What is the initial treatment for hyponatremia in the emergency room (ER)?

Initial Treatment of Hyponatremia in the Emergency Room

The initial treatment of hyponatremia in the ER depends critically on symptom severity and volume status: severely symptomatic patients require immediate 3% hypertonic saline to correct 6 mmol/L over 6 hours, while asymptomatic or mildly symptomatic patients need careful volume status assessment to guide therapy—hypovolemic patients receive isotonic saline, euvolemic patients get fluid restriction, and hypervolemic patients require fluid restriction with possible diuretics. 1, 2

Immediate Assessment in the ER

Determine Symptom Severity First

Severe symptoms (seizures, coma, altered mental status, respiratory distress) indicate hyponatremic encephalopathy requiring emergency treatment regardless of sodium level 1, 2, 3:

• These patients need 3% hypertonic saline immediately 1, 2, 4
• Administer as 100 mL boluses over 10 minutes, repeatable up to 3 times 1
• Goal: increase sodium by 6 mmol/L over 6 hours or until symptoms resolve 1, 2
• Monitor sodium every 2 hours initially 1, 2

Mild symptoms (nausea, headache, confusion) or asymptomatic patients require volume status assessment before treatment 1, 2

Assess Volume Status

Physical examination findings guide treatment 1, 2:

Hypovolemic (orthostatic hypotension, dry mucous membranes, poor skin turgor, tachycardia):

• Check urine sodium: <30 mmol/L suggests hypovolemia 1
• Treat with 0.9% normal saline for volume repletion 1, 4
• Discontinue diuretics 1

Euvolemic (no edema, normal blood pressure, normal skin turgor):

• Suspect SIADH if urine osmolality >100 mOsm/kg and urine sodium >20-40 mmol/L 1, 5, 6
• Implement fluid restriction to 1 L/day as first-line 1, 2, 5
• Rule out hypothyroidism and adrenal insufficiency 1

Hypervolemic (edema, ascites, jugular venous distention):

• Common in heart failure and cirrhosis 7, 1
• Implement fluid restriction to 1-1.5 L/day 7, 1
• Discontinue or reduce diuretics temporarily if sodium <125 mmol/L 1
• Consider albumin infusion in cirrhotic patients 1

Critical Correction Rate Guidelines

Never exceed 8 mmol/L correction in 24 hours to prevent osmotic demyelination syndrome 1, 2, 3, 4:

• For severe symptoms: correct 6 mmol/L over first 6 hours, then slow down 1, 2
• For chronic hyponatremia (>48 hours): aim for 4-6 mmol/L per day 1, 3
• High-risk patients (cirrhosis, alcoholism, malnutrition): limit to 4-6 mmol/L per day 1, 2

Specific ER Treatment Protocols

For Severe Symptomatic Hyponatremia

1. Start 3% hypertonic saline immediately 1, 2, 4, 8
2. Give 100 mL bolus over 10 minutes 1
3. Can repeat twice more at 10-minute intervals 1
4. Check sodium after 1-2 hours 1, 2
5. Stop when symptoms resolve or 6 mmol/L increase achieved 1, 2
6. Transfer to ICU for continued monitoring 2, 5

For Hypovolemic Hyponatremia

1. Administer 0.9% normal saline 1, 4
2. Stop diuretics 1
3. Monitor sodium every 4-6 hours 1
4. Once euvolemic, reassess if sodium normalizes 1

For Euvolemic Hyponatremia (SIADH)

1. Restrict fluids to 1 L/day 1, 2, 5
2. If severe symptoms present, use 3% saline first 1, 2
3. Identify and treat underlying cause 1, 5
4. Consider vasopressin antagonists (tolvaptan 15 mg) for resistant cases 7, 9

For Hypervolemic Hyponatremia

1. Restrict fluids to 1-1.5 L/day 7, 1
2. Temporarily stop diuretics if sodium <125 mmol/L 1
3. Avoid hypertonic saline unless life-threatening symptoms 1
4. In cirrhosis: consider albumin infusion 1
5. In heart failure: optimize guideline-directed medical therapy 7

Common ER Pitfalls to Avoid

Do not use normal saline in euvolemic hyponatremia (SIADH) - it will worsen hyponatremia by providing free water 1

Do not correct too rapidly - exceeding 8 mmol/L in 24 hours risks osmotic demyelination syndrome, which causes irreversible neurological damage 1, 2, 3, 8, 10

Do not use hypertonic saline in asymptomatic hypervolemic patients - it worsens fluid overload 1

Do not ignore mild hyponatremia (130-135 mmol/L) - even mild hyponatremia increases fall risk and mortality 1, 3

In neurosurgical patients, distinguish SIADH from cerebral salt wasting - CSW requires volume replacement, not fluid restriction 1, 2

Monitoring Requirements

• Severe symptoms: check sodium every 2 hours initially 1, 2
• After symptom resolution: check every 4-6 hours 1
• Watch for overcorrection: if exceeds 8 mmol/L in 24 hours, give D5W and desmopressin to relower sodium 1, 10
• Monitor for osmotic demyelination: dysarthria, dysphagia, quadriparesis typically appear 2-7 days after rapid correction 1

When to Consider Vasopressin Antagonists

Tolvaptan may be considered in the ER for 7, 9:

• Persistent severe hyponatremia despite fluid restriction
• Hypervolemic hyponatremia with volume overload
• Starting dose: 15 mg once daily
• Contraindicated in hypovolemic hyponatremia 1
• Use with extreme caution in cirrhosis due to bleeding risk 1