Treatment for Hyponatremia
The treatment of hyponatremia depends critically on symptom severity and volume status: severely symptomatic patients require immediate 3% hypertonic saline to correct sodium by 6 mmol/L over 6 hours, while asymptomatic patients are managed based on whether they are hypovolemic (isotonic saline), euvolemic (fluid restriction), or hypervolemic (fluid restriction with underlying disease management), with correction never exceeding 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome. 1
Initial Assessment
Before initiating treatment, rapidly determine two critical factors:
- Symptom severity: Assess for severe neurological symptoms including seizures, coma, altered mental status, confusion, or cardiorespiratory distress, which constitute medical emergencies requiring immediate intervention 1, 2
- Volume status: Classify the patient as hypovolemic (orthostatic hypotension, dry mucous membranes, decreased skin turgor), euvolemic (no edema, normal blood pressure), or hypervolemic (peripheral edema, ascites, jugular venous distention) 1, 3
- Serum osmolality: Obtain to exclude pseudohyponatremia from hyperglycemia or hyperlipidemia 1, 3
- Urine studies: Check urine sodium and osmolality to differentiate causes—urine sodium <30 mmol/L suggests hypovolemia, while >20-40 mmol/L with high urine osmolality suggests SIADH 1, 2
Treatment Based on Symptom Severity
Severe Symptomatic Hyponatremia (Medical Emergency)
For patients with seizures, coma, or severe altered mental status:
- Administer 3% hypertonic saline immediately as 100-150 mL IV bolus over 10 minutes, which can be repeated up to three times at 10-minute intervals until symptoms improve 1, 4
- Target correction: Increase sodium by 6 mmol/L over the first 6 hours or until severe symptoms resolve 1, 5
- Maximum correction limit: Never exceed 8 mmol/L in 24 hours (or 10-12 mmol/L in susceptible patients) to prevent osmotic demyelination syndrome 1, 6, 2
- Monitor serum sodium every 2 hours during initial correction phase 1
- ICU admission is recommended for close monitoring 1
Asymptomatic or Mildly Symptomatic Hyponatremia
Treatment is determined by volume status:
Hypovolemic Hyponatremia
- Discontinue diuretics immediately if contributing to hyponatremia 1
- Administer isotonic saline (0.9% NaCl) for volume repletion at 15-20 mL/kg/h initially, then 4-14 mL/kg/h based on response 1, 5
- Urine sodium <30 mmol/L predicts good response to saline infusion (positive predictive value 71-100%) 1
- Avoid hypotonic fluids including lactated Ringer's solution, which can worsen hyponatremia 1
Euvolemic Hyponatremia (SIADH)
- Fluid restriction to 1 L/day is the cornerstone of first-line treatment 1, 4, 2
- Adequate solute intake with salt and protein is essential 4
- If no response to fluid restriction: Add oral sodium chloride 100 mEq three times daily 1
- Second-line therapies for resistant cases include:
Important: Nearly half of SIADH patients do not respond to fluid restriction as first-line therapy 4
Hypervolemic Hyponatremia (Heart Failure, Cirrhosis)
- Fluid restriction to 1-1.5 L/day for serum sodium <125 mmol/L 1, 5
- Treat the underlying condition (optimize heart failure management, manage cirrhosis) 5, 3
- Discontinue diuretics temporarily if sodium <125 mmol/L 1
- For cirrhotic patients: Consider albumin infusion alongside fluid restriction 1, 2
- Avoid hypertonic saline unless life-threatening symptoms are present, as it worsens edema and ascites 1
- Vaptans may be considered for persistent severe hyponatremia despite conventional therapy, but use with extreme caution in cirrhosis due to increased gastrointestinal bleeding risk (10% vs 2% placebo) 1, 2
Critical Correction Rate Guidelines
The single most important safety principle is avoiding overly rapid correction:
- Standard maximum: 8 mmol/L per 24 hours for most patients 1, 6, 4
- High-risk patients (advanced liver disease, alcoholism, malnutrition, severe hyponatremia): Limit to 4-6 mmol/L per day 1, 6, 2
- Acute hyponatremia (<48 hours): Can be corrected more rapidly without osmotic demyelination risk 1
- Chronic hyponatremia (>48 hours): Requires slower correction rates 1, 2
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
- Monitor for osmotic demyelination syndrome (dysarthria, dysphagia, oculomotor dysfunction, quadriparesis) typically occurring 2-7 days after rapid correction 1, 6
Special Considerations
Neurosurgical Patients
- Distinguish cerebral salt wasting (CSW) from SIADH, as treatments are opposite 1, 2
- CSW requires volume and sodium replacement, not fluid restriction 1
- Consider fludrocortisone for hyponatremia in subarachnoid hemorrhage patients at risk of vasospasm 1
- Never use fluid restriction in subarachnoid hemorrhage patients at risk of vasospasm 1
Cirrhotic Patients
- Hyponatremia increases risk of spontaneous bacterial peritonitis (OR 3.40), hepatorenal syndrome (OR 3.45), and hepatic encephalopathy (OR 2.36) 1
- Sodium restriction (not fluid restriction) results in weight loss as fluid follows sodium 1
- More cautious correction (4-6 mmol/L per day) is required due to higher osmotic demyelination risk 1, 6
Common Pitfalls to Avoid
- Overly rapid correction exceeding 8 mmol/L in 24 hours leads to osmotic demyelination syndrome 1, 6
- Inadequate monitoring during active correction 1
- Using fluid restriction in CSW worsens outcomes 1
- Failing to recognize and treat the underlying cause 1
- Using hypertonic saline in hypervolemic hyponatremia without life-threatening symptoms 1
- Ignoring mild hyponatremia (130-135 mmol/L), which increases fall risk and mortality 1, 2