Management of Hyponatremia

Initial Assessment and Classification

The American College of Physicians recommends that hyponatremia be defined as serum sodium <135 mmol/L and should be further investigated when <131 mmol/L, with even mild hyponatremia (130-135 mmol/L) requiring attention due to increased fall risk and mortality 1
Initial workup must include serum and urine osmolality, urine sodium, and assessment of extracellular fluid volume status to determine if the patient is hypovolemic, euvolemic, or hypervolemic 1

For severe symptomatic hyponatremia, the European Society of Intensive Care Medicine recommends administering 3% hypertonic saline immediately with an initial goal to correct 6 mmol/L over 6 hours or until severe symptoms resolve 1
The American Heart Association suggests that total correction must not exceed 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome 1

For hypovolemic hyponatremia, the American College of Physicians recommends discontinuing diuretics immediately and administering isotonic saline (0.9% NaCl) for volume repletion 1
A spot urine sodium <30 mmol/L has a positive predictive value of 71-100% for response to saline infusion 1
For euvolemic hyponatremia (SIADH), fluid restriction to 1 L/day is the cornerstone of treatment, with oral sodium chloride 100 mEq three times daily if no response to fluid restriction 1
For hypervolemic hyponatremia, the European Association for the Study of the Liver recommends implementing fluid restriction to 1-1.5 L/day for serum sodium <125 mmol/L, with consideration of albumin infusion alongside fluid restriction in cirrhotic patients 2, 1

The American College of Physicians recommends a maximum correction rate of 8 mmol/L in 24 hours for average-risk patients, with limitation to 4-6 mmol/L per day for high-risk patients (advanced liver disease, alcoholism, malnutrition, severe hyponatremia, prior encephalopathy) 1
Monitoring sodium levels every 2 hours during initial correction for severe symptoms, then every 4 hours after symptom resolution is recommended 1

The American Association for the Study of Liver Diseases suggests that hyponatremia in cirrhosis is associated with higher prevalence of refractory ascites, hepatic encephalopathy, spontaneous bacterial peritonitis, and hepatorenal syndrome, requiring more cautious correction rates (4-6 mmol/L per day) due to higher risk of osmotic demyelination syndrome 2, 1
In neurosurgical patients, avoiding fluid restriction in subarachnoid hemorrhage patients at risk of vasospasm and considering fludrocortisone to prevent vasospasm or hydrocortisone to prevent natriuresis is recommended 1

The American College of Physicians recommends checking serum sodium every 2 hours during initial correction for severe symptoms, every 4 hours initially for moderate symptoms, then daily, with tracking of daily weight and monitoring for signs of overcorrection and osmotic demyelination syndrome throughout treatment 1, 2