The effect of methylene blue on peritoneal adhesion formation

Postoperative adhesions following abdominopelvic surgery may cause significant morbidity. In this study, the effect of different doses of methylene blue in the formation of adhesions and the role of allopurinol in revealing the possible mechanism of action was evaluated.

Seventy five male Wistar-Albino rats weighing 200g-220g. were divided into five groups of 15 rats each. After laparotomy, cecal serosal abrasions were performed. In Group I, 1ml of saline was administered intraperitoneally, while Group II, III and IV were given 1mg/kg, 5mg/kg and 9mg/kg of intraperitoneal methylene blue respectively. In Group V after 1 ml of saline administration at surgery, allopurinol 30 mg/kg/ day was administered postoperatively for 14 days. On day 14, laparotomies were repeated. Adhesions were graded and tissue samples were taken from incisions and adhesions. Hydroxyproline contents representing adhesions were measured quantitatively.

Low dose methylene blue (Group II) caused inhibition of adhesion formation when compared with that of other groups (p<0.05). With a higher dose (Group III), this effect disappeared and methylene blue actually induced adhesion formation (p<0.05) at the highest dose (Group IV). Allopurinol treatment (Group V) also provoked adhesion formation when compared with Group I (p<0.05).

Methylene blue has diverse effects on postoperative adhesions in a dose-dependent manner. While with low doses there is evidence of inhibition, it promotes adhesion formation at higher doses. As allopurinol also provokes adhesion formation, it is thought that the preventive role of methylene blue may not be due to its free oxygen radical inhibitor effect but the mechanism has yet to be clarified.