Anesthesiology Considerations and Management of Venous Air Embolism in Patients in the Semisitting Position: A...

The semisitting position is often preferred for neurosurgical procedures requiring access to the cerebellopontine angle or posterior fossa. Despite benefits such as improved venous drainage and reduced intracranial pressure, its use has been controversial due to risks like venous air embolism. Recent advancements in intraoperative monitoring and management have caused renewed interest in this position. This study reviews our institution's experience, focusing on strategies to mitigate complications and improve outcomes in semisitting craniotomies.

Ninety-four consecutive adult patients who underwent intracranial neurosurgery in the semisitting position were enrolled in the study. The surgery and anesthesiology reports were reviewed to extract data regarding demographics, intraoperative monitoring, and postoperative complications. For each patient who experienced a venous air embolism, an additional set of hemodynamic data was collected. Data management and statistical analyses were performed using Statistical Analysis System (SAS) software (version 9.4, 2023, SAS Institute Inc., Cary, NC, USA).

Venous air embolism occurred in a total of 21 patients (22.34%). Out of these 21 patients, one experienced a venous air embolism that coincided with a decrease in end-tidal carbon dioxide (EtCO₂) of > 3 mmHg. Three patients (3.19%) were transitioned from semisitting to another position, with only one of these due to persistent occult air entrainment despite management efforts.

The semisitting position remains a valuable approach in neurosurgery. We identified multiple factors important in reducing the risk of complications and managing them when they occur. Robust anesthesia guidelines should be developed so that this modality can be used more broadly.