What question did this study set out to answer?

The trial aims to determine if intrathecal hydromorphone prolongs analgesia and minimizes rescue analgesic needs after anorectal surgery.

February 27, 2026Open Access

Effect of Intrathecal Hydromorphone on the Duration and Efficacy of Postoperative Analgesia in Patients Undergoing Benign Anorectal Surgery: Protocol for a Randomized, Double-Blind, Controlled Trial

Key Points

The trial aims to determine if intrathecal hydromorphone prolongs analgesia and minimizes rescue analgesic needs after anorectal surgery.
Enrolled 76 patients for elective surgery, randomized to receive either ropivacaine with hydromorphone or ropivacaine alone.
Measured primary outcome as the duration until first rescue analgesia request.
Assessed secondary outcomes including pain scores at multiple time points and total analgesic consumption.
Expected findings include a longer duration of analgesia in the hydromorphone group compared to control.
Reduced total rescue analgesic consumption within 24 hours is anticipated.
Pain scores across various time points are expected to show significant differences favoring hydromorphone.

Abstract

Background: Intrathecal anesthesia is commonly used for analgesia in anorectal surgery, often supplemented with low-dose opioids such as morphine or fentanyl to prolong the duration of analgesia. However, the utility of these opioids is constrained by their adverse effects or inadequate analgesia. Hydromorphone, an opioid with pharmacodynamic properties intermediate between those of morphine and fentanyl, theoretically offers a favourable balance of prolonged analgesia and reduced side effects. Nevertheless, evidence regarding the efficacy and safety of intrathecal hydromorphone for postoperative analgesia in anorectal surgery remains scarce. Purpose: To determine whether the addition of hydromorphone can effectively prolong the duration of analgesia provided by single-agent intrathecal ropivacaine, reduce the requirement for rescue analgesics, and avoid a significant increase in adverse effects. Patients and Methods: A total of 76 patients scheduled for elective benign anorectal surgery will be enrolled and randomly allocated in a 1:1 ratio to either the intervention group (Group H: intrathecal ropivacaine 10 mg + hydromorphone 75 μg) or the control group (Group C: intrathecal ropivacaine 10 mg). The primary outcome will be the duration of postoperative analgesia, defined as the time to first request for rescue analgesia. Secondary outcomes will include Numerical Rating Scale (NRS) pain scores at various postoperative time points (4, 6, 8, 10, 12, and 24 hours), total 24-hour rescue analgesic consumption, the incidence of adverse effects, and patient satisfaction. Conclusion: To our knowledge, this is one of the first randomized controlled trials to evaluate the analgesic value of intrathecal hydromorphone in patients undergoing anorectal surgery. If the outcomes are positive, this approach may offer a superior multimodal analgesic option for anorectal procedures, support the implementation of Enhanced Recovery After Surgery (ERAS) protocols, and provide high-quality evidence to inform clinical decision-making in this field. Trial Registration: The study was registered with the Chinese Clinical Trial Registry (Registration No.: ChiCTR2500100994). Keywords: hydromorphone, intrathecal anesthesia, anorectal surgery, postoperative analgesia, randomized controlled trial

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