Hyponatremia

About Hyponatremia

Hyponatremia, serum sodium below 135 mEq L, is the most common electrolyte disorder in hospitalized patients, occurring in approximately 15 to 30 percent. Classification by volume status includes hypovolemic sodium and water loss from diuretics, vomiting, diarrhea, burns, hypervolemic water excess exceeds sodium excess in heart failure, cirrhosis, nephrotic syndrome, and euvolemic most commonly SIADH syndrome of inappropriate antidiuretic hormone, also primary polydipsia, hypothyroidism, adrenal insufficiency. SIADH causes include malignancy small cell lung cancer, CNS disorders stroke, trauma, infection, medications SSRIs, carbamazepine, cyclophosphamide, and pulmonary disease pneumonia, mechanical ventilation. The rate of sodium correction is critical. Mild or chronic hyponatremia may cause headache, nausea, fatigue, muscle cramps, and confusion, while very low or rapidly falling levels can cause seizures and coma; confusion, seizures, or reduced consciousness are a medical emergency. Overly rapid correction of chronic hyponatremia over 8 to 10 mEq L in 24 hours can cause osmotic demyelination syndrome ODS, previously called central pontine myelinolysis, a devastating neurological condition causing quadriparesis, pseudobulbar palsy, and potentially death. Acute hyponatremia developing in under 48 hours, as in exercise associated hyponatremia or Ecstasy MDMA use, can cause cerebral edema and requires rapid correction. Diagnosis involves clinical assessment of volume status, urine osmolality, urine sodium, and serum osmolality to determine cause. Treatment is cause specific and supervised by clinicians. Hypovolemic hyponatremia is typically treated with isotonic saline. SIADH is commonly managed with fluid restriction, and sometimes salt tablets, urea, or vaptans tolvaptan, conivaptan. Hypertonic 3 percent saline is used for severe symptomatic hyponatremia, carefully monitoring correction rate.