Occurrence and Severity of Venous Air Embolism During Neurosurgical Procedures in Semi-Sitting Versus Supine Position

Background: Patients undergoing neurosurgical procedures in the posterior cranial fossa can be placed in different positions: the semi-sitting position or the supine position. The major risk of the semi-sitting positioning is venous air embolism (VAE). However, VAEs may also occur in the supine position.Objective: In a prospective study, we investigated the incidence of VAE based on the positioning of the patients (trial registration 553/2013BO1).Methods: In a single-center study with 137 patients, we prospectively evaluated the occurrence of VAEs in patients in the supine and semi-sitting position over the period from January 2014 to April 2015. All patients were monitored for VAE by the use of a transesophageal echocardiography (TEE).Results: 50% of all participating patients experienced a VAE (with 56% of these patients undergoing surgery in the semi-sitting position and 11% in the prone position). 86% of the VAEs were just detected by the use of a TEE. We only observed VAEs with a decrease in EtCO2 in the semi-sitting position. However, none of the patients had any hemodynamic changes due to the VAE. We found that surgeries in patients with a preexisting intracardial shunt such as a patent foramen ovale (PFO) less likely resulted in VAEs (42% vs. 58%).Conclusion: The semi-sitting position with TEE monitoring and a standardized protocol, including a deep central venous line is a safe and advantageous technique, taking also account of a significant rate of VAEs. VAEs also occur in the supine position, however, less frequently.