Title: Safety of diamorphine based epidural mixture in postoperative analgesia: experience from a tertiary hospital in United Kingdom

Background and Goal of Study: Diamorphine, a long acting opioid had been regularly used in the past to provide post-operative epidural analgesia in UK[1]. Its use has rapidly declined in the last 2 decades[2]. Diamorphine based local anaesthetic mixture is infused at lower rates in comparison to Fentanyl based solutions; hence, produces less sympathetic and motor blockade.
The goal of this retrospective study was to evaluate the “Safety” of Diamorphine based epidural analgesia in post-surgical patients.

Materials and Methods: We obtained approval from local audit and research department. All the patients who had postoperative epidural analgesia between Feb.2014 and Oct.2015 were included in the study.Data was obtained from acute pain audit data, patient's electronic and paper notes.Data collected include demographics, surgical details, epidural procedure details, pain scores and the side effects.

Results and discussion: We collected data on 310 (n) patients, with median age of 67 ± 13 years (SD).85% of epidurals were performed for elective surgeries.35% (110) of the patients developed hypotension. 61%(191) patients needed additional fluids and or ionotropic support.19% (59) patients were sedated(sores 1-3) needing alterations in epidural rate and concentration of Diamorphine. Lower limb motor block was documented by modified Bromage score (1-3) in 6% (18) patients of which 72.2% patients had Lumbar epidural. 6.1% (19) patients developed respiratory complications, of which 68.4% had supra-umbilical incision. 14.8% (46) patients developed itching and 3.8% (12) patients suffered from post-operative nausea and vomiting.None of the non-catheterised patients (29) had urinary retention. 
There was no correlation between epidural infusion rate and the development of postoperative hypotension or increased use of intravenous fluids and vasopressors although other causes of hypotension could not be excluded.

Conclusion: Our study shows that Diamorphine could be safely used as an alternative opioid in epidural mixture for providing post-operative analgesia.