Target Sodium and Correction Rate in Symptomatic Hyponatremia
For symptomatic hyponatremia, immediately administer 3% hypertonic saline with a target correction of 6 mmol/L over the first 6 hours or until symptoms resolve, with a strict maximum total correction of 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome. 1, 2
Immediate Management for Severe Symptomatic Hyponatremia
Severe symptoms (seizures, coma, altered mental status, respiratory distress) constitute a medical emergency requiring urgent intervention: 1, 3
- Administer 3% hypertonic saline as 100 mL boluses over 10 minutes 1, 4
- Repeat boluses up to 3 times at 10-minute intervals until severe symptoms resolve 1, 4
- Target: 4-6 mmol/L increase within the first 1-2 hours to reverse hyponatremic encephalopathy 5, 6
- Once symptoms improve, slow correction to reach total of 6 mmol/L over 6 hours 1, 2
Critical Correction Rate Limits
The correction rate is the single most important safety parameter: 1, 2
Standard Risk Patients
- Maximum 8 mmol/L in 24 hours 1, 2, 7
- Target 6-8 mmol/L in 24 hours 6
- Do not exceed 10-12 mmol/L in any 24-hour period 2, 7
High-Risk Patients
Patients with advanced liver disease, alcoholism, malnutrition, or prior encephalopathy require even more cautious correction: 1, 2
- Maximum 4-6 mmol/L per day 1, 2
- Absolute maximum 8 mmol/L in 24 hours 1, 2
- These patients have completed brain adaptation and are at highest risk for osmotic demyelination 2
Target Sodium Levels
Do not aim for complete normalization. The goal is symptom resolution and safety: 1, 8
- Initial target: 125-130 mmol/L (mildly hyponatremic range) 1, 8
- Stop active correction once this range is reached 8
- Further gradual improvement can occur with underlying cause treatment 1
Monitoring Protocol
Frequency of sodium monitoring is critical to prevent overcorrection: 1, 2
- Severe symptoms: Check serum sodium every 2 hours during initial correction 1, 2
- After symptom resolution: Check every 4-6 hours during active correction 1, 2
- Monitor urine output closely as spontaneous water diuresis can cause inadvertent overcorrection 6
Management of Overcorrection
If sodium correction exceeds 8 mmol/L in 24 hours, immediate intervention is required: 1, 2
- Immediately discontinue all sodium-containing fluids 1, 2
- Switch to D5W (5% dextrose in water) to provide free water 1, 2
- Administer desmopressin to terminate water diuresis and reverse overcorrection 1, 6
- Goal: Bring total 24-hour correction back to ≤8 mmol/L from starting point 1
Common Pitfalls to Avoid
Never correct chronic hyponatremia faster than 8 mmol/L in 24 hours - this is the primary cause of osmotic demyelination syndrome, which can result in dysarthria, dysphagia, quadriparesis, or death. 1, 7, 5
Do not use fluid restriction as initial treatment for severely symptomatic hyponatremia - this is a medical emergency requiring hypertonic saline, not conservative management. 1
Inadequate monitoring during active correction is a critical error that can lead to unrecognized overcorrection. 1
Failing to distinguish acute (<48 hours) from chronic (>48 hours) hyponatremia - acute hyponatremia can be corrected more rapidly without risk of osmotic demyelination, while chronic hyponatremia requires strict adherence to correction limits. 2, 8
Special Considerations by Etiology
SIADH (Euvolemic)
After initial symptom resolution with hypertonic saline: 1
- Implement fluid restriction to 1 L/day 1
- Add oral sodium chloride 100 mEq three times daily if no response to fluid restriction 1
Cerebral Salt Wasting (Hypovolemic)
- Continue volume and sodium replacement with isotonic or hypertonic saline 1
- Never use fluid restriction - this worsens outcomes 1
- Consider fludrocortisone 0.1-0.2 mg daily for severe symptoms 1