Comparing the efficacy and safety of continuous epidural analgesia in abdominal and urological surgery between two opioids with different kinetic properties: Morphine and sufentanyl

Background. Ample evidence is now available showing the analgesic efficacy of a local anaestheric-opioid combination to control postoperative pain. This retrospective study aimed to analyze any improvement in the ability of sufentanyl, a highly lipophilic opioid, and morphine, a poorly lipophilic opioid, to control postoperative pain at rest and in motion when combined with ropivacaine 0.2%. Methods. In this retrospective study, 171 patients who underwent major abdominal or urological surgery were evaluated. The therapeutic protocol provided for continuous epidural perfusion (5 mL/h) of ropivacaine 0.2% + morphine 0.03 mg/mL or ropivacaine 0.2% + sufentanyl 0.75 μg/mL for 48 h. Pain at rest (numeric rate scale, NRS) and in motion (NRSm) was evaluated by means of the NRS upon waking and at 3, 6, 12, 24, 36, and 48 hs, providing for the administration of a rescue dose if NRS >4. The overall analgesic effect was evaluated by comparing the area under the NRS curve (AUC) of both treatments using the Mann Whitney U test. Any differences between treatments in terms of NRS and NRSm in time were evaluated using ordinal logistic regression. To compare the frequency of patients who reported NRS >4 at least once during the follow-up period, logistic regression was used. Finally, the frequency of patients who required at least one additional drug or reported side effects was compared using Fisher's exact test. Results. While both groups showed a comparable overall analgesic effect, the baseline values of NRS and NRSm were lower for the sufentanyl group (P