What treatment to give a patient with severe hyponatremia?

Treatment of Severe Hyponatremia

For severe hyponatremia, immediately administer 3% hypertonic saline with a target correction of 6 mmol/L over 6 hours or until severe symptoms resolve, but never exceed 8 mmol/L total correction in 24 hours to prevent osmotic demyelination syndrome. 1

Defining Severe Hyponatremia and Symptom Assessment

Severe hyponatremia is defined as serum sodium <120-125 mmol/L 1, 2. However, symptom severity—not just the sodium number—determines treatment urgency 1.

Severe symptoms requiring immediate hypertonic saline include: 1

• Seizures
• Coma or altered consciousness
• Cardiorespiratory distress
• Somnolence or obtundation

Moderate symptoms that may require hospitalized correction: 1

• Confusion or delirium
• Nausea and vomiting
• Headache
• Gait instability or ataxia

Emergency Treatment Protocol

Immediate Management for Severe Symptoms

Administer 3% hypertonic saline as 100 mL boluses over 10 minutes, repeatable up to three times at 10-minute intervals until symptoms improve 1. This approach rapidly increases sodium by approximately 2 mmol/L per bolus 1.

Alternative dosing: Target 6 mmol/L correction over the first 6 hours, then stop aggressive correction 1, 3. After initial symptom resolution, the remaining correction to reach the 8 mmol/L limit should occur slowly over the next 18 hours 1.

Critical Correction Rate Limits

Standard patients: Maximum 8 mmol/L in 24 hours 1, 2, 3, 4, 5

High-risk patients (cirrhosis, alcoholism, malnutrition, prior encephalopathy): Maximum 4-6 mmol/L per day, absolute limit 8 mmol/L in 24 hours 1, 2

The evidence is unequivocal: exceeding these limits risks osmotic demyelination syndrome, a devastating and potentially fatal complication 1, 6, 3, 4, 5.

Treatment Based on Volume Status

Determining Volume Status

Assess for: 1

• Hypovolemia: Orthostatic hypotension, dry mucous membranes, decreased skin turgor, flat neck veins
• Hypervolemia: Peripheral edema, ascites, jugular venous distention, pulmonary congestion
• Euvolemia: Normal volume status without signs of either extreme

Check urine sodium: <30 mmol/L suggests hypovolemia (71-100% positive predictive value for saline responsiveness); >20-40 mmol/L with high urine osmolality suggests SIADH 1, 2.

Hypovolemic Hyponatremia

After initial symptom control with hypertonic saline, switch to isotonic saline (0.9% NaCl) for volume repletion 1, 2. Start at 15-20 mL/kg/h initially, then 4-14 mL/kg/h based on response 1.

Discontinue diuretics immediately if sodium <125 mmol/L 1.

Euvolemic Hyponatremia (SIADH)

After resolving severe symptoms with hypertonic saline, implement fluid restriction to 1 L/day 1, 2, 3. If no response, add oral sodium chloride 100 mEq three times daily 1.

For refractory cases, consider vaptans (tolvaptan 15 mg once daily, titrate to 30-60 mg) 1, 3, though these carry risk of overly rapid correction and require intensive monitoring 3.

Hypervolemic Hyponatremia (Heart Failure, Cirrhosis)

After initial hypertonic saline for severe symptoms, implement fluid restriction to 1-1.5 L/day 1, 2.

For cirrhotic patients, consider albumin infusion (6-8 g per liter of ascites drained) 1. Avoid hypertonic saline beyond emergency symptom control, as it worsens ascites and edema 1.

Temporarily discontinue diuretics if sodium <125 mmol/L 1.

Special Populations and Critical Considerations

Neurosurgical Patients: SIADH vs. Cerebral Salt Wasting

This distinction is critical because treatments are opposite 1, 2:

SIADH characteristics: 1

• Euvolemic state
• Urine sodium >20-40 mmol/L
• Urine osmolality >300 mOsm/kg
• Treatment: Fluid restriction

Cerebral Salt Wasting characteristics: 1

• True hypovolemia (CVP <6 cm H₂O)
• Urine sodium >20 mmol/L despite volume depletion
• Orthostatic hypotension, tachycardia
• Treatment: Volume and sodium replacement with isotonic or hypertonic saline, fludrocortisone 0.1-0.2 mg daily

Never use fluid restriction in cerebral salt wasting—this worsens outcomes 1. Never use fluid restriction in subarachnoid hemorrhage patients at risk of vasospasm 1.

Cirrhotic Patients

These patients require the most cautious correction (4-6 mmol/L per day maximum) due to exceptionally high risk of osmotic demyelination 1, 2. Hyponatremia in cirrhosis increases risk of spontaneous bacterial peritonitis (OR 3.40), hepatorenal syndrome (OR 3.45), and hepatic encephalopathy (OR 2.36) 1.

Intensive Monitoring Protocol

Severe symptoms: Check serum sodium every 2 hours during initial correction 1, 2

After symptom resolution: Check every 4 hours 1

Continue frequent monitoring until correction is complete and patient is stable 1, 4

Managing Overcorrection

If sodium correction exceeds 8 mmol/L in 24 hours: 1, 6, 4, 5

1. Immediately discontinue current fluids
2. Switch to D5W (5% dextrose in water)
3. Administer desmopressin to induce water retention and slow/reverse the rise
4. Goal: Bring total 24-hour correction back to ≤8 mmol/L from starting point

Relowering sodium after overcorrection may prevent osmotic demyelination syndrome 6, 4, 5.

Common Pitfalls to Avoid

Never ignore mild hyponatremia (130-135 mmol/L)—it increases fall risk (21% vs 5%) and mortality (60-fold increase at <130 mmol/L) 1, 3

Never use fluid restriction as initial treatment for altered mental status—this is a medical emergency requiring hypertonic saline 1

Never exceed 8 mmol/L correction in 24 hours, even if symptoms persist 1, 2, 3, 4, 5

Never use lactated Ringer's solution for hyponatremia—it is hypotonic (130 mEq/L sodium) and will worsen hyponatremia 1

Never delay treatment while pursuing diagnostic workup in severely symptomatic patients 2

Watch for osmotic demyelination syndrome signs 2-7 days after correction: dysarthria, dysphagia, oculomotor dysfunction, quadriparesis 1, 6