Chronic postoperative opioid use after open cardiac surgery: A Danish population-based cohort study

Background: Knowledge of chronic opioid use after cardiac surgery is sparse. We therefore aimed to describe the proportion of new chronic post-operative opioid use after open cardiac surgery. Methods: We used prospectively registered data from a national prescription registry and a clinical registry of 29 815 first-time cardiac surgeries from three Danish university hospitals. Data collection spanned from 2003 to 2016. The main outcome was chronic post-operative opioid use, defined as at least one opioid dispensing in the fourth post-operative quarter. Data were assessed for patient-level predictors of chronic post-operative opioid use, including pre-operative opioid use, opioid use at discharge, comorbidities, and procedural related variables. Results: The overall proportion of post-operative opioid use was 10.6% (95% CI: 10.2-10.9). The proportion of new chronic post-operative opioid use was 5.7% (95% CI: 5.5-6.0) among pre-operative opioid naïve patients. The corresponding proportions among patients, who pre-operatively used low or high dose opioid (1-500 mg or > 500 mg cumulative morphine equivalent opioid), were 68.3% (95% CI: 66.1-70.4) and 76.3% (95% CI: 74.0-78.5) respectively. Risk factors associated with new chronic post-operative opioid use included: female gender, underweight and obesity, pre-operative comorbidities, acute surgery, ICU-time > 1 day, and post-operative complications. Strongest predictor of chronic post-operative opioid use was post-discharge use of opioid within one month after surgery (odds ratio 3.3, 95% CI: 2.8-4.0). Conclusion: New chronic post-operative opioid use after open cardiac surgery is common. Focus on post-discharge opioid use may help clinicians to reduce rates of new chronic opioid users.