Opioids Increase the Risk of Delirium in Critically Ill Patients: A Propensity Score Analysis

Background: Medications are biologically plausible and potentially modifiable risk factors for delirium. Therapies for delirium might involve more specific strategies such as avoiding the use of delirium inducing drugs to reduce the incidence of delirium. The association between opioid exposure within 24 hours prior to delirium assessment and the risk of delirium was studied. Materials and methods: Using three large databases, the MIMIC III v1.4, MIMIC-IV v0.4 and eICU Collaborative Research, we performed a multicenter, observational cohort study with two cohorts to estimate the relative risks of outcomes among patients administered opioids within 24 hours prior to delirium assessment. Propensity score matching was performed to generate a balanced 1 : 1 matched cohort and to identify potential prognostic factors. The outcomes included mortality, length of intensive care unit (ICU) stay, length of hospitalization, and odds of being discharged home. Results: Propensity matching successfully balanced the covariates for the 9,529 patients in each group. Opioid use was associated with a significantly higher risk for delirium than not using opioids (p < 0.001). Additionally, treatment with opioids was associated with higher mortality and a longer ICU stay (p < 0.001) than treatment without opioids. However, patients treated with opioids were more likely to be discharged home (p < 0.001). Conclusion: Opioids may be an independent risk factor for delirium in critically ill patients.