Hypernatremia in the Intensive Care Unit- An Overview

What Is Hypernatremia?

When too much water gets lost from the body, sodium levels increase, leading to a medical condition called hypernatremia. This means that the body water will be significantly less compared to the sodium levels. Sudden changes in fluid consumption due to thirst changes or altered urine concentration may lead to hypernatremia. Due to the loss of excess body water, the person may feel extremely thirsty. The patient may also feel fatigued, tired, and confused. In advanced stages, the person may experience muscle spasms. Hypernatremia should be treated as an emergency when severe sodium level elevation leads to coma or seizures.

How Frequently Does Hypernatremia Develop in Critically Ill Patients?

Hypernatremia commonly develops in elderly or child patients with severe diarrhea. It is common to develop in a critically ill or injured patient admitted to an intensive care unit (ICU). A lower percentage of these patients will already have hypernatremia before ICU admissions. Most critically ill patients develop hypernatremia during treatment provided by a surgical or medical intensive care unit. If a patient admitted to an ICU develops hypovolemia (decreased extracellular fluid volume), a large number of fluids will be administered as a significant management step. Compared to the fluid lost from the patient's body, the fluid introduced during treatment may be hypertonic (high solute and low water concentration). If the patient has hypokalemia (low potassium levels in the blood), the fluid administered may be rich in potassium, increasing the sodium level and leading to hypernatremia. In addition, loop diuretics (medicines used to treat conditions associated with fluid overload) are also associated with hypernatremia.

Since an excess sense of thirst is the primary symptom of hypernatremia, intubated patients may get agitated. In addition, it may also lead to delirium, thus increasing the need for mechanical ventilation and prolonging the ICU admission period.

What Causes Hypernatremia in a Critically Ill Patient?

The following are the causes of hypernatremia in a critically ill patient admitted to an intensive care unit:

• Inability to drink water due to the medical condition of the patient.

• Failure to provide adequate water or fluid to the ventilated or ICU-admitted patients.

• Vomiting is induced due to the usage of a nasogastric tube.

• Osmotic cathartics are used to increase fecal water content and weight.

• Diuretic medications are given to increase urine output.

• Use of hypertonic saline.

What Are the Consequences of Hypernatremia in Critically Ill Patients?

Hypernatremia leads to many consequences in bodily functions. This may also be associated with hyperosmolality (increased levels of sodium, glucose, and other substances in the blood). Some of the consequences of hypernatremia are explained below:

• Neurologic Consequences: Hypernatremia and hyperosmolality create a tendency to shift free water (water in the intercellular space or the space between the cells) from intracellular space (space within the cell) to extracellular (space outside the cell). These changes shrink the brain cells and rupture the blood vessels in the area, leading to severe neurologic conditions. In addition, there are reported cases where the patient developed cerebral demyelination (a condition affecting the protective covering or myelin sheath of the nerve fibers in the brain) due to underlying hypernatremia. In some cases, Hypernatremia may also lead to coma, restlessness, or lethargy.

• Neuromuscular Consequences: Hypernatremia leads to an electrolytic imbalance in the body, leading to muscle cramps. The sodium-potassium pump overworks to correct the defect when the body develops an electrolyte imbalance. This overworking may utilize muscular energy, leading to muscle weakness. In some cases, severe hypernatremia leads to rhabdomyolysis. It is a condition in which the muscle tissues break down, leading to the release of the contents of muscle fibers into the blood.

• Hyperglycemia: Hypernatremia is associated with glucose utilization impairment and affects glucose metabolism. This may lead to hyperglycemia (high blood glucose or sugar level) in critically injured or ill patients.

• Inflammation: Hypernatremia is associated with proinflammatory cytokine response. As a result, pro-inflammatory cytokines may be produced and released, leading to inflammation and pain.

• Liver Consequences: Hypernatremia impairs the gluconeogenesis pathway. Gluconeogenesis is the pathway that leads to the formation of glucose within the body.

• Venous Thromboembolism: In critically ill patients with diabetes (a condition due to increased blood sugar), venous thromboembolism is likely due to hypernatremia. Venous thromboembolism is a severe condition due to the development of blood clots in the veins.

• Cardiac Consequences: Hypernatremia may decrease the contractility of the left ventricle, impairing cardiac function.

• Renal Consequences: Hypernatremia causes the breakdown of muscle tissues, leading to the release of the contents of the muscle fibers into the blood. These substances are harmful to the kidneys and may lead to renal failure.

How Is Hypernatremia Managed in the ICU?

• The patient may feel extremely thirsty in case of hypernatremia. If the person can drink, they should be encouraged to drink water.

• Osmolality and electrolytes in the serum and urine should be constantly monitored to make adjustments in the flid provided.

• In case of increased severity or the patient cannot take the fluids orally or digest those, the IV or intravenous route can be opted to provide the fluid.

• The patient should be frequently monitored for hyperglycemia and hypocalcemia, as both are likely to develop during the treatment period.

• If the patient develops shock, normal saline should be administered first. Dilute fluids can then be substituted after correction of tissue perfusion rate.

• In case of hypervolemia, the patient may be given loop diuretics to increase urine output.

• The doctor may suggest dialysis (a procedure by which waste and excess fluid will be removed from the body) if the patient has renal impairment.

Conclusion

A high level of sodium in the blood is called hypernatremia. It occurs due to excess water loss or increased sodium intake. Inadequate free water intake is the leading cause of hypernatremia. In addition, water loss through the gastrointestinal tract or renal system may also lead to the condition. Based on the cause, adequate treatment should be provided to cure the condition, which may otherwise lead to severe health problems. The health problems can even be life-threatening or increase the duration of ICU admission time.