Diuretics in renal failure

Fluid retention following reduction in the glomerular filtration rate cause s extracellular fluid volume expansion that reduces tubular reabsorption by residual nephrons, thereby maintaining the external sodium balance. The pr ice paid for this is salt-dependent hypertension. Thus, loop diuretics are the best treatment for uremic hypertension. Diuretics are also used in chro nic renal failure to treat edema due to nephrotic syndrome and congestive h eart failure (CHF). In nephrotics, edema is often refractory to diuretics b ecause of low plasma protein, depletion of the intravascular compartment, d ecrease in the protein-bound fraction of the diuretic in peritubular blood, and increase in tubular fluid. Thus, higher doses are needed. In uremics w ith CHF the efficacy of diuretics may be hampered because of the reduced re nal blood flow. The association of dopamine (1-1.5 mu/kg body weight/min) m ay overcome this resistance; improvement in cardiac function by dialysis ul trafiltration may also help. Diuretic resistance is sometimes observed; it may be overcome by the following procedures: in CHF by the use of digitalis and/or angiotensin-converting enzyme inhibitors; by substitution of an ine ffective loop diuretic for another one; by using larger doses of diuretic; by intravenous infusion rather than bolus therapy, and by a combination of diuretics acting in different segments of the tubule: loop diuretic+ thiazi de+amiloride. Intravenous infusion of 20% albumin has also been suggested.