From the Guidelines
Hyponatremia is primarily caused by an imbalance of sodium in the body, often resulting from conditions such as liver cirrhosis, heart failure, and kidney disease, as well as from certain medications and excessive water intake, with treatment depending on the etiology, chronicity, severity, and urgency of the condition. When considering the causes of hyponatremia, it's essential to differentiate between hypovolemic, euvolemic, and hypervolemic hyponatremia.
- Hypovolemic hyponatremia can be caused by the discontinuation of diuretics and/or laxatives and providing fluid resuscitation, typically with 5% IV albumin or crystalloid (preferentially lactated Ringer’s) solution 1.
- Euvolemic hyponatremia should be managed based on the specific underlying cause, which can include syndrome of inappropriate antidiuretic hormone secretion (SIADH), certain endocrine disorders like hypothyroidism, and other medical conditions.
- Hypervolemic hyponatremia, often seen in patients with liver cirrhosis and ascites, can be treated with fluid restriction, reduction or discontinuation of diuretics and laxatives, administration of hyperoncotic albumin, and/or vasopressin receptor antagonists (“vaptans”) 1. Key considerations in managing hyponatremia include the onset (acute vs. chronic), severity, and the patient's volume status, as these factors influence the risk of complications such as osmotic demyelination syndrome (ODS) and guide the appropriate correction rate of sodium levels. In clinical practice, identifying and addressing the underlying cause of hyponatremia, whether it be a medical condition, medication, or other factor, is crucial for effective management and prevention of recurrence, as emphasized in the 2021 practice guidance by the American Association for the Study of Liver Diseases 1.
From the Research
Causes of Hyponatremia
- Hyponatremia can result from various causes, including water retention, certain medications, excessive alcohol consumption, very low-salt diets, and excessive free water intake during exercise 2
- Thiazide-associated hyponatremia is a significant cause of decreased sodium levels, particularly in elderly individuals, and is often observed in patients with certain risk factors such as heart failure, liver disease, or malignancy 3
- The pathophysiology of thiazide-associated hyponatremia is incompletely understood and includes some combination of excessive fluid intake, cation depletion, osmotic inactivation of sodium, and reduced ability to excrete free water 4
- Other causes of hyponatremia include the syndrome of inappropriate antidiuresis, heart failure, cirrhosis, and excessive fluid intake 5, 6
Classification of Hyponatremia
- Hyponatremia can be classified as hypovolemic, euvolemic, or hypervolemic, depending on the patient's fluid volume status 5, 2
- Hypovolemic hyponatremia is treated with normal saline infusions, while euvolemic hyponatremia is treated with restricting free water consumption or using salt tablets or intravenous vaptans 2
- Hypervolemic hyponatremia is treated primarily by managing the underlying cause, such as heart failure or cirrhosis, and free water restriction 2
Risk Factors for Hyponatremia
- Risk factors for thiazide-associated hyponatremia include age, female sex, low body mass, and genetic susceptibility 4, 3
- Patients with certain comorbidities, such as heart failure, liver disease, or malignancy, are also at increased risk of developing thiazide-associated hyponatremia 3
- The use of certain medications, such as non-steroidal anti-inflammatory drugs, selective serotonin re-uptake inhibitors, or tricyclic antidepressants, can also increase the risk of developing thiazide-associated hyponatremia 3