The sitting position and the patent foramen ovale. Commentary: a streamlined protocol for the use of the semi-sitting position in neurosurgery?

In this issue of the Journal of Clinical Neuroscience, Ammirati et al.1 report on their series of 48 patients presenting for intracranial neurosurgical procedures in the sitting position. Following exclusions for patent foramen ovale (PFO) and technical failure, 41 patients were finally treated in the sitting position. Eleven patients (26.8 ) experienced a decrease in the end-tidal carbon dioxide (CO2) of >5 mmHg. Seven patients (17 ) experienced two or more of decreased end-tidal CO2, decreased systolic blood pressure or a change in the sound of the pre-cordial Doppler, with aspiration of air from a central venous catheter in two of these patients (4.9 ). There was no clinical evidence of paradoxical arterial air embolism or other post-operative morbidity. These results are similar to numerous other audits of venous air embolism (VAE) during intracranial surgery in the sitting position.2