EVALUATION OF FETAL AND UTERINE HEMODYNAMICS DURING MATERNAL CARDIOPULMONARY BYPASS

Background: About 4% of pregnant women have concomitant cardiac diseas e and a few of these do not respond to medical therapy and require sur gical correction during pregnancy. We report a unique case describing fetal hemodynamics and uterine blood flow before, during, and after ma ternal cardiopulmonary bypass, and compare them to normal reference va lues in the second trimester. Case: A woman with severe aortic regurgi tation underwent aortic valve replacement at 19 weeks' gestation. A no npulsatile cardiac pump was used for cardiopulmonary bypass, maintaini ng the mean arterial pressure at 77-90 mmHg, with a peak flow rate of 3.5-4.0 L/minute/m(2) and core temperature of 34-35C throughout surger y. Blood velocity waveforms were recorded by Doppler ultrasound at the level of maternal main uterine artery and fetal vessels. Pulsatility index (PI) values were calculated. Preoperatively, fetal hemodynamic c haracteristics were within normal limits. Preoperatively, uterine arte ry PI was 3.9 (normal 0.5-1.5 at 20 weeks). Intraoperatively, fetal br adycardia ensued after aortic clamping (120 to 75 beats per minute), w ith a rise in umbilical artery PI (1.7 to 7.1) and disappearance of di astolic now. The middle cerebral artery PI decreased (2.0 to 0.92) and the PI increased in the descending aorta (2.22 to 3.55), inferior ven a cava (2.7 to 9.3), and ductus venosus (0.6 to 1.7). During bypass, a fter aortic clamping, nonpulsatile uterine artery flow was noted. Post operatively, the uterine artery PI improved, to 1.0. Two days later, h ydrocephalus and hydrops were observed. Conclusion: Despite high peak flow rates, normal mean arterial pressure, and normothermia, fetal out come was dismal. Nonpulsatile cardiopulmonary bypass under normothermi a may not be able to meet the demands of the fetoplacental circulation .