Homeostatic indications for the administration of diuretics

The authors monitored the effects of the different diuretics upon the natrium and water homeostasis and acid-base balance. The aim of the study was to clarify the exact mechanisms of their action and possible ways of monitoring of their homeostatic effects. The effects of furosemide (18 patients), hydrochlorothiazide (eight patients), spironolactone (14 patients), acetazolamide (10 patients), amiloride (four patients) and manitol (eight patients) were monitored in critically ill patients using computer programme utilizing 17 routinely monitored input values and calculating creatinine clearance, tubular resorbtion excretion fractions of sodium, potassium, water and osmotically active substances, clearance of the osmotically active substances, clearance of solute free water, electrolyte clearance, electrolyte free water clearance, urine outputs of sodium, potassium and urea, urea concentration index and serum and urine anion gaps. The development of parameters typical for each diuretic was evaluated using Student's t-test comparing the values before and during the treatment with the agent.

Main results

The natriuresis caused by furosemide is less important than the disturbing of the kidney concentrating ability. It is indicated in hyponatremia. Any of the evaluated parameters except serum potassium levels were not typical for the treatment with spironolactone. Hydrochlorothiazide reduces adverse effects of furosemide upon the kidney concentrating ability. It is useful in hypernatremia especially in the secondary nephrogenic diabetes insipidus and it is indicated in the secondary renal tubular acidosis. Amiloride was proved as the ideal therapy of chloride resistant metabolic alkalosis and hypokalemia. In comparison to acetazolamide it is potassium sparing drug and it seems to be less natriuretic. The indication for the use of acetazolamide is metabolic acidosis with the need for quick correction. Hyponatremia and hypoosmolality were not proven as the homeostatic indications for manitol.