Figure 129

Pathogenesis of hypernatremia. The renal concentrating mechanism is the first line of defense against water depletion and hyper-osmolality. When renal concentration is impaired, thirst becomes a very effective mechanism for preventing further increases in serum osmolality. The components of the normal urine concentrating mechanism are shown in Figure 1-2. Hypernatremia results from disturbances in the renal concentrating mechanism. This occurs in interstitial renal disease, with administration of loop and osmotic diuretics, and with protein malnutrition, in which less urea is available to generate the medullary interstitial tonicity.

Hypernatremia usually occurs only when hypotonic fluid losses occur in combination with a disturbance in water intake, typically in elders with altered consciousness, in infants with inadequate access to water, and, rarely, with primary disturbances of thirst [24]. GFR—glomerular filtration rate; ADH—antidiuretic hormone; DI—diabetes insipidus.

0 0

Post a comment