CO2 pneumoperitoneum increases survival in mice with polymicrobial peritonitis

Purpose: Laparoscopic techniques are commonly used in patients with bacterial peritonitis. CO2 is known to suppress local and systemic inflammatory responses. Nonetheless, an active immune system is needed to contain bacterial contamination of the abdominal cavity. Therefore, we investigated the early and late effects of CO2 pneumoperitoneum on the ability of mice to overcome polymicrobial peritonitis. Material and Methods: Male C57/B6 mice were subjected to pneumoperitoneum with CO2 or helium, or underwent a midline laparotomy. In a first set, changes of arterial blood gases were monitored. in further experiments, polymicrobial peritonitis was induced after 1 h of pneumoperitoneum/laparotomy by cecal ligation and puncture. In a second set of experiments polymicrobial peritonitis was induced 4 h prior to exposure to pneumoperitoneum/laparotomy. After the interventions, survival rates (early survival: 6 to 48 h; late survival > 48 h) were monitored for 7 days. Results: There was no significant effect of pneumoperitoneum or laparotomy on arterial blood gas parameters. CO2 pneumoperitoneum significantly reduced the early (6 to 48 h) mortality of subsequent peritonitis after CO2 pneumoperitoneum compared to laparotomy (2/20 vs. 9/25; p < 0.05). The protective effect did not reach significance after 7 days (late mortality). The application of a helium peritoneum did not show any beneficial effect. Application of a CO2 pneumoperitoneum during polymicrobial peritonitis significantly reduced overall mortality (p < 0.05) compared to laparotomy. Conclusions: The modulation of immune responses by CO2, but not helium pneumoperitoneum, has a significant positive impact on survival during abdominal sepsis in a mouse model. Thus, application of a CO2 pneumoperitoneum may be beneficial in conditions with bacterial contamination of the abdominal cavity.