Symptoms and Treatment of Hyponatremia
Hyponatremia (serum sodium <135 mmol/L) presents with symptoms ranging from mild to severe based on severity and onset rate, and requires treatment tailored to volume status and symptom severity, with careful correction rates to prevent osmotic demyelination syndrome. 1
Symptoms of Hyponatremia
Mild to Moderate Symptoms (Na 126-134 mmol/L)
- Nausea and vomiting 2, 3
- Headache 3
- Muscle weakness and cramps 4
- Cognitive impairment and attention deficits 2
- Gait disturbances and increased fall risk 2
- Irritability of muscles 4
Severe Symptoms (Na <125 mmol/L)
- Mental status changes and confusion 3
- Seizures 1, 3
- Coma 3
- Delirium 3
- Ataxia 3
- Brain herniation (rare) 3
- Respiratory distress 1
Diagnostic Approach
Initial Assessment
- Determine volume status: hypovolemic, euvolemic, or hypervolemic 1, 2
- Measure serum and urine osmolality 1
- Check urine sodium concentration 1
- Assess for underlying causes (medications, excessive alcohol, low-salt diets, excessive water intake) 3
Treatment Based on Symptom Severity
Severe Symptomatic Hyponatremia
- For severe symptoms (seizures, coma), administer 3% hypertonic saline with a goal to correct 6 mmol/L over 6 hours or until symptoms improve. 1, 5
- Maximum correction should not exceed 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome 1, 5
- Monitor serum sodium every 2 hours during initial correction 1
- Consider ICU admission for close monitoring 1
Mild to Moderate Symptomatic Hyponatremia
- For mild symptoms or asymptomatic patients, fluid restriction to 1 L/day is the cornerstone of treatment 1, 5
- If no response to fluid restriction, add oral sodium chloride 100 mEq three times daily 1, 5
- Monitor sodium levels every 4-6 hours initially, then daily 5
Treatment Based on Volume Status
Hypovolemic Hyponatremia
- Discontinue diuretics 1
- Administer isotonic saline (0.9% NaCl) for volume repletion 1, 3
- Treat the underlying cause of volume depletion 6
Euvolemic Hyponatremia (SIADH)
- Fluid restriction to 1 L/day 1, 5
- Consider additional options if needed: oral sodium supplements, urea, diuretics, demeclocycline 1
- High protein diet to augment solute intake 5
- For resistant cases, consider vasopressin receptor antagonists (vaptans) 1, 2
Hypervolemic Hyponatremia (e.g., cirrhosis, heart failure)
- Fluid restriction to 1-1.5 L/day for moderate to severe hyponatremia (Na <125 mmol/L) 1, 5
- Consider albumin infusion for patients with cirrhosis 1
- Avoid hypertonic saline unless life-threatening symptoms are present 1
- Treat the underlying cause (heart failure, cirrhosis) 3
Special Considerations
Patients at Higher Risk for Osmotic Demyelination
- Patients with advanced liver disease, alcoholism, malnutrition, or prior encephalopathy require more cautious correction (4-6 mmol/L per day) 1, 5
- If overcorrection occurs, consider relowering with electrolyte-free water or desmopressin 1
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
- Consider fludrocortisone for hyponatremia in subarachnoid hemorrhage patients 1
Common Pitfalls to Avoid
- Overly rapid correction of chronic hyponatremia leading to osmotic demyelination syndrome 1
- 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
Long-term Complications
- Even mild chronic hyponatremia is associated with cognitive impairment, gait disturbances, and increased rates of falls and fractures 2
- Hyponatremia is a secondary cause of osteoporosis 2
- Osmotic demyelination syndrome can occur 2-7 days after rapid correction, presenting with dysarthria, dysphagia, oculomotor dysfunction, or quadriparesis 1