Date Published: August 15, 2017
Author(s): Dewi Fransiska, Wifanto Saditya Jeo, Yefta Moenadjat, Dewi Friska.
Methylene blue (MB) has been found to have unique analgesic property through temporary disruption of sensory nerve conduction. In anorectal surgery, MB is widely used as a biologic stain but the analgesic effect has never been studied. Thus, a literature review completed with critical appraisal is required to find out its efficacy.
A review has been run to find out its efficacy. Literature search proceeded in database sites, namely, PubMed, EBSCO, Cochrane, Wiley, and ProQuest using the following keywords: “anorectal” OR “hemorrhoid” OR “anal fistula” OR “anal fissure” OR “anal abscess” OR “anal pruritus” AND “methylene blue” AND “analgesic”; then the critical appraisal and its implication were discussed.
There were 491 articles in full text found, and four studies met the inclusion criteria. Two studies were focused on the evaluation of VAS in hemorrhoid surgery whereas the rest were focused on the evaluation of symptom score in anal pruritus.
A study with level of evidence 2 on VAS showed the efficacy. The rest showed insufficient evidence due to variations of anorectal surgery and the methods and techniques of MB application. A further prospective clinical study is required.
Nowadays, methylene blue (MB) is widely used as biologic stain. In anorectal surgery, the use of high concentrated topical MB is not only staining the tip and nerve fibers, but also disrupting their function temporarily. To this knowledge, MB has been used in the treatment of neuritis, to reduce pruritus and analgesia in anorectal surgery [1–3].
Literature search was run with clinical questions based on PICO: population was those having anorectal surgery, the intervention was the application of MB, the comparison was to those who were not injected with MB, and the outcome was decrease of pain or symptom score. Literature search proceeded in database sites, namely, PubMed, EBSCO, Wiley, Cochrane, and ProQuest with clinical question “Does application of MB post anorectal surgery can give analgesic effect?” and keywords “anorectal” OR “hemorrhoid” OR “anal fistula” OR “anal fissure” OR “anal abscess” OR “anal pruritus” AND “methylene blue” AND “analgesic”. Inclusion criteria for literature research were English or Bahasa language, full text, and publication in recent ten years. Exclusion criteria were congenital disease, autoimmune, malignancy, subject with age under 12 years, molecular study, animal study, short communication, editorial, and commentary letter. Critical appraisal of validity, importance, and applicability was addressed based on Oxford critical appraisal tools which can be downloaded from http://www.cebm.net/critical-appraisal/.
On literature searching based on the steps shown in a diagram explained in Figure 1, there were 4 studies that met the criteria and were summarized in Table 1.
All the studies included showed different subjects’ characteristics and methods of MB applications. Xiang and Feng and Sim and Tan focused on hemorrhoid while another two studies focused on anal pruritus. In the studies on hemorrhoid, evaluation was addressed to VAS pain score, while as in anal pruritus the evaluation was using degree of symptom score. Study of Xiang and Feng which was a case control study showed low level of evidence (LOE 4). In contrast, study of Sim and Tan which was a randomized single-blind clinical trial showed a higher level of evidence (LOE 2).
MB was shown to be effective in reducing degree of pain (VAS) with level of evidence 2 which is quite strong and effectively reduce anal pruritus (level of evidence 4), which is weak. Somehow, this review may initiate further study on the use of MB as a local analgesic for postoperative management of those who had anorectal surgery.