A comparison of the pathophysiologic effects of carbon dioxide, nitrous oxide, and helium pneumoperitoneum on intracranial pressure.

BACKGROUND: Previous studies have suggested that diagnostic laparoscopy may be contraindicated in multiple trauma patients with closed head injuries because of the detrimental effects of carbon dioxide (CO2) pneumoperitoneum on intracranial pressure (ICP). In this study we compared the effects of two alternative inflation gases, helium (He) and nitrous oxide (N2O), against the standard agent used in most hospitals, CO2. ICP was monitored in experimental animals both with and without a space occupying intracranial lesion designed to simulate a closed head injury.

METHODS: Twenty-four domestic pigs (mean, 30 kg) were divided into four groups (6 CO2, 6 He, 6 N2O, and 6 control animals without insufflation). All animals were monitored for ICP, intraabdominal pressure, mean arterial pressure, end-tidal CO2 (ETCO2), and arterial blood gases. These parameters were measured for 30 minutes prior to introducing a pneumoperitoneum and then for 80 minutes thereafter. The measurements were repeated after artificially elevating the ICP with a balloon placed in the epidural space.

RESULTS: The mean ICP increased significantly in all groups during peritoneal insufflation compared with the control group (P < 0.005). The CO2-insufflated animals also showed a significant increase in PaCO2 (P < 0.05) and ETCO2 (P < 0.05), as well as a decrease in pH (P < 0.05). After inflating the epidural balloon the ICP remained significantly higher in animals inflated with CO2 as compared with the He and N2O groups (P < 0.05).

CONCLUSIONS: Peritoneal insufflation with He and N2O resulted in a significantly less increase in ICP as compared with CO2. That difference was most likely due to a metabolically mediated increase in cerebral perfusion (PaCO2) in the CO2 group. Further studies need to be conducted to determine the safety and efficacy of using He and N2O as inflation agents prior to attempting diagnostic or therapeutic laparoscopy in patients with potential closed head injuries.