Effects of pneumoperitoneum created through CO₂ insufflation and parameters of mechanical ventilation (PEEP application) on systemic dissemination of intraabdominal infections

Abstract

Background

To examine whether CO₂ pneumoperitoneum and positive end expiratory pressure (PEEP) in mechanical ventilation affect the systemic spread of intraabdominal infection.

Methods

Sprague-Dawley male rats weighing 200–300 g were allocated to three groups of 12 animals in each. All rats received mechanical ventilation under general anesthesia. An intraabdominal infection model was established by injecting with 1 ml of Escherichia coli (10⁹ CFU/mL) intraperitoneally. Half of the animals in each group were exposed to PEEP (10 cmH₂O). CO₂ pneumoperitoneum at 13 mmHg was applied to the rats in group 1. Group 2 rats underwent laparotomy. Group 3 served as controls. In addition, TNF-α serum levels were measured at baseline and 3 h. A peritoneal specimen for histopathological examination were obtained after the rats were killed at the end of 3 h. For the assessment of data, descriptive statistical methods (mean, standard deviation) as well as Friedman test for repeated measurements in multiple groups, Kruskal-Wallis test for intergroup comparisons, Dunn’s multiple comparison test for subgroup comparisons, Mann-Whitney U test for comparisons between paired groups, chi-square and Fisher’s exact test for comparison of qualitative data, and McNemar’s test for assessment of changes in group variables over time were used. The results were considered statistically significant if probability (p) values were <0.05.

Results

Grades of peritonitis in group 1 and 2 were seen to differ nonsignificantly. In group 1, baseline blood cultures were not included in the assessment between the subgroups that received PEEP or not, as there was no growth in any of the subgroups. No significant difference was detected between growth in blood cultures at 1, 2, and 3 h (p > 0.05). Aplication of PEEP in subgroups did not alter the blood culture results (p > 0.05). Significant differences were seen between the initial and final TNF-α values of groups (KW: 18.94, p < 0.0001). The values in control group were observed to be significantly lower than those in groups 1 and 2 (p < 0.01, p < 0.001). Bacteremia and systemic spread of the intraabdominal infection did appear to be different according to the PEEP application. After the assessments of ventilation parameters in our study, significant reductions in pH and HCO₃ levels were detected in group 1 as a result of pneumoperitoneum, which was consistent with the literature. There is a significant difference between pH values at baseline and at the end of 1 h because of pneumoperitoneum (Fr: 10.01, p < 0.05). PEEP application in subgroups did not create significant differences in terms of respiratory parameters (p < 0.01).

Conclusion

No difference was found between the applications of CO₂ pneumoperitoneum and laparotomy with regard to bacteremia and infection-induced peritonitis. It was determined that pneumoperitoneum along with PEEP application had neither a positive nor a negative impact on intraabdominal infection.