Optic Nerve Sheath Diameter in Low-flow and Normal-flow Rate Anesthesia

Laparoscopic cholecystectomy is one of the regularly performed laparoscopic surgical procedures. It resulted in shorter hospital stays, improved cosmetic outcomes, and reduced bleeding and pain. However, during laparoscopic surgeries, the pneumoperitoneum is known to raise intracranial pressure (ICP), reduction in cerebral blood flow (CBF), and as a consequence, cerebral hypoxia. Near-infrared spectroscopy (NIRS), a noninvasive and continuous measuring method used to evaluate the appropriateness of cerebral perfusion, is therefore utilized in conjunction with cerebral oximetry to quantify regional tissue oxygenation. On the other, BIS is the most reliable technique for determining the level of sedation and anesthesia. Patients experience fewer intraoperative wake-ups thanks to BIS monitoring. Increased intra-abdominal pressure, decreased cerebrospinal fluid (CSF) absorption and obstruction of lumbar venous plexus drainage, increased pressure in the sacral spaces' vascular compartment, and cerebral vasodilation brought on by hypercarbia are some of the suggested mechanisms for why ICP increases during laparoscopy. Intraventricular and intraparenchymal catheterization remains the gold standard for determining and monitoring ICP. However, due to worries about severe complications like bleeding, infection, and equipment failure, invasive ICP monitoring during laparoscopic surgery is almost impossible. Recently, ultrasound-guided optic nerve sheath diameter (ONSD) measurement is a simple and reliable method of predicting elevated ICP. There are various possible advantages of low-flow anesthesia. It boosts mucociliary clearance, preserves body temperature, lessens fluid loss, generates savings of up to 75%, and lowers greenhouse gas emissions as well as the cost of treatment. It also improves the flow dynamics of the breathed air. During laparoscopic procedures, low-flow anesthesia may be used as a means of preventing a rise in intracranial pressure and cerebral hypoxia. But low flow anesthesia effects on İCP are not known in Laparoscopic cholecystectomy. The primary aim of this study is to compare the effects of low-flow (0.75 l/min) and normal-flow (1.5 l/min) anesthesia on ONSD in patients undergoing laparoscopic cholecystectomy. Seconder aims are regional cerebral oxygen saturation (rSO2), bispectral index (BIS), and evaluate the status of cognitive function in the postoperative 24th hours.

Inclusion Criteria: * Inclusion criteria of the patients will be determined as age between 18 and 65 years, ASA status 1-2. Exclusion Criteria: * Exclusion criteria of the patients are defined as patients younger than 18, pregnant women, patients with any ophthalmological disease affecting optic nerve diameters, patients with acute or chronic eye disease, patients using drugs known to affect intracranial pressure, and patients abusing alcohol or psychoactive substances.