Background <p>Propofol sedation for gastroenteroscopy, with advantages such as safety and comfort, is popular among a large number of patients. However, more than one-third of patients receiving propofol sedation experience intraoperative hypotension (IOH), which should not be ignored in patients of any age. The therapeutic effect of preloading in various in-operating-room anesthesias has been confirmed and widely applied. However, there are relatively few studies on preloading in outpatient intravenous anesthesia at home and abroad, and the required dose for preloading has not been explored.</p> Methods <p>This is a prospective randomized, single-center controlled trial. A total of 606 eligible participants scheduled for painless gastroenteroscopy will be enrolled and randomly assigned in a 1:1 ratio to either receive crystalloid preloading or no fluid infusion. The primary outcome of our study is the incidence of IOH. Secondary outcomes include inferior vena cava collapse index (IVC-CI), ΔIVC-CI, intraoperative dosage of ephedrine, BP (blood pressure), HR (heart rate), SpO₂ (peripheral oxygen saturation), perfusion index, recovery time, and incidence of postoperative adverse reactions.</p> Discussion <p>This study aims to explore the impact of a certain dose of crystalloid preloading on the incidence of intraoperative hypotension during propofol-sedated gastroenteroscopy, in order to provide a reference for hemodynamic management in painless gastroenteroscopy.</p> Trial registration <p>ChiCTR ChiCTR2400082021. Registered on March 19, 2024.</p>