The effect of negative wound pressure therapy on haemodynamics in a laparostomy wound model.

We have recently shown that negative pressure wound therapy (NPWT) induces a decrease in microvascular blood flow in the small intestinal loop close to the dressing. The effect of NPWT is thus thought to be local. In this study, we investigate whether the application of NPWT in laparostomy affects the haemodynamics. Midline incisions were made in six pigs followed by NPWT at -120 mmHg for 20 minutes. The cardiac output, mean systemic arterial pressure, mean pulmonary artery pressu re, central venous pressure, left atrial pressure and superior mesenteric artery blood flow were recorded. The blood flow in a small branch of the superior mesenteric artery was then recorded under NPWT between -50 and -175 mmHg. Cardiac output was not affected by NPWT [P = not significant (n.s.)]. Neither the mean arterial pressure nor the mean pulmonary artery pressure was affected by NPWT (P = n.s.). Negative pressures of -50, -75, -100 and -125 mmHg did not alter the blood flow in the small branch of the superior mesenteric artery (P = n.s.). After application of -150 mmHg, a significant decrease in blood flow was seen (P < 0·01), while the application of -175 mmHg resulted in only a slight decrease in blood flow (P = n.s.). The effect of NPWT in laparotomy seems to be local and to have no influence on central haemodynamics or the blood flow to the superior mesenteric artery.