The occurrence of diuresis in humans in stressful situations and its possible relation to the diuresis of early starvation

DDAVP test for estimation of renal concentrating capacity in infants and children

A new method for the estimation of the renal capacity to concentrate urine is described. Intranasal administration of DDAVP (1-deamino-8-D-arginine vasopressin), a synthetic analogue of the antidiuretic hormone, has been used for the measurement of urine concentrating performance in 79 children and 25 infants. By comparative studies of different doses of intravenous and intranasal administration of DDAVP, a standard procedure has been elaborated with the intranasal administration of 20 μg in children and 10 μg in infants. The maximum urine osmolality values obtained with the DDAVP test are compared to those achieved with other renal concentration tests, i.e. dehydration test and pitressin test. The present investigation shows that intranasal administration of DDAVP, with no or only moderate short-term fluid restriction, yields urine osmolality values comparable to those after 22 hours of prolonged dehydration, and higher than those after combined pitressin and fluid deprivation test. No side effects have been observed with the procedure described.

Effect of a simple deconditioning procedure on the diuretic and natriuretic response of hypertensive patients to a hypertonic salt load

The increased diuretic and natriuretic response of hypertensive patients to an intravenous salt load was modified toward normal by a deconditioning procedure which consisted in repeated exposure to the external situation of the test without, however, infusing any fluid into the vein. After this deconditioning, ratios between amounts of urine and sodium excreted in the first and the second 90-minute period of the test and the total 3-hour quantity of urine excreted were significantly reduced, but blood pressure was not changed. The response of normotensive patients to the same deconditioning was modified in the same direction but to a much smaller extent. It is suggested that the increased diuretic and natriuretic responses of hypertensive patients to an intravenous salt load are similar to the hyperreactive pressor and diuretic responses of these patients when exposed to stimuli that seem threatening to them, and that these responses are caused (at least in part) by hyperreactivity of the central nervous system to the external situation of the test.