What is the diagnosis for a patient with hyponatremia (low Sodium (Na)) and hypochloremia (low Chloride (Cl))?

From the Guidelines

The patient with hyponatremia and hypochloremia should be diagnosed and managed based on the underlying cause, with careful correction of sodium levels to avoid osmotic demyelination syndrome, and the most recent guidelines recommend a goal rate of increase of serum sodium of 4-6 mEq/L per 24-hour period, not to exceed 8 mEq/L per 24-hour period 1. To determine the diagnosis, it is essential to obtain additional laboratory values, including:

• Serum osmolality
• Urine sodium
• Urine osmolality
• Assessment of volume status to determine if this is hypovolemic, euvolemic, or hypervolemic hyponatremia The management of hyponatremia should focus on correcting the underlying cause, and the treatment approach may vary depending on the severity of symptoms and the presence of underlying conditions such as cirrhosis. For mild to moderate symptomatic hyponatremia, fluid restriction to 800-1000 mL/day is appropriate if the patient is euvolemic 1. If hypovolemic, isotonic saline (0.9% NaCl) should be administered. For severe symptoms like seizures or altered mental status, 3% hypertonic saline at 100-150 mL over 10-20 minutes may be needed. It is crucial to monitor electrolytes every 4-6 hours during correction to ensure appropriate rate of correction and avoid osmotic demyelination syndrome. The hypochloremia likely accompanies the hyponatremia and will correct with sodium repletion. Underlying causes such as medications (diuretics, SSRIs), SIADH, heart failure, cirrhosis, or adrenal insufficiency should be identified and addressed. In patients with cirrhosis, the use of vasopressin receptor antagonists can raise serum sodium during treatment, but they should be used with caution only for a short term (≤30 days) 1. The use of hypertonic saline is reserved for short-term treatment of patients with symptomatic or severe hyponatremia or those with imminent liver transplant 1.

From the Research

Diagnosis of Hyponatremia and Hypochloremia

• Hyponatremia is defined as a serum sodium concentration less than 135 mmol/l 2
• Hypochloremia is often associated with hyponatremia, and the diagnosis should consider the underlying cause of these electrolyte imbalances
• The severity of hyponatremia can be classified as mild (130-134 mEq/L), moderate (125-129 mEq/L), or severe (<125 mEq/L) 3

Clinical Presentation

• Patients with mild hyponatremia may exhibit few or no symptoms, while those with severe hyponatremia can present with delirium, confusion, impaired consciousness, ataxia, seizures, and rarely, brain herniation and death 3, 2
• Hypochloremia can contribute to the development of diuretic resistance, which can worsen the clinical presentation of hyponatremia 4

Treatment Options

• The treatment of hyponatremia depends on the underlying cause, severity, and volume status of the patient 3, 2, 5
• Hypovolemic hyponatremia is treated with normal saline infusions, while euvolemic hyponatremia may require fluid restriction, salt tablets, or intravenous vaptans 3, 2
• Hypervolemic hyponatremia is treated primarily by managing the underlying cause (e.g., heart failure, cirrhosis) and free water restriction 3, 5
• In cases of severe hyponatremia, intravenous hypertonic saline solution may be necessary to rapidly correct the sodium concentration 6

Considerations for Hypochloremia

• Hypochloremia can be associated with diuretic resistance, and the use of high-saline solutions in addition to loop diuretics may be beneficial in these cases 4
• Aquaretics, such as vaptans, may also be effective in treating hyponatremia, but require caution to avoid overcorrection 5, 4