Considering air embolism

Letters

CJEM 2004;6(2):77-78

To the Editor: I would like to commend Dr. Tang for her excellent discussion of paradoxical embolism consequent to arterialization of venous thrombi through a right-to-left shunt.¹

A related phenomenon, paradoxical air embolism, has been of interest to the diving medicine community, since it may account for at least some cases of "undeserved" neurological decompression sickness occurring on relatively conservative dives within the limits of standard dive tables.^2,3 Venous gas bubbles forming after normal dives are usually filtered and eliminated harmlessly in the pulmonary vasculature; however, there remains a chance that bubbles can pass across a patent foramen ovale, present in perhaps 28% of the general population, into the arterial circulation.⁴ This is a separate mechanism from cerebral air embolism, occurring secondary to pulmonary barotrauma in divers who breath-hold on ascent from scuba dives.

There have also been many cases of iatrogenic arterial air embolism reported in the literature following inadvertent air injection at central line placement, vascular interventions in the catheterization lab, or surgery.⁵

It is important that emergency physicians consider the possibility of air embolism whenever neurological symptoms present after any dive or potential vascular misadventure. The treatment for suspected arterial air embolism, regardless of cause, is prompt hyperbaric oxygen therapy.

John Fitz-Clarke, MD, PhD
Hyperbaric Medicine Unit
Queen Elizabeth II
Health Sciences Centre
Halifax, NS

References

1. Tang CE. Paradoxical embolism: a rare life- and limb-threatening emergency. Can J Emerg Med 2004;6(1):40-4.
2. Wilmshurst PT, Byrne JC, Webb- Peploe MM. Relation between intraatrial shunts and decompression sickness in divers. Lancet 1989;2:1302-5.
3. Bove AA. Risk of decompression sickness with patent foramen ovale. Undersea Hyperb Med 1998;25(3):175-8.
4. Hagen PT, Scholz DG, Edwards WD. Incidence and size of patent foramen ovale during the first 10 decades of life: an autopsy study of 965 normal hearts. Mayo Clin Proc 1984;59:17-20.
5. Blanc P, Boussuges A, Henriette K, Sainty JM, Deleflie M. Iatrogenic cerebral air embolism: importance of early hyperbaric oxygenation. Intensive Care Med 2002;28(5): 559-63.