Minimal Important Difference for Rescue Opioid Consumption in Adults With Acute Pain: A Scoping Review

BACKGROUND: The minimal important difference (MID) is established for pain intensity scores in acute pain management, but not for rescue opioid consumption. This scoping review aimed to estimate the MID in rescue opioid consumption for acute pain among adult patients in the postoperative and emergency settings.

METHODS: We searched MEDLINE, Embase, CENTRAL, clinicaltrials.gov and clinicaltrialsregister.eu for studies published in English from inception to May 2024. We included studies investigating the MID of rescue opioid consumption in adults with acute pain in the postoperative and emergency settings. Because limited studies explicitly investigated the MID, we also included studies assessing the dose-response relationship between opioid consumption and relevant anchors (e.g., pain intensity scores). The primary outcome was MID for 0-24 h rescue opioid consumption; secondary outcomes included longer postoperative periods.

RESULTS: We screened 11,748 citations and included 14 studies (8190 patients). Three studies explicitly evaluated MID for rescue opioid consumption. In the remaining 11 studies, we estimated the MID using a 10-point difference (0-100 scale) in pain intensity score as an anchor. The anchor-based estimates ranged from 2 to 5 mg IV morphine equivalents, varying by population, method and context.

CONCLUSIONS: Based on the currently available evidence, we propose a provisional MID of 5 mg IV morphine equivalent in rescue opioid consumption for acute pain. This is lower than the value used in most sample size calculations.

SIGNIFICANCE STATEMENT: These results can guide sample size calculations and support patient-centered approaches in acute pain settings.

TRIAL REGISTRATION: PROSPERO identifier: CRD42024547409.