Hyponatremia Management

Initial Assessment and Classification

The American College of Physicians recommends confirming true hypotonic hyponatremia by checking serum osmolality (<275 mOsm/kg) and excluding pseudohyponatremia from hyperglycemia (correct sodium by adding 1.6 mEq/L for each 100 mg/dL glucose >100 mg/dL) 1
Assess extracellular fluid volume status through physical examination to determine the underlying mechanism of hyponatremia, looking for signs of hypovolemia or hypervolemia 1
Check serum creatinine, thyroid function, and cortisol to exclude endocrine causes of hyponatremia 1

For severe symptomatic hyponatremia, administer 3% hypertonic saline immediately with a target correction of 6 mmol/L over 6 hours or until severe symptoms resolve, but never exceed 8 mmol/L total correction in 24 hours, as recommended by the European Society of Intensive Care Medicine 1
Give 100 mL boluses of 3% saline over 10 minutes, repeatable up to three times at 10-minute intervals until symptoms improve, with monitoring by the American Heart Association 1
Monitor serum sodium every 2 hours during initial correction, as advised by the American College of Cardiology 1

For hypovolemic hyponatremia, discontinue diuretics and administer isotonic (0.9%) saline for volume repletion, as recommended by the National Institute of Diabetes and Digestive and Kidney Diseases 1
For euvolemic hyponatremia (SIADH), fluid restriction to 1 L/day is the cornerstone of treatment, with the option to add oral sodium chloride or vasopressin receptor antagonists if necessary, as suggested by the Endocrine Society 1
For hypervolemic hyponatremia, implement fluid restriction to 1-1.5 L/day for serum sodium <125 mmol/L and treat the underlying condition, such as heart failure or cirrhosis, as recommended by the American Association for the Study of Liver Diseases and the European Association for the Study of the Liver 2, 1

For serum sodium 126-135 mmol/L, continue diuretic therapy with close electrolyte monitoring, as advised by the European Society of Cardiology 2, 1
For serum sodium <120 mmol/L, stop diuretics immediately and consider severe fluid restriction plus albumin infusion or volume expansion, as recommended by the American College of Gastroenterology 2, 1
Avoid increasing serum sodium by >8 mmol/L per 24 hours to prevent osmotic demyelination syndrome, as warned by the American Academy of Neurology 2, 1

Patients with advanced liver disease, alcoholism, malnutrition, or prior encephalopathy require more cautious correction at 4-6 mmol/L per day due to higher risk of osmotic demyelination syndrome, as recommended by the American Association for the Study of Liver Diseases 1
Cirrhotic patients with sodium ≤130 mEq/L have increased risk of spontaneous bacterial peritonitis, hepatorenal syndrome, and hepatic encephalopathy, as reported by the European Association for the Study of the Liver 1

If sodium correction exceeds 8 mmol/L in 24 hours, immediately discontinue current fluids and switch to D5W (5% dextrose in water), and consider administering desmopressin to slow or reverse the rapid rise, as recommended by the American College of Emergency Physicians 1

Severe symptoms: Check serum sodium every 2 hours during initial correction, as advised by the Society of Critical Care Medicine 1
Mild symptoms: Check every 4 hours after resolution of severe symptoms, with daily monitoring until target sodium achieved, as recommended by the American College of Physicians 1