Hemodynamic and ventilatory effects of abdominal CO₂ insufflation at various pressures in the young swine

Laparoscopic procedures requiring abdominal CO₂ insufflation are applied with increasing frequency to the pediatric age group. Whereas the physiological effects accompanying insufflation have been studied in laboratory and clinical adult subjects, little is known of these effects in the juvenile subject. Young swine (weight, 10 to 12 kg, approximate age, 6 weeks) were subjected to abdominal CO₂ insufflation at 10 and 15-mm Hg insufflation pressures (IP) to evaluate potential metabolic and hemodynamic effects. After intubation, minute ventilation was adjusted to obtain a baseline Pco₂ between 38 and 42 mm Hg, and was kept constant during the subsequent study period. Four subjects underwent a total of eight trials, with insufflation periods of 1 hour each. Serial measurements of peak ventilatory pressure, tidal volume, end tidal CO₂ arterial pH, Pco₂, Po₂, right atrial (RA), and inferior vena caval (IVC) pressure were obtained. Mean pH decreased from 7.45 ± 0.03 to 7.22 ± 0.03 at 10 mm Hg IP, and from 7.44 ± 0.01 to 7.19 ± 0.03 at 15 mm Hg IP. Mean Pco₂ increased from 39.9 ± 0.4 to 70.0 ± 1.0 mm Hg at 10 mm Hg IP, and from 39.9 ± 0.5 to 76.8 ± 1.6 mm Hg at 15 mm Hg IP. Po₂ decreased by approximately 37% at both IPs. End-tidal CO₂ increased by 53% at 10 mm Hg IP, and by 68% at 15 mm Hg IP. Right atrial pressure did not increase significantly, and IVC pressure increased in proportion to the IP. Abdominal CO₂ insufflation in this model produced marked acidemia, hypercapnia, decreased oxygenation, and increased exhaled CO₂. Decreasing insufflation pressure to 10 mm Hg decreased Pco₂ but did not alter pH or Po₂. Close monitoring of blood gas values during laparoscopy is warranted to allow appropriate adjustment of minute ventilation.