Journal of Ultrasound in Medicine, Vol 12, Issue 9 517-523, Copyright © 1993 by American Institute of Ultrasound in Medicine
Computer simulations in comparison with in vivo measurements of nifedipine-induced changes in renal allograft hemodynamics
J. W. Merkus, W. N. van Asten, L. B. Hilbrands, A. J. Hoitsma, R. A. Koene and S. H. Skotnicki
Clinical Vascular Laboratory, University Hospital St Radboud, Nijmegen, Netherlands.
Analysis of Doppler spectrum waveforms is increasingly used in the
differential diagnosis of human renal allograft dysfunction. The
physiologic interpretation of changes in Doppler spectra obtained from
renal allografts, however, remains a major problem. Computer simulation
models of the renal circulation may provide insight into the physiologic
mechanisms responsible for changes in Doppler spectrum characteristics. The
results of measurements of renal allograft hemodynamics with both
determinations of PAH clearance and Doppler spectrum analysis in 11 kidney
allograft recipients were explained physiologically using a computer
simulation model of kidney allograft hemodynamics. Using PAH clearance and
blood pressure measurements a significant decrease in RVR was found (from
0.32 +/- 0.17 to 0.20 +/- 0.07 mm Hg x min/ml, P < 0.05) after
administration of the vasodilatory drug nifedipine. The Doppler spectrum
waveform obtained from interlobar renal arteries showed a decrease in the
RI (from 0.60 +/- 0.04 to 0.56 +/- 0.06; P < 0.05) and Tmax (from 133
+/- 32 to 98 +/- 32 ms; P < 0.05). The user-designed simulation model of
renal hemodynamics showed comparable changes of the waveform when, in the
model, the analogs of blood pressure, impedance of the artery, and the
impedance of the peripheral vascular bed were altered proportionally.
