Relationship of opioid tolerance to patient and wound factors, and wound micro-environment in patients with open wounds.

Objective: Opioid tolerance is a criterion for opioid use disorder, which is currently an epidemic in the US. Individuals with open wounds are frequently administered opioids; however, the phenomenon of opioid tolerance has not been examined in the context of wounds. The purpose of this exploratory study was to compare patient/wound factors, wound microbiome and inflammatory mediators between individuals who were opioid-tolerant versus those who were not opioid-tolerant.

Method: Patients with acute open wounds were enrolled in this cross-sectional study. All study data were collected before and during a one-time study dressing change.

Results: The study included a total of 385 participants. Opioid-tolerant participants were significantly younger (p<0.0001); had higher levels of depression (p=0.0055) and anxiety (p=0.0118); had higher pain catastrophising scores (p=0.0035); reported higher resting wound pain (p<0.0001); had a higher number of wounds of <30 days' duration (p=0.0486); and had wounds with lower bacterial richness (p=0.0152) than participants who were not opioid-tolerant. A backward elimination logistic regression model showed that four predictors-resting wound pain, age, bacterial richness and depression-were the most important variables in predicting opioid-tolerance status.

Conclusion: These findings provide the first insights into the phenomenon of opioid tolerance in the context of open wounds. This study provides findings from which to guide hypothesis-driven research in the future.