From the Guidelines
Hyponatremia is primarily caused by an imbalance of sodium in the body, resulting from excessive water intake, certain medications, medical conditions like heart failure and cirrhosis, hormonal disorders, and poor dietary sodium intake, leading to abnormally low sodium levels in the blood (below 135 mEq/L) 1. The main causes of hyponatremia can be categorized into three main types: hypovolemic, euvolemic, and hypervolemic hyponatremia.
- Hypovolemic hyponatremia is caused by a loss of sodium and water, but with a greater loss of sodium, leading to a decrease in the extracellular fluid volume.
- Euvolemic hyponatremia is caused by an increase in water intake or retention, without a corresponding increase in sodium, leading to a dilution of sodium in the blood.
- Hypervolemic hyponatremia is caused by an increase in both sodium and water, but with a greater increase in water, leading to an expansion of the extracellular fluid volume. Some of the specific causes of hyponatremia include:
- Excessive water intake, which dilutes sodium concentration
- Medications such as diuretics (especially thiazides), antidepressants (SSRIs), and certain antiepileptic drugs
- Medical conditions like heart failure, cirrhosis, kidney disease, and adrenal insufficiency
- Hormonal disorders, particularly syndrome of inappropriate antidiuretic hormone secretion (SIADH)
- Excessive sweating or vomiting without adequate sodium replacement
- Certain endurance sports where athletes drink too much water without electrolyte replacement
- Poor dietary sodium intake, especially in elderly patients
- Administration of hypotonic fluids in hospital settings The treatment of hyponatremia depends on identifying and addressing the specific cause while carefully correcting sodium levels to prevent complications, with the goal of improving morbidity, mortality, and quality of life 2. In general, the treatment of hyponatremia involves:
- Correcting the underlying cause of the hyponatremia
- Restricting fluid intake in patients with hypervolemic hyponatremia
- Administering hypertonic saline in patients with severe hyponatremia
- Using vasopressin receptor antagonists (vaptans) in patients with euvolemic or hypervolemic hyponatremia
- Monitoring serum sodium levels closely to avoid overcorrection or undercorrection. It is essential to note that the treatment of hyponatremia should be individualized based on the patient's specific condition and the severity of the hyponatremia, and should always prioritize the prevention of complications and the improvement of morbidity, mortality, and quality of life 3, 4, 5.
From the FDA Drug Label
In two double-blind, placebo-controlled, multi-center studies (SALT-1 and SALT-2), a total of 424 patients with euvolemic or hypervolemic hyponatremia (serum sodium <135 mEq/L) resulting from a variety of underlying causes (heart failure, liver cirrhosis, syndrome of inappropriate antidiuretic hormone [SIADH] and others)
The causes of hyponatremia (low sodium levels in the blood) include:
- Heart failure
- Liver cirrhosis
- Syndrome of inappropriate antidiuretic hormone (SIADH)
- Other underlying causes 6
From the Research
Causes of Hyponatremia
The causes of hyponatremia can be classified into four categories:
- Pseudohyponatremia: due to hyperproteinemia, hyperlipidemia, or hyperglycemia 7
- Hypovolemic hyponatremia: commonly due to fluid loss 7, 8
- Hypervolemic hyponatremia: commonly due to fluid retention from heart failure, cirrhosis, or renal failure 7, 8, 9
- Euvolemic hyponatremia: most often due to syndrome of inappropriate secretion of antidiuretic hormone (SIADH) 7, 8, 10, 11
Other Causes
Other causes of hyponatremia include:
- Certain medications 8
- Excessive alcohol consumption 8
- Very low-salt diets 8
- Excessive free water intake during exercise 8
- Liver cirrhosis and portal hypertension, characterized by excessive renal retention of water relative to sodium due to reduced solute-free water clearance 9
- Increased release of arginine vasopressin 9
Associated Conditions
Hyponatremia is associated with various conditions, including: