Macroscopic and pathological assessment of methylene blue and normal saline on postoperative adhesion formation in a rat cecum model

Effect of methylene blue on experimental postoperative adhesion: A systematic review and meta-analysis

Adhesion is a primary challenge following surgery, and the anti-adhesive effect of methylene blue (MB) has been investigated. This systematic review and meta-analysis aimed to evaluate the effect of MB on postoperative adhesions in experimental studies. We initially searched OVID-MEDLINE, EMBASE, and Google Scholar in February 2021, and then in May 2021. The anti-adhesive efficacy of MB was compared with that of the control (either placebo or nothing) after the surgical procedure. The primary and secondary outcomes were the macroscopic and microscopic adhesion scores, respectively. Traditional meta-analysis, meta-regression, and trial sequential analysis (TSA) were performed to analyze the retrieved outcomes. We included 13 experimental studies of 367 rats (200 rats received MB and 167 rats received placebo or nothing). The macroscopic adhesion scores were significantly lower in the MB-administered group than in the control group (standardized mean difference, 2.313; 95% confidence interval, 1.104 to3.523; I² = 94.0%, Tau = 2.059). Meta-regression analysis showed that macroscopic adhesion tended to decrease with an increase in MB dose. TSA demonstrated that the cumulative Z curve crossed both the conventional test and trial sequential monitoring boundary for the macroscopic adhesion score. MB had a beneficial effect on intraperitoneal adhesion following laparotomy, and adhesions decreased with increase in dose.

Platelet-rich fibrin prevents postoperative intestinal adhesion

Platelet-rich fibrin (PRF) was prepared from the blood of BALB/C inbred mice to explore potential effects on postoperative intestinal adhesion. A murine model of intestinal adhesion characterized by abdominal wall defect/and cecum damage was established by scraping caecum serosa and cutting peritoneum and muscles in the abdominal wall. The wound was covered with PRF (group A), sodium hyaluronate (group B), or left alone (blank control; group C). All animals were monitored for 28 days. The incidence of adhesion was 35.0, 66.7, and 73.7% in groups A, B, and C, respectively. The incidence of adhesion in group A was significantly lower than that in group C (p < .05). Histopathologically, severity of fibrosis and the number of fibroblasts or inflammatory cells in group A were lower than those in groups B and C (p < .05), whereas the number of mesothelial cells was higher (p = .001). Furthermore, the severity of fibrosis and number of fibroblasts or inflammatory cells were lower in low grade than those in high grade of adhesion (p < .05), whereas the number of mesothelial cells was higher (p < .05). Collectively, PRF applied to abdominal surgery may reduce the incidence of intestinal adhesion by promoting proliferation of mesothelial cells whereas inhibiting proliferation of fibroblasts and infiltration of inflammatory cells.

Use of methylene blue in the prevention of recurrent intra-abdominal postoperative adhesions

Objective

To evaluate the efficacy of methylene blue in preventing recurrent symptomatic postoperative adhesions.

Methods

Patients with a history of >2 surgeries for intra-abdominal adhesion-related complications were selected for this study. Adhesiolysis surgery was subsequently performed using administration of 1% methylene blue. The follow-up period was 28.5 ± 11.1 months.

Results

Data were available from 20 patients (seven men and 13 women) whose mean ± SD age was 51.2 ± 11.4 years. Adhesions took longer to become symptomatic after the first abdominal surgery when the initial pathology was malignant compared with benign. However, the recurrence of adhesions after a previous adhesiolysis surgery had a similar time onset regardless of the initial disease. Following adhesiolysis surgery with methylene blue, the majority of patients did not present with symptoms associated with adhesion complications (i.e., chronic abdominal pain, bowel obstruction) for the length of the follow-up period.

Conclusions

The use of methylene blue during adhesiolysis surgery appears to reduce the recurrence of adhesion-related symptoms, suggesting a beneficial effect in the prevention of adhesion formation.