How do you treat hyponatremia?

Treatment of Hyponatremia

The treatment of hyponatremia depends critically on symptom severity and volume status, with severe symptomatic cases requiring immediate 3% hypertonic saline to correct sodium by 6 mmol/L over 6 hours, while asymptomatic or mildly symptomatic cases are managed based on whether the patient is hypovolemic, euvolemic, or hypervolemic. 1

Initial Assessment and Classification

Before initiating treatment, determine three key factors:

• Symptom severity: Severe symptoms include seizures, coma, altered mental status, or cardiorespiratory distress; mild symptoms include nausea, headache, or weakness 1, 2, 3
• Volume status: Assess for signs of hypovolemia (orthostatic hypotension, dry mucous membranes, poor skin turgor), euvolemia (normal volume status), or hypervolemia (edema, ascites, jugular venous distension) 1
• Acuity: Acute (<48 hours) versus chronic (>48 hours) onset, as this affects correction rate safety 1, 4

The 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 severe symptoms (seizures, coma, confusion, obtundation), immediately administer 3% hypertonic saline as 100-150 mL IV boluses over 10 minutes, which can be repeated up to three times at 10-minute intervals until symptoms improve. 1, 2, 5

• The goal is to increase sodium by 4-6 mmol/L over the first 6 hours or until severe symptoms resolve 1, 4
• Total correction must not exceed 8 mmol/L in the first 24 hours to prevent osmotic demyelination syndrome 1, 2, 5
• Monitor serum sodium every 2 hours during initial correction 1
• Rapid intermittent bolus administration of hypertonic saline is preferred over continuous infusion for symptomatic cases 5

Asymptomatic or Mildly Symptomatic Hyponatremia

Treatment is based on volume status:

Hypovolemic Hyponatremia

• Discontinue diuretics immediately and administer isotonic (0.9%) saline for volume repletion 1, 3
• Urine sodium <30 mmol/L suggests hypovolemic hyponatremia and predicts response to saline infusion 1
• Once euvolemia is achieved, reassess sodium levels 1

Euvolemic Hyponatremia (SIADH)

• Fluid restriction to 1 L/day (or 500 mL/day initially) is the cornerstone of first-line treatment 1, 5
• Ensure adequate solute intake (salt and protein) alongside fluid restriction 5
• If no response to fluid restriction after 24-48 hours, add oral sodium chloride 100 mEq three times daily 1
• Nearly half of SIADH patients do not respond to fluid restriction alone and require second-line therapy 5

Second-line pharmacological options for SIADH:

• Urea (15-30 g twice daily) is considered very effective and safe 1, 5
• Tolvaptan 15 mg once daily, titrated to 30-60 mg as needed 6, 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 sodium <125 mmol/L 1, 3
• Treat the underlying condition (optimize heart failure management, manage cirrhosis complications) 1, 3
• In 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
• Temporarily discontinue diuretics if sodium <125 mmol/L 1

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, 5, 4

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

• Advanced liver disease 1, 4
• Chronic alcoholism 1, 4
• Malnutrition 1, 4
• Severe hyponatremia (<120 mmol/L) 1
• Prior encephalopathy 1

Monitoring During Correction:

• Severe symptoms: Check sodium every 2 hours initially 1
• After symptom resolution: Check every 4 hours 1
• Chronic correction: Daily monitoring to ensure <8 mmol/L increase per 24 hours 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 1, 4
• The goal is to bring total 24-hour correction back to ≤8 mmol/L from baseline 1
• Therapeutic relowering with desmopressin has been found safe in clinical trials 4

Pharmacological Interventions

Vasopressin Receptor Antagonists (Vaptans)

Tolvaptan is FDA-approved for euvolemic and hypervolemic hyponatremia, with demonstrated efficacy in increasing serum sodium levels. 6, 2

• Starting dose: 15 mg once daily, can titrate to 30-60 mg 6
• In clinical trials, tolvaptan increased serum sodium by 3.7 mmol/L at Day 4 and 4.6 mmol/L at Day 30 compared to placebo 6
• Use with extreme caution in cirrhosis due to higher risk of gastrointestinal bleeding (10% vs 2% with placebo) 1
• Avoid fluid restriction during first 24 hours of vaptan therapy to prevent overly rapid correction 6
• Monitor closely to avoid overcorrection 1, 2

Special Populations

Neurosurgical Patients

• Distinguish between SIADH and cerebral salt wasting (CSW), as treatment approaches differ fundamentally 1
• CSW requires volume and sodium replacement (isotonic or hypertonic saline), 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 in cirrhosis increases risk of spontaneous bacterial peritonitis (OR 3.40), hepatorenal syndrome (OR 3.45), and hepatic encephalopathy (OR 2.36) 1
• Correction rates should be conservative (4-6 mmol/L per day) due to higher osmotic demyelination risk 1
• Sodium restriction (not fluid restriction) is what produces weight loss, as fluid follows sodium 1

Common Pitfalls to Avoid

• Overly rapid correction exceeding 8 mmol/L in 24 hours leading to osmotic demyelination syndrome 1, 2, 4
• Using fluid restriction in cerebral salt wasting, which 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 (23.8% vs 16.4%) and fracture rates 1, 2

Clinical Significance

• Even mild chronic hyponatremia is associated with cognitive impairment, gait disturbances, increased falls, and osteoporosis 2, 4
• Hyponatremia affects approximately 5% of adults and 35% of hospitalized patients 2
• Sodium levels <130 mmol/L are associated with 60-fold increase in mortality (11.2% vs 0.19%) 1