Hypercarbia during carbon dioxide pneumoperitoneum.

Patients with cardiopulmonary insufficiency undergoing laparoscopic surgery with carbon dioxide (CO2) pneumoperitoneum may retain CO2 resulting in clinically significant respiratory acidosis. A canine model of pulmonary emphysema induced by papain inhalation was utilized to evaluate the respiratory effects of both CO2 and helium pneumoperitoneum. Prior to papain inhalation and 5 and 8 weeks after initial treatment under general anesthesia, mechanical ventilation was adjusted to maintain the end-tidal CO2 (ETCO2) at 40 mm Hg during baseline and pneumoperitoneum physiologic monitoring periods. Utilizing an analysis of variance, hemodynamic and respiratory physiologic parameters were compared. In this canine model, all dogs demonstrated consistent hypercarbia during CO2 pneumoperitoneum prior to papain treatments, but CO2 retention was significantly increased in the emphysematous state. The occurrence of hypercarbia during CO2 pneumoperitoneum may be underestimated by ETCO2 monitoring as was revealed by an increased PaCO2 (arterial carbon dioxide pressure)-ETCO2 gradient with an increasing time interval between papain exposure and period of physiologic monitoring. Irrespective of the pulmonary condition of the dog, helium pneumoperitoneum did not produce any hypercarbic or acidic changes when compared with the concomitant baseline period of dogs prior to the induction of pneumoperitoneum, thus suggesting that helium pneumoperitoneum may be a reasonable alternative in patients at risk for CO2 retention.