Normal Saline Administration Rate for Mild Hyponatremia
For mild hyponatremia, isotonic saline (0.9% NaCl) should be administered at 50-100 mL/kg/day, with careful monitoring of serum sodium levels to prevent overcorrection. 1, 2
Assessment and Classification
- Mild hyponatremia is defined as serum sodium between 126-135 mEq/L 2
- Before initiating treatment, assess volume status to determine if the patient has hypovolemic, euvolemic, or hypervolemic hyponatremia, as this will guide appropriate treatment 2
- Check urine sodium and osmolality to help distinguish between SIADH and Cerebral Salt Wasting (CSW), as normal saline may worsen hyponatremia in SIADH but is appropriate for CSW 2
- A urinary sodium <30 mmol/L has a positive predictive value of 71-100% for response to 0.9% saline infusion 1
Treatment Based on Volume Status
Hypovolemic Hyponatremia
- For hypovolemic hyponatremia (CVP <6 cm H₂O), administer normal saline at 50-100 mL/kg/day 1
- This approach is particularly effective in cerebral salt wasting, where volume repletion with normal saline is the primary treatment 2
Euvolemic Hyponatremia (SIADH)
- For euvolemic hyponatremia (SIADH), normal saline is generally not recommended as it may worsen hyponatremia 2
- Fluid restriction to 1L/day is the primary approach for SIADH 2
Hypervolemic Hyponatremia
- For hypervolemic hyponatremia (cirrhosis, heart failure), avoid normal saline as it may worsen fluid overload 2
- Implement fluid restriction to 1-1.5 L/day instead 2
Correction Rate Guidelines
- Do not exceed correction of 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome 2, 3
- For mild hyponatremia, aim for a correction rate of <0.5 mmol/L per hour 4
- Monitor serum sodium levels every 4-6 hours during initial correction 2, 5
Special Considerations
- In neurosurgical patients, distinguish between SIADH and CSW, as treatment approaches differ significantly 1, 2
- Patients with advanced liver disease, alcoholism, or malnutrition require more cautious correction rates (4-6 mmol/L per day) due to higher risk of osmotic demyelination syndrome 2
- For patients with subarachnoid hemorrhage at risk for vasospasm, avoid fluid restriction 2
Common Pitfalls to Avoid
- Using normal saline in SIADH can worsen hyponatremia 2
- Overly rapid correction exceeding 8 mmol/L in 24 hours can lead to osmotic demyelination syndrome 2, 3
- Inadequate monitoring during active correction 2
- Using fluid restriction in CSW can worsen outcomes 2
- Failing to recognize and treat the underlying cause 2