Journal of Ultrasound in Medicine, Vol 8, Issue 4 177-181, Copyright © 1989 by American Institute of Ultrasound in Medicine
Hemodynamic validation of Doppler assessment of fetoplacental circulation in a sheep model system
D. Maulik, P. Yarlagadda, P. W. Nathanielsz and J. P. Figueroa
School of Medicine, University of Missouri, Kansas City.
Several clinical studies suggest that the Doppler indices (DI) derived from
Doppler waveform analysis may be powerful predictors of perinatal
compromise. In contrast, significant paucity exists in experimental
verification of the central premise that the DI reliably reflect
hemodynamic state downstream from the measurement point. This paper
presents the results from two sets of acute animal experiments in which
experimentally induced changes in the ovine fetoplacental circulation as
reflected by the independently measured hemodynamic parameters were
correlated with the corresponding variations in the DI. Doppler
velocimetric measurements were performed under general anesthesia in ovine
fetuses with gestational ages ranging from 100 to 110 days. A continuous
wave Doppler instrument with a 4-MHz transducer was used. In three fetuses,
variable vascular constriction was produced by a ligature placed
approximately 10 cm from the probe location. In four fetuses, vasopressin
was rapidly infused. The hemodynamic parameters measured included the
peripheral resistance, volumetric flow, and pressure. The DI included the
systolic-diastolic ratio, pulsatility index, and resistance index. The
results indicate that, in hemodynamically stable and well-defined
obstruction to downstream flow as achieved in the constriction experiments,
the DI highly correlated with the hemodynamic state (p less than .005);
however, during the more complex and unstable circulatory changes
associated with vasopressin administration, these correlations were
inconsistent and poor (p greater than .05). This study experimentally
establishes in an in vivo animal system the hemodynamic validity of the DI
within certain limits. However, the validity does not extend to hemodynamic
changes associated with vasopressin administration. Further studies are
required to address this issue.(ABSTRACT TRUNCATED AT 250 WORDS)
