Effect of Carbon Dioxide Pressure on Optic Nerve Sheath Diameter in Laparoscopic Transperitoneal Nephrectomy

Effect of CO2 Pressure on Optic Nerve Sheath Diameter in Laparoscopic Transperitoneal Nephrectomy

Nephrectomy is a surgical procedure performed for various indications, and with the development and increasing availability of advanced diagnostic techniques, its incidence has been rising. Today, in appropriate cases, laparoscopic surgery is recommended due to its minimally invasive nature and its surgical success rates being comparable to those of open surgery. In laparoscopic surgery, to achieve optimal visualization, a 45° lateral decubitus position is applied, followed by the creation of a pneumoperitoneum using carbon dioxide gas. While the cardiopulmonary effects of this procedure have been shown to be minimal, studies on its intracranial effects are limited. Cerebral perfusion pressure is defined as the difference between mean arterial pressure and either central venous pressure or intracranial pressure, whichever is higher. Intracranial pressure can be assessed non-invasively using ultrasonographic measurement of the Optic Nerve Sheath Diameter (ONSD). The retrobulbar segment of the optic nerve is surrounded by a distensible subarachnoid space, which expands in response to increased intracranial pressure. The effect of increased intra-abdominal pressure during laparoscopic surgery on intracranial pressure, and its impact on ONSD, will be evaluated non-invasively.

In patients scheduled for laparoscopic kidney surgery, the Optic Nerve Sheath Diameter will be measured transorbitally using ultrasonography by the investigator at various stages of the surgery (before anesthesia, after anesthesia, in the lateral decubitus position, during pneumoperitoneum, and at routine intraoperative pressure levels). Additionally, standard monitoring parameters such as pulse rate, blood pressure, oxygen saturation, and End-Tidal CO₂ will be recorded. The Optic Nerve Sheath Diameter, which serves as an indicator of increased intracranial pressure, will be compared with variables such as surgical positioning, BMI, ASA score, and other relevant factors.

Inclusion Criteria:

• Male and female patients aged 31-69 years.
• Diagnosis of renal cancer (ICD Code C64).
• Planned laparoscopic radical or partial nephrectomy based on current guidelines and patient consent in the Urology Council.

Exclusion Criteria:

• Presence of any condition that prevents transorbital measurement of the optic nerve sheath (e.g., orbital trauma, severe periorbital edema, or ocular abnormalities affecting optic nerve imaging)
• Presence of a medical condition that precludes positioning the patient in a 45-degree lateral decubitus position (e.g., severe scoliosis, respiratory compromise, or spinal instability)
• Known or suspected intracranial pathology that may independently elevate intracranial pressure (e.g., intracranial tumors, hydrocephalus, recent traumatic brain injury)