Cerebral Oxygen Monitoring: An Observational Prospective Study on Seated Position Neurosurgical Procedures

Seated position is a debated position for posterior fossa and cervical spine procedures. This study was designed to monitor cerebral oxygenation and hemodynamic changes in seated position neurosurgical procedures.
Ninety-five candidates for elective craniotomies in seated position were included. Before the sitting positioning patients received isotonic crystalloid fluid and a vasoconstrictor agent, if necessary. The applied seated position in this study was a modified sitting position so that the legs were elevated to the point that toes were at the Tragus level. Mean Arterial Pressure (MAP), regional cerebral oxygen saturation level (rSO2) and end tidal CO2 were recorded before anesthesia induction until the end of surgery.
Fifteen minutes after the establishment of the sitting position, there was a statistically significant decrease in rSO2 compared with the pre-sitting time (67.30 ± 9.21 vs 68.24 ± 8.96) (P = 0.037). Furthermore, in comparison with pre-sitting time, a decrease in MAP on the 15th minute after sitting positioning was observed (66.55 ± 11.52 versus 69.88 ± 11.51) (P = 0.018). The incidence of Cerebral Desaturation Event (CDE) defined as rSO2 reduction to less than 40% or less than 80% from baseline, as a marker of cerebral hypoxia, was 7.3%. Also, the incidence of definite venous air emboli (VAE) detected by aspirating air bubbles from the right atrium was 7.3%.
Although there was a statistically significant reduction in MAP and rSO2, 15 minutes following sitting positioning, it was not clinically significant and considering the low incidence of CDE, it seemed that sitting position may not increase the risk of cerebral hypoxia in elective sitting craniotomies.