Continuous epidural versus wound infusion plus single morphine bolus as postoperative analgesia in open abdominal aortic aneurysm repair: a randomized non-inferiority trial

BACKGROUND: We compared a bundle of interventions including wound infiltration and continuous infusion with local anaesthetics plus a single morphine bolus (CWI-M) with continuous epidural infusion (CEI) as postoperative analgesia. METHODS: Fifty-one adults undergoing open abdominal aortic aneurysm repair were randomised in this non-inferiority open-label trial. In the CEI group, patients received thoracic epidural levobupivacaine 0.12% plus sufentanil 0.4 g·ml-1 infusion for 48h. In the CWI-M group, the wound was infiltrated with 10 ml levobupivacaine 0.5%, patients received a morphine bolus before the end of anaesthesia and levobupivacaine 0.25% infusion through two multi-holed pre-peritoneal catheters for 48h. Systemic morphine was administered as rescue in both groups. The primary endpoint was the mean NRS in the first 48h after surgery. RESULTS: Mean NRS was 1.7 (95% CI: from 1.2 to 2.2) in the CEI and 2.2 (95% CI: from 1.7 to 2.7) in the CWI-M group, the 90% CI of difference was from -0.1 to 1.1, not including the non- inferiority margin of 1.3. The cumulative rescue morphine dose per patient was higher in CWI-M than in CEI group (3.7 ± 4.4 mg vs. 0.8 ± 2.4, p = 0.006); moreover, NRS at arousal was higher in CWI-M (p = 0.003). No differences were observed in postoperative haemodynamic parameters, recovery-related outcomes, length of stay nor complications. CONCLUSIONS: CWI-M was comparable to CEI in in postoperative pain control, but it was associated with higher need of rescue systemic opiates and with a worse early pain control.