Sonographic investigation of flow patterns in the perfused human placenta and their modulation by vasoactive agents with enhanced visualization by the ultrasound contrast agent albunex

Purpose. Our objective was to demonstrate sonographically the flow distribu tion in the circulation of human placentae as well as the sensitivity of th e human fetal capillary bed to vasoconstriction and dilatation. Methods. Five human full-term placental lobules were maintained in vitro wi th fetal and maternal flow. Commercial ultrasound scanners were used for im aging. Albunex (1 ml bolus) was administered to the fetal "artery" to monit or patterns of flow. U46619 (1 ml, 10(-6) M; a thromboxane agonist and pote nt vasoconstrictor) and/or nitroglycerin (a potent vasodilator) were added to the fetal artery. Results. Following the addition of U46619, mean "fetal pressures" rapidly r ose from 23.2 +/- 0.8 to 118 +/- 2.9 mm Hg (mean +/- standard error of mean ; p < 0.001); venous flow rates decreased. As demonstrated by color Doppler imaging, flow markedly changed from a pattern of general distribution thro ughout the lobule to flow only near the chorionic plate. Color persistence was 94.4 +/- 6.5 seconds with Albunex after nitro-glycerin and 39.8 +/- 3.4 seconds with Albunex after injection of U46619 (p < 0.001). Nitroglycerin had no effect when injected by itself but returned "constricted" flow to a "normal" pattern when injected after U46619. Conclusions. The contrast medium Albunex improved visualization of the feta l circulation throughout the lobule. Flow in the human placental capillary bed can be regionally manipulated throughout the placental lobule by vasomo dulators and monitored by Albunex-enhanced sonographic examination. (C) 199 9 John Wiley & Sons, Inc.