Treatment for Hyponatremia
The treatment of hyponatremia depends critically on symptom severity, volume status (hypovolemic, euvolemic, or hypervolemic), and chronicity, with the overriding principle being to avoid correction rates exceeding 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome. 1
Immediate Assessment and Classification
Before initiating treatment, determine three key factors:
- Symptom severity: Severe symptoms (seizures, coma, altered mental status) require immediate intervention with 3% hypertonic saline, targeting 6 mmol/L correction over 6 hours or until symptoms resolve 1, 2
- Volume status: Assess for hypovolemia (orthostatic hypotension, dry mucous membranes, decreased skin turgor), euvolemia (no edema, normal blood pressure), or hypervolemia (peripheral edema, ascites, jugular venous distention) 1, 3
- Chronicity: Acute (<48 hours) versus chronic (>48 hours) onset—chronic cases require slower correction to avoid osmotic demyelination 1, 4
Initial workup should include serum and urine osmolality, urine sodium, and assessment of extracellular fluid volume status 1
Treatment Based on Symptom Severity
Severe Symptomatic Hyponatremia (Medical Emergency)
For patients with seizures, coma, or severe neurological symptoms, immediately administer 3% hypertonic saline with a target correction of 6 mmol/L over 6 hours or until severe symptoms resolve. 1, 2
- Administer 100 mL boluses of 3% saline over 10 minutes, repeatable up to three times at 10-minute intervals 1
- Monitor serum sodium every 2 hours during initial correction 1
- Critical safety limit: Total correction must not exceed 8 mmol/L in 24 hours 1, 2, 4
- ICU admission is recommended for close monitoring 1
Mild to Moderate Symptomatic or Asymptomatic Hyponatremia
Treatment is guided by volume status rather than immediate hypertonic saline 1, 3
Treatment Based on Volume Status
Hypovolemic Hyponatremia
Discontinue diuretics and administer isotonic saline (0.9% NaCl) for volume repletion. 1, 3
- Urinary sodium <30 mmol/L suggests hypovolemia and predicts response to saline infusion 1
- Once euvolemic, reassess sodium levels and adjust management accordingly 1
- Correction rate should not exceed 8 mmol/L in 24 hours 1
Euvolemic Hyponatremia (SIADH)
Fluid restriction to 1 L/day is the cornerstone of treatment for SIADH. 1, 3, 2
- If no response to fluid restriction after 24-48 hours, add oral sodium chloride 100 mEq three times daily 1
- For resistant cases, consider vasopressin receptor antagonists (tolvaptan 15 mg once daily, titrating to 30-60 mg as needed) 1, 5, 2
- Alternative pharmacological options include urea, demeclocycline, or loop diuretics 1, 2
- Monitor serum sodium every 4 hours initially, then daily 1
Important distinction: In neurosurgical patients, cerebral salt wasting (CSW) is more common than SIADH and requires fundamentally different treatment—volume and sodium replacement with isotonic or hypertonic saline, NOT fluid restriction 1, 3
Hypervolemic Hyponatremia (Heart Failure, Cirrhosis)
Implement fluid restriction to 1-1.5 L/day for serum sodium <125 mmol/L. 1, 3
- Temporarily discontinue diuretics if sodium <125 mmol/L 1
- For cirrhotic patients, consider albumin infusion alongside fluid restriction 1
- Avoid hypertonic saline unless life-threatening symptoms are present, as it may worsen edema and ascites 1
- Vasopressin receptor antagonists (tolvaptan) may be considered for persistent severe hyponatremia despite fluid restriction and maximization of guideline-directed medical therapy 1, 5
- In cirrhotic patients, tolvaptan carries higher risk of gastrointestinal bleeding (10% vs 2% placebo) and should be used with extreme caution 1
Critical Correction Rate Guidelines
The maximum correction rate is 8 mmol/L in 24 hours for most patients. 1, 2, 4
High-Risk Patients Requiring Slower Correction (4-6 mmol/L per day):
- Advanced liver disease 1
- Alcoholism 1
- Malnutrition 1
- Severe hyponatremia (<120 mmol/L) 1
- Prior encephalopathy 1
Monitoring During Correction:
- Severe symptoms: Check sodium every 2 hours 1
- Mild symptoms: Check sodium every 4 hours 1
- After symptom resolution: Check sodium daily 1
Management of Overcorrection
If sodium correction exceeds 8 mmol/L in 24 hours, immediately intervene to prevent osmotic demyelination syndrome. 1
- Discontinue current fluids and switch to D5W (5% dextrose in water) 1
- Consider administering desmopressin to slow or reverse the rapid rise 1
- Target relowering to bring total 24-hour correction to no more than 8 mmol/L from baseline 1
Common Pitfalls to Avoid
- Overly rapid correction exceeding 8 mmol/L in 24 hours leads to osmotic demyelination syndrome 1, 4
- Using fluid restriction in cerebral salt wasting worsens outcomes—CSW requires volume replacement 1
- Inadequate monitoring during active correction increases risk of complications 1
- Failing to recognize the underlying cause leads to inappropriate treatment 1
- Using hypertonic saline in hypervolemic hyponatremia without life-threatening symptoms worsens fluid overload 1
- Ignoring mild hyponatremia (130-135 mmol/L) as clinically insignificant—even mild hyponatremia increases fall risk and mortality 1, 2
Special Populations
Neurosurgical Patients (Subarachnoid Hemorrhage)
- Distinguish between SIADH and cerebral salt wasting 1
- Do NOT use fluid restriction in patients at risk for vasospasm 1
- Consider fludrocortisone or hydrocortisone to prevent natriuresis 1
- Treat CSW with volume and sodium replacement, potentially requiring 3% hypertonic saline plus fludrocortisone in ICU 1