Correction Rate for Severe Hyponatremia (Sodium 118 mEq/L)
For a sodium of 118 mEq/L, correct by 6 mmol/L over the first 6 hours if severely symptomatic (seizures, altered mental status, coma), then limit total correction to a maximum of 8 mmol/L in the first 24 hours. 1, 2
Initial Emergency Management (First 6 Hours)
If the patient has severe symptoms (seizures, coma, altered mental status, cardiorespiratory distress):
- Administer 3% hypertonic saline as 100 mL boluses over 10 minutes 1, 2
- Repeat boluses up to 3 times at 10-minute intervals until symptoms improve 1
- Target: increase sodium by 6 mmol/L over 6 hours or until severe symptoms resolve 1, 2
- Check serum sodium every 2 hours during this phase 1
If the patient is asymptomatic or mildly symptomatic:
- Slower correction is safer, targeting 4-6 mmol/L over the first 24 hours 1, 2
- Treatment depends on volume status (hypovolemic, euvolemic, or hypervolemic) 1
Critical 24-Hour Limit
The absolute maximum correction is 8 mmol/L in any 24-hour period to prevent osmotic demyelination syndrome 1, 2, 3, 4. This means:
- If you correct 6 mmol/L in the first 6 hours for severe symptoms, you can only correct an additional 2 mmol/L over the remaining 18 hours 1
- This translates to approximately 0.33 mmol/L per hour on average 2
High-Risk Patients Requiring Even Slower Correction
For patients with advanced liver disease, alcoholism, malnutrition, or prior encephalopathy, limit correction to 4-6 mmol/L per day, not exceeding 8 mmol/L in 24 hours 1, 2, 5. These patients have completed brain adaptation and face higher risk of osmotic demyelination 1.
Monitoring Requirements
- Severe symptoms: Check sodium every 2 hours initially 1, 2
- Mild symptoms or asymptomatic: Check every 4-6 hours during active correction 1, 2
- Monitor urine output continuously, as spontaneous water diuresis can cause inadvertent overcorrection 4
Managing Overcorrection
If sodium rises >8 mmol/L in 24 hours:
- Immediately discontinue all sodium-containing fluids 1, 2
- Switch to D5W (5% dextrose in water) 1, 2
- Administer desmopressin to terminate water diuresis and prevent further rise 1, 2, 4
Common Pitfalls to Avoid
- Never correct chronic hyponatremia faster than 8 mmol/L in 24 hours - this risks osmotic demyelination syndrome with devastating neurological consequences including quadriparesis, dysarthria, and death 1, 3, 4
- Avoid correcting to normonatremia acutely - the goal is 125-130 mEq/L, not 135-145 mEq/L 6
- Do not use fixed infusion rates - correction is guided by serial sodium measurements, not mL/hour calculations 2
- Inadequate monitoring during active correction leads to overcorrection 1
- In severely malnourished patients, even rates within "recommended" ranges can cause osmotic demyelination 5
Treatment Based on Volume Status
Once severe symptoms are controlled, ongoing management depends on etiology: