The effects of CO₂ pneumoperitoneum on hemodynamics in hemorrhaged animals

Background. Carbon dioxide (CO₂), the primary gas currently used for pneumoperitoneum, has been known to cause systemic effects on acid-base balance and hemodynamic stability. We studied the hemodynamic effects of CO₂ pneumoperitoneum in a hemorrhagic shock model to assess the safety of laparoscopic procedures in acute trauma patients. Methods. After 1 hour of baseline, 32 anesthetized adult pigs were randomized into four groups. Group 1 animals had no hemorrhage, serving as a control group. Group 2 animals had a mild hemorrhage of 10 ml/kg/hr. Group 3 animals had a moderate hemorrhage of 20 ml/kg/hr. Group 4 animals had a moderate hemorrhage but were resuscitated with 40 ml/kg of lactated Ringer's solution. All animals were then insufflated to an intraabdominal pressure of 15 mm Hg with CO₂ gas for 1 hour. The abdomen was then decompressed, and the animals were observed for another hour. All animals survived hemorrhage. One death each occurred in moderate hemorrhage groups, both near the end of CO₂ pneumoperitoneum. These animals were not included in statistical analysis. Results. In euvolemic animals, CO₂ pneumoperitoneum induced hypercapnia (from 34 ± 1 mm Hg to 48 ± 1 mm Hg), acidemia (from 7.45 ± 0.02 to 7.36 ± 0.02), and a 20% reduction in stroke volume. Mild hemorrhage and CO₂ insufflation resulted in a similar degree of acidemia (7.35 ± 0.01), but moderate hemorrhage and CO₂ insufflation led to more severe acidemia (7.26 ± 0.02). Fluid resuscitation failed to prevent this severe fall in pH (7.30 ± 0.03) for group 4. PaCO₂ was not affected by hemorrhage, but CO₂ pneumoperitoneum induced significant hypercapnia in all groups, ranging from 48 ± 1 mm Hg for euvolemic animals to 52 ± 1 mm Hg for moderate hemorrhage animals. Stroke volume declined as a function of blood loss, and it was further depressed by CO₂ insufflation, to as low as 75% of baseline in mild hemorrhage and 55% of baseline in moderate hemorrhage. Both stroke volume and cardiac index initially responded to large-volume fluid replacement after moderate hemorrhage but quickly decreased to levels comparable to those of unresuscitated animals when CO₂ pneumoperitoneum was created. Conclusions. Intraperitoneal insufflation with CO₂ for diagnostic laparoscopy may be hazardous in acute hypovolemic trauma patients.