Peritoneal and systemic pH during pneumoperitoneum with CO2 and helium in a pig model

Background: Local peritoneal effects of laparoscopic gases might be important in peritoneal biology during and after laparoscopic surgery. The most commonly used gas, CO2, is known to be well tolerated, but also causes changes in acid-base balance. Helium is an alternative gas for laparoscopy. Although safe, it is not widely used. In this study a method for monitoring peritoneal pH during laparoscopy was evaluated and peritoneal pH during CO2 and helium pneumoperitoneum was studied as well as its systemic reflection in arterial pH. Methods: For these experiments 20 pigs were used, with ten exposed to pneumoperitoneum with CO2, and ten to helium. Peritoneal and sub-peritoneal pH were continuously measured before and during gas insufflation, during a 30-minute period with a pneumoperitoneum and during a 30-minute recovery period. Arterial blood-gases were collected immediately before gas insufflation, at its completion, at 30 minutes of pneumoperitoneum and after the recovery period. Results: Peritoneal pH before gas insufflation was in all animals 7.4. An immediate local drop in pH (6.6) occurred in the peritoneum with CO2 insufflation. During pneumoperitoneum pH declined further, stabilising at 6.4, but was restored after the recovery period (7.3). With helium, tissue pH increased slightly (7.5) during insufflation, followed by a continuous decrease during pneumoperitoneum and recovery, reaching 7.2. Systemic pH decreased significantly with CO2 insufflation, and increased slightly during helium insufflation. Systemic pH showed co-variation with intra-peritoneal pH at the the end of insufflation and after 30 minutes of pneumoperitoneum. Conclusions: Insufflation of CO2 into the peritoneal cavity seemed to result in an immediate decrease in peritoneal pH, a response that might influence biological events. This peritoneal effect also seems to influence systemic acid-base balance, probably due to trans-peritoneal absorption.