To the Editor:
We read with great interest the article by Kim et al. 1in the July 2009 issue of Anesthesiology. In this study, the authors warn us of the high frequency of venous gas embolism that can occur during laparoscopic hysterectomy as opposed to total abdominal hysterectomy. Their study calls for several comments.
The authors found approximately 25% of patent foramen ovale (PFO) among their patients, which is consistent with what we know from autopsic series.2However, the detection of a PFO could have been enhanced by an end-inspiratory occlusion maneuver or by the application of positive end-expiratory pressure during transesophageal echocardiography.3–5
No indication on the filling of the left heart by bubbles, especially for patients presenting with a PFO, was reported. This would have informed us of the risk of systemic air embolism, which is ultimately the most daunting complication.
Only major neurologic complications that are rare in clinical practice were evaluated. It would have been interesting to assess the risk of minor neurologic complications that are often underdiagnosed, especially in elderly patients.
When venous air embolism occurs, the authors suggest placing the patient in a left lateral recumbent position. Animal studies have found no benefit from the left lateral position in improving hemodynamic performance,6,7and human data are lacking. Conversely, in the case of a major event, such as cerebral gas embolism, the authors did not mention hyperbaric oxygen therapy. This therapy has potential benefits in the case of arterial gas embolism8,9and has to be mentioned in the therapeutic arsenal.
Finally, we are clearly faced with a paradox. Venous air embolism is frequently found during laparoscopic procedures,1,10PFO exists in 25 to 30% of patients, and mechanical ventilation increases right atrial pressure favoring right-to-left flow through a foramen ovale, especially if there is positive end-expiratory pressure.11However, systemic complications as a result of paradoxical embolism, especially cerebral complications, are rare. An explanation often evoked is the high solubility of carbon dioxide in blood. However, a gas embolism is rapidly transformed into a nongas embolism because of the adhesion of platelets to the bubble.12Moreover, if bubbles are detected in the heart, they can be in the brain, only a few seconds later through a PFO.
To conclude, it is perhaps time to call for a large study allowing the evaluation of the frequency of cerebral complications of gas embolism during laparoscopic surgery, especially minor ones, and to open a database of major complications, which are possibly underestimated today and most of them not being published. After all, we want to ask a question: should we contraindicate laparoscopic surgery in patients with a known PFO and prefer total abdominal surgery?
*Hôpital Foch, Suresnes, France. email@example.com