[Diuretics in renal failure]

The indications for the use of diuretics in patients with renal failure are edema and hypertension. An ancillary measure is dietary sodium restriction which permits reduction of the diuretic dose and reduces the frequency of diuretic induced side effects. The natriuretic action of diuretics is attenuated in renal failure both for pharmacokinetic and pharmacodynamic reasons. The most important cause for reduced efficacy of diuretics in renal patients is binding of diuretics to proteins within the tubular lumen so that the absolute free concentration of diuretics is diminished. Further important reasons for the diminished increment in urinary sodium excretion that is seen in patients with renal failure include a) reduced number of nephrons (i.e. reduced functional mass) and b) intrarenal compensatory mechanisms which increase sodium activity and tubular reabsorption of sodium. These difficulties can be overcome by dietary sodium restriction, by selection of higher doses of diuretics, by selection of appropriate intervals of administration and by combination of loop diuretics and thiasides. In order to recognize side effects resulting from excessive diuresis with hypovolemia and increase of serum creatinine concentration from prerenal causes it is necessary to closely monitor the patients.