Early detection of opioid-induced hyperalgesia after an ICU stay using quantified sensory testing: An observational cohort case-control study.

Background: Opioids can heighten sensitivity to noxious stimuli, leading to opioid-induced hyperalgesia (OIH). Despite the frequent use of high opioid doses in ICU settings, the presence of OIH following ICU stays remains undocumented.

Methods: This prospective observational study aimed to assess OIH presence and its clinical implications in post-ICU patients. Adults with confirmed Sars-CoV-2 infection hospitalized in the ICU for over 48 h were included, with opioid dosage recorded. At ICU discharge, 11 quantitative sensory tests (QSTs) were conducted at two non-painful sites, and pain presence, intensity, and characteristics were assessed at discharge and 4 months later.

Results: Analysis of 41 patients (20 opioid-treated, 21 controls) revealed significantly higher hyperalgesia levels in the opioid-treated group across six tests at both sites, including cold pain thresholds, heat and cold tolerance thresholds, duration of tolerance to a 47°C stimulus, and thermal and mechanical temporal summation.

Conclusions: Our findings underscore the importance of QST in early OIH detection, identifying thermal tolerance thresholds and thermal/mechanical temporal summation tests as sensitive indicators. Subclinical hyperalgesia in ICU patients on opioids heightens susceptibility to chronic pain development, emphasizing the need for vigilant opioid monitoring and adjustment in ICU care.