Hyponatremia

Hyponatremia is a metabolic disorder characterized by low concentration of sodium in the blood relative to the amount of water in the body. It occurs due to an imbalance in the complex physicochemical system that regulates the absorption and excretion of water and sodium in our body, and it is associated with the aging process

However, certain medications and diseases—such as tumors and heart, liver, and kidney failure—can also trigger or worsen the condition. Mental confusion, increased risk of falls, seizures, coordination deficits, and behavioral changes—common symptoms in the elderly—may be related to the disease

According to Dr. Maysa Seabra Cendoroglo, a geriatric physician at Einstein, a healthy person has a stable sodium level in the blood plasma ranging from 135 to 145 mEq/L (milliequivalents per liter). Below this threshold, the condition is classified as hyponatremia, which can be detected through a blood test. The lower the sodium level and the more sudden and rapid the drop, the more intense the symptoms—mainly affecting the neurological system due to the adverse conditions caused in the brain by water accumulation

“The sodium level in blood plasma usually remains stable while the individual is healthy or their conditions are under control. But as a person ages, this regulatory system may begin to deteriorate,” explains Dr. Maysa

Dysfunctions That Can Lead to Hyponatremia

Broadly speaking, the system can be affected by dysfunctions in three main ways. One of them is related to a decreased sensitivity of the receptors located in the chest, kidneys, and blood vessels, which are responsible for detecting drops in sodium levels in the blood plasma. When this sensitivity is impaired, the stimulation of the neurohypophysis gland to produce antidiuretic hormone (ADH)—a substance that helps regulate the balance between water and sodium in the body—becomes less accurate. As a result, there is excessive production of this hormone. The higher its presence, the greater the water retention in the body and, consequently, the greater the dilution of sodium. It is also important to note that older adults have lower levels of vasopressinase, an enzyme that deactivates the action of ADH

Another common dysfunction among the elderly, especially those with heart failure, is the increased presence of atrial natriuretic peptide (ANP), a hormone produced by the heart’s muscle cells. The more this hormone is present, the higher the rate of sodium excretion

Hyponatremia can also be related to the failure of the renal endocrine system known as the renin-angiotensin-aldosterone system, which is responsible for reabsorbing part of the sodium that is naturally excreted by the body, preventing it from being lost in the urine. When this system is deficient, it fails to help maintain sodium levels

Many elderly individuals, even with such dysfunctions, are able to reestablish sodium balance. These are less efficient systems, but they do not necessarily lead to hyponatremia. The problem arises in more acute metabolic dysfunctions, mainly due to the body’s inability to eliminate the right amount of water to maintain sodium balance, the action of tumors that may stimulate the production of ADH, or conditions that promote water retention—such as heart, liver, and kidney failure—as well as the effects of certain medications. Some diuretics, anticonvulsants, antidiabetics, chemotherapeutic agents, and antidepressants may contribute to hyponatremia either by promoting fluid retention (which reduces sodium concentration) or by stimulating inappropriate sodium elimination. It is also important to highlight that, in this context as well, self-medication can be harmful

Treatment Approaches

How is hyponatremia treated? Faced with the complexity of this metabolic dysfunction, physicians must first identify the possible causes behind the condition

Severe cases of hyponatremia—which, in extreme situations, can lead to coma due to adverse neurological conditions—are often linked to other diseases and may even serve as markers of the severity of heart and liver failure. Milder cases, which are often asymptomatic, are usually related to isolated metabolic issues and may only require monitoring. In cases where hyponatremia is associated with medication use, auxiliary drugs may be needed to prevent the development of the condition, or the medication causing the dysfunction may need to be discontinued

Ideally, the underlying causes of hyponatremia should be eliminated. However, if that is not possible, medicine offers ways to restore metabolic balance to satisfactory levels. Rarely is the solution as simple as sodium replacement. In general, treatment involves controlling the level of free water (water without salts) in the body through the use of specific diuretics and, in some cases, drugs that block the action of the antidiuretic hormone. It is important to understand that hyponatremia should not be treated with home remedies or by increasing dietary salt intake. Regardless of the approach, proper medical guidance and close monitoring are essential

By the Einstein Editorial Board