Comparison of cumulative opioid consumption between variable-rate feedback infusion and fixed-rate basal infusion modes of intravenous patient-controlled analgesia following mixed surgery: protocol for a prospective randomised controlled trial.

introductionInadequately managed postoperative pain remains a significant clinical challenge, often leading to delayed mobilisation and increased complications. While intravenous patient-controlled analgesia (PCA) is a mainstay of treatment, conventional fixed-rate basal infusion modes may not align with the fluctuating biphasic nature of postoperative pain. This often results in either insufficient analgesia or unnecessary opioid overexposure. Advanced network-integrated PCA pumps now allow for 'variable-rate feedback infusion,' which dynamically adjusts the background rate based on real-time patient demand. This study aims to determine whether a variable-rate feedback infusion mode reduces total cumulative opioid consumption at 48 hours postoperatively while providing non-inferior analgesic efficacy compared with a fixed-rate basal infusion mode. METHODS AND ANALYSIS: This is a multicentre, randomised, double-blind, controlled trial to be conducted at three hospitals in China. A total of 1170 patients (aged 18-65 years, American Society of Anaesthesiologists I-III) undergoing elective mixed surgery under general anaesthesia, including thoracic, abdominal, spinal, orthopaedic and cranial procedures performed using either minimally invasive or open approaches, will be recruited and randomised in a 1:1 ratio to either the fixed-rate basal infusion group or the variable-rate feedback infusion group. Both groups will receive a standardised PCA solution of sufentanil. In the variable-rate feedback infusion group, the background infusion rate will automatically increase by 0.5 mL/hour on demand boluses during lockout intervals and decrease by 0.5 mL/hour after 1 hour of inactivity. The primary outcome is the total cumulative opioid consumption at 48 hours postoperatively, including sufentanil delivered via PCA and opioid-equivalent rescue analgesics. Key secondary outcomes include resting and movement pain scores, cumulative PCA volume consumption, number and dosage of additional rescue analgesia and postoperative quality of recovery. Exploratory outcomes include sleep quality, sedation and agitation levels, and the degree of nausea and vomiting, patient's satisfaction with PCA. These outcomes are assessed at predefined postoperative time points. ETHICS AND DISSEMINATION: The study has been approved by the Institutional Review Board of Beijing Tiantan Hospital (KY2025-387-02) and the Affiliated Hospital of Youjiang Medical University for Nationalities (YYFY-LL-2026-006), and the Second Affiliated Hospital of Hainan Medical University (2026-K140-01). The study will be conducted in accordance with the Declaration of Helsinki and Good Clinical Practice guidelines. Written informed consent will be obtained from all participants before enrolment. Findings from this study will be disseminated through peer-reviewed journals and at scientific conferences. A summary of the findings will also be made available to participants on request. TRIAL REGISTRATION NUMBER: NCT07361822.