How to Correct Hyponatremia
Correction of hyponatremia must be guided by three critical factors: symptom severity (severe vs. mild/asymptomatic), acuity of onset (acute <48 hours vs. chronic >48 hours), and volume status (hypovolemic, euvolemic, or hypervolemic), with the absolute maximum correction limit of 8 mmol/L in any 24-hour period to prevent osmotic demyelination syndrome. 1
Initial Assessment
Before initiating treatment, rapidly determine:
Symptom severity: Severe symptoms include seizures, coma, altered consciousness, confusion, or respiratory distress requiring immediate hypertonic saline 1, 2. Mild symptoms include nausea, headache, muscle cramps, or gait instability 2.
Acuity: Acute hyponatremia (<48 hours) causes more severe symptoms at the same sodium level and can be corrected more rapidly without risk of osmotic demyelination 1, 3. Chronic hyponatremia (>48 hours) requires slower, more cautious correction 1, 3.
Volume status: Assess for hypovolemia (orthostatic hypotension, dry mucous membranes, decreased skin turgor), euvolemia (normal volume status), or hypervolemia (peripheral edema, ascites, jugular venous distention) 1, 4.
Laboratory workup: Obtain serum and urine osmolality, urine sodium, urine electrolytes, serum uric acid, and assess extracellular fluid volume status 1.
Treatment Based on Symptom Severity
Severe Symptomatic Hyponatremia (Medical Emergency)
For patients with seizures, coma, altered consciousness, or respiratory distress, immediately administer 3% hypertonic saline with a goal to correct 6 mmol/L over 6 hours or until severe symptoms resolve. 1
Administer 3% hypertonic saline as 100 mL boluses over 10 minutes, repeating up to three times at 10-minute intervals until symptoms improve 1.
Critical safety limit: Total correction must not exceed 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome 1, 5.
Monitor serum sodium every 2 hours during initial correction 1.
After severe symptoms resolve, switch to monitoring every 4 hours and slow the correction rate 1.
Mild or Asymptomatic Hyponatremia
Treatment depends on volume status and underlying cause rather than hypertonic saline 1, 4.
Treatment Based on Volume Status
Hypovolemic Hyponatremia
Discontinue diuretics immediately and administer isotonic saline (0.9% NaCl) for volume repletion. 1
Initial infusion rate: 15-20 mL/kg/h, then 4-14 mL/kg/h based on response 1.
Urine sodium <30 mmol/L predicts good response to saline infusion (positive predictive value 71-100%) 1.
For patients with cirrhosis, consider albumin infusion (6-8 g per liter of ascites drained) alongside isotonic saline 1.
Do not exceed 8 mmol/L correction in 24 hours even with volume repletion 1.
Euvolemic Hyponatremia (SIADH)
Fluid restriction to 1 L/day is the cornerstone of treatment for SIADH. 1, 6
For mild/asymptomatic cases: Implement strict fluid restriction to 1 L/day 1.
If no response to fluid restriction: Add oral sodium chloride 100 mEq three times daily 1.
For severe symptomatic cases: Use 3% hypertonic saline with careful monitoring, targeting 6 mmol/L correction over 6 hours 1.
Alternative pharmacological options for resistant cases include vasopressin receptor antagonists (tolvaptan 15 mg once daily), urea, demeclocycline, or lithium 1, 6.
Never exceed 8 mmol/L correction in 24 hours 1.
Hypervolemic Hyponatremia (Heart Failure, Cirrhosis)
Implement fluid restriction to 1000-1500 mL/day for serum sodium <125 mmol/L. 1
Discontinue diuretics temporarily if sodium <125 mmol/L 1.
For cirrhosis: Consider albumin infusion alongside fluid restriction 1.
Avoid hypertonic saline unless life-threatening symptoms are present, as it may worsen edema and ascites 1.
Sodium restriction (2-2.5 g/day or 88-110 mmol/day) is more effective than fluid restriction alone for weight loss, as fluid passively follows sodium 1.
For resistant cases: Consider vasopressin receptor antagonists (tolvaptan) with extreme caution, starting at 15 mg once daily 1.
Special Consideration: Cerebral Salt Wasting (Neurosurgical Patients)
In neurosurgical patients, cerebral salt wasting (CSW) is more common than SIADH and requires opposite treatment—volume and sodium replacement, NOT fluid restriction. 1
CSW is characterized by true hypovolemia with high urine sodium (>20 mmol/L) despite volume depletion 1.
Treatment: Aggressive volume and sodium replacement with isotonic or hypertonic saline (50-100 mL/kg/day) 1.
For severe symptoms: Add fludrocortisone 0.1-0.2 mg daily 1.
Never use fluid restriction in CSW or subarachnoid hemorrhage patients at risk of vasospasm, as this worsens outcomes 1.
Critical Correction Rate Guidelines
Standard-Risk Patients
Target rate: 4-8 mmol/L per day, not exceeding 10-12 mmol/L in 24 hours 1.
For chronic hyponatremia: Avoid rapid correction exceeding 1 mmol/L/hour 1.
High-Risk Patients (Advanced Liver Disease, Alcoholism, Malnutrition)
Patients with advanced liver disease, chronic alcoholism, malnutrition, or prior encephalopathy require even more cautious correction at 4-6 mmol/L per day, with an absolute maximum of 8 mmol/L in 24 hours. 1
These patients have a 0.5-1.5% risk of osmotic demyelination syndrome even with careful correction 1.
Monitor sodium levels every 2 hours during initial correction for severe symptoms, then every 4 hours after symptom resolution 1.
Management of Overcorrection
If sodium correction exceeds 8 mmol/L in 24 hours, immediately discontinue current fluids and switch to D5W (5% dextrose in water). 1
Consider administering desmopressin to slow or reverse the rapid rise in serum sodium 1.
Goal: Bring the total 24-hour correction back to ≤8 mmol/L from the starting point 1.
Watch for signs of osmotic demyelination syndrome (dysarthria, dysphagia, oculomotor dysfunction, quadriparesis) typically occurring 2-7 days after rapid correction 1.
Common Pitfalls to Avoid
Overly rapid correction of chronic hyponatremia (>8 mmol/L in 24 hours) leading to osmotic demyelination syndrome 1, 5.
Inadequate monitoring during active correction—check sodium every 2 hours initially for severe symptoms 1.
Using fluid restriction in cerebral salt wasting, which worsens outcomes and can precipitate cerebral ischemia 1.
Failing to recognize and treat the underlying cause of hyponatremia 1.
Using hypertonic saline in hypervolemic hyponatremia without life-threatening symptoms, which worsens fluid overload 1.
Ignoring mild hyponatremia (130-135 mmol/L) as clinically insignificant—even mild chronic hyponatremia increases fall risk (21% vs 5%), mortality (60-fold increase with sodium <130 mmol/L), and cognitive impairment 1, 2, 5.