Methylene blue induces an analgesic effect by significantly decreasing neural firing rates and improves pain behaviors in rats

Analgesic effect of ropivacaine combined with methylene blue in fascia Iliaca block for patients undergoing hip arthroplasty

BACKGROUND

The duration of a single fascia iliaca compartment block (FICB) with ropivacaine is limited. This study investigated whether methylene blue as an adjuvant anesthetic in FICB can enhance the postoperative analgesic effect following total hip arthroplasty (THA).

METHODS

Patients who planned to undergo THA were recruited for this randomized clinical trial from June 2023 to February 2024. Ninety elderly patients undergoing THA were randomly divided into two groups that received ultrasound-guided FICB with either ropivacaine and methylene blue (MB + R group, n = 45) or ropivacaine only (R group, n = 45) before induction of general anesthesia. The primary outcomes were postoperative Visual Analog Scale (VAS) scores. Secondary outcomes included inflammatory factor levels, heart rate (HR), mean arterial pressure (MAP), postoperative analgesic use, postoperative activity, and adverse events.

RESULTS

The MB + R group had significantly lower VAS scores at both rest and with activity at 24 and 48 h postoperatively than the R group (P < 0.001). Additionally, the hypersensitive C-reactive protein, procalcitonin, and neutrophil-to-lymphocyte ratio values were significantly lower in the MB + R group than in the R group on the first and second days after surgery (P < 0.05). The number of patients requiring supplemental analgesia postoperatively was significantly lower in the MB + R group (P = 0.020). Additionally, the MB + R group had a significantly longer walking distance on the first time out of bed and a higher number of out-of-bed activities within 48 h postoperatively (P < 0.001).

CONCLUSION

Compared to ropivacaine alone, the combination of ropivacaine and methylene blue in FICB provided better analgesic effects over a longer duration. Additionally, the addition of methylene blue reduced the postoperative production of inflammatory markers and promoted patients' functional recovery.

TRIAL REGISTRATION

ClinicalTrials.gov, Registration number: NCT06284941, Retrospectively registered, Date of registration: February 04, 2024.

Analgesic efficacy and safety of methylene blue combined with cocktail for periarticular infiltration following total knee arthroplasty: a prospective, randomized, controlled study

OBJECTIVE

This study aims to explore the analgesic effects and safety of periarticular injections of methylene blue (MB) combined with a cocktail formulation following total knee arthroplasty (TKA).

METHODS

A total of 70 patients undergoing total knee arthroplasty were selected and divided into two groups based on the cocktail formula used for periarticular infiltration, including the methylene blue group (M group, n = 35) and the control group (C group, n = 35). Both groups underwent spinal anesthesia. At the end of the surgery, the M group received a 0.05% methylene blue combined cocktail for periarticular infiltration block, while the C group received a conventional cocktail infiltration block. Postoperatively, both groups used intravenous patient-controlled analgesia. Then, the rest and movement Numeric Rating Scale (NRS) scores, postoperative sufentanil consumption, postoperative inflammatory markers, and the occurrence of adverse reactions such as wound infection and poor wound healing were compared after postoperative 24 h, 48 h, 72 h, and 7-day, 14-day, 28-day between the two groups.

RESULTS

The rest and during movement, NRS scores at postoperative 24 h, 48 h, 72 h, 7-day, 14-day, and 28-day were significantly lower in the C group compared with the M group (P < 0.05). The total sufentanil consumption at postoperative 72 h was less in the M group (98.9 ± 11.3 µg) compared to the C group (129.1 ± 12.3 µg) (P < 0.01). It also showed a lower IL-6 in the M group at postoperative 24 h and 72 h (P < 0.05). However, there were no significant differences in CRP levels between the two groups at 24 h and 72 h post-surgery (P > 0.05), and neither group experienced complications such as wound infection or poor wound healing.

CONCLUSION

Methylene blue combined with a cocktail can be safely used for local infiltration after knee arthroplasty, which reduces postoperative opioid consumption and suppresses the release of inflammatory factors. Moreover, it synergistically enhanced the local anesthetic analgesia and provided sustained pain relief for at least 4 weeks.

Intradermal methylene blue analgesic application in posthemorrhoidectomy pain management: a randomized controlled trial

Introduction

Unbearable post-hemorrhoidectomy pain is a well-documented challenge, significantly impacting patient well-being and satisfaction after surgery, often influencing patients to decline in undergoing this procedure. It is widely recognized that methylene blue has an effect of reducing inflammation and pain by reduces the production of nitric oxide and inhibiting the action potentials production in nerves. This study aims to explore the potential benefits of postoperative regional administration of methylene blue in providing extended relief from post-hemorrhoidectomy pain.

Methods

This study included 97 patients aged 18-75 undergoing hemorrhoidectomy for stage III or IV hemorrhoids. A double-blind, randomized controlled trial compared postoperative intradermal injections of 1% methylene blue to 0.5% Marcaine as the control group. Two-week follow-up assessed pain. Statistical analysis, adherence to ethical standards, and registration were conducted.

