The nerves and muscles need sodium to work normally. Sodium also helps maintain water balance and blood pressure in the body. Normally, there is more sodium in the bloodstream and less inside the cells. When the concentration of sodium in the bloodstream is higher than normal, it is described as hypernatremia. This situation is typically caused by loss of water from the body or dehydration.
Diabetes Insipidus
Diabetes insipidus is a disorder characterized by production of excessive amounts of urine. This disorder could be central or nephrogenic. Central diabetes insipidus is characterized by low levels of a hormone called antidiuretic hormone or ADH. This hormone is produced in the hypothalamus and secreted by the pituitary gland. ADH acts on the kidneys -- it stimulates them to retain water. Nephrogenic diabetes insipidus occurs when the kidneys do not respond to the action of ADH. In diabetes insipidus, large volumes of water leave the body because the kidneys do not respond to ADH or because the amount of ADH in the body is low. Consequently, the blood's sodium concentration goes up. This simply means that in this condition, the body has more sodium than water.
Impaired Thirst Mechanism
The kidneys and the thirst response regulate the amount of sodium in the body, according to Medscape. The kidneys remove excess sodium from the body, while the thirst response drives individuals to drink water when sodium levels start to rise due to unreplaced water loss. People with impaired thirst mechanisms may not feel thirsty or drink water as water leaves their body. This can lead to hypernatremia because the concentration of sodium in their bodies becomes higher than the amount of water present. The elderly typically have inadequate thirst response and are therefore at risk for hypernatremia.
Effects
In hypernatremia, cells shrink because water moves out of the cells and into the bloodstream. In addition, the Merck Manuals Online Medical Library explains that the major effect of hypernatremia is nervous system dysfunction. This effect occurs because brain cells shrink in hypernatremia. Therefore, people who have high blood sodium levels may experience neurologic symptoms, such as seizures, confusion and a coma. Increased thirst is another effect of this condition.
References
- Medscape: Hypernatremia
- Merck Manuals Online Medical Library: Hypernatremia
- "The Renal System at a Glance"; Christopher O'Callaghan; 2009
