The kidney and strategies for the treatment of hypertension

Long-term outcome of surgical revascularization in ischemic nephropathy: normalization of average decline in renal function

OBJECTIVE

Renovascular disease may lead to ischemia of the nephrons and to fibrosis, which is generally considered to be irreversible and progressive. We investigated the potential of revascularization to recover and stabilize renal function in patients with ischemic nephropathy.

METHODS

In a retrospective analysis of all our 61 patients with ischemic nephropathy who underwent treatment with surgical revascularization, we determined the long-term course of renal function decline with an estimated glomerular filtration rate (EGFR; Cockcroft and Gault formula). With the assumption of normal renal function at age 25 years, the preoperative slope of EGFR and the postoperative slope of EGFR were determined from the EGFR before surgery, at the short-term follow-up examination (on average, 8 months after surgery), and at the long-term follow-up examination (on average, at 47 months after surgery). These declines in renal function were compared with EGFR values in age-matched and sex-matched samples from a large cross-sectional population study.

RESULTS

The overall surgical mortality rate amounted to 13.1%. Five patients became dialysis dependent-two with preexisting end-stage renal disease and three at later follow-up examination-and two patients, who before surgery were dialysis dependent, could be withdrawn from dialysis treatment. Shortly after the operation, the mean EGFR level had increased from 28.3 to 43.1 mL/min/1.73 m2 ( P <. 01). The rate of decline in renal function had decreased from an estimated -2.57 mL/min/1.73 m2/year before surgery (weighted mean: interquartile range, -2.71 to -1.98) to -0.66 mL/min/1.73 m2/year (weighted mean: interquartile range, -2.00 to -0.18) in the short-term interval to the long-term interval, which was even slightly better than the slope of -0.84 mL/min/1.73 m 2/year in the age-matched and sex-matched control population.

CONCLUSION

Surgical revascularization in selected patients with renovascular disease and ischemic nephropathy restores renal function and makes the average long-term rate of decline in renal function equal to that of the general population. This indicates that in most patients a "point-of-no-return" has not yet been passed even though their renal function is already markedly impaired before surgery. Therefore, in well-selected patients with ischemic nephropathy, considerable improvement of renal function can be realized.

Nitrendipine and the humoral control of sodium homeostasis

1. Nine healthy volunteers received 10 mg nitrendipine or placebo orally in random order. 2. In the subsequent 5 h urinary sodium excretion was 20% higher after nitrendipine, without any significant difference between the volume of urine excreted after nitrendipine or placebo. Mean blood pressure fell by 5 mm Hg (P less than 0.001), and mean heart rate increased by 5 beats min-1 (P less than 0.01) after nitrendipine but did not change after placebo. 3. These changes were accompanied by a significant elevation in plasma renin activity (P less than 0.001). A fall in plasma aldosterone following placebo appeared to be attenuated by nitrendipine. Plasma noradrenaline increased to a peak 3 h after nitrendipine administration (P less than 0.05) but did not change following placebo. A fall in the excretion of 6-keto PGF1 alpha following placebo was attenuated by nitrendipine. The total excretion of 6-keto PGF1 alpha after nitrendipine was significantly greater (P less than 0.05) than after placebo but not difference in the total excretion of PGE2 was detected. Nitrendipine did not affect urinary kallikrein excretion. 4. The natriuretic action of nitrendipine is not mediated by the kallikrein-kinin system, but may be related to changes in renal prostaglandins.

Moderate sodium restriction in hypertensive subjects: renal effects of ACE-inhibition

It has been suggested that AII-mediated renal mechanisms limit the efficacy of moderate sodium restriction in the lowering of blood pressure (BP) in hypertension. We therefore studied renal hemodynamics and sodium handling in nine essential hypertensives in balance on 200 and on a 50 mmol sodium diet, before and during ACE-inhibition (enalapril 10 mg bid for 8 days) in a cross-over fashion. BP was similar on 50 and 200 mmol Na before enalapril, the fall in BP during enalapril was significantly more pronounced on 50 mmol Na. On 50 mmol Na, GFR and filtered Na were significantly lower, and tubular reabsorption was significantly higher than on 200 mmol Na. GFR increased during enalapril in 50 but not on 200 mmol Na. Consequently, the differences in GFR and filtered load elicited by sodium restriction were no longer present during ACE-inhibition. In contrast, the differences in tubular reabsorption between 50 and 200 mmol Na persisted during enalapril. In conclusion, moderate sodium restriction, not affecting BP, can elicit a renal hemodynamic response. As this response is blunted by ACE-inhibition it is probably mediated by AII. This blunting may contribute to the increased sodium sensitivity of BP during ACE-inhibition. The adaptation of tubular sodium reabsorption is not affected by ACE-inhibition.