Treatment of Hypotonic Hyponatremia
The treatment of hypotonic hyponatremia should be based on volume status assessment, symptom severity, and onset timing, with a maximum correction rate of 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome. 1
Initial Assessment
- Evaluate volume status (hypovolemic, euvolemic, or hypervolemic) and serum osmolality to determine the underlying cause of hyponatremia 1
- Obtain serum and urine osmolarity, urine electrolytes, and uric acid to differentiate between various causes 1
- Assess symptom severity (mild/asymptomatic vs. severe symptoms like seizures or coma) to guide treatment approach 1, 2
Treatment Based on Volume Status
Hypovolemic Hyponatremia
- Discontinue diuretics and administer isotonic saline (0.9% NaCl) for volume repletion 1
- Once euvolemia is achieved, reassess sodium levels to determine if further intervention is needed 1
Euvolemic Hyponatremia (SIADH)
- Implement fluid restriction to 1L/day for mild/asymptomatic cases 1, 3
- Consider pharmacological options for resistant cases:
Hypervolemic Hyponatremia (e.g., cirrhosis, heart failure)
- Implement fluid restriction to 1000-1500 mL/day for moderate to severe hyponatremia (Na <125 mmol/L) 1
- Consider albumin infusion for patients with cirrhosis 1
- Avoid hypertonic saline unless life-threatening symptoms are present, as it may worsen edema and ascites 1
Treatment Based on Symptom Severity
Severe Symptomatic Hyponatremia (seizures, coma)
- Administer 3% hypertonic saline with an initial goal to correct 6 mmol/L over 6 hours or until severe symptoms resolve 1, 5
- Can be given as boluses of 100 mL over 10 minutes, repeated up to three times at 10-minute intervals until symptoms improve 1
- Monitor serum sodium every 2 hours during initial correction 1
Mild/Asymptomatic Hyponatremia
- Fluid restriction to 1L/day is the cornerstone of treatment, especially for SIADH 1, 6
- Address underlying cause when possible 2
- Monitor sodium levels every 4-6 hours initially, then daily 1
Correction Rate Guidelines
- Maximum increase of 8 mmol/L in 24 hours for most patients to prevent osmotic demyelination syndrome 1, 2
- For patients with advanced liver disease, alcoholism, malnutrition, or prior encephalopathy, use more cautious correction (4-6 mmol/L per day) due to higher risk of osmotic demyelination 1
- If overcorrection occurs, consider relowering with electrolyte-free water or desmopressin 1, 3
Special Considerations
Cerebral Salt Wasting (CSW) in Neurosurgical Patients
- Treatment focuses on volume and sodium replacement, not fluid restriction 1
- For severe symptoms, administer 3% hypertonic saline and consider fludrocortisone 1
- Fluid restriction should NOT be used in CSW as it can worsen outcomes 1
Subarachnoid Hemorrhage Patients
- Avoid fluid restriction in patients at risk of vasospasm 1
- Consider fludrocortisone or hydrocortisone to prevent natriuresis 1
Common Pitfalls to Avoid
- Overly rapid correction of chronic hyponatremia leading to osmotic demyelination syndrome 1, 7
- Inadequate monitoring during active correction 1
- Using fluid restriction in cerebral salt wasting 1
- Failing to recognize and treat the underlying cause 1
- Using hypertonic saline in hypervolemic hyponatremia without life-threatening symptoms 1
- Co-administration of tolvaptan with hypertonic saline (contraindicated) 4
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
- Watch for signs of osmotic demyelination syndrome (dysarthria, dysphagia, oculomotor dysfunction, quadriparesis) typically occurring 2-7 days after rapid correction 1
- When using tolvaptan, monitor for liver injury, especially during the first 18 months of therapy 4