From the Guidelines
Hypotonic hyponatremia is primarily caused by an excess of water relative to sodium in the body, which can be due to impaired water excretion, as seen in conditions like SIADH or heart failure, or excessive water intake overwhelming normal excretion capacity, with the most common causes being hypovolemic and hypervolemic hyponatremia. The management of hypotonic hyponatremia depends on the underlying cause, with hypovolemic hyponatremia requiring fluid resuscitation and correction of the causative factor, and hypervolemic hyponatremia requiring attainment of a negative water balance, often through fluid restriction or the use of hypertonic sodium chloride administration in severe cases 1. Some key points to consider in the management of hypotonic hyponatremia include:
- The use of hypertonic sodium chloride administration, which may improve hyponatremia but can worsen fluid overload and should be limited to severely symptomatic cases or those expected to undergo liver transplant within a few days 1.
- The importance of careful monitoring to avoid rapid correction of sodium levels, which can increase the risk of central pontine myelinolysis, a serious neurological complication 1.
- The potential role of albumin infusion in improving serum sodium concentration, although more information is needed 1.
- The use of vasopressin receptor antagonists like tolvaptan in resistant cases, starting at 15 mg daily, as supported by the most recent and highest quality study 1. It is essential to address the underlying cause of hypotonic hyponatremia, whether it be discontinuing offending medications, treating infections, or managing heart failure, to effectively manage the condition and prevent further complications.
From the Research
Causes of Hypotonic Hyponatremia
Hypotonic hyponatremia is a condition characterized by low sodium levels in the blood with low blood osmolality. The causes of hypotonic hyponatremia can be attributed to two general mechanisms:
- Defective water excretion, usually due to elevated serum vasopressin levels 2
- Excessive fluid intake 2
Etiologies of Hypotonic Hyponatremia
Some common etiologies of hypotonic hyponatremia include:
- Syndrome of inappropriate antidiuresis (SIAD) 3, 4, 5, 6
- Heart failure 3, 4, 5
- Cirrhosis 4, 5
- Renal failure 5
- Excessive free water intake during exercise 4
- Certain medications, such as diuretics, antidepressants, and proton pump inhibitors 6
- Poor solute intake 6
- Infections 6
- Stroke-related conditions or complications, such as cerebral salt wasting syndrome and secondary adrenal insufficiency 6
Classification of Hyponatremia
Hyponatremia can be classified into three categories based on the patient's fluid volume status: