Evaluation of the Effect of Internal Jugular Vein Catheterization on Intracranial Pressure Using Optic Nerve Sheath Diameter in Intubated Patients in the Intensive Care Unit

Before central venous catheter insertion, the baseline ONSD value will be determined by measuring the optic nerve sheath diameter in the supine and Trendelenburg positions (15 degrees head down).

Immediately after central venous catheter insertion, the measurement will be taken while the patient is still in the Trendelenburg position. The measurement will be repeated at 5, 15, and 30 minutes after the patient is placed in the supine position.

Transorbital optic nerve sheath diameter measurements will be performed using the linear probe of the ultrasound device routinely used in our clinic. The ultrasound linear probe will be gently placed on the eyelid over the closed eye, ensuring no pressure is applied to the patient's eye. The length of the line representing the optic nerve sheath diameter, which intersects the line drawn 3 mm downwards from the lower edge of the eyeball seen on the ultrasound, will be measured and recorded. The optic nerve sheath diameter will be measured transorbitally vertically once from each eye during the first measurement, and the average will be taken.