Effect of prone position on middle cerebral artery mean flow velocity and optic nerve sheath diameter in spinal surgeries

Aim: Prone position is frequently used in spinal surgeries as well as in many surgical procedures. Prone position may cause adverse events such as intracranial pressure increase, hemodynamic instability, facial edema and conjunctivitis. In this study, we aimed to measure middle cerebral artery flow velocity with Transcranial Doppler and optic nerve sheath diameter in patients who will undergo spinal surgery in prone position and to see effect of prone position on these values. Material and method: Our study was conducted prospectively on 55 patients undergoing spinal surgery in prone position. Patients aged 18-80 years with ASA scores between I-III were included. After anesthesia induction in supine position, hemodynamic data of patients were recorded, right and left optic nerve sheath diameters, right and left middle cerebral artery mean flow velocities were measured. Then, patients were placed in prone position, and measurements were repeated and compared 30 minutes after first measurement. Results: In our study, we found that the optic nerve sheath diameter increased from supine to prone position. Statistically significant difference was detected in the right (z=6.182, p<0.001) and the left (z=5.911, p<0.001) optic nerve sheath diameter values from supine to prone position. Statistically significant difference was detected in right mean flow velocity values in prone position (z=2.110, p=0.035). No statistically significant difference was detected in left mean flow velocity values in prone position (p>0.05). Conclusion: Prone positioning may increase intracranial pressure. Patients undergoing spinal surgery with high risk of intracranial hypertension, intracranial pressure measurements can be made using noninvasive methods.