hyponatmi

Hyponatremia is a condition defined by a low serum sodium concentration, typically below 135 mEq/L. It is a laboratory finding rather than a disease in itself and reflects an imbalance between free water and solute in the body's compartments. Symptoms, when present, range from mild nausea and confusion to seizures, coma, or cerebral edema, and depend on both the degree and rapidity of sodium decline.

Most hyponatremia is hypotonic, meaning the serum osmolality is low. Hyponatremia can be categorized by volume status: hypovolemic (loss of fluids with ongoing sodium loss), euvolemic (normal fluid status often due to increased water retention, as in SIADH or hypothyroidism), and hypervolemic (fluid overload with conditions such as heart failure or cirrhosis). Less common are hypertonic hyponatremia, caused by elevated serum osmolality from substances like glucose, and isotonic (pseudohyponatremia) due to laboratory artifacts from hyperlipidemia or hyperproteinemia.

Diagnosis relies on a combination of laboratory tests and clinical assessment. Measurements typically include serum osmolality, serum sodium, urine osmolality, and urine sodium, along with evaluation of volume status and possible underlying causes (thyroid and adrenal function, medications, and comorbidities).

Treatment aims to correct the underlying cause and prevent complications. Mild or asymptomatic hyponatremia often responds to fluid restriction. More severe or symptomatic cases, such as those with seizures or coma, may require cautious administration of hypertonic saline (3% NaCl) with careful monitoring to avoid overly rapid correction. General targets limit correction to about 6–8 mEq/L in the first 24 hours and 8–12 mEq/L per 24 hours thereafter. In chronic hyponatremia, correction should be gradual to reduce the risk of osmotic demyelination syndrome. Additional strategies include addressing SIADH with salt administration, diuretics, or vasopressin receptor antagonists in selected patients.