COMPUTER-SIMULATIONS IN COMPARISON WITH IN-VIVO MEASUREMENTS OF NIFEDIPINE-INDUCED CHANGES IN RENAL-ALLOGRAFT HEMODYNAMICS

Analysis of Doppler spectrum waveforms is increasingly used in the dif ferential diagnosis of human renal allograft dysfunction. The physiolo gic interpretation of changes in Doppler spectra obtained from renal a llografts, however, remains a major problem. Computer simulation model s of the renal circulation may provide insight into the physiologic me chanisms 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 ki dney allograft recipients were explained physiologically using a compu ter simulation model of kidney allograft hemodynamics. Using PAH clear ance 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 dec rease in the RI (from 0.60 +/- 0.04 to 0.56 +/- 0.06; P < 0.05) and Tm ax (from 133 +/- 32 to 98 +/- 32 ms; P < 0.05). The user-designed simu lation model of renal hemodynamics showed comparable changes of the wa veform when, in the model, the analogs of blood pressure, impedance of the artery, and the impedance of the peripheral vascular bed were alt ered proportionally.