It is unclear whether addition of opioids to epidural solutions for postoperative analgesia is beneficial. In this multicenter randomized double-blinded trial, we aim to test the primary hypothesis that epidural solutions containing only bupivacaine are as effective as solutions containing both bupivacaine and fentanyl in promoting analgesia in patients recovering from open abdominal surgery. We also aim to assess the incidence of epidural-induced hypotension, the difference in patient-reported opioid side-effects between the two groups. If we demonstrate no clinically important difference between the two interventions, clinicians will be able to substantially reduce the amount of opioids patients receive during their postoperative recovery, and potentially decrease the associated high incidence of opioid adverse effects in post-surgical patients.

Inclusion Criteria:

1. Written informed consent
2. 18-85 years old
3. Undergoing open abdominal surgery (including colorectal, intestinal, gastric, pancreatic, hepatobiliary, urological, or gynecological surgery)
4. For which a clinical decision has been made to provide epidural analgesia preoperatively and extending to the post-operative period
5. Anticipated hospitalization of at least 2 nights

Exclusion Criteria:

1. Known allergy to bupivacaine or fentanyl
2. Chronic liver disease, defined as cirrhosis, portal hypertension, or variceal bleeding
3. Patients under chronic alpha-blocking agents for hypertension
4. Clinical contraindications to epidural introduction, as judged by the anesthesia provider (thrombocytopenia, un-interrupted anticoagulation, clinically-significant atrio-ventricular conduction block, etc.)
5. Pregnant women