Hyponatremia: when sodium levels are below normality ranges

Hyponatremia is an hydroelectrolytic disorder that is characterised by low levels of sodium in blood. If sodium levels are too low, it often causes water to enter the cells, leading to overhydration. In this state, the cells swell due to the excess water they accumulate.

Sodium is an electrolyte found in the blood that plays a critical role in maintaining blood pressure. 

It is also essential for the proper functioning of muscles, neurons, and other body tissues.

The sodium imbalance characteristic of hyponatremia may result from one of the following three conditions:

• Euvolemic hyponatremia: total body water increases, but the body's sodium content remains the same
• Hypervolemic hyponatremia: both water and sodium content in the body increase, but water gain is greater
• Hypovolemic hyponatremia: the body loses both water and sodium, but sodium loss is greater

Hyponatremia can be a serious condition if not diagnosed and corrected promptly. The most characteristic symptoms include:

• Confusion, irritability, restlessness
• Seizures
• Fatigue
• Headache
• Loss of appetite
• Muscle weakness, spasms, or cramps
• Nausea and vomiting

As the condition progresses to more severe stages, it can lead to potentially life-threatening effects, including:

• Rapid brain swelling
• Hallucinations
• Reduced consciousness
• Brain herniation
• Coma
• Death

There are many potential causes, including:

• Burns affecting a large area of the body
• Diarrhea
• Diuretic medications that increase urinary output and sodium loss
• Heart failure
• Kidney disease
• Cirrhosis (advanced liver disease)
• Syndrome of inappropriate antidiuretic hormone secretion (SIADH)
• Sweating
• Vomiting

The primary risk factors for hyponatremia include:

• Age: as people age, the risk of chronic diseases that contribute to hyponatremia increases. Aging and certain medications can also affect sodium metabolism
• Some medications: medications that increase the risk of hyponatremia include thiazide diuretics, certain antidepressants, and painkillers. Additionally, the recreational drug "ecstasy" has been linked to fatal cases of hyponatremia
• Disorders reducing water elimination: diseases that may increase the risk of hyponatremia include kidney disease and SIADH
• Intense physical activity: people who drink excessive water during marathons, ultramarathons, triathlons, or other intense activities covering long distances are at greater risk of hyponatremia.

Measuring blood sodium levels is the primary method for diagnosing hyponatremia. Additional evaluations may include:

• A comprehensive metabolic panel, including sodium
• Blood osmolality
• Urine osmolality
• Urine sodium levels

Treatments typically include:

• Intravenous (IV) fluids
• Medications to alleviate symptoms
• Limiting water intake

Hyponatremia can be prevented by following a balanced diet rich in sodium or, if necessary, taking dietary sodium supplements. Additional measures to prevent hyponatremia include:

• Treating related conditions: managing diseases such as adrenal insufficiency can help maintain normal sodium levels
• Taking precautions during high-intensity activities: athletes should drink only the amount of fluid lost through sweat during an event. Thirst is a good indicator of fluid needs
• Moderate water intake: drinking water in appropriate amounts is crucial for health. Thirst and urine color are often the best indicators of how much water is needed