Hypertonic Dehydration · What Is It, Causes, Treatment, and More

Hypertonic dehydration, also known as hypernatremic dehydration, refers to an imbalance of water and sodium in the body characterized by relatively increased levels of sodium. When water is excreted from the body, electrolyte (e.g., sodium) concentrations in the blood increase. Hypertonic dehydration occurs when an individual excretes too much water without also excreting electrolytes, leaving a high sodium concentration in the blood.   

Hypertonic dehydration is one of three types of dehydration. Hypotonic dehydration, in contrast to hypertonic dehydration, refers to a decrease in electrolyte concentration in the extracellular fluid. Isotonic dehydration, the third type of dehydration, occurs when the electrolyte concentrations remain normal, but there is an overall bodily fluid loss.  

A variety of underlying conditions can cause hypertonic dehydration. Overall, these conditions result in loss of bodily fluids, usually through the skin, gastrointestinal (GI) tract, or urinary system. 

Fluid loss through sweating and expiration often leads to hypertonic dehydration. Overexposure to heat, increased exercise, and the development of burns can increase fluid loss. On top of that, decreased fluid intake often leads to hypertonic dehydration. This is more common if an individual has an impaired thirst mechanism, is immobile, or has cognitive deficits. Their water intake may not compensate for the fluid lost through daily activities.  

Diarrhea and vomiting are common causes of dehydration due to rapid fluid loss through the gastrointestinal tract. Children with gastroenteritis, colloquially referred to as a stomach bug, are especially susceptible to developing dehydration. Aside from illness, the use of laxatives, which are medications that stimulate bowel movements, may cause diarrhea and subsequent hypertonic dehydration. In some rare instances, hypertonic dehydration may result from the development of a fistula, an atypical opening in the digestive tract. Gastric suctioning, a procedure to remove stomach contents, can lead to significant fluid loss. Abdominal swelling, known as ascites, and abdominal infections, such as pancreatitis and peritonitis, have also been linked to hypertonic dehydration. 

In addition, there are many urinary and kidney-related fluid losses that can lead to hypertonic dehydration. These conditions include kidney disease, in which the kidneys are not functioning properly; post-obstructive diuresis, causing excessive water excretion through urine; salt-wasting tubular disease, marked by excessive water and salt excretion through urine; Addison disease, in which there is insufficient adrenal hormone secretion; hypoaldosteronism, characterized by reduced aldosterone levels; and hyperglycemia, characterized by high glucose levels. Moreover, diabetes insipidus, which occurs when the kidneys cannot regulate bodily fluids, typically leads to frequent urination and can cause hypertonic dehydration. The use of diuretics, medications used to increase urine excretion, may also lead to dehydration.  

Diagnosis begins with a thorough health history and physical examination. 

To definitively diagnose hypertonic dehydration, blood tests can assess serum osmolality, which is a measure of dissolved particles (e.g., electrolytes, glucose); blood and urine sodium concentration; and urine electrolytes. Blood test results that suggest hypertonic dehydration include elevated serum sodium, elevated serum osmolality, elevated blood urea nitrogen (BUN), elevated glucose, and in some cases, decreased calcium and potassium levels. Additionally, urine tests may show an elevated specific gravity (i.e., osmolality of the urine).