Methylene blue soldered microvascular anastomoses in vivo

Objectives: solders containing chromophores and proteins enhance tire strength of lasered anastomoses. Methylene blue (MB) solder anastomoses in vitro are strong but no in vivo work has been reported. We used an MB solder in vivo and studied the effects of two laser powers on patency and histological appearance. Design, materials and methods: two groups of 15 rabbits had unilateral end-to-end carotid anastomoses (1.5-2.0mm) formed using three stay sutures and MB solder. Group 1 anastomoses were formed at 5.7Wcm(-1) and Group 2 at 2.8 Wcm(-1). The vessels were examined at carious points by necropsy for patency and gross macroscopic appearance, with subsequent histological examination. Results: group 2 showed patency of 93.3% v 0% (p<0.001) endothelialisation of 100% v 26.6% (p<0.001), giant cell formation 0% v 40.0% (p<0.01), but stenosis was not significantly different (0% v 13.3%: p=0.06). Group 2 showed a higher rate of intimal hyperplasia (IH) (66.6 % v 20.0%: p<0.05) but neither group exhibited thermal injury or aneurysm formation. Conclusions: laser soldered microvascular anastomoses were formed in vessels of 1.5-2.0 arm with a high degree of patency. A relationship appears to exist between laser power and anastomotic patency. Methylene blue fading has the potential to act as a switch against over exposure and a visual indicator of solder activation.