FETAL RESPONSE TO CARBON-DIOXIDE PNEUMOPERITONEUM IN THE PREGNANT EWE

Objective: To determine the effects of maternal abdominal carbon dioxi de (CO2 insufflation on placental blood now and fetal blood gas measur ements in the pregnant ewe. Method: Five time-bred ewes at 110 days' g estation were surgically prepared with maternal and fetal catheters pl aced for subsequent measurement of vascular pressures, blood gas tensi ons, and placental blood flows. On surgical recovery day 3, the ewe wa s anesthetized, placed on her right side, intubated, and manually vent ilated to maintain a constant maternal carbon dioxide pressure (PCO2) range (37.1 +/- 3.3 mmHg) for the duration of the experiment. The mate rnal abdomen was inflated with CO2 to maintain an intraabdominal press ure of 20.7 +/- 0.6 mmHg. Maternal and fetal blood flows and blood gas es were determined at 30 minutes of ventilation, 60 minutes of insuffl ation, and 40 minutes of desufflation. Simultaneous maternal and fetal organ blood flows were determined using the radioactive microsphere t echnique. Results: Maternal perfusion pressure fell 22% (P = .01) in r esponse to insufflation, whereas pressure in the inferior vena cava ro se 53% (P = .003). Maternal placental blood now fell to 61% (P = .002) of control. Seventy-seven percent of this blood-flow change was in re sponse to the decreased perfusion pressure, with 23% resulting from an increased placental vascular resistance of 32% (P = .02). Maternal bl ood gas values did not change with insufflation or desufflation. Despi te the marked decrease in maternal placental blood now, the fetal plac ental perfusion pressure and blood flow, pH, and blood gas tensions we re unaffected by insufflation or desufflation. Conclusion: The sheep f etus has sufficient placental flow reserves or compensatory responses to maintain adequate gas exchange during a 1-hour, 20 mmHg maternal pn eumoperitoneum. Laparoscopic surgical procedures may prove to safe alt ernative to laparotomy during pregnancy.