Preadmission chronic opioid usage and its association with 90-day mortality in critically ill patients: a retrospective cohort study.

Background: The aim of this study was to investigate the association of chronic opioid usage with 90-day mortality in critically ill patients after admission to the ICU.

Methods: This retrospective cohort study analysed the medical records of adult patients admitted to ICUs in a tertiary academic hospital between January 2012 and December 2017. Patients taking opioids regularly for more than 4 weeks before ICU admission were defined as chronic opioid users, whereas the others were defined as opioid-naïve patients.

Results: We selected 18 409 patients for this study, including 757 (4.1%) chronic opioid users. After propensity matching, 2990 patients (chronic opioid users, 757; opioid-naïve, patient: 2233) were included in the analysis. The odds of 90-day mortality were higher in chronic opioid users than in opioid-naïve patients using both the generalised estimating equation model for the propensity-matched cohort (odds ratio=1.90; 95% confidence interval, 1.57-2.31; P<0.001) and the multivariable logistic regression model for the entire cohort (odds ratio=2.20; 95% confidence interval, 1.81-2.66; P<0.001). Additionally, this association was significant in cancer patients and non-chronic kidney disease (CKD) patients and was not significant in non-cancer and CKD patients.

Conclusions: Our results suggest that in a cohort of critically ill adult patients, chronic opioid use is associated with an increase in 90-day mortality. This association was more evident in cancer patients and non-CKD patients.