Learning objectives

• Describe common causes of VAE and high-risk procedures
• Prevent VAE
• Manage VAE 

Definition and mechanisms

• Venous air embolism (VAE) is caused by the ingress of gas into the venous system, most commonly air
• Rare iatrogenic complication in a wide range of clinical scenarios involving line placement, trauma, barotrauma, and several types of surgical procedures including cardiac, vascular, and neurosurgery 
• Traditionally, surgery and trauma were the most significant causes of air embolism; now, endoscopy, angiography, tissue biopsy, thoracocentesis, hemodialysis, and central/peripheral venous access comprise a greater proportion
• May cause end-organ ischemia or infarction.
• May cause direct endothelial injury leading to the release of inflammatory mediators, activation of the complement cascade, and in situ thrombus formation

Signs & symptoms

• The presentation of VAE is dependent on the rate and volume of air entrained; Signs include:
  • Apnea
  • Hypoxia
  • Cardiopulmonary collapse
  • Tachypnea
  • Tachycardia
  • Hypotension
  • Altered mental status
  • Decreased conscious level 
  • Focal neurological deficits
  • ‘Mill wheel’ murmur on cardiac auscultation 
  • Pulmonary edema may develop later
  • Light-headedness, vertigo
  • Breathing difficulties
  • Shortness of breath
  • Chest pain 
  • Sense of impending death
  • ETCO2 falls
  • Arterial oxygen saturation falls
  • Hypoxemia
  • ECG abnormalities (tachyarrhythmias, atrioventricular block, signs of right ventricular strain, ST-segment elevation or depression, non-specific T wave changes)
• Transesophageal echocardiography is the most reliable monitor to detect VAE

Prevention

• Patient positioning: avoid the sitting position and Trendelenburg position during the insertion of central venous catheters, try to prevent a negative gradient between the open site veins and the right atrium (increasing right atrial pressure via leg elevation and using the “flex” option on the operating table control)
• Holding ventilation when placing tunnel catheters
• Removal of temporary catheter synchronized with active exhalation/Valsalva maneuver or positive end-expiratory pressure
• Avoid nitrous oxide

Management

Suggested reading

• Chuang DY, Sundararajan S, Sundararajan VA, Feldman DI, Xiong W. Accidental Air Embolism. Stroke. 2019;50(7):e183-e186.
• McCarthy CJ, Behravesh S, Naidu SG, Oklu R. Air Embolism: Diagnosis, Clinical Management and Outcomes. Diagnostics (Basel). 2017;7(1):5. Published 2017 Jan 17.
• Mirski MA, Lele AV, Fitzsimmons L, Toung TJ. Diagnosis and treatment of vascular air embolism. Anesthesiology. 2007;106(1):164-177.
• Webber S, Andrzejowski J, Francis G. Gas embolism in anaesthesia. BJA CEPD Reviews. 2002;2(2):53-7.