THE EFFECTS OF CO2 PNEUMOPERITONEUM ON HEMODYNAMICS IN HEMORRHAGED ANIMALS

Background. Carbon dioxide (CO2), the primary gas currently used for p neumoperitoneum, 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 sa fety of laparoscopic procedures in acute trauma patients. Methods. Aft er 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 a nimals 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 R inger's solution. All animals were then insufflated to an intraabdomin al 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 anim als survived hemorrhage. One death each occurred in moderate hemorrhag e groups, both near the end Of CO2 Pneumoperitoneum. These animals wer e 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 resu lted in a similar degree of acidemia (7.35 +/- 0.01), but moderate hem orrhage and CO2 insufflation led to more severe acidemia (7.26 +/- 0.0 2). 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, rangin g from 48 +/- 1 mm Hg for euvolemic animals to 52 +/- 1 mm Hg for mode rate 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 hem orrhage. Both stroke volume and cardiac index initially responded to l arge-volume fluid replacement after moderate hemorrhage but quickly de creased to levels comparable to those of unresuscitated animals when C O2 pneumoperitoneum was created. Conclusions. Intraperitoneal insuffla tion with CO2 for diagnostic laparoscopy may be hazardous in acute hyp ovolemic trauma patients.