How is hyponatremia treated?

Treatment of Hyponatremia

Hyponatremia treatment must be guided by symptom severity, volume status, and correction rate limits to prevent both neurological complications from the hyponatremia itself and osmotic demyelination syndrome from overly rapid correction. 1

Initial Assessment and Classification

Before initiating treatment, determine three critical factors:

• Symptom severity: Severe symptoms (seizures, coma, altered mental status, respiratory distress) require immediate intervention with hypertonic saline, while mild or asymptomatic cases allow for more conservative management 1, 2
• Volume status: Classify 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
• Chronicity: Acute (<48 hours) versus chronic (>48 hours) hyponatremia—this distinction is critical because chronic cases have completed brain adaptation and carry higher risk of osmotic demyelination with rapid correction 1, 4

Obtain serum and urine osmolality, urine sodium concentration, and urine electrolytes to determine the underlying etiology 1, 5

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 the first 6 hours or until symptoms resolve. 1, 2

• Administer 3% hypertonic saline as 100 mL boluses over 10 minutes, which can be repeated up to three times at 10-minute intervals until symptoms improve 1
• The total correction must not exceed 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome 1, 2, 3
• Monitor serum sodium every 2 hours during initial correction 1
• Once severe symptoms resolve, slow the correction rate and monitor sodium every 4 hours 1

Asymptomatic or Mildly Symptomatic Hyponatremia

Treatment depends on volume status rather than immediate hypertonic saline administration 1, 5

Treatment Based on Volume Status

Hypovolemic Hyponatremia

Administer isotonic saline (0.9% NaCl) for volume repletion in patients with true volume depletion. 1, 5

• Urine sodium <30 mmol/L predicts good response to saline infusion with 71-100% positive predictive value 1
• Discontinue diuretics that may be contributing to hyponatremia 1
• Once euvolemia is achieved, reassess sodium levels and adjust management accordingly 1

Euvolemic Hyponatremia (SIADH)

Fluid restriction to 1 L/day is the cornerstone of treatment for SIADH. 1, 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 pharmacological options:
  • Vasopressin receptor antagonists (vaptans): Tolvaptan starting at 15 mg once daily can effectively increase serum sodium in euvolemic hyponatremia 1, 6
  • Urea (15-30 grams twice daily) provides effective water diuresis with potentially lower risk of osmotic demyelination 1, 2
  • Demeclocycline or lithium (less commonly used due to side effects) 1

Hypervolemic Hyponatremia (Heart Failure, Cirrhosis)

Implement fluid restriction to 1-1.5 L/day for serum sodium <125 mmol/L. 1, 5

• 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
• Vaptans may be considered for persistent severe hyponatremia despite fluid restriction and optimization of guideline-directed medical therapy, but use with extreme caution in cirrhosis due to higher risk of gastrointestinal bleeding (10% vs 2% with placebo) 1, 6

Critical Correction Rate Guidelines

The maximum correction rate is 8 mmol/L in 24 hours for most patients to prevent osmotic demyelination syndrome. 1, 2, 3

High-Risk Patients Requiring Slower Correction (4-6 mmol/L per day):

• Advanced liver disease or cirrhosis 1, 4
• Chronic alcoholism 1, 4
• Malnutrition or poor nutritional state 1, 4
• Prior encephalopathy 1
• Hypokalemia, hypophosphatemia, or hypoglycemia 1

If Overcorrection Occurs:

• 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, 4
• The goal is to bring the total 24-hour correction to no more than 8 mmol/L from the starting point 1

Special Considerations for Neurosurgical Patients

Distinguish between SIADH and cerebral salt wasting (CSW), as treatment approaches are fundamentally opposite. 1

• SIADH: Euvolemic with urine sodium >20-40 mmol/L and urine osmolality >300 mOsm/kg—treat with fluid restriction 1
• CSW: True hypovolemia with urine sodium >20 mmol/L despite volume depletion—treat with volume and sodium replacement, NOT fluid restriction 1
• For CSW with severe symptoms, administer 3% hypertonic saline plus fludrocortisone (0.1-0.2 mg daily) in ICU setting 1
• Never use fluid restriction in subarachnoid hemorrhage patients at risk of vasospasm 1
• Consider hydrocortisone to prevent natriuresis in subarachnoid hemorrhage patients 1

Common Pitfalls to Avoid

• Overly rapid correction exceeding 8 mmol/L in 24 hours leads to osmotic demyelination syndrome—this is the most critical error to avoid 1, 2, 4
• Using fluid restriction in cerebral salt wasting worsens outcomes 1
• Inadequate monitoring during active correction 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) as clinically insignificant—even mild hyponatremia increases fall risk (21% vs 5%) and mortality 1, 2

Monitoring Requirements

• Severe symptoms: Check serum sodium every 2 hours during initial correction 1
• After symptom resolution: Check every 4 hours 1
• Stable patients: Daily monitoring until sodium normalizes 1
• Watch for signs of osmotic demyelination syndrome (dysarthria, dysphagia, oculomotor dysfunction, quadriparesis) typically occurring 2-7 days after rapid correction 1