Haemodynamic changes in human kidney allografts following administration of nifedipine: assessment with Doppler spectrum analysis.
Cyclosporin (CyA) has been demonstrated to increase the vascular resistance of renal allografts (RVR), whereas calcium channel blocking agents like nifedipine may counteract this effect. In this study RVR was calculated from renal blood flow (RBF), measured by the clearance of para-aminohippurate (PAH), and mean arterial pressure (MAP). Analysis of Doppler spectra obtained under ultrasonographic guidance was used as a non-invasive method of assessing renal haemodynamics. A comparison was made between these two methods to detect changes in renal haemodynamics which were caused by the administration of 10 mg nifedipine orally to 11 renal transplant recipients treated with CyA. RBF increased significantly (444 +/- 176 vs 559 +/- 192 ml/min per 1.73 m2; P < 0.05) despite a decrease in MAP (116 +/- 10 vs 101 +/- 11 mmHg; P < 0.05) after administration of nifedipine. Calculated RVR decreased from 0.31 +/- 0.17 to 0.20 +/- 0.07 mmHg x min/ml (P < 0.05). Results of Doppler spectrum analysis were in concordance with these observations. Resistance index (RI) in interlobar arteries decreased from 0.60 +/- 0.04 to 0.56 +/- 0.06 (P < 0.05) and acceleration time (Tmax) of the Doppler spectrum decreased from 133 +/- 32 to 98 +/- 32 ms (P < 0.05). Theoretically, a lower RI and decreased Tmax indicate a reduced vascular resistance and changes in vascular wall compliance, respectively. Analysis of Doppler spectra may thus become a useful device for non-invasive assessment of acute changes in RVR.