Relationship between acute pain trajectories after an emergency department visit and chronic pain: a Canadian prospective cohort study

OBJECTIVES: Inadequate acute pain management can reduce the quality of life, cause unnecessary suffering and can often lead to the development of chronic pain. Using group-based trajectory modelling, we previously identified six distinct pain intensity trajectories for the first 14-day postemergency department (ED) discharge; two linear ones with moderate or severe pain during follow-up (~40% of the patients) and four cubic polynomial order trajectories with mild or no pain at the end of the 14 days (low final pain trajectories). We assessed if previously described acute pain intensity trajectories over 14 days after ED discharge are predictive of chronic pain 3 months later. DESIGN: Prospective cohort study. SETTING: Tertiary care trauma centre academic hospital. PARTICIPANTS: This study included 18 years and older ED patients who consulted for acute (≤2 weeks) pain conditions that were discharged with an opioid prescription. Patients completed a 14-day diary in which they listed their daily pain intensity (0–10 numeric rating scale). OUTCOMES: Three months after ED visit, participants were questioned by phone about their current pain intensity (0–10 numeric rating scale). Chronic pain was defined as patients with current pain intensity ≥4 at 3 months. RESULTS: A total of 305 participants remained in the study at 3 months, 49% were women and a mean age of 55±15 years. Twelve per cent (11.9; 95% CI 8.2 to 15.4) of patients had chronic pain at the 3-month follow-up. Controlling for age, sex and pain condition, patients with moderate or severe pain trajectories and those with only a severe pain trajectory were respectively 5.1 (95% CI 2.2 to 11.8) and 8.2 (95% CI 3.4 to 20.0) times more likely to develop chronic pain 3 months later compared with patients in the low final pain trajectories. CONCLUSION: Specific acute pain trajectories following an ED visit are closely related to the development of chronic pain 3 months later. TRIAL REGISTRATION NUMBER: NCT02799004; Results.