The systematic review and meta-analysis by Grape et al. [1] suggests that there is no evidence of benefit to doses of intrathecal diamorphine exceeding 0.2 mg. Their systematic review identified 12 trials (712 patients), 11 of which included only patients undergoing orthopaedic or obstetric procedures. There was a single trial including 30 patients having inguinal hernia repair, lower limb arterial or transurethral surgery [2].

A review of 20 major general surgical procedures in our department from the last 2 months (bowel resections, open, and laparoscopic and robot assisted laparoscopic cystectomies) where we use intrathecal diamorphine for analgesia rather than as a sole technique, found a median (IQR [range]) intrathecal diamorphine dose of 0.73 mg (0.50–0.85 [0.40–1.00]). Such dosing has been typical for years and has produced good results. Recognising the significant evidential shortcomings of a small 20 patient retrospective cohort, 17 out of 20 had nil or mild pain, and moderate pain was only found in those with below average dosing. In total, 90% of patients did not experience nausea or vomiting in the post-anaesthesia care unit, none needed naloxone and there were no unplanned ICU admissions or need for chlorphenamine for pruritus.

The included article by Abuzaid et al. detailed general surgical and vascular operations and was published in 1993 [2]. We are concerned it may not represent the current patient cohort for whom single-shot spinal analgesia is administered specifically to cover long and complex abdominal surgeries. There have been substantial developments in surgical practice since 1993; the growth of laparoscopic and robotic surgery, along with enhanced recovery pathways has meant that operations that might historically have used a thoracic epidural, are now having intrathecal opioid administration. Epidurals are known to have a failure rate of around 30% and can cause hypotension and leg weakness [3]. Anecdotally, there is a fear that they will reduce patient mobilisation postoperatively and prolong hospital stay. Single-shot spinals are a middle ground, providing good analgesia in the immediate postoperative period but allowing patients to mobilise with full leg strength the next day, unencumbered by syringe pumps.

Considering this systematic review, we acknowledge that further dose-finding trials could be conducted. However, it is unlikely that we will convince our colleagues to reduce their dose of intrathecal diamorphine for major abdominal procedures.

Grape 等人 [1] 的系统评价和荟萃分析表明，没有证据表明鞘内注射二吗啡剂量超过 0.2 mg 有益。他们的系统评价确定了 12 项试验（712 名患者），其中 11 项仅包括接受骨科或产科手术的患者。有一项试验纳入了 30 例接受腹股沟疝修补术、下肢动脉或经尿道手术的患者 [2]。

对过去 2 个月我们科室 20 例主要普通外科手术（肠切除术、开腹手术、腹腔镜和机器人辅助腹腔镜膀胱切除术）的回顾，我们使用鞘内注射二吗啡进行镇痛，而不是作为唯一技术，发现鞘内注射二吗啡的中位剂量 （IQR [范围]）为 0.73 mg （0.50-0.85 [0.40-1.00]）。这种剂量多年来一直很常见，并产生了良好的效果。认识到一个小型 20 名患者回顾性队列的重大证据缺陷，20 名患者中有 17 名没有或轻度疼痛，而中度疼痛仅在剂量低于平均水平的患者中发现。总的来说，90% 的患者在麻醉后监护病房中没有出现恶心或呕吐，没有人需要纳洛酮，也没有计划外入住 ICU 或需要氯苯那敏治疗瘙痒。

Abuzaid 等人收录的文章详细介绍了普通外科和血管手术，并于 1993 年发表 [2]。我们担心它可能无法代表当前的患者群体，这些患者专门针对这些患者进行单次脊髓镇痛以涵盖漫长而复杂的腹部手术。自 1993 年以来，外科实践取得了长足的发展;腹腔镜和机器人手术的发展，以及增强的恢复途径，意味着历史上可能使用胸部硬膜外麻醉的手术现在正在鞘内注射阿片类药物。已知硬膜外麻醉的失败率约为 30%，可导致低血压和腿部无力 [3]。有趣的是，人们担心它们会在术后减少患者活动并延长住院时间。单次脊髓注射是一种中间地带，在术后即刻提供良好的镇痛作用，但允许患者在第二天以全力活动，而不受注射泵的阻碍。

考虑到本系统综述，我们承认可以进行进一步的剂量探索试验。然而，我们不太可能说服我们的同事减少他们在主要腹部手术中鞘内注射二吗啡的剂量。