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Vacuum-assisted closure (VAC) for postoperative secondary peritonitis: Effect on bacterial load as well as local and systemic cytokine response (initial results).

BACKGROUND
It is still a matter of debate what the best management of peritonitis is following eliminating the source of infection. This particularly concerns the amplitude of local and systemic inflammatory response as well as bacterial clearence at the infectious site.


AIM
To investigate the effects of vacuum-assisted closure (VAC) vs. relaparotomy on demand (ROD) onto the i) severity and course of disease, ii) surgical outcome, iii) intraperitoneal bacterial load as well as iv) local and systemic inflammatory and immune response in postoperative secondary peritonitis.


METHODS
Over a defined time period, all consecutive patients of the reporting surgical department with a secondary peritonitis (assessed by Mannheim's Peritonitis Index [MPI] and APPACHE II score) were enrolled in this systematic unicenter clinical prospective observational pilot study reflecting daily surgical practice and as a contribution to internal quality assurance. Patients were subclassified into VAC or ROD group according to surgeon's individual decision at the time point of primary surgical intervention with the intent to sanitize the source of infection. Early postoperative result was assessed by 30-d and in-hospital mortality. Bacterial load was characterized by microbiological culture of intraperitoneal fluid collection obtained on postoperative days (POD) 0 (primary surgical intervention), 1, 4, 7, 10, 13 and following description of the microbial spectrum including semiquantitative assessment of bacterial load. Local and systemic inflammatory and immune response was determined by ELISA-based analysis of CrP, PCT and the representative cytokines such as TNF-α, IL-1β, IL-6, IL-8, and IL-10 of serum and peritoneal fluid samples.


RESULTS
Over a 26-months investigation period, 18 patients (sex ratio, male:female=9:9) were eligible for study criteria: n=8 were enrolled in the VAC (m:f=4:4) and n=10 in the ROD group (m:f=5:5). With regard to early postoperative results represented by mortality, there is no significant difference between both patients groups. Despite the relatively low number of cases enrolled in this study, a trend for more severe findings associated with the VAC group could be detected based on MPI score. There was also a trend of higher APACHE II scores in the VAC group from the 7th POD on and, in addition, patients of this group had a longer hospital stay. For patients with persisting infection, there were no relevant differences comparing VAC therapy and ROD. Cytokines released, in particular, at the beginning of the inflammation cascade with proinflammatory characteristics, showed higher values within the peritoneal fluid whereas CrP and PCT were found to be higher within the serum samples. Summary & Conclusion: Comparing data of various local and systemic inflammatory and immune parameters, there were only a few correlations. This may indicate a compartimentation of the inflammatory process within the abdominal cavity. Based on the observed inter-individual variation of this pilot study data, the clinically applicable benefit appears questionable. In this context, a reliable effect of VAC therapy onto reduction of bacterial burden within the abdominal cavity could not clearly be detected.