Patients with chronic pain syndrome (CPS) may develop central sensitization wich may lead to increased pain intensity and lower pain threshold sometimes to the extend of hyperalgesia and allodynia. Furthermore, patients with daily use of opioids may develop opioid tolerance, and to a lesser extent opioid induced hyperalgesia.

These factors may lead to a higher pain intensity in the perioperative setting resulting in the observed increased opioid dosage needed to treat the acute pain. Furthermore opioid titration may be difficult with higher levels of pain and a higher risk of opioid related adverse effects incl. respiratory depression and sedation.

The factors above advocate for utilizing opioid sparing analgesic techniques. In our department as in many others we use an multimodal opioid sparing approach for surgical procedures including epidural anesthesia (EA) as a standard part of the perioperative analgesia strategy after upper laparotomy, as a sufficient epidural anesthesia has shown to provide a stable and often better pain relief than systemic opioids in these patients.

Clinically, there is a suspicion that patients with CPS on fixed opioid treatment have a higher frequency of need for epidural optimization, despite the lack of an anatomical reason for this. One potential explanation could be an altered nociception, requesting another EA strategy than in non-opioid patients.

Purpose and hypothesis This study will explore the frequency of failed EA, defined as EA with insufficient analgesic effect to the extent were replacements of the epidural is needed within the first 5 postoperative days (PODs), testing the hypothesis that failed epidural occurs more frequent in patients with CPS on fixed opioid treatment than in non-opioid patients without CPS.

Inclusion Criteria:

• Patients undergoing elective laparotomy with epidural anesthesia as a part of the postoperative pain treatment
• For the intervention group - Patients with chronic pain disorder defined as pain for more than 3 months and a daily use of opioids regardless of dosage.
• For the control group - No chronic pain disorder defined as no daily use of opioid or other medicine with strong analgetic effect. A daily use of Acetaminophen and NSAIDs were deemed acceptable.

Exclusion Criteria:

• Patients with substance abuse
• Suspected withdrawal due to opioid deficiency - noted in the medical chart

Adult patients with or without chronic pain and opioid use undergoing elective laparotomi with epidural anesthesia as a part of the postoperative pain treatment.