Cerebral air embolism with multiple air bubbles.

Fatal cerebral arterial gas embolism. (a) CT head showing air bubbles predominantly in the right cerebral hemisphere (b) CT head showing air bubbles predominantly in the right cerebral hemisphere

• Low ETCO2 in significant venous air embolism
• TEE: most sensitive, invasive not available in emergencies
• Doppler US: noninvasive; air in chamber = high pitch sound

Management

• Central line aspiration of air from right heart
• 100% O2 non-rebreather
  • Regardless of SaO2 (to reduce embolism size)
• Hemodynamic support with positive inotropes
• CPR in large air embolus
• Positioning
  • Durant's maneuver - left lateral decubitus and Trendelenburg
  • Traps air in apex of RV, relieves obstruction of pulmonary outflow tract
• May require open surgical or angiography for recovery of residual intracardiac or intrapulmonary air

Dialysis Related

• Prevent any further air entry
  • Immediately cover puncture site with saline soaked gauze

Scuba Related

• IVF (increases tissue perfusion)
• Rapid recompression

Disposition

• Likely admission

See Also

• Dialysis complications
• Scuba diving emergencies