The lower limit of tissue blood flow for safe colonic anastomosis: an experimental study using laser Doppler velocimetry.

In order to determine the absolute minimum tissue blood flow (TBF) for safe colonic anastomosis, the wound healing process of anastomotic sites with varying degrees of TBF, measured by laser Doppler velocimetry (LDV), was examined in dogs. Firstly, to clarify how well the LDV value reflects TBF, the correlation between the LDV value and TBF measured by the hydrogen gas clearance method was examined. There was a good correlation between the two methods, with an r value of 0.91. Secondly, after transection and anastomosis of the colon had been performed with varying degrees of devascularization, the anastomotic wound healing process was examined. The LDV values at the anastomotic sites of all dogs in which anastomotic dehiscence had occurred were less than 0.8. In the 2-cm and 4-cm devascularization groups, the mean LDV values were 1.23 +/- 0.34 and 0.88 +/- 0.20, respectively. There were significant differences between the latter two groups concerning postoperative course, histological features, and hydroxyproline concentration ratio. Thus, as far as TBF is concerned, if the LDV value at the anastomotic site is at least 1.0, corresponding to about 30% of the TBF of the intact colonic wall, the anastomosis is considered to be safe, without risk of dehiscence.