Intraabdominal carbon dioxide insufflation in the pregnant ewe. Uterine blood flow, intraamniotic pressure, and cardiopulmonary effects.

BACKGROUND

Laparoscopic surgical procedures are being performed in pregnant women with increasing frequency. Maternal-fetal physiologic changes occurring during intraabdominal carbon dioxide insufflation are poorly understood, and maternal-fetal safety is of concern during carbon dioxide pneumoperitoneum. A previous pilot study using end-tidal carbon dioxide-guided ventilation resulted in maternal and fetal acidosis and tachycardia during carbon dioxide pneumoperitoneum. Using serial arterial PCO2 to guide ventilation, this study was designed to evaluate maternal-fetal cardiopulmonary status, uterine blood flow, and the intraamniotic pressure effects of intraabdominal carbon dioxide insufflation in singleton pregnant ewes between 120 and 135 days of gestation.

METHODS

In a prospective randomized cross-over study, nine ewes were to receive either abdominal insufflation with carbon dioxide to an intraabdominal pressure of 15 mmHg (n = 9; insufflation group) or receive no insufflation (n = 9; control group). Anesthesia was induced with thiopental and maintained with end-tidal halothane (1 to 1.5 minimum alveolar concentration/100% oxygen). Mechanical ventilation was guided by serial maternal arterial blood gas analysis to maintain PaCO2 between 35 and 40 mmHg. Data from insufflated animals were collected during insufflation (60 min) and after desufflation (30 min). Control group data were collected and matched to similar time intervals for 90 min. Ewes were allowed to recover, and after a rest period (48 h) they were entered in the cross-over study.

RESULTS

During insufflation there was a significant increase (P < 0.05) in maternal PaCO2 to end-tidal carbon dioxide gradient and minute ventilation, with concomitant decreases in maternal end-tidal carbon dioxide and PaO2. Intraamniotic pressure increased significantly during insufflation. No significant changes were observed in maternal hemodynamic variables, fetal variables, or in uterine blood flow during the study. There were no fetal deaths or preterm labor in any of the animals during the experiment.

CONCLUSIONS

During the 1-h insufflation, a marked increase in PaCO2-to-end-tidal carbon dioxide gradient was observed, suggesting that capnography may be an inadequate guide to ventilation during carbon dioxide pneumoperitoneum in the pregnant patient. No other significant circulatory changes were observed.