ABSTRACT
Changes of the renal function of a three-phase course originate from the application of hypertonic infusions. The first phase is characterized by a copious osmotic diuresis and the decrease of the re-absorption of osmotic free water. The second phase shows a lower osmotic diuresis and the re-absorption of osmotic free water attains the values before the beginning of the infusion. The third phase produces a urine time volume like before the infusion, however, the re-absorption of osmotic free water exceeds the starting-value. A biphasic course with isotonic electrolyte infusion is opposed to the three-phase course with osmotic load. Changes of the osmolarity in plasma and urine is to be recommended in order to take it into consideration more in the clinical practice.
