A service evaluation of the newly introduced sciatic nerve local anaesthetic infusion catheters for acute pain management of major lower limb amputations

Abstract

Background: Patients who undergo lower limb amputations experience severe acute postoperative pain. Despite having no strong evidence for the efficacy of peripheral nerve blocks in reducing phantom limb pain, the reduction in acute postoperative pain and opioid-sparing effect1 make these techniques important to consider. Acute pain management has been identified as a key priority in the management of patients undergoing amputation.2 An initial audit, in October 2021, found that postoperative pain scores and opiate use were high. In April 2022, postoperative local anaesthetic nerve catheters for major lower limb amputations were introduced at our institution. The aim of this service evaluation was to ascertain the postoperative pain scores and analgesic consumption for patients having undergone a lower limb amputation and who subsequently received a continuous postoperative local anaesthetic infusion (levobupivacaine 0.125%, at 6–10 ml h−1 for up to 5 days) via a sciatic nerve catheter. Methods: A retrospective audit was undertaken between July and September 2022 at Birmingham Heartlands Hospital. We included patients having undergone a lower limb amputation with a sciatic nerve catheter placed intraoperatively by surgeons under direct vision and left along the nerve in the cut nerve sheath. Data collected included patient characteristics, postoperative pain scores days 1–5, postoperative opioid use including opioid side-effects, postoperative neuropathic pain, and block related complications. Results: We collected data for 24 patients. Compared with the period before the introduction of sciatic nerve catheters, we observed that the mean pain scores on the numeric rating scale (NRS) decreased. This was particularly evident on day 1 postoperatively when the mean pain scores decreased from the moderate to mild range. On days 1–5 of the postoperative period, the mean immediate-release opioid consumption was 16.1 mg day−1 and mean prolonged-release opioid consumption was 11.6 mg day−1. This was in comparison to the audit in October 2021 that found mean opioid use of 24.1 mg day−1 and 21 mg day−1, respectively. Opioid side-effects reported were sedation (18%), constipation (13%), and nausea or vomiting (8%). Fifty percent of patients reported neuropathic pain. Conclusion: The postoperative pain scores improved and the postoperative opioid consumption reduced slightly with the addition of a sciatic nerve catheter. Opioid side-effects and acute neuropathic pain remain an issue for this group of patients postoperatively. Overall, the introduction of a continuous local anaesthetic infusion via a sciatic nerve catheter after major lower limb amputations in our hospital has been a success and the technique is likely to play a significant future role as part of our multi-modal analgesia regimen for these patients. The Acute Pain Team at University Hospitals Birmingham NHS Foundation Trust. 1.Ilfeld BM. Anesth Analg 2011; 113: 904–252.Gough MJ, Juniper M, Freeth H, Butt A, Mason M. Lower limb amputation: Working together. A report by the National Confidential Enquiry into Patient Outcome and Death, 2014. https://www.hqip.org.uk/wp-content/uploads/2018/02/lower-limb-amputation-report.pdf (accessed 20/03/23)