gms | German Medical Science

Objective: The semi-sitting position during posterior fossa surgery is known to ensure significant advantages, yet due to the danger of venous air embolism (VAE) it remains controversial and is not exclusively used. In our center we tend to operate almost all complex lesions of the posterior fossa in a semi-sitting position, therefore a retrospective analysis of the incidence of VAE and related complications in the semi-sitting position was performed.

Methods: Data from 45 patients (Pt.) who underwent surgery for complex posterior fossa lesions in the semi-sitting position from October 2015 until November 2016 were retrospectively analyzed. All patient data including patient information, clinical details, intraoperative anesthesiological details, postoperative course and follow-up information were collected and statistically analyzed.

Results: Tumor entities in our series comprised acoustic neurinomas (30 Pt., 67%), petrous bone or petroclival meningiomas (5 Pt., 11,1%), Epidermoid cysts (2 Pt., 4,4%), and Ependymomas (2 Pt., 4,4%). 29 Pt. (64%) were females and 16 Pt. were males (36%) with a mean age of 53 Years. 27 Pt. (60%) had BMI larger than 25. Preoperatively determined ASA (American Society of Anaesthesiologists) classification revealed ASA I in 7 Pt. (15,5%), ASA II in 28 Pt. (62,2%), ASA III in 10 Pt. (22,2%). Preoperative transthoracic echocardiography (TTE) to rule out patent foramen ovale (PFO) was proven positive in 3 Pt. (6,6 %), negative in 38 Pt. and could not be determined in 4 Pt. (8,9%). Intraoperatively performed transesophageal echokardiography (TEE) proved PFO existence in 2 Pt. (4,4%), one of them was falsely negative in preoperative TTE. Mean operation time was 4 hours 58 minutes. VAE was detected using an intraoperative continuous TEE in 3 Pt. (6,6%) once and in 2 of those Pt. twice. (4,4%) One of these Pt. also had a corresponding decrease in end tidal CO2 of 7mm Hg, while none of the Pt. with detected intraoperative VAE had a timely corresponding drop of systolic blood pressure or an increase of heart rate. Postoperative complaints consisted of nausea and vomiting (26 Pt., 58%) , headache (23 Pt., 51%), vertigo (12 Pt., 26,7%). 6 Pt. (13,2%) suffered from perioperative complications such as pneumonia (2 Pt., 4,4%), subdural hematoma (2 Pt., 4,4%), local wound infection (1 Pt., 2,2 %), subcutaneous collection of CSF (1 Pt, 2,2%).

Conclusion: In a 1 – year overview of our Pt. operated in a semi-sitting position intraoperative VAE occurred only in 3 Pt. without paradox embolism and any neurological sequelae. Intraoperative and postoperative pulmonary function was also not compromised. The semi-sitting position can therefore safely be used in the neurosurgical treatment of complex posterior fossa lesions even in selected cases with PFO. However, in our opinion intraoperative continuous TEE and standardized perioperative management is mandatory.