When the literature is examined, it has been reported in many studies that intracranial pressure increases due to laparoscopic procedures performed in the intraperitoneal area. The mechanism of increased intracranial pressure (ICP) associated with insufflation is most likely due to impaired venous drainage of the lumbar venous plexus at increased intra-abdominal pressure. Changes in ICP can be monitored by ultrasonographic measurement of optic nerve sheath diameter (ONSD), which is a generally accepted simple, reliable and non-invasive ICP measurement technique. In meta-analyses conducted on this subject, it has been revealed that ICP elevation during laparoscopy can be observed with a significant increase in ONSD in the early (0 30 minutes) and late (30-120 minutes) periods during carbondioxid (CO2) pneumoperitoneum.

However, the effect of laparoscopic procedures performed in the extraperitoneal area on the central nervous system is not clear. There is not found any study in the literature comparing laparoscopic procedures, especially performed extraperitoneally and transperitoneally, and their effects on intracranial pressure.

The aim of the study compare to laparoscopic cholecystectomy performed in the transperitoneal area and (totally extra-peritoneal) TEP inguinal hernia repair performed in the extraperitoneal area in terms of intracranial pressure relationship.

A total of 60 patients, including 30 patients who underwent laparoscopic cholecystectomy and 30 patients who underwent TEP inguinal hernia repair between December 2022 and January 2023, were included in the study.

Inclusion criteria: 18-70 years old, ASA (American Society of Anesthesiologists) I-II, patients who will undergo laparoscopic cholecystectomy with the diagnosis of symptomatic cholelithiasis or TEP due to inguinal hernia.

Exclusion criteria: patients who were switched to open surgery, glaucoma, corneal disease, eye surgery, cerebrovascular disease, any neurological disease, chronic kidney disease, liver cirrhosis, and patients whose peritoneum was opened during TEP.

Anesthesia

All patients will undergo general anesthesia and will be given Propofol 2 mg/kg and Fentanyl 2 μg/kg intravenously (IV) for analgesia. Endotracheal intubation will be performed after a 4-minute injection of 0.1 mg/kg Vecuronium. Anesthesia will be maintained with an oxygen-air ratio of 50:50 propofol. For postoperative nausea and vomiting prophylaxis, 4 mg of dexamethasone will be given at induction. Intermittent doses of Fentanyl and Vecuronium will be given from time to time as needed. At the end of the surgery, the neuromuscular paralysis will be reversed with 0.05 mg/kg Neostigmine and 0.02 mg/kg Glycopyrrolate Injection, and the patient will be extubated.

Surgical Method in Patients Undergoing Laparoscopic Cholecystectomy:

With a mini incision made under the umbilicus, the abdomen will be entered with a 10 mm trocar. Pneumoperitoneum will be created with CO2 gas. The intra-abdominal pressure will be set to 14 mmHg. Under the guidance of the laparoscope, 1 10 mm trocar from the subxiphoid region and 2 more 5 mm trocars from the subcostal region will be inserted. The cystic artery and cystic duct will be clipped and cut, exposing the Callot's triangle. The gallbladder will then be separated from the liver bed and removed through the abdomen. The CO2 in the abdomen will be evacuated and the trocars will be removed. The operation will be terminated by closing the fascia defect and the skin.

Surgical Method in Patients with Totally Extra-peritoneal (TEP) Repair:

The outer sheath of the rectus muscle will be seen by passing through the skin and subcutaneous tissue with a mini incision made from the umbilicus. A 10 mm trocar will be placed in the preperitoneal space and CO2 insufflation will be applied. The pressure will be set to 14 mmHg. Two more 5 mm trocars will be placed between the umbilicus and the sympisis pubis under the laparoscope. The preperitoneal inguinal region will be dissected with a laparoscopic dissector and holder. The hernial sac will be released. A 10x15 cm prolene mesh will be fixed to cover the femoral, direct and indirect hernia areas. The trocars will be removed by evacuating the CO2 gas. The skin will be closed and the operation will be terminated.

Results

The primary outcome of the study is the comparison of ONSD measurements between patients who underwent laparoscopic cholecystectomy and TEP repair.

Secondary outcomes are age, gender, ASA score, height, weight, comorbidities, heart rate, blood pressure, oxygen saturation (SpO2), end tidal CO2 (ETCO2) measurements.

ONSD measurement:

ONSD will be performed with transorbital sonography by 2 investigators unaware of the study protocol. Transorbital sonography will be performed using an E-CUBE i7 ultrasound system (mechanical index, 0.2; thermal index, 0) using a linear 6-13 Hz probe (Alpinion Medical Systems, Seoul, Republic of Korea). To prevent eye damage, a sterile occlusion gel will be used and gently probed without applying pressure to the eyelid. Ultrasonographic images of the area will be obtained at the optic nerve level and the ONSD image will be taken 3 mm behind the optic nerve head. The optic nerve sheath will be taken from both eyes at certain times, preoperatively (T0), at the end of insufflation (T1), and at the end of the operation (T2). The average value of the 3 measurements will be recorded as ONSD. Heart rate (HR), blood pressure, SPO2 and EtCO2 will be recorded separately at each time point.

Statistical analysis The primary aim of this study is to compare the effect of laparoscopic surgeries performed in the preperitoneal and intraperitoneal areas on OSD. For clinically reliable results, at least 30 subjects in each group had to detect a difference of 0.3 mm in ONSD measurements. Sample size was calculated based on a pilot study. Multivariate observational analyzes of all data will be performed. Descriptive statistics will be given for hidden variables. Mean and standard deviation will be given for continuous variables, frequency and percentage will be given for categorical variables. Mixed effects models will be created for constant variables. Group, time and group-time interaction will be evaluated. The t-test will be used to measure continuous variables between the 2 groups. When group-time interaction is important, least squares means will be compared. Statistical Analysis SAS (University Edition 9.4) software will be used for data analysis. A P value of <0.05 will be considered significant.

Inclusion Criteria:

• 18-70 years old,
• ASA (American Society of Anesthesiologists) I-II,
• patients who will undergo laparoscopic cholecystectomy with the diagnosis of symptomatic cholelithiasis or TEP due to inguinal hernia.

Exclusion Criteria:

• patients who were switched to open surgery,
• glaucoma, corneal disease, eye surgery,
• cerebrovascular disease,
• any neurological disease,
• chronic kidney disease,
• liver cirrhosis,
• patients whose peritoneum was opened during TEP.