Renal 131I-hippuran extraction in man: effects of dopamine

Abstract

Aims: This study examined the 131I-hippuran extraction fraction during baseline renal blood flow rates and at high flow rates induced by dopamine.

Methods: In 12 healthy subjects, arterial and renal venous sampling was used to measure the renal extraction of 131I-hippuran. Effective renal plasma flow values determined by the urinary clearance of 131I-hippuran were compared with renal plasma flow values corrected for incomplete extraction of 131I-hippuran.

Results: Dopamine (3 micro g kg-1 min-1) decreased 131I-hippuran extraction from 75 +/- 4% at baseline to 62 +/- 6% (means +/- 95% confidence intervals, P < 0.001). Hence, the increase in renal plasma flow (85 +/- 23%) greatly exceeded the rise in effective renal plasma flow (51 +/- 15%, P < 0.002).

Conclusions: Dopamine induced increases in renal blood flow are largely under-estimated when measurements are not corrected for incomplete extraction of 131I-hippuran.

Figures

Figure 1

Dopamine induced effects on renal perfusion when assessed without (effective renal plasma flow) and with correction for incomplete extraction of 131I-hippuran (renal plasma flow). Significance of differences: * P < 0.002 compared with ERPF. Both methods revealed a highly significant increase in renal perfusion (P < 0.001).

Figure 2

Effects of dopamine infusion (3 µg kg−1 min−1) on the fractional renal extraction of 131I-hippuran. Significance of differences: * P < 0.001 compared with baseline.