Management of Hyponatremia

Initial Assessment and Classification

The American College of Neurosurgery recommends that hyponatremia is defined as serum sodium <135 mmol/L and should be further investigated when levels are <131 mmol/L 2, 1
Initial workup should include serum and urine osmolarity, urine electrolytes, uric acid, and assessment of extracellular fluid volume status to determine the underlying cause 1
Patients should be classified according to volume status: hypovolemic, euvolemic, or hypervolemic hyponatremia 1, 2

For severe symptomatic hyponatremia, the American College of Neurosurgery recommends administering 3% hypertonic saline with an initial goal to correct 6 mmol/L over 6 hours or until severe symptoms resolve 1, 2
The correction rate should not exceed 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome, as recommended by the American College of Neurosurgery 1, 2
The American College of Neurosurgery suggests considering ICU admission for close monitoring during treatment 1
Serum sodium should be monitored every 2 hours during initial correction, as recommended by the American College of Neurosurgery 1

For euvolemic hyponatremia, fluid restriction to 1L/day is the cornerstone of treatment for mild/asymptomatic cases, as recommended by the American College of Neurosurgery 1, 2
The American College of Neurosurgery suggests considering pharmacological options for resistant cases, including urea, diuretics, lithium, and demeclocycline 1, 2
For hypervolemic hyponatremia, fluid restriction to 1000-1500 mL/day for moderate hyponatremia (Na <125 mmol/L) is recommended by the American College of Neurosurgery 1

The American College of Neurosurgery recommends that cerebral salt wasting (CSW) should be treated with replacement of sodium and intravenous fluids, not fluid restriction 2, 1
Fludrocortisone may be considered in the treatment of hyponatremia in subarachnoid hemorrhage patients at risk of vasospasm, as suggested by the American College of Neurosurgery 2
Hydrocortisone may be used to prevent natriuresis in subarachnoid hemorrhage patients, as recommended by the American College of Neurosurgery 2

The American College of Neurosurgery recommends calculating sodium deficit using formula: Desired increase in Na (mEq/L) × (0.5 × ideal body weight in kg) 1
If overcorrection occurs, consider relowering with electrolyte-free water or desmopressin, as suggested by the American College of Neurosurgery 1
Watch for signs of osmotic demyelination syndrome (dysarthria, dysphagia, oculomotor dysfunction, quadriparesis) typically occurring 2-7 days after rapid correction, as recommended by the American College of Neurosurgery 1, 2

Overly rapid correction of chronic hyponatremia leading to osmotic demyelination syndrome, as warned by the American College of Neurosurgery 1, 2
Inadequate monitoring during active correction, as cautioned by the American College of Neurosurgery 1
Using fluid restriction in CSW, which can worsen outcomes, as warned by the American College of Neurosurgery 2, 1
Failing to recognize and treat the underlying cause, as emphasized by the American College of Neurosurgery 1
Using hypertonic saline in hypervolemic hyponatremia without life-threatening symptoms, as cautioned by the American College of Neurosurgery 1