The Effect of Optic Nerve Diameter on Postoperative Cognitive Function in Laparoscopic Hysterectomy

To show whether the relationship between increased intracranial pressure and optic nerve diameter after long (> 2.5 hours) Trendelenburg laparoscopic hysterectomies has an effect on postoperative cognitive functions.

Laparoscopic surgery has been developing rapidly in recent years. The fact that the bleeding risk and hospital stay are less, less pain, faster return to normal work, better cosmetic results and superior patient morbidity have made laparoscopic interventions more preferable (1). CO2 pneumoperitoneum and upright upside-down position (Trendelenburg position) are applied to patients who will undergo laparoscopic surgery for better visualization of the surgical field. However, the combined use of the pneumoperitoneum and trendelenburg position causes an increase in intraabdominal pressure, which triggers many systemic physiological changes, along with a decrease in venous return, and increases cerebral blood flow, intracranial pressure, and intraocular pressure (2,3).

Optic nerve sheath diameter (ONSD), determined by non-invasive ocular sonography, is a simple and reliable method that is an indicator of increased intracranial pressure (ICP) in patients (4). Studies have found 100% sensitivity and specificity in the prediction that if ONSD is >5.5, ICP will be >20 mmHg (5,6).

The effect of ONSD on postoperative delirium or postoperative cognitive dysfunction has not been fully explained in the literature. The aim of our study; To show whether the relationship between increased intracranial pressure and ONSD after long-lasting (>2.5 hours) Trendelenburg laparoscopic hysterectomies has an effect on postoperative cognitive functions.

In this prospective and observational study, 40 patients ASA 2-3, 30-75 years old who were planned for laparoscopic hysterectomy operation will be included. Patients with a previous history of ocular disease, ocular surgery, neurological disease and transient ischemic attack will be excluded from the study. Cases returning to open surgery will be excluded from the study. One day before the operation and postoperative 1.3.7. A mini mental assessment test (MMSE-Mini Mental State Examination) will be performed on these days.

Standard monitoring (electrocardiography-ECG, pulse oximetry, noninvasive arterial blood pressure) and Near-Infrared Spectroscopy (NIRS) monitoring to measure cerebral oxygen saturation will be performed on the patients. NIRS sensors will be placed on the right and left sides of the forehead, 2 cm above the eyebrow, before induction of anesthesia. Before the induction of anesthesia, the measurement will begin and the FiO2 (fraction of inspiration oxygen) will be kept at 60%. If cerebral oxygen decreases by more than 20% or is below 50% absolute, position will be changed or FiO2 will be increased.

General anesthesia induction will be made with propofol 2mg/kg, remifentanil 0.5 µg/kg and rocuronium 0.6mg/kg, and maintenance will be provided with 2% sevoflurane. The patient will be intubated and ventilation support will be provided so that the tidal volume is 6-8 ml/kg and the end tidal CO2 is 30-40 mmHg. PEEP (Positive end expiratory pressure) will not be applied to any patient. Intra-abdominal pressure will be maintained at 15 mmHg. All patients will be given 1gr paracetamol and 100mg tramadol for postoperative analgesia.

During the measurement of optic nerve diameter, a layer of sterile water-soluble gel will be applied on the closed eyelid with a linear 10-5 MHz ultrasound probe. In our study, ONSDs of all patients will be measured by the same experienced anesthetist.

SPSS 21.0 computer program will be used for statistical analysis. Based on our pilot study data, a minimum sample size of 23 patients with 0.05 alpha and 90% power indicated that a sample size would be required.