Efficacy and safety of methylene blue for postoperative pain of haemorrhoids: a systematic review and meta-analysis

Pain is a common complication after haemorrhoid surgery. In addition to anaesthetic methods, surgical techniques and postoperative interventions, surgeons also use intraoperative adjuncts to alleviate postoperative pain. This study aims to evaluate the effectiveness and safety of methylene blue in reducing postoperative pain in haemorrhoid patients. A search was conducted in PubMed, Embase, Cochrane Library and Web of Science for randomized controlled trials (RCTs) up until 9 December 2024, involving methylene blue use for pain relief after haemorrhoid surgery. Two reviewers independently assessed the study eligibility, extracted data and evaluated the risk of bias. Data analysis was performed using Stata 18 software. The primary outcome was the visual analogue scale (VAS) pain scores at different time points within 14 days postoperatively. Secondary outcomes included the number of patients requiring analgesics and the occurrence of complications. 358 articles were retrieved and six studies involving 598 patients were included after screening. Compared with the control group, the use of methylene blue reduced pain within 12 h postoperatively(WMD −1.582, 95% CI −2.834 to −0.330, p = .013), as well as on day 2 (WMD −1.441, 95% CI − 1.874 to −1.008, p p p = .028) and day 7 (WMD −0.679, 95% CI −1.257 to −0.101, p = .021), decreased the number of patients using analgesics(RR 0.293, 95% CI 0.203 to 0.422, p p = .111) such as urinary retention, secondary haemorrhage, pruritus, temporary incontinence, wound infection, or local skin reactions. This study shows that methylene blue can reduce postoperative pain, decrease analgesic use and does not increase complications after haemorrhoid surgery. Methylene blue can alleviate pain within 12 h postoperatively, as well as on days 2, 3, 5, 7 and reduce the patients’ need for analgesics.Methylene blue does not cause urinary retention, nor does it lead to secondary haemorrhage, pruritus, temporary urinary incontinence, wound infection, or local skin reactions.It is recommended to develop detailed methylene blue usage guidelines and create specialized methylene blue products for the treatment of colorectal diseases to ensure that doctors can use the medication compliantly and effectively. Methylene blue can alleviate pain within 12 h postoperatively, as well as on days 2, 3, 5, 7 and reduce the patients’ need for analgesics. Methylene blue does not cause urinary retention, nor does it lead to secondary haemorrhage, pruritus, temporary urinary incontinence, wound infection, or local skin reactions. It is recommended to develop detailed methylene blue usage guidelines and create specialized methylene blue products for the treatment of colorectal diseases to ensure that doctors can use the medication compliantly and effectively.

疼痛是痔疮术后常见并发症。除麻醉方式、手术技术及术后干预措施外，外科医师还可借助术中辅助手段缓解术后疼痛。本研究旨在评估亚甲蓝（methylene blue）用于减轻痔疮术后患者疼痛的有效性与安全性。本研究检索了PubMed、Embase、Cochrane图书馆及Web of Science数据库，筛选截至2024年12月9日发表的、探讨亚甲蓝用于痔疮术后镇痛的随机对照试验（RCTs）。由2名研究者独立评估研究纳入资格、提取数据并评价偏倚风险，数据分析采用Stata 18软件完成。主要结局指标为术后14天内不同时间点的视觉模拟量表（VAS）疼痛评分；次要结局指标包括需使用镇痛药物的患者例数及并发症发生情况。最终共检索到358篇文献，经筛选后纳入6项研究，合计598例患者。与对照组相比，术中使用亚甲蓝可降低术后12小时内的疼痛水平（加权均数差WMD=-1.582，95%置信区间CI：-2.834~-0.330，P=0.013）、术后第2天（WMD=-1.441，95%CI：-1.874~-1.008，P<0.001）、第3天（P=0.028）及第7天（WMD=-0.679，95%CI：-1.257~-0.101，P=0.021）的疼痛评分，同时可减少需使用镇痛药物的患者数量（相对危险度RR=0.293，95%CI：0.203~0.422，P=0.111），且未显著增加相关并发症的发生风险。本研究结果显示，亚甲蓝可减轻痔疮术后疼痛、减少镇痛药物使用，且不会增加术后并发症发生率。亚甲蓝可缓解术后12小时内及术后第2、3、5、7天的疼痛，降低患者对镇痛药物的需求；同时不会引发尿潴留、继发性出血、瘙痒、暂时性尿失禁、切口感染或局部皮肤反应等不良事件。建议制定详细的亚甲蓝使用指南，并开发用于结直肠疾病治疗的专用亚甲蓝制剂，以确保临床医师能够合规且有效地使用该药物。