Lung protective ventilation and intraocular pressure in Trendelenburg laparoscopic myomectomy: a randomised trial

The Trendelenburg position frequently elevates intraocular pressure (IOP), potentially leading to adverse outcomes, particularly in sensitive patients. Carbon dioxide pneumoperitoneum can exacerbate this effect. Lung protective ventilation strategies (LPVS), which employ small tidal volumes, induce mild positive intrathoracic pressure that may mitigate the rise in IOP during Trendelenburg positioning. This study aimed to investigate the effects of LPVS, utilizing small tidal volumes and permissive hypercapnia, on IOP in patients undergoing laparoscopic myomectomy in the Trendelenburg position. Eighty-six patients scheduled for laparoscopic myomectomy under general anesthesia were randomized into two groups: the LPVS group (Group A) and the conventional ventilation strategy group (Group B). IOP, heart rate (HR), mean arterial pressure (MAP), and end-tidal carbon dioxide partial pressure (PETCO₂) were measured at specific time points: after tracheal intubation (T0), upon pneumoperitoneum establishment (T1), immediately upon assuming the Trendelenburg position (T2), 20 min (T3) and 45 min (T4) into Trendelenburg, immediately upon returning to the horizontal position (T5), and 15 min post-horizontal positioning (T6). Arterial blood gas (ABG) analysis was performed at T0, T4 and T6. Perioperative characteristics including myoma features, anesthesia duration, and Trendelenburg position duration were recorded. Within each group, IOP at T3, T4, and T5 was significantly higher than at T1 and T2 (P < 0.05). Simple effect analysis with Bonferroni correction showed that at T4, IOP in Group A was significantly lower than in Group B (P < 0.05). HR increased significantly from baseline (T0) at T3 and T4 in both groups (P < 0.05) and was significantly higher in Group A than in Group B at T4 (P < 0.05). MAP at T2, T3, T4, and T5 differed significantly from T0 within each group (P < 0.05) and was significantly different between groups at T4 (P < 0.05). PETCO₂ at T3, T4, and T5 was significantly higher than at T0 in both groups (P < 0.05); PETCO₂ was significantly higher in Group A than in Group B at T4 and T5 (P < 0.05). No severe hypercapnia-related adverse events or respiratory complications were observed in either group. In young, low-risk patients without pre-existing ophthalmic or systemic comorbidities undergoing laparoscopic myomectomy, LPVS with small tidal volumes and moderate permissive hypercapnia significantly attenuated IOP elevation at 45 min after Trendelenburg positioning. However, this approach may be associated with increased transient mild increases in blood pressure and heart rate, without affecting post-anesthesia care unit (PACU) duration.