Background: Posterior cranial fossa surgery is commonly performed under sitting and horizontal position in our institution. Venous air embolism is a potentially serious complication of neurosurgery especially in the sitting position.
Objective: We aim to compare the incidence of severe venous air embolism and other complications of both positions.
Material and Method: A retrospective analysis of medical record was performed in 192 patients undergoing posterior cranial fossa craniotomy from January 2010 to December 2013. Data collected from the records included demographic profile, patient position, hemodynamic changes, venous air embolism (VAE), blood loss/transfusion, duration of surgery, postoperative complications, duration of ICU stay, and postoperative discharge status. The definition of severe air embolism was identified as suspected VAE with decreased systolic blood pressure greater than 20%.
Results: There were 92 patients in sitting position (SP) group and 100 patients in horizontal position (HP) group. The incidence of severe venous air embolism was significantly higher in SP group compared with HP group (41.3% vs. 11.0%,
p<0.001). SP group had more complications than HP group in both central nervous system (71% vs. 34.0%, p = 0.001), and
cardiovascular system (17% vs. 6%, p = 0.001). Although postoperative ventilator time in SP group was less than HP group (1.24 vs. 1.60 days, p = 0.029), ICU and hospital stay were not different in either group.
Conclusion: The incidence of severe venous air embolism detected by end tidal CO2 was significantly higher in SP group.
However, 11% of HP group were suspected of severe air embolism.

Keywords: Posterior fossa surgery, Sitting position, Horizontal positions, Venous air embolism