Harvey's Garden

Nonthrombotic embolism

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Air Embolism

  • Epidemiology & Risk Factors

    • Iatrogenic (Most common): Central venous catheter (CVC) insertion/removal (esp. if pt is sitting up or taking a deep inspiration). c
    • Surgical: Neurosurgical procedures in the sitting position (e.g., posterior fossa tumor resection), cardiothoracic surgery.
    • Barotrauma: Scuba diving (rapid ascent), positive pressure ventilation (alveolar rupture).
    • Trauma: Penetrating chest trauma.

  • Clinical Features

    • Venous Air Embolism (VAE): Sudden onset dyspnea, tachypnea, hypoxemia, cough.
    • Hemodynamics: Obstructive shock (hypotension, tachycardia, ↑ JVP, sudden ↓ in ETCO2).
    • Auscultation: “Mill-wheel” murmur (loud, churning, continuous machine-like murmur over the precordium).
    • Arterial Air Embolism (AAE): Occurs via paradoxical embolism (e.g., patent foramen ovale[PFO], ASD) or direct pulmonary vein entry. Presents with acute neurologic deficits (stroke-like sx, altered mental status, seizures) or myocardial ischemia.

  • Diagnosis

    • Initial/Screening: Primarily a clinical diagnosis. Intraoperative monitoring shows sudden drop in end-tidal CO2 (ETCO2) due to ↑ alveolar dead space.
    • Confirmatory/Gold Standard: Transesophageal echocardiogram (TEE). Most sensitive modality; visualizes air bubbles in the right atrium/ventricle or crossing a PFO.
    • Key Labs/Imaging: ABG shows hypoxemia and hypercapnia. CT head/chest may reveal air pockets but is rarely done acutely due to HD instability.

  • Differential Diagnostics

    • Thrombotic Pulmonary Embolism: Diff by timeline and triggers (e.g., prolonged immobility, active cancer vs. sudden onset during CVC removal); lacks the classic mill-wheel murmur.
    • Tension Pneumothorax: Diff by unilateral absent breath sounds, hyperresonance to percussion, and tracheal deviation.
    • Acute Myocardial Infarction: Diff by classic ECG findings (ST elevations), though AAE can cause coronary ischemia; onset is typically less abrupt than an iatrogenic air embolism.

  • Management

    1. Immediate/First-line:
      • Stop further air entry: Immediately occlude the CVC site/leak (or flood surgical field with saline).
      • Positioning: Place pt in Left lateral decubitus AND Trendelenburg (Durant’s maneuver). Mechanism: Traps air in the right ventricular apex, preventing it from entering and obstructing the right ventricular outflow tract (RVOT) and pulmonary artery.
      • Oxygenation: Administer 100% O2 (creates a diffusion gradient that accelerates resorption of nitrogen from the air bubble).
    2. Second-line: Aspiration of air via a CVC (if the catheter tip is already situated in the right atrium). Provide hemodynamic support (IVF, vasopressors).
    3. Refractory/Special Circumstances: Hyperbaric Oxygen Therapy (HBOT). Treatment of choice for Arterial Air Embolism (especially with severe neurologic deficits or HD instability) to rapidly decrease bubble size.

  • Complications

    • Cardiovascular collapse and cardiac arrest (due to RVOT obstruction), Cardiac arrhythmia
    • Cerebral infarction (stroke).
    • Myocardial infarction.
    • Death.

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