Comparison of Cumulative Opioid Consumption Between Time-Programmed Decremental Infusion and Fixed-Rate Basal Infusion Modes of Intravenous Patient-Controlled Analgesia Following Mixed Surgery: Protocol for a Randomized Controlled Trial.

Background: Effective postoperative pain management remains a clinical challenge, with a substantial proportion of patients experiencing moderate to severe pain after surgery. Intravenous patient-controlled analgesia (PCA) is widely used; however, conventional fixed-rate basal infusion does not account for the dynamic temporal pattern of postoperative pain, potentially leading to suboptimal analgesia and unnecessary opioid exposure. Time-programmed decremental infusion has been proposed as an alternative strategy to better align opioid delivery with postoperative pain trajectories, but high-quality evidence in mixed surgical populations is limited. Methods and Analysis: This study is a prospective, multicenter, randomized, double-blind controlled trial conducted across three tertiary hospitals. A total of 1444 adult patients undergoing elective thoracic, abdominal, spinal, and orthopaedic procedures performed using either minimally invasive or open approaches will be randomized in a 1:1 ratio to receive either time-programmed decremental infusion or fixed-rate basal infusion PCA. All patients will receive a standardized PCA solution containing sufentanil 200 μg and ondansetron 32 mg diluted to 200 mL. The control group will receive a constant background infusion of 2 mL/h, whereas the intervention group will receive a predefined decremental infusion schedule (4.0, 3.0, 2.0, and 1.0 mL/h across successive postoperative time intervals). The primary outcome is cumulative opioid consumption at 48 hours postoperatively. Secondary outcomes include pain intensity, cumulative PCA volume, bolus demand frequency, rescue analgesic use, quality of recovery, sleep quality, sedation level, incidence of nausea and vomiting, and patient satisfaction. Analyses will be performed on the intention-to-treat and per-protocol populations. Ethics and Dissemination: The study protocol has been approved by the institutional review boards of all participating centers. The trial will be conducted in accordance with the Declaration of Helsinki, and written informed consent will be obtained from all participants. The findings will be disseminated through peer-reviewed journals and academic conferences. Trial Registration: Clinical Trials.gov identifier: NCT07375121. Registered on January, 2026. (https://clinicaltrials.gov/study/NCT07375121?term=NCT07375121&viewType=Card&rank=1).