Result

No significant differences were found in baseline demographics, surgical parameters, or complications between the Methylene Blue and control groups. Intervention group remained lower in mean pain score until the 12th day. Methylene blue group reported significantly lower postoperative pain scores from days 1 to 7, with no significant differences afterward.

Conclusion

This ongoing randomized controlled trial reveals the potential analgesic benefits of intradermal injection 1% methylene blue. It demonstrates comparable efficacy in reducing post-hemorrhoidectomy pain, with negligible side effects and complications.

Methylene blue dose-dependently induces cutaneous inflammation and heat hyperalgesia in a novel rat model

Methylene blue (MB) has been shown to reduce mortality and morbidity in vasoplegic patients after cardiac surgery. Though MB is considered to be safe, extravasation of MB leading to cutaneous toxicity has been reported. In this study, we sought to characterize MB-induced cutaneous toxicity and investigate the underlying mechanisms. To induce MB-induced cutaneous toxicity, we injected 64 adult male Sprague-Dawley rates with 200 µL saline (vehicle) or 1%, 0.1%, or 0.01% MB in the plantar hind paws. Paw swelling, skin histologic changes, and heat and mechanical hyperalgesia were measured. Injection of 1%, but not 0.1% or 0.01% MB, produced significant paw swelling compared to saline. Injection of 1% MB produced heat hyperalgesia but not mechanical hyperalgesia. Pain behaviors were unchanged following injections of 0.1% or 0.01% MB. Global transcriptomic analysis by RNAseq identified 117 differentially expressed genes (111 upregulated, 6 downregulated). Ingenuity Pathway Analysis showed an increased quantity of leukocytes, increased lipids, and decreased apoptosis of myeloid cells and phagocytes with activation of IL-1β and Fos as the two major regulatory hubs. qPCR showed a 16-fold increase in IL-6 mRNA. Thus, using a novel rat model of MB-induced cutaneous toxicity, we show that infiltration of 1% MB into cutaneous tissue causes a dose-dependent pro-inflammatory response, highlighting potential roles of IL-6, IL-1β, and Fos. Thus, anesthesiologists should administer dilute MB intravenously through peripheral venous catheters. Higher concentrations of MB (1%) should be administered through a central venous catheter to minimize the risk of cutaneous toxicity.

Application of methylene blue combined with ropivacaine intercostal nerve block in postoperative analgesia of autologous costal cartilage augmentation rhinoplasty

OBJECTIVE

To observe the effect of methylene blue combined with ropivacaine intercostal nerve block on postoperative analgesia after autologous costal cartilage augmentation rhinoplasty.

METHODS

In this study 100 female patients who underwent autologous costal cartilage comprehensive augmentation rhinoplasty in Chongqing Huamei Plastic Surgery Hospital from April to November 2021 were randomly divided into an experimental group and a control group, with 50 cases in each group. In the experimental group methylene blue was combined with ropivacaine intercostal nerve block as patient controlled intravenous analgesia (PCIA), and the control group was ropivacaine intercostal nerve block combined with PCIA. The visual analogue scale (VAS) scores of resting and coughing at 6 h (T1), 24 h (T2), 48 h (T3), 72 h (T4) after surgery were recorded and evaluated. At the same time, the number and times of oral analgesics were recorded as well as nausea, vomiting, burning pain and paresthesia.

RESULTS

The VAS scores of the experimental group were lower than those of the control group at all time points. At 6 h, 24 h and 48 h after surgery, the VAS score of the experimental group was lower than that in the control group, but the difference was not statistically significant (P > 0.05). The VAS score of calm 72 h after surgery in the experimental group was significantly lower than that in the control group (P < 0.05). The analgesic effect of the two groups was better when they coughed after surgery. At 6 h after surgery, the VAS score of coughing in the experimental group was lower than that in the control group, but the difference was not statistically significant (P > 0.05); At 24 h, 48 h and 72 h after surgery, the VAS score of the coughing state in the experimental group was significantly lower than that in the control group (P < 0.05).

CONCLUSION

Intercostal nerve block with methylene blue combined with ropivacaine can achieve good postoperative analgesic effects in augmentation rhinoplasty with autologous costal cartilage.

Methylene Blue Application to Lessen Pain: Its Analgesic Effect and Mechanism

Methylene blue (MB) is a cationic thiazine dye, widely used as a biological stain and chemical indicator. Growing evidence have revealed that MB functions to restore abnormal vasodilation and notably it is implicated even in pain relief. Physicians began to inject MB into degenerated disks to relieve pain in patients with chronic discogenic low back pain (CDLBP), and some of them achieved remarkable outcomes. For osteoarthritis and colitis, MB abates inflammation by suppressing nitric oxide production, and ultimately relieves pain. However, despite this clinical efficacy, MB has not attracted much public attention in terms of pain relief. Accordingly, this review focuses on how MB lessens pain, noting three major actions of this dye: anti-inflammation, sodium current reduction, and denervation. Moreover, we showed controversies over the efficacy of MB on CDLBP and raised also toxicity issues to look into the limitation of MB application. This analysis is the first attempt to illustrate its analgesic effects, which may offer a novel insight into MB as a pain-relief dye.