Search
air embolism
gas/air bubbles in the vacsular system
Etiology:
- surgery, neurosurgery in sitting position
- central venous catheterization
- penetrating & blunt chest trauma
- high-pressure mechanical ventilation
- thoracocentesis
- hemodialysis
- other invasive vascular procedures
- radiocontrast injection for computerized tomography
- direct injection into the vein
- rare cases of air embolism from the uterus or tears in female genitalia
- see related bends
Pathology:
- can occur whenever a blood vessel is open & a pressure gradient exists favoring entry of gas
- pressure in most arteries & veins is greater than atmospheric pressure, thus an air embolus does not accompany most blood vessel injuris
- in the veins of the head & neck, pressure is less than atmospheric; these veins are at risk
- when air enters the veins, it travels to the right heart, & then to the lungs
- this can cause the vessels of the lung to constrict, resulting in pulmonary hypertension
- if the right atrial pressure is sufficient in patients with a patent foramen ovale, the gas bubble can reach the left atrium, & on to the brain or coronary arteries
- in most cases venous air embolisms stop in the lungs & cause no symptoms
Laboratory:
- neither sensitive or specific
- arterial blood gas:
- hypoxemia, hypercapnia, & metabolic acidosis secondary to right-to-left pulmonary shunting
- hypoxia, hypocapnia, respiratory alkalosis similar to pulmonary embolism
Special laboratory:
- transesophageal echocardiography
- central venous catheter
- aspiration of air can help make the diagnosis
- useful for monitoring central venous pressure
Radiology:
- chest X-ray may be normal, but can detect
- gas in pulmonary arterial system
- pulmonary arterial dilatation
- focal oligemia (Westermark sign)
- pulmonary edema
- computed tomography can detect
- air emboli in the central venous system
- pneumothorax
- hemothorax
- emphysematous blebs
Management:
- abort offending procedure
- during central venous catheterization, one attempt at aspirating air back from line may be useful
- the tip of the catheter should be in the right atrium
- place patient in Trendelenburg, left lateral decubitus position
- helps trap air in apex of right ventricle
- supportive therapy
- recompression in a recompression chamber
- hyperbaric oxygen (more easily tolerated than nitrogen)
- prevention:
- tilt the head of the bed down when inserting or removing a central venous catheter from the jugular vein or subclavian vein
Useful
bends (Caisson disease, decompression disease)
General
embolism
References
- Wikipedia: Air embolism
http://en.wikipedia.org/wiki/Air_embolism
- Natal BL
eMedicine (Medscape): Venous Air Embolism
http://emedicine.medscape.com/article/761367-overview