• G Schwarz, G Fuchs, W Weihs, H Tritthart, H V Schalk, and F Kaltenböck.
• Department of Anesthesiology, University of Graz, Austria.
• J Neurosurg Anesthesiol. 1994 Apr 1;6(2):83-8.

AbstractA persisting foramen ovale (PFO) is the most common cause of paradoxical air embolism. To detect right-to-left shunting, transthoracic contrast echocardiography was performed preoperatively in 301 patients scheduled for neurosurgical procedures in the sitting position. Echocardiography yielded evaluable results in 285 patients (94.7%). In 72 of 285 patients (25.2%), a PFO was diagnosed on the basis of contrast echo signals appearing in the left atrium or ventricle within 5 heart cycles after application of contrast medium via a peripheral vein. If echo signals appeared in the left heart after more than 5 heart cycles, an intrapulmonary right-to-left shunt was considered (11 patients, 3.9%). Venous air embolism (VAE) occurred in 27.4% of 226 patients operated on in the sitting position and in none of the 59 patients operated on in a nonsitting position. We conclude that the sitting position during neurosurgery should be avoided in patients with preoperative evidence of a right-to-left shunt at contrast echocardiography to reduce the risk of paradoxical air embolism (PAE).

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