UCSF

OBJECTIVES: Opioid therapy for chronic pain complicates post-operative pain management. This study evaluated the incidence of failed epidural analgesia, defined as epidural catheter replacement, in opioid-treated chronic pain patients vs. pain-free opioid-naïve controls undergoing elective upper laparotomy. METHODS: We conducted a retrospective case-control cohort study of adult patients undergoing elective upper laparotomy with epidural anesthesia (EA) for postoperative pain management. The intervention group comprised chronic pain patients, defined as pain lasting >3 months with stable daily opioid use. Controls were pain-free opioid-naïve patients. Patients with known illegal opioid use were excluded. A sample size of 75 chronic opioid-treated pain patients and 75 pain-free patients would allow for detection of a 15 % between group difference in epidural catheter replacement at a 0.05 significance level. RESULTS: Seventy-five chronic pain patients and 75 pain-free opioid-naïve controls were included. Chronic pain patients were more often female, had more co-morbidities, and more frequently underwent pancreatic resections; liver resections were more common among controls. The median preoperative daily oral morphine equivalent use among chronic pain patients was 45 mg (IQR, 20-80). Epidural analgesia failure occurred four times more often in chronic pain patients compared with controls (41.3 % vs. 10.7 %; p<0.01). CONCLUSIONS: Chronic preoperative opioid use for pain significantly increased the rate of postoperative epidural catheter replacement. The findings were not explained by external preoperative, technical or surgical factors, supporting further pathophysiological investigations to tailor mechanism based interventions.