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Variable-rate feedback infusion reduces cumulative opioid consumption at 48 hours postoperatively compared with fixed-rate basal infusion in patients undergoing mixed surgery

This protocol describes a prospective, multicentre, randomised, double-blind, controlled trial to compare cumulative opioid consumption at 48 hours postoperatively between variable-rate feedback infusion and fixed-rate basal infusion modes of intravenous patient-controlled analgesia (PCA). The study will enrol 1170 patients undergoing mixed surgery and will measure total cumulative opioid consumption as the primary outcome, with secondary outcomes including pain scores and quality of recovery. The hypothesis is that variable-rate feedback infusion reduces opioid consumption while providing non-inferior analgesia.

Last updated: Aug 30, 2026•1 RCTs•📖 Read as article →

Evidence Score

Evidence Score44/100
Human RCT★★☆☆☆
Meta-analysis☆☆☆☆☆
Mechanism★★★★★
Safety★★★★☆
Confidencelow

Study Evidence

Study 1. 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.

rct

Xing Y, Liu M, Sun Y, Mao X, Li J, Zhang Z, Sun H, Luo F · BMJ open (2026)

Participants: 1170
Duration: 48 hours postoperatively (primary outcome)
Intervention: Variable-rate feedback infusion mode of PCA (background rate automatically increases by 0.5 mL/hour on demand boluses during lockout intervals and decreases by 0.5 mL/hour after 1 hour of inactivity) versus fixed-rate basal infusion mode
Outcome: Total cumulative opioid consumption at 48 hours postoperatively (including sufentanil via PCA and opioid-equivalent rescue analgesics); secondary outcomes include resting and movement pain scores, cumulative PCA volume, rescue analgesia use, and postoperative quality of recovery
Effect Size: N/A (protocol paper, no results reported)
Population: Adults aged 18-65 years, American Society of Anaesthesiologists (ASA) I-III, undergoing elective mixed surgery (thoracic, abdominal, spinal, orthopaedic, cranial) under general anaesthesia

Result: This protocol describes a prospective, multicentre, randomised, double-blind, controlled trial to compare cumulative opioid consumption at 48 hours postoperatively between variable-rate feedback infusion and fixed-rate basal infusion modes of intravenous patient-controlled analgesia (PCA). The study will enrol 1170 patients undergoing mixed surgery and will measure total cumulative opioid consumption as the primary outcome, with secondary outcomes including pain scores and quality of recovery. The hypothesis is that variable-rate feedback infusion reduces opioid consumption while providing non-inferior analgesia.

PubMed: 42665353DOI: 10.1136/bmjopen-2026-117278

Mechanism Graph

Postoperative pain follows a biphasic pattern, with fluctuating intensity over time.
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Fixed-rate basal infusion provides a constant background rate, which may not match the changing pain levels.
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Variable-rate feedback infusion adjusts the background rate based on real-time patient demand (increases with bolus requests, decreases after inactivity).
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This dynamic adjustment may reduce unnecessary opioid exposure while maintaining adequate analgesia, leading to lower cumulative opioid consumption.

Limitations

  • ⚠This is a protocol paper; no results are yet available to confirm the hypothesis.
  • ⚠The study is limited to Chinese hospitals, which may affect generalizability to other populations.
  • ⚠The mixed surgical population may introduce heterogeneity in pain profiles, potentially confounding the comparison.

Frequently Asked Questions

What is the primary outcome of this trial?▼

The primary outcome is the total cumulative opioid consumption at 48 hours postoperatively, including sufentanil delivered via PCA and opioid-equivalent rescue analgesics.

How does variable-rate feedback infusion differ from fixed-rate basal infusion?▼

Variable-rate feedback infusion automatically adjusts the background infusion rate based on patient demand: it increases by 0.5 mL/hour when the patient presses the bolus button during lockout intervals and decreases by 0.5 mL/hour after 1 hour of no demand. Fixed-rate basal infusion delivers a constant background rate regardless of demand.

Who is eligible to participate in this study?▼

Patients aged 18-65 years with ASA physical status I-III, undergoing elective mixed surgery (thoracic, abdominal, spinal, orthopaedic, cranial) under general anaesthesia, are eligible.

What are the secondary outcomes of this trial?▼

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, nausea and vomiting, and patient satisfaction.

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References

  1. 1.Xing Y, Liu M, Sun Y, Mao X, Li J, Zhang Z, Sun H, Luo F. "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.." BMJ open, 2026. PMID: 42665353 DOI: 10.1136/bmjopen-2026-117278
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