Air embolism is an uncommon, but potentially catastrophic, event that occurs as a consequence of the entry of air into the vasculature. Venous air embolism (also called pulmonary air embolism) occurs when air enters the systemic venous circulation and travels to the right ventricle and pulmonary circulation. In contrast, arterial air embolism occurs when air enters the arterial system. Arterial air embolism can produce ischemia in any organ that has insufficient collateral circulation [1-4].
The causes, pathophysiology, clinical features, diagnosis, treatment, and prognosis of air embolism are reviewed here. Embolization of thrombi, amniotic fluid, fat, or tumor is discussed separately. (See "Overview of acute pulmonary embolism" and "Amniotic fluid embolism syndrome" and "Fat embolism syndrome" and "Pulmonary tumor embolism".)
Two conditions must exist for air embolism to occur. There must be direct communication between a source of air and the vasculature, and there must be a pressure gradient favoring the passage of air into the circulation rather than bleeding from the vessel. The clinical settings associated with air embolism are listed in the table (table 1) [1,2,5,6]. They can be conceptualized as three general categories: surgery and trauma, intravascular catheterization, and barotrauma.
Surgery and trauma — Venous air embolism complicates neurosurgical and otolaryngological procedures more often than other types of surgical procedures. The major reason for this is that the surgical incision is usually superior to the heart at a distance that is greater than the central venous pressure. This sets up a condition of negative venous pressure relative to the atmosphere, which favors the passage of air into the circulation, especially when the patient is in a sitting position (ie, Fowler’s position) [7,8]. The estimated incidence of venous air embolism during neurosurgical procedures ranges from 10 percent (for surgical patients in the prone position) to 80 percent (for patients undergoing repair of cranial synostosis in Fowler's position) [1,7,9-12].
Venous air embolism has been reported following neodymium-yttrium-aluminum-garnet (Nd:YAG) laser treatment of endobronchial lesions, probably due to the coolant gas from the bronchoscope entering the systemic circulation through pulmonary venules [2,13]. It has also been described during needle biopsy of the lung , lung resection , arthroscopy , total joint arthroplasty , hysteroscopy [18-22], laparoscopy , cesarean section , colonoscopy , cardiopulmonary bypass , and various types of trauma [27,28]. (See "Bronchoscopic laser resection", section on 'Complications' and "Hysteroscopy: Managing fluid and gas distending media", section on 'Gas embolism' and "Rare complications of endoscopic retrograde cholangiopancreatography (ERCP)", section on 'Portal vein gas and air embolism'.)