How can fluid overload cause hyponatremia (low sodium levels)?

From the Guidelines

Fluid overload can cause hyponatremia through dilution of sodium in the blood, particularly in conditions like liver cirrhosis, where it is associated with a poor prognosis and multiple complications 1. When excess fluid accumulates in the body, it can dilute the concentration of sodium in the bloodstream, leading to hyponatremia. This is often seen in patients with liver cirrhosis and ascites, where the serum sodium concentration can decrease to less than 130 mmol/L, indicating dilutional hyponatremia 1. Some key points to consider in the management of hyponatremia due to fluid overload include:

• Restricting fluid intake to 1.0-1.5 L/day when the serum sodium concentration falls below 120-125 mmol/L 1
• Considering the administration of a plasma expander, such as albumin, for the treatment of hyponatremia 1 It is essential to address the underlying cause of fluid overload and hyponatremia, as the management of these conditions can significantly impact patient outcomes, including morbidity, mortality, and quality of life. In clinical practice, it is crucial to monitor serum sodium levels closely and adjust treatment accordingly to prevent complications associated with hyponatremia, such as cerebral edema and seizures. By understanding the mechanisms of fluid overload and dilutional hyponatremia, healthcare providers can provide targeted and effective management, improving patient outcomes and reducing the risk of associated complications 1.

From the Research

Causes of Hyponatremia

• Hyponatremia is defined by a serum sodium level of less than 135 mEq/L and most commonly results from water retention 2
• In heart failure, inadequate release of vasopressin may result in excess fluid retention and hyponatremia 3
• Hyponatremia can be caused by various conditions, including dilutional disorders, such as congestive heart failure and the syndrome of inappropriate antidiuretic hormone secretion, and depletional disorders, such as diarrhea and vomiting or blood loss 4

Relationship between Fluid Overload and Hyponatremia

• Fluid overload can lead to hyponatremia, as excess fluid retention can dilute the sodium levels in the blood 2, 3
• In patients with heart failure, fluid overload can cause hyponatremia due to the inadequate release of vasopressin, leading to excess fluid retention 3
• Hyponatremia can be categorized into three types based on fluid volume status: hypovolemic hyponatremia, euvolemic hyponatremia, and hypervolemic hyponatremia 2

Treatment of Hyponatremia

• Treatment for euvolemic and hypervolemic hyponatremia with arginine vasopressin receptor antagonists is presented, which provides a new treatment option for patients with disorders of water metabolism 4
• Vasopressin receptor antagonists can be effective in managing the syndrome of inappropriate antidiuresis and hyponatremia in patients with heart failure 3
• Hypertonic saline is reserved for patients with severely symptomatic hyponatremia 2