VENOUS AND PARADOXICAL AIR-EMBOLISM IN THE SITTING POSITION - A PROSPECTIVE-STUDY WITH TRANSESOPHAGEAL ECHOCARDIOGRAPHY

This prospective study investigates the frequency of patent foramen ov ale (PFO), venous air embolism (VAE) and paradoxical air embolism (PAE ) by transoesophageal echocardiography (TOE) in neurosurgical patients operated on in the sitting position. The risk of PAE after exclusion of PFO is assessed, A PFO was identified by pre-operative TOE and VAE and PAE by continuous intraoperative TOE. Sixty-two patients were divi ded into two groups, 22 patients were studied in group 1 (posterior fo ssa surgery) and group 2 (cervical surgery) contained 40 patients. Pre -operative TOE demonstrated a PFO in 5 of the 22 patients in group 1 ( 23%). Patients with proven PFO were excluded from the sitting position . Two further patients of this group (12% of 17 patients), in whom a P FO had been excluded pre-operatively, nevertheless had PAE, air occurr ing in all cavities of the heart. In group 2 the incidence of PFO was 4 out of 40 patients (10%). No PAE was observed in this group. Three m orphological types of VAE with different haemodynamic and ventilation changes were demonstrated. VAE was observed in 76% of all posterior fo ssa operations and in 25% of cervical laminectomies. We conclude that a pre-operative search for PFO is mandatory considering its incidence of 23% in group 1 and of 10% in group 2, and the risk of PAE. If a PFO is detected, the sitting position should be avoided. A residual risk for PAE remains despite exclusion of PFO because the reliability of TO E is limited. TOE is the method of choice for detecting VAE and PAE.