After reading this I think I'm going to stop drinking water.Originally Posted by Trung Q Pham, MD
Background: Hypernatremia is an electrolyte problem that is not uncommon, especially in elderly people who are hospitalized. Poor water intake, inability to express thirst, insensible water loss, or increased urinary water loss lead to dehydration and an increased concentration of serum electrolytes relative to water.
The development of hyperosmolality from the water loss leads to neuronal cell shrinkage and resultant brain injury. Loss of volume leads to circulatory problems (eg, tachycardia, hypotension). Water replacement can lead to cerebral edema.
Pathophysiology: The fundamental problem is that hypernatremia strictly defined is hyperosmolality, ie, an overall deficit of total body water. This deficit accrues by 2 mechanisms, which are inadequate fluid intake and water loss. Because thirst is a potent mechanism in the response to hyperosmolality, hypernatremia patients either have an inadequate thirst mechanism or have an inability to respond to thirst. If the thirst response to hyperosmolality is impaired, ongoing water losses raise serum sodium concentration. Ongoing water losses include insensible (always) water in excess of solute or renal loss (with a solute diuresis such as hyperglycemia or water diuresis). Increased sodium intake (salt tablets) is a rare cause of hypernatremia in hot, humid weather. The brain cell response to hypernatremia is critical and is contained in Image 1.
The keys to the pathophysiology of hypernatremia include the following:
Thirst should lead to water intake.
Vasopressin is critical to water reabsorption in the cortical collecting tubule.
The CNS is sensitive to changes in osmolality.
Water may be lost by renal and extrarenal mechanisms.
In the US: Overall, incidence ranges from 0.12-3.5% in hospitalized patients. Hypernatremia is most prevalent in the geriatric population.
The mortality rate across all age groups is approximately 45%.
The mortality rate in the geriatric age group is as high as 79%.
Race: No race predilection exists.
Sex:No sex predilection exists.
The groups most commonly affected are elderly people and young people.
People typically affected are aged 59-83 years.