Simple effect at T2, T3, T4.

ObjectiveThis study aimed to evaluate the effect of combining dexmedetomidine infusion with a modified Trendelenburg position on intraocular pressure (IOP) in patients undergoing robot-assisted laparoscopic surgery (RALS).MethodsIn a single-center, prospective, 2 × 2 factorial randomized controlled trial, 160 patients scheduled for RALS were allocated to one of four groups: control (normal saline + traditional position), modified position alone, dexmedetomidine alone, or the combination of both. IOP was measured at baseline, during key surgical phases, and after extubation. The primary outcome was IOP during surgery. Secondary outcomes included the incidence of cardiovascular adverse events and the requirement for vasoactive drugs.ResultsA total of 153 patients completed the study protocol. Both dexmedetomidine and the modified position significantly reduced IOP during surgery (main effect of drug: F = 35.2, P P P = 0.030), indicating a synergistic effect. The combination group demonstrated the greatest reduction in IOP from time points T2 to T4, ranging from 3.6 to 4.8 mmHg lower than the control group. There were no significant differences in the overall incidence of adverse events among the groups.ConclusionsIn conclusion, for patients undergoing prolonged robotic laparoscopic surgery (with a mean operative time of 217 minutes), the combined use of dexmedetomidine infusion and a modified Trendelenburg position provides an effective and synergistic strategy for intraocular pressure control. This approach offers a practical means to enhance intraoperative ocular safety during such lengthy procedures.Trial registrationChinese Clinical Trial Registry ChiCTR2300072961

## 研究目的
本研究旨在评估右美托咪定（dexmedetomidine）输注联合改良特伦德伦伯卧位（modified Trendelenburg position）对拟行机器人辅助腹腔镜手术（robot-assisted laparoscopic surgery, RALS）患者眼内压（intraocular pressure, IOP）的影响。
## 研究方法
本研究为单中心前瞻性2×2析因随机对照试验，将160例计划接受RALS的患者随机分为四组：对照组（生理盐水+传统体位）、单纯改良体位组、单纯右美托咪定组以及联合干预组。分别于基线状态、关键手术阶段及拔管后测量患者IOP。主要结局指标为术中IOP；次要结局指标包括心血管不良事件发生率及血管活性药物使用需求。
## 研究结果
最终共有153例患者完成研究方案。右美托咪定与改良体位均可显著降低术中IOP（药物主效应：F=35.2，P<0.001；体位主效应：F=18.7，P=0.030），提示二者存在协同效应。联合干预组在T2至T4时间点的IOP降低幅度最大，较对照组低3.6~4.8 mmHg。各组不良事件总发生率无显著差异。
## 研究结论
综上，对于需接受长时间机器人辅助腹腔镜手术（平均手术时长217分钟）的患者，联合使用右美托咪定输注与改良特伦德伦伯卧位是一种有效且具备协同作用的IOP控制策略。该方案为这类长时手术术中眼部安全性的提升提供了实用途径。
## 试验注册
中国临床试验注册中心（Chinese Clinical Trial Registry）ChiCTR2300072961