Microvascular blood flow response in the intestinal wall and the omentum during negative wound pressure therapy of the open abdomen

Higher closure rates of the open abdomen have been reported with negative pressure wound therapy (NPWT) compared with other wound therapy techniques. However, the method has occasionally been associated with increased development of intestinal fistulae. The present study measures microvascular blood flow in the intestinal wall and the omentum before and during NPWT. Six pigs underwent midline incision and application of NPWT to the open abdomen. The microvascular blood flow in the underlying intestinal loop wall and the omentum was recorded before and after the application of NPWT of -50, -70, -100, -120, -150, and -170 mmHg respectively, using laser Doppler velocimetry. A significant decrease in microvascular blood flow was seen in the intestinal wall during application of all negative pressures levels. The blood flow was 2.7 (+/- 0.2) Perfusion Units (PU) before and 2.0 (+/- 0.2) PU (*p < 0.05) after application of -50 mmHg, and 3.6 (+/- 0.6) PU before and 1.5 (+/- 0.2) PU (**p < 0.01) after application of -170 mmHg. In the present study, we show that negative pressures between -50 and -170 mmHg induce a significant decrease in the microvascular blood flow in the intestinal wall. The decrease in blood flow increased with the amount of negative pressure applied. One can only speculate that a longstanding decreased blood flow in the intestinal wall may induce ischemia and secondary necrosis in the intestinal wall, which, theoretically, could promote the development of intestinal fistulae. We believe that NPWT of the open abdomen is a very effective treatment but could probably be improved.