The effect of positive end-expiratory pressure (PEEP) on optic nerve sheath diameter, an indicator of intracranial pressure increase in laparoscopic abdomi̇nal surgery

Introduction and Purpose: Laparoscopic surgery, as an alternative to open surgery; It is often preferred because of its advantages such as reduced bleeding and postoperative pain, and reduced hospital stay. Laparoscopy requires the use of carbon dioxide (CO2) pneumoperitoneum (PP). Increased intra-abdominal pressure (IAP) resulting from PP causes many systemic physiological consequences such as decreased venous return, hypercapnia due to CO2 absorbed from the peritoneal surface, and respiratory acidosis. Increased IAP due to PP causes an increase in venous pressure in the central nervous system and cerebrospinal fluid (CSF) pressure. PP application causes changes in respiratory mechanics. In order to compensate for this situation, positive effects of lung (AC) protective ventilation and positive end- expiratory pressure (PEEP) on respiratory system compliance (C) and resistance have been demonstrated. PEEP application has also been shown to be associated with an increase in intracranial pressure (ICP). Ultrasonographic (USG) measurement of optic nerve sheath diameter (SC) is a simple, non-invasive and reliable technique for ICP evaluation. In this study, we aimed to evaluate the effect of PEEP applications on optic nerve sheath diameter in patients scheduled for laparoscopic surgery (appendectomy, umbilical hernia, cholecystectomy, diagnostic laparoscopy) under general anesthesia. Materials and Methods: Our study was planned as a randomized, prospective clinical study between March 2022 and December 2022 in the Operating Room of Karadeniz Technical University Medical Faculty Hospital.The study was carried out in a total of 48 patients, ASA I, II, III risk group, aged 18-65 years, who underwent laparoscopic abdominal surgery under general anesthesia under elective conditions in the operating room. All patients were randomly divided into two study groups, PEEP=0 and PEEP=8, by drawing lots with a numbered sealed envelope. During the case period, patients' systolic and diastolic blood pressures, mean arterial pressures (MAP), pulse, peripheral oxygen saturation, etCO2, Ppeak, Pplato, compliance values were 10. minutes after induction of anesthesia (T0), and 5th minutes after selected ventilation v was started (T1), PP 5th minute (T2), PP 30th minute (T3), surgical end (T4) were recorded. In addition, PP, surgery, and anesthesia times of the patients were recorded. The ONSDs of the patients included in the study were determined by ultrasonographic method; It was measured 5 times, each time in both eyes. Results: 24 patients in the PEEP 0 group and 24 patients in the PEEP 8 group completed the study. There was no difference in demographic (age, BMI, comorbidity, ASA) and hemodynamic data between the groups. When optic nerve sheath diameters were compared between the groups according to PEEP use, a statistically significant difference was found in T2 and T3 values (p<0.05). There was no statistically significant difference in other T0, T1 and T4 values. When the optic nerve sheath diameters in the group with PEEP=8 were compared within the group; a statistically significant difference was found between T0 and T2, T0 and T3, T0 and T4, T1 and T2, T1 and T3, T1 and T4, T2 and T4, and T3 and T4 values. There was no statistically significant difference in other values. When the optic nerve sheath diameters were compared in the group with PEEP=0; T0 to T2 (p<0.001), T0 to T3 (p<0.001), T0 to T4 (p<0.001), T1 to T2 (p<0.001), T1 to T3 (p<0.001), T1 to T4 (p) =0.009), a statistically significant difference was found between T2 and T4 (p<0.001) and T3 and T4 (p=0.003) values. There was no statistically significant difference in other values. When the optic nerve sheath diameters in the group with PEEP=0 were compared within the group; A statistically significant difference was found between T0 and T2, T0 and T3, T0 and T4, T1 and T2, T1 and T3, T1 and T4, T2 and T4, and T3 and T4 values. Conclusion: We think that the use of PEEP at 8 cmH20 level in hemodynamically stable patients without known comorbidities that increase intracranial pressure in laparoscopic surgeries is a method that can be used to prevent intraoperative and postoperative AC complications without causing an increase in ICP. Keywords: laparoscopy, optic nerve sheath diameter, PEEP