We faced technical problem before conducting this study

Our hypothesis is that there will be a decrease in internal jugular venous flow in the park bench position when compared to the supine position. There will also be a change in blood flow between the right and left internal jugular veins in the park bench position. In particular, there will be a greater reduction of flow on the dependent side. However, the internal jugular venous flow will be the same in both the prone and supine positions.

The different positions used in neurosurgery for better accessibility to the operating field (park bench, prone) can impact cerebral venous drainage due to the effects of internal jugular venous outflow of blood, and may increase intracranial pressure. Excessive neck flexion and rotation in the park bench position, or flexion in the prone position, may lead to kinking or twisting of the internal jugular vein. This has been hypothesized as the major cause of disturbed venous drainage during surgery and may lead to neck swelling, brachial plexus injury, macroglossia (swollen tongue), delayed airway obstruction, and increases in intracranial pressure in postoperative patients. Optimal brain perfusion is best in the neutral position of the head, but surgery cannot always be performed in this position. Thus, we look to measure the internal jugular venous flow at different positions, as there have been few studies looking at this important contributing factor.

Inclusion Criteria:

• Adult neurosurgical patients who are above the age of 18
• Patients undergoing neurosurgery requiring general anesthesia and placement in either in prone or park bench position for surgical accessibility

Exclusion Criteria:

• Lack of informed consent
• Patients undergoing surgical procedures only in the supine position
• Patients needing a central venous catheter in the neck

Neurosurgical patients in either park bench or prone position for their surgery