Hydralazine and the tourniquet test in renal vein renin sampling: A comparison

A total of 36 salt-depleted patients with suspected renovascular hypertension received intravenous hydralazine and 36 were subjected to the tourniquet test at the time of renal vein renin sampling. Simultaneous bilateral renal vein samples were obtained sequentially over 30 minutes. Both measures resulted in an increase in renin secretion. The number of patients showing a positive ratio (≥ 1.5) between the angiographically abnormal kidney and the contralateral kidney increased in both groups. In the hydralazine group, 47% had positive ratios at 0 min compared with 80% following hydralazine administration. In the tourniquet group, 53% had positive ratios at 0 min compared with 78% afterward. In neither group did all patients have positive ratios throughout the entire sampling period. Hydralazine produced a greater increase in renin, but more variable results. It is concluded that salt depletion is inadequate for detection of a pressor kidney, and an additional stress is required. Multiple simultaneous samples should be obtained.