Hypernatremia - Causes, Symptoms, Diagnosis, Management, and Complications

What Is Hypernatremia?

The normal blood levels of sodium ions are generally about 135 to 145 mmol/l. Hypernatremia is the increased sodium concentration in the blood to a level of more than 145 mmol/l. It is not a disease but a condition associated with the disease. Sodium is a positively charged ion called a cation. It is present in the extracellular fluid and plays a vital role in maintaining the homeostasis of the human body. It maintains the intravascular volume, thereby regulating blood pressure, blood volume, and osmotic equilibrium.

What Is the Epidemiology of Hypernatremia?

Hypernatremia is more common among children and elderly people. In children, it is commonly seen among the ones affected by gastroenteritis and poorly breastfed babies. Old age is another risk group because of impaired thirst mechanisms and improper care.

What Are the Types of Hypernatremia?

1. Hypovolemic or Low Volume Hypernatremia: Hypovolemia is the decrease in the fluid content of the body; hypernatremia can occur as a result of water and solute loss from the body.

2. Euvolemic or Normal Volume Hypernatremia: In this type, hypernatremia develops in the presence of the normal amount of fluid and blood in the body.

3. Hypervolemic or High Volume Hypernatremia: In this type, hypernatremia develops in the presence of an excessive amount of fluid in the body.

What Is the Etiology of Hypernatremia?

The etiology of hypernatremia is mainly due to the excessive loss of water from the body with the increasing concentration of solutes in the blood. The etiological factors for the above-discussed types of hypernatremia include;

Hypovolemic or Low Volume Hypernatremia:

• Inadequate Water Intake - Due to several reasons.

• Old Age - Hypernatremia may develop due to inadequate water intake or inability to get adequate water.

• Glycosuria - Causing increased loss of water from the urinary tract.

• Extreme Sweating - This may contribute to excessive water loss from the body.

• Vomiting - Continuous vomiting would result in water loss from the body.

• Diarrhea - A severe watery diarrhea would result in loss of water from the body and increases the sodium concentration in the blood.

• Gastroenteritis - Gastroenteritis is more common in children who receive less water intake, thereby increasing serum concentration.

• Impaired Thirst Response - This would result in decreased intake of water.

• Breast-Fed Babies - Chances of hypernatremia in breastfed babies are low but may occur as a result of decreased water intake.

Euvolemic or Normal Volume Hypernatremia:

• Diabetes Insipidus - Hypernatremia may develop as a result of inadequate production of vasopressin which is responsible for the reabsorption of water from the kidneys. Due to inadequate water reabsorption, excess water is lost from the kidneys, and increased sodium concentration would lead to hypernatremia.

Hypervolemic or High Volume Hypernatremia:

• Excessive Sodium Bicarbonate Ingestion - This may occur in hospital settings where patients may develop hypernatremia after receiving excessive sodium bicarbonate intravenous administration.

• Salt Poisoning - Salt poisoning is most commonly seen in children due to excessive intake of sodium.

• Drinking Seawater - Drinking seawater can also increase the risk of hypernatremia.

• Hyperaldosteronism or Conn’s Syndrome - Increased aldosterone levels would increase the reabsorption of sodium from the distal convoluted tubules of the kidneys, thereby increasing the serum sodium levels.

What Is the Pathogenesis of Hypernatremia?

As a result of hypernatremia developed due to the above-said etiologies, the water from the cells in the tissues would move out and reach the bloodstream, the cells shrink, and the sodium concentration in the blood increased. This, in turn, activates the feedback mechanisms to restore the water content as well as to reduce the increased serum sodium levels. The activation of regulatory mechanisms such as renin-angiotensin-aldosterone mechanisms will activate the thirst response, and the secretion of antidiuretic hormone (ADH) would result in water retention and concentrated urine.

What Are the Symptoms of Hypernatremia?

The symptoms include,

• Lethargy.

• Tiredness.

• Muscle weakness and spasms.

• Confusion.

• Seizures.

• Irritability.

• Excessive thirst.

• Dehydration.

• Tachycardia (increased heart rate).

• Orthostatic hypotension (this is a form of low blood pressure that happens when a person stands immediately after lying down or sitting).

• Somnolence (it is the state of being drowsy).

• Restlessness.

• Polyuria and polydipsia in patients with diabetes insipidus.

How Is Hypernatremia Diagnosed?

1. History: A complete history should be collected from the patient regarding the symptoms.

2. Physical Examination: Includes, checking for the signs of dehydration, assessing the consciousness status, and monitoring the vital signs.

3. Blood Test: It involves the basic metabolic panel, which would indicate elevated serum sodium levels.

4. Water Deprivation Test: This test is done to check whether the patient has diabetes insipidus. The patient is asked to take fluids till night, and is asked to be deprived of fluids for eight hours or until he loses five percent of his body mass. The weight is checked once every hour, plasma osmolality is measured once every four hours, and urine volume and osmolality every two hours.

5. Water Deprivation Test with Desmopressin: The patient can eat and drink until 1.5 to two times the volume is excreted during the dehydration phase. One to two hours after the desmopressin, the urine output, urine osmolality, serum sodium levels, and serum plasma osmolality are measured. In patients with central diabetes insipidus, there will be an increase in urine osmolality, whereas, in patients with nephrogenic type, there will not be any response to desmopressin.

How Is Hypernatremia Managed?

The main aim of the treatment is to control the elevated serum sodium levels and to treat the underlying etiologies.

• Fluid Administration: The first prime step is to treat dehydration by administering fluids; oral fluids should be given frequently in case of unconscious patients or severely dehydrated patients; immediate intravenous administration of isotonic fluids is mandatory. Reestablishing the water and normal sodium levels should be a slow process as the rapid correction would lead to potential complications.

• Desmopressin: Can be given to adult patients with central diabetes insipidus either in oral or intranasal forms.

• Peritoneal Dialysis: Is recommended in patients with sodium intoxication; peritoneal dialysis is performed to remove excess sodium.

What Are the Complications Involved in the Treatment of Hypernatremia?

The rearranged sodium and water levels need to be reestablished slowly with a goal to decrease the elevated serum sodium levels by 12 meq in 24 hours. The rapid or sudden decrease would result in seizures and cerebral edema, which is a medical emergency, so the free water deficit should be restored slowly within 48 to 72 hours, and reduce sodium levels to a limit of 0.5 meq per hour. The most serious complication of hypernatremia is subdural hemorrhage as a result of cranial vein rupture and thrombosis of the dural sinus. This can lead to death or permanent brain damage.

Conclusion

Hypernatremia shows a good prognosis with prompt treatment. At the same time, it may lead to serious complications if not managed properly and even death if left untreated. Hence, early diagnosis and prompt management are necessary for patients with hypernatremia to prevent further complications.