What is the initial treatment for a patient with hyponatremia?

Treatment for Hyponatremia

The initial treatment for hyponatremia depends critically on symptom severity and volume status, with severely symptomatic patients requiring 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). 1

Immediate Assessment of Symptom Severity

The first critical decision point is determining whether the patient has severe symptoms requiring emergency intervention:

• Severe symptoms include seizures, coma, altered consciousness, confusion, or cardiorespiratory distress—these constitute a medical emergency 1, 2, 3
• Mild-moderate symptoms include nausea, vomiting, headache, weakness, gait instability, or lethargy 2, 4
• Asymptomatic patients may still have significant hyponatremia requiring treatment 1

Emergency Treatment for Severe Symptomatic Hyponatremia

For patients with 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, 3, 4

• Administer 3% hypertonic saline as 100-150 mL boluses over 10 minutes, which can be repeated up to three times at 10-minute intervals until symptoms improve 1, 5
• Monitor serum sodium every 2 hours during initial correction 1
• Critical safety limit: Never exceed 8 mmol/L correction in 24 hours to prevent osmotic demyelination syndrome 1, 3, 4
• If 6 mmol/L is corrected in the first 6 hours, only 2 mmol/L additional correction is allowed in the remaining 18 hours 1

Treatment Based on Volume Status (For Non-Emergency Cases)

Once severe symptoms are addressed or if the patient is asymptomatic/mildly symptomatic, treatment is guided by volume status:

Hypovolemic Hyponatremia

Administer isotonic saline (0.9% NaCl) for volume repletion. 1, 4, 6

• Initial infusion rate: 15-20 mL/kg/h, then 4-14 mL/kg/h based on response 1
• Discontinue any diuretics immediately 1, 4
• Urine sodium <30 mmol/L predicts good response to saline (positive predictive value 71-100%) 1
• Continue until euvolemia is achieved 1

Euvolemic Hyponatremia (SIADH)

Fluid restriction to 1 L/day is the cornerstone of treatment. 1, 3, 4

• Implement strict fluid restriction to <1000 mL/day 1, 6
• If no response to fluid restriction after 24-48 hours, add oral sodium chloride 100 mEq three times daily 1
• For persistent cases despite fluid restriction, consider vasopressin receptor antagonists (tolvaptan 15 mg once daily, titrate to 30-60 mg) 1, 7
• Alternative second-line options include urea or demeclocycline 1, 3, 5

Hypervolemic Hyponatremia (Heart Failure, Cirrhosis)

Implement fluid restriction to 1-1.5 L/day for sodium <125 mmol/L. 1, 4, 6

• Fluid restriction to 1000-1500 mL/day is first-line therapy 1, 6
• 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 worsens edema and ascites 1
• Treat underlying condition (optimize heart failure management, manage cirrhosis) 4, 6

Critical Correction Rate Guidelines

The maximum correction rate must never exceed 8 mmol/L in 24 hours for most patients. 1, 3, 4

• Standard correction rate: 4-8 mmol/L per day, not exceeding 10-12 mmol/L in 24 hours 1
• High-risk patients require even slower correction at 4-6 mmol/L per day: 1, 3
  • Advanced liver disease
  • Alcoholism
  • Malnutrition
  • Prior encephalopathy
  • Severe hyponatremia (<120 mmol/L)
• Overly rapid correction causes osmotic demyelination syndrome, a devastating neurological complication 1, 3, 8

Special Considerations for Neurosurgical Patients

In neurosurgical patients, distinguishing between SIADH and cerebral salt wasting (CSW) is critical because they require opposite treatments. 1

• SIADH: Euvolemic state, treat with fluid restriction 1
• CSW: True hypovolemia with high urine sodium despite volume depletion, treat with volume and sodium replacement (isotonic or hypertonic saline), NOT fluid restriction 1
• For severe CSW symptoms, administer 3% hypertonic saline plus fludrocortisone 0.1-0.2 mg daily 1
• Never use fluid restriction in subarachnoid hemorrhage patients at risk of vasospasm—this worsens outcomes 1

Monitoring During Treatment

• Severe symptoms: Check serum sodium every 2 hours during initial correction 1
• Mild symptoms: Check every 4 hours after symptom resolution 1
• Asymptomatic/chronic: Check every 24-48 hours initially 1
• Watch for signs of osmotic demyelination syndrome (dysarthria, dysphagia, oculomotor dysfunction, quadriparesis) typically occurring 2-7 days after rapid correction 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
• This is critical to prevent osmotic demyelination syndrome 1, 3

Common Pitfalls to Avoid

• Never use fluid restriction as initial treatment for severely symptomatic hyponatremia—this is a medical emergency requiring hypertonic saline 1
• Never exceed 8 mmol/L correction in 24 hours—overcorrection risks osmotic demyelination syndrome 1, 3
• Never use fluid restriction in cerebral salt wasting—this worsens outcomes 1
• Never ignore mild hyponatremia (130-135 mmol/L) as clinically insignificant—it increases mortality, falls, and cognitive impairment 1, 2, 3
• Never use hypertonic saline in hypervolemic hyponatremia without life-threatening symptoms—it worsens fluid overload 1