Hypertonic Saline Rate in Hyponatraemia
For symptomatic severe hyponatremia, administer 3% hypertonic saline to correct 6 mmol/L over 6 hours or until severe symptoms resolve, with a maximum total correction of 8 mmol/L in the first 24 hours. 1
Initial Management Algorithm
Severe Symptoms (Seizures, Coma, Mental Status Changes)
Immediate treatment with 3% hypertonic saline:
- Target: Increase sodium by 6 mmol/L over 6 hours OR until severe symptoms resolve 1
- Maximum limit: Do not exceed 8 mmol/L total correction in 24 hours 1
- Subsequent correction: If 6 mmol/L corrected in first 6 hours, limit additional increase to only 2 mmol/L over the following 18 hours 1
Practical administration:
- Calculate sodium deficit: Desired increase (mmol/L) × 0.5 × ideal body weight (kg) 1
- Administer as bolus or continuous infusion through large vein 2
- Monitor sodium every 2 hours in ICU setting 1
- Stop 3% saline when severe symptoms resolve, then transition to less aggressive protocol 1
Critical Distinction: Acute vs Chronic Hyponatremia
Rapid correction (>1 mmol/L/hour) should be reserved ONLY for:
- Severely symptomatic patients (seizures, coma, cerebral edema) 1
- Acute hyponatremia (<48 hours duration) 1
Chronic hyponatremia requires slower correction:
- Goal rate: 4-6 mmol/L per 24 hours 3
- Maximum: 8 mmol/L per 24 hours to prevent osmotic demyelination syndrome (ODS) 3
Bolus Dosing Approach
Recent evidence supports bolus administration over continuous infusion:
- 250 mL bolus of 3% NaCl is more effective than 100 mL (52% vs 32% achieving ≥5 mmol/L increase within 4 hours) 4
- European guidelines recommend 150 mL bolus of 3% hypertonic saline 5, 6
- Can repeat boluses as needed while monitoring closely 4, 5
Critical Monitoring Requirements
Essential monitoring to prevent overcorrection:
- Check sodium every 2-4 hours initially 1
- Monitor urine output closely—water diuresis is a major cause of inadvertent overcorrection 7, 5
- Diuresis correlates positively with overcorrection risk (r=0.6) 5
High-risk populations for overcorrection:
- Patients with unrecognized hypovolemia 7
- Those with reversible causes of water retention 7
- Severe hyponatremia (<120 mmol/L) 7
Prevention of Overcorrection
If overcorrection occurs (>8-10 mmol/L in 24 hours):
- Administer desmopressin and/or intravenous dextrose 3, 8
- Consider electrolyte-free water 3
- Tromethamine may reduce ODS risk 3
Important Caveats
The Adrogué-Madias formula significantly underestimates sodium increase:
- In 74.2% of patients with sodium <120 mmol/L, observed increase exceeded predicted 7
- Average correction in "overcorrectors" was 2.4 times predicted 7
- Therefore, infuse at lower rates than formula-predicted 7
Special considerations:
- Administer through large vein for rapid dilution due to hypertonicity (1,027 mOsmol/L) 2
- Risk of venous damage with peripheral administration 2
- Neurosurgical patients may require more aggressive correction (up to 1 mmol/L/hour for acute/severe cases) 1
Context-specific modifications:
- Cirrhotic patients: Maximum 4-6 mmol/L per 24 hours, not exceeding 8 mmol/L per 24 hours 3
- Patients with advanced liver disease have higher ODS risk 3
Hypertonic saline is NOT recommended for: