Vacuum-assisted closure has become a new technique in the challenging management of contaminated, acute, and chronic wounds. Although promising clinical results have been described, scientific proof to substantiate the mechanism of action of this therapy is scarce. In the present study, we examined whether the positive effect on wound healing found in vacuum-assisted closure-treated wounds could be explained by an effect on the bacterial load. Fifty-four patients who needed open wound management before surgical closure were included in this study. Wounds were randomized to either vacuum-assisted closure therapy (n= 29) or treatment by conventional moist gauze therapy (n= 25). Healing was characterized by development of a clean granulating wound bed ("ready for surgical therapy") and reduction of wound surface area. To quantify bacterial load, biopsies were collected. No significant difference was found in time needed to reach "ready for surgical therapy" comparing both therapies. Wound surface area reduction was significantly larger in vacuum-assisted closure-treated wounds: 3.8 +/- 0.5 percent/day (mean +/- SEM) compared to conventional-treated wounds (1.7 +/- 0.6 percent/day; p < 0.05). The total quantitative bacterial load was generally stable in both therapies. However, nonfermentative gram negative bacilli showed a significant decrease in vacuum-assisted closure-treated wounds (p < 0.05), whereas Staphylococcus aureus showed a significant increase in vacuum-assisted closure-treated wounds (p < 0.05). In conclusion, this study shows a positive effect of vacuum-assisted closure therapy on wound healing, expressed as a significant reduction of wound surface area. However, this could not be explained by a significant quantitative reduction of the bacterial load.

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Ninety-degree anterior displacement of the beating porcine heart caused primarily right ventricular dysfunction as a result of mechanical interference with diastolic expansion without concurring valvular incompetence. Right heart bypass normalized stroke volume and mean arterial pressure by increasing left ventricular preload; in contrast, left heart bypass failed to restore systemic circulation.

The clinical effects of topical negative pressure therapy (TNP) on wound healing are well described in numerous articles. While the mechanism(s) of action are not completely understood, it is postulated that reduction of local and interstitial tissue edema, increased perfusion of the (peri-) wound area, changed bacterial composition, and mechanical stimulation of the woundbed contribute to the clinical success. Our hypothesis is that with the removal of excessive fluid, proteolytic enzymes negatively influencing the healing process are removed. Our aim was to assess whether the concentrations of albumin, matrixmetalloproteinase-9 (MMP-9), and tissue inhibitor of metalloproteinase (TIMP-1) were different between wounds treated with TNP and conventional gauze therapy. We analyzed wound fluid samples of 33 wounds treated with either TNP therapy (n=15) or conventional therapy (n=18) on albumin, pro- and activated MMP-9, TIMP-1, and the ratio of total MMP-9/TIMP-1. Albumin levels were found to increase significantly in acute wounds compared with chronic wounds; however, no difference could be found on comparing TNP with conventional therapy. We did find significantly lower levels of pro-MMP-9 and lower total MMP-9/TIMP-1 ratio in TNP-treated wounds during the follow-up of 10 days. These data strongly suggest that TNP therapy influences the microenvironment of the wound.