Initial Approach to Treating Hyponatremia
The initial approach to hyponatremia must be guided by symptom severity and volume status: severely symptomatic patients require immediate 3% hypertonic saline to correct sodium by 6 mmol/L over 6 hours, while asymptomatic patients should be managed based on whether they are hypovolemic (isotonic saline), euvolemic (fluid restriction), or hypervolemic (fluid restriction ± albumin). 1
Immediate Assessment
Determine Symptom Severity
- Severe symptoms (seizures, coma, altered mental status, cardiorespiratory distress) require emergency treatment with 3% hypertonic saline 1, 2
- Mild symptoms (nausea, vomiting, headache, weakness) or asymptomatic cases allow time for systematic evaluation 1, 3
- Even mild chronic hyponatremia increases fall risk (23.8% vs 16.4% in normonatremic patients) and mortality 2
Essential Initial Workup
- Serum and urine osmolality 1
- Urine sodium and electrolytes 1
- Serum uric acid 1
- Assessment of extracellular fluid volume status 1
- Serum creatinine and glucose 1
Treatment Algorithm Based on Symptom Severity
Severe Symptomatic Hyponatremia (Medical Emergency)
- Administer 3% hypertonic saline immediately with goal to correct 6 mmol/L over 6 hours or until symptoms resolve 1, 2
- Can give as 100-150 mL boluses over 10 minutes, repeatable up to 3 times at 10-minute intervals 4
- Maximum correction: 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome 1, 2
- Monitor serum sodium every 2 hours during initial correction 1
- Consider ICU admission for close monitoring 1
Asymptomatic or Mildly Symptomatic Hyponatremia
Step 1: Assess Volume Status
Hypovolemic Hyponatremia (orthostatic hypotension, dry mucous membranes, decreased skin turgor):
- Discontinue diuretics 1
- Administer isotonic saline (0.9% NaCl) for volume repletion 1
- Urine sodium <30 mmol/L predicts 71-100% response to saline 1
Euvolemic Hyponatremia (SIADH - no edema, normal blood pressure, normal skin turgor):
- Fluid restriction to 1 L/day is cornerstone of treatment 1, 3
- If no response to fluid restriction, add oral sodium chloride 100 mEq three times daily 1
- Serum uric acid <4 mg/dL has 73-100% positive predictive value for SIADH 1
- Consider urea or vaptans for resistant cases 1, 2
Hypervolemic Hyponatremia (edema, ascites, jugular venous distention from heart failure or cirrhosis):
- Fluid restriction to 1-1.5 L/day for sodium <125 mmol/L 1
- Discontinue diuretics temporarily if sodium <125 mmol/L 1
- Consider albumin infusion in cirrhotic patients 1
- Avoid hypertonic saline unless life-threatening symptoms present as it worsens edema 1
Critical Correction Rate Guidelines
Standard Patients
High-Risk Patients (Advanced liver disease, alcoholism, malnutrition, prior encephalopathy)
- More cautious correction: 4-6 mmol/L per day maximum 1
- These patients have significantly higher risk of osmotic demyelination syndrome 1
Special Considerations and Common Pitfalls
Neurosurgical Patients
- Distinguish cerebral salt wasting (CSW) from SIADH - treatment approaches differ fundamentally 1
- CSW requires volume and sodium replacement (isotonic or hypertonic saline), NOT fluid restriction 1
- CSW is more common than SIADH in neurosurgical patients 1
- Evidence of volume depletion (hypotension, tachycardia) suggests CSW over SIADH 1
Critical Pitfalls to Avoid
- Overly rapid correction (>8 mmol/L in 24 hours) causes osmotic demyelination syndrome 1, 2
- Using fluid restriction in CSW worsens outcomes 1
- Inadequate monitoring during active correction 1
- Failing to recognize and treat underlying cause 1
- Using hypertonic saline in hypervolemic hyponatremia without life-threatening symptoms 1
If Overcorrection Occurs
- Immediately discontinue current fluids and switch to D5W 1
- Consider desmopressin to slow or reverse rapid sodium rise 1
- Target bringing total 24-hour correction to ≤8 mmol/L 1