From the Guidelines
Persistent hyponatremia is primarily caused by hypovolemia, euvolemia, or hypervolemia, and its management depends on the underlying etiology, chronicity, severity, and urgency, as outlined in the 2021 practice guidance by the American Association for the Study of Liver Diseases 1. The causes of persistent hyponatremia can be categorized into three main types:
- Hypovolemic hyponatremia, which is often due to excessive diuretic administration or other causes of volume depletion
- Euvolemic hyponatremia, which can be caused by the syndrome of inappropriate antidiuretic hormone secretion (SIADH) or other conditions
- Hypervolemic hyponatremia, which is commonly seen in patients with cirrhosis and ascites, and is characterized by an increase in total body water.
According to the most recent guidelines, the treatment of hyponatremia in cirrhotic patients should aim to correct the underlying cause, with hypovolemic hyponatremia requiring fluid resuscitation, euvolemic hyponatremia managed based on the specific underlying cause, and hypervolemic hyponatremia treated with fluid restriction, reduction or discontinuation of diuretics and laxatives, administration of hyperoncotic albumin, and/or vasopressin receptor antagonists (“vaptans”) 1. Some key points to consider in the management of hyponatremia include:
- Correction rates should not exceed 8 mEq/L in 24 hours to prevent osmotic demyelination syndrome
- Severe symptomatic hyponatremia requires more urgent correction with 3% hypertonic saline
- The use of vaptans, such as tolvaptan, can be effective in improving serum sodium concentration in patients with hypervolemic hyponatremia, but requires close monitoring to avoid complications such as hypernatremia, dehydration, and renal impairment 1.
In terms of specific treatment approaches, the 2021 practice guidance recommends that patients with acute hyponatremia can have their hyponatremia corrected rapidly, while patients with chronic hyponatremia require more gradual and measured correction to avoid overcorrection and mitigate the risk of osmotic demyelination syndrome 1. Overall, the management of persistent hyponatremia requires a systematic approach based on the underlying cause, with careful consideration of the potential risks and benefits of different treatment strategies.
From the FDA Drug Label
resulting from a variety of underlying causes (heart failure, liver cirrhosis, syndrome of inappropriate antidiuretic hormone [SIADH] and others)
The causes of persistent hyponatremia include:
- Heart failure
- Liver cirrhosis
- Syndrome of inappropriate antidiuretic hormone (SIADH)
- Other underlying causes 2
From the Research
Causes of Persistent Hyponatremia
The causes of persistent hyponatremia can be complex and multifaceted. Some of the key causes include:
- Water retention, which is the most common cause of hyponatremia 3
- Syndrome of inappropriate antidiuretic hormone secretion (SIADH), which can lead to euvolemic hyponatremia 4, 5, 6
- Heart failure, liver cirrhosis, and renal disease, which can cause hypervolemic hyponatremia 3, 5, 6
- Medications, such as those that affect ADH secretion or renal function 6
- Gastrointestinal losses, such as diarrhea or vomiting, which can lead to hypovolemic hyponatremia 5, 6
- Severe burns, which can cause hypovolemic hyponatremia 6
Classification of Hyponatremia
Hyponatremia can be classified according to the volume status of the patient, including:
- Hypovolemic hyponatremia, which is characterized by a low extracellular fluid volume 5, 6
- Euvolemic hyponatremia, which is characterized by a normal extracellular fluid volume 4, 5, 6
- Hypervolemic hyponatremia, which is characterized by an increased extracellular fluid volume 3, 5, 6
Pathophysiology of Hyponatremia
The pathophysiology of hyponatremia involves an imbalance of water and sodium in the body, often due to increased levels of ADH or impaired renal function 3, 5, 7. This can lead to water retention and a subsequent decrease in serum sodium levels.