Initial Approach to Treating Hyponatremia
The initial approach to treating hyponatremia should be based on volume status assessment, symptom severity, and the underlying cause, with correction rates not exceeding 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome. 1
Initial Assessment
- Evaluate serum sodium level, osmolality, urine osmolality, urine electrolytes, uric acid, and extracellular fluid volume status to determine the underlying cause of hyponatremia 1
- Classify hyponatremia based on severity: mild (126-135 mEq/L), moderate (120-125 mEq/L), and severe (<120 mEq/L) 2
- Determine if hyponatremia is hypotonic (most common) or non-hypotonic (e.g., hyperglycemia-induced) 3
- For hyperglycemia-induced hyponatremia, correct sodium by adding 1.6 mEq/L to measured sodium for every 100 mg/dL of glucose above 100 mg/dL 3
Treatment Based on Symptom Severity
Severe Symptomatic Hyponatremia (seizures, coma)
- Administer 3% hypertonic saline immediately with an initial goal to increase sodium by 4-6 mmol/L over 6 hours or until severe symptoms resolve 1
- Can be given as boluses of 100 mL over 10 minutes, repeated up to three times at 10-minute intervals until symptoms improve 1
- Total correction should not exceed 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome 1, 2
- Consider ICU admission for close monitoring during treatment 1
Mild to Moderate Symptomatic Hyponatremia
- Correction rate should be slower than for severe symptoms but still not exceed 8 mmol/L in 24 hours 1
- Monitor serum sodium every 4-6 hours during initial correction 1
Asymptomatic Hyponatremia
- Treatment based on volume status (see below) 1
- Slower correction is safer, with a maximum of 8 mmol/L in 24 hours 1
Treatment Based on Volume Status
Hypovolemic Hyponatremia
- Discontinue diuretics if applicable 1
- Administer isotonic (0.9%) saline for volume repletion 1, 4
- Once euvolemia is achieved, reassess and adjust treatment accordingly 1
Euvolemic Hyponatremia (e.g., SIADH)
- Implement fluid restriction to 1 L/day as first-line treatment 1, 5
- If no response to fluid restriction, add oral sodium chloride 100 mEq three times daily 1
- Consider second-line therapies if fluid restriction fails:
Hypervolemic Hyponatremia (e.g., cirrhosis, heart failure)
- Implement fluid restriction to 1-1.5 L/day for sodium <125 mmol/L 1
- Consider albumin infusion for patients with cirrhosis 1
- Avoid hypertonic saline unless life-threatening symptoms are present 1
- Address underlying condition (heart failure, cirrhosis) 4
Special Considerations
- Patients with advanced liver disease, alcoholism, malnutrition, or prior encephalopathy require more cautious correction (4-6 mmol/L per day) due to higher risk of osmotic demyelination syndrome 1
- In neurosurgical patients, distinguish between SIADH and cerebral salt wasting (CSW) as treatment approaches differ significantly 1
- For CSW, treatment focuses on volume and sodium replacement, not fluid restriction 1
- Avoid fluid restriction in subarachnoid hemorrhage patients at risk of vasospasm 1
Monitoring and Follow-up
- For severe symptoms: monitor serum sodium every 2 hours during initial correction 1
- For mild/moderate symptoms: monitor every 4-6 hours initially, then daily 1
- If overcorrection occurs, consider relowering with electrolyte-free water or desmopressin 1, 5
- Watch for signs of osmotic demyelination syndrome (dysarthria, dysphagia, oculomotor dysfunction, quadriparesis) typically occurring 2-7 days after rapid correction 1
Common Pitfalls to Avoid
- Overly rapid correction exceeding 8 mmol/L in 24 hours leading to osmotic demyelination syndrome 1
- Inadequate monitoring during active correction 1
- Using fluid restriction in CSW, which can worsen outcomes 1
- Failing to recognize and treat the underlying cause 1
- Using hypertonic saline in hypervolemic hyponatremia without life-threatening symptoms 1