Dynamic effects of low- and high-pressure pneumoperitoneum on optic nerve sheath diameter during laparoscopic cholecystectomy: a prospective, randomized, observer-blinded clinical trial

Abstract Background This study aimed to compare the time-dependent changes in optic nerve sheath diameter (ONSD) associated with low-pressure (8 mmHg) and high-pressure (14 mmHg) pneumoperitoneum during laparoscopic cholecystectomy. Methods In this prospective, randomized, observer-blinded clinical trial, 76 adult patients with ASA physical status I–II were randomized into two groups receiving pneumoperitoneum at either 8 mmHg (low-pressure group) or 14 mmHg (high-pressure group). ONSD measurements were obtained using transorbital ultrasonography at five predefined time points (T0–T4). The primary outcome was the comparison of time-dependent changes in ONSD between the groups. Secondary outcomes included the incidence of postoperative nausea and vomiting and postoperative headache. Results All 76 patients were included in the final analysis. Baseline demographic characteristics and perioperative variables were comparable between the groups. Generalized linear model analysis demonstrated significant effects of group, time, and group × time interaction on ONSD (all p < 0.001). ONSD increased after pneumoperitoneum induction in both groups; however, the increase was more pronounced in the high-pressure group, particularly at T1 and T2. At the second postoperative hour (T4), ONSD values in both groups approached baseline levels. The incidence of postoperative nausea, vomiting, and headache was significantly higher in the high-pressure group (nausea: p < 0.001; vomiting: p = 0.018; headache: p = 0.001). Conclusion High-pressure pneumoperitoneum during laparoscopic cholecystectomy was associated with greater and more pronounced transient increases in optic nerve sheath diameter. This was accompanied by a higher incidence of early postoperative nausea, vomiting, and headache in the high-pressure group. Trial registration The trial was registered at ClinicalTrials.gov on August 20, 2025 (NCT07162922).