Dysnatremia is a medical term for an imbalance of sodium in the body and is one of the most common electrolyte disturbances. Sodium is an electrolyte obtained from food and drink that carries an electric charge when dissolved in fluids like blood. The body requires sodium to maintain a normal fluid balance, facilitate nerve impulses, and support muscle function.
The kidneys play a large part in regulating the body’s sodium by controlling how much is released in the urine. When the intake and output of sodium are not balanced, it affects the total amount of this mineral in the body.
Hyponatremia vs. Hypernatremia
A normal blood sodium level falls within the range of 135 to 145 milliequivalents per liter (mEq/L). Dysnatremia is categorized into two main types based on whether the sodium concentration is below or above this range.
Hyponatremia is characterized by a low sodium concentration in the blood, specifically below 135 mEq/L. This condition often arises from an excess of water in the body relative to the amount of sodium, which creates a dilution effect.
Conversely, hypernatremia is defined by a high sodium concentration in the blood, exceeding 145 mEq/L. This state is a problem of water deficiency relative to the body’s sodium content, indicating a state of dehydration where the blood becomes more concentrated.
What Causes Sodium Levels to Shift?
Shifts in sodium levels can be attributed to a variety of medical conditions, medications, and lifestyle factors. The causes differ significantly between low and high sodium states.
Hyponatremia, or low sodium, can result from scenarios that lead to either water retention or sodium loss. Common causes include:
- Excessive water intake, particularly in endurance athletes who overhydrate.
- Certain medications, such as thiazide diuretics and some antidepressants.
- The Syndrome of Inappropriate Antidiuretic Hormone (SIADH), where the body retains too much water.
- Severe vomiting or diarrhea, which can cause a significant loss of sodium.
- Chronic conditions affecting the heart, kidneys, or liver that impair fluid regulation.
Hypernatremia, or high sodium, stems from a deficit of water. This is often caused by inadequate water intake or significant water loss. Common causes include:
- Inadequate water intake, a risk for older adults with a diminished thirst sense or for infants.
- Conditions that lead to significant water loss, such as a high fever or excessive sweating.
- Diabetes insipidus, a disorder where the kidneys are unable to conserve water.
- While rare, ingesting an excessive amount of salt.
Recognizing the Warning Signs
The symptoms of dysnatremia are primarily neurological, stemming from the brain’s sensitivity to changes in sodium concentration. When sodium levels are imbalanced, it disrupts the normal flow of water into and out of brain cells, which triggers the physical and cognitive symptoms.
In hyponatremia, the low concentration of sodium in the blood causes water to move into the brain cells, leading to swelling. This can manifest as nausea, headache, and fatigue in milder cases. As the condition becomes more severe, symptoms can escalate to include confusion, muscle spasms or cramps, and in serious instances, seizures or a coma.
In hypernatremia, the high concentration of sodium in the blood pulls water out of the brain cells, causing them to shrink. A hallmark sign of this condition is intense thirst. Other symptoms can include confusion, lethargy, and muscle twitching. Severe cases of hypernatremia can also lead to seizures and coma.
Diagnosis and Corrective Treatments
Diagnosing and managing dysnatremia requires medical evaluation to identify the underlying cause and correct the imbalance safely. The primary tool for diagnosis is a basic metabolic panel, a blood test that measures the concentration of sodium. This test indicates whether sodium levels are low, high, or normal. A urine test is also often performed to assess how the kidneys are excreting salt and water.
Treatment for dysnatremia depends on the underlying cause. For hyponatremia, treatment may involve restricting fluid intake or, in more severe cases, administering a concentrated sodium solution intravenously. For hypernatremia, the focus is on rehydration, which is done using intravenous fluids to restore the body’s water balance.
It is important that the correction of sodium levels is done slowly under close medical supervision. Correcting hyponatremia too quickly can lead to a severe neurological condition called osmotic demyelination syndrome. Rapid correction of hypernatremia can cause cerebral edema, or swelling of the brain.