Peritoneal acidosis mediates immunoprotection in laparoscopic surgery

Area of Science:

• Immunology
• Surgical Inflammation
• Laparoscopic Procedures

Background:

• Carbon dioxide (CO2) insufflation increases IL-10 and TNFalpha, improving survival in lipopolysaccharide (LPS)-induced sepsis.
• Previous studies show CO2 effect is independent of systemic pH, despite local peritoneal acidosis.
• Hypothesis: Peritoneal acidification, not CO2 itself, alters inflammatory response.

Purpose of the Study:

• To test if peritoneal acidification, independent of CO2, modifies inflammatory response to LPS.
• To investigate the role of peritoneal pH in mediating the anti-inflammatory effects observed with CO2 pneumoperitoneum.

Main Methods:

• 42 rats randomized into 7 groups: LPS only, anesthesia control, helium pneumoperitoneum, CO2 pneumoperitoneum, mild acid lavage, strong acid lavage, and strong acid lavage + helium pneumoperitoneum.
• Animals received anesthesia and abdominal treatment (pneumoperitoneum/lavage) for 30 min, followed by systemic LPS (1 mg/kg, IV).
• Serum IL-10 and TNFalpha levels measured by ELISA 60 min post-LPS injection.

Main Results:

• Peritoneal pH decreased significantly with CO2 pneumoperitoneum, strong acid lavage, and strong acid lavage + helium.
• IL-10 levels increased (P < .01) and TNFalpha levels decreased (P < .001) in acidic peritoneal cavities compared to normal pH.
• Decreasing peritoneal pH correlated with increased IL-10 (r = -.465) and decreased TNFalpha (r = 0.448).

Conclusions:

• Peritoneal acidification, via insufflation or lavage, increases IL-10 and decreases TNFalpha in response to LPS.
• The degree of peritoneal acidification correlates with reduced inflammatory response.
• Results support peritoneal cell acidification as the mechanism for reduced inflammation in pneumoperitoneum-mediated responses.