Treatment of Hypernatremia and Hyponatremia
HYPERNATREMIA TREATMENT
Hypernatremia is treated by correcting the free water deficit with hypotonic fluids (oral or intravenous D5W), addressing the underlying cause (impaired thirst mechanism, lack of water access, diabetes insipidus, osmotic diuresis, or lactulose-induced diarrhea), and avoiding rapid correction to prevent cerebral edema. 1, 2
Correction Rate Guidelines
- Reduce sodium at a rate of 10-15 mmol/L per 24 hours to avoid cerebral edema from overly rapid correction 3
- Use D5W as the primary fluid for free water replacement 3
- Correction rates faster than 48-72 hours for severe hypernatremia increase the risk of pontine myelinolysis 3
Special Populations
- In cirrhotic patients, hypernatremia typically follows hypotonic fluid losses from osmotic diuresis (glycosuria) or lactulose-induced diarrhea 2
- Patients with renal concentrating defects (e.g., nephrogenic diabetes insipidus) can develop hypernatremia if administered isotonic fluids and require hypotonic fluid replacement 4
- Elderly patients with impaired thirst mechanisms or inability to access water are at highest risk 5
HYPONATREMIA TREATMENT OVERVIEW
Initial Assessment Framework
All hyponatremia requires classification by volume status (hypovolemic, euvolemic, or hypervolemic) and symptom severity (mild, moderate, severe) before initiating treatment. 3, 1, 6
- Check serum and urine osmolality, urine sodium, and assess extracellular fluid volume status 3
- Mild hyponatremia: 130-135 mEq/L 1
- Moderate hyponatremia: 125-129 mEq/L 1
- Severe hyponatremia: <125 mEq/L 1
Universal Correction Rate Limits
Never exceed 8 mmol/L correction in 24 hours to prevent osmotic demyelination syndrome. 3, 7, 6
- For severe symptoms: correct 6 mmol/L over 6 hours or until symptoms resolve 3
- For high-risk patients (advanced liver disease, alcoholism, malnutrition): limit to 4-6 mmol/L per day 3, 7
- Monitor sodium every 2 hours during initial correction for severe symptoms 3
HYPOVOLEMIC HYPONATREMIA
Treat with isotonic saline (0.9% NaCl) to restore intravascular volume, discontinue diuretics, and monitor for correction not exceeding 8 mmol/L in 24 hours. 3, 8, 5
Diagnostic Criteria
- Urine sodium <30 mmol/L has 71-100% positive predictive value for response to saline 3
- Clinical signs: hypotension, tachycardia, dry mucous membranes, decreased skin turgor 3
- Elevated serum creatinine and BUN 3
Treatment Protocol
- Administer isotonic saline for volume repletion 3, 1
- For severe dehydration with neurological symptoms, consider hypertonic saline with careful monitoring 3
- Once euvolemic, reassess if hyponatremia persists (may indicate SIADH) 3
EUVOLEMIC HYPONATREMIA (SIADH)
Fluid restriction to 1 L/day is the cornerstone of SIADH treatment; for resistant cases or severe symptoms, add oral sodium chloride 100 mEq three times daily or consider vaptans. 3, 8, 5
Diagnostic Criteria for SIADH
- Hypotonic hyponatremia with inappropriate urinary concentration 3
- Euvolemic state: no edema, no orthostatic hypotension, normal skin turgor, moist mucous membranes 3
- Urine sodium >20-40 mmol/L and urine osmolality >300 mOsm/kg 3
- Normal renal, adrenal, and thyroid function 3
Treatment Algorithm
Mild to Moderate Asymptomatic SIADH:
- Fluid restriction to 1 L/day 3, 8
- If no response, add oral sodium chloride 100 mEq three times daily 3
- Alternative options: urea, diuretics, lithium, demeclocycline 3, 5
Severe Symptomatic SIADH:
- Administer 3% hypertonic saline immediately 3, 1
- Target correction of 6 mEq/L over 6 hours or until symptoms resolve 3
- Maximum 8 mEq/L in 24 hours 3, 7
Vaptan Therapy (FDA-Approved):
- Tolvaptan is FDA-approved for euvolemic hyponatremia at starting dose of 15 mg once daily, titrated to 30 mg then 60 mg as needed 7
- Must initiate in hospital with close sodium monitoring 7
- Avoid fluid restriction during first 24 hours of vaptan therapy 7
- Maximum treatment duration: 30 days to minimize liver injury risk 7
- Contraindicated with strong CYP3A inhibitors 7
HYPERVOLEMIC HYPONATREMIA
Treat hypervolemic hyponatremia (cirrhosis, heart failure) with fluid restriction to 1-1.5 L/day for sodium <125 mmol/L, discontinue diuretics temporarily, and consider albumin infusion in cirrhotic patients; avoid hypertonic saline unless life-threatening symptoms present. 4, 3
Treatment Protocol
For Moderate Hyponatremia (120-125 mmol/L):
- Fluid restriction to 1000 mL/day 3
- Discontinue diuretics 3
- In cirrhosis: consider albumin infusion 4, 3
For Severe Hyponatremia (<120 mmol/L):
- More severe fluid restriction plus albumin infusion 3
- Temporarily discontinue diuretics until sodium improves 3
- Sodium restriction (not fluid restriction) results in weight loss as fluid passively follows sodium 3
Vaptan Therapy:
- Conivaptan (IV): FDA-approved for euvolemic and hypervolemic hyponatremia, used for 2-4 days 4
- Frequent adverse events: phlebitis (70%), hypotension, rapid sodium increase (10%) 4
- Reduce dose by 50% in uncompensated cirrhosis 4
- Lixivaptan (oral): normalized sodium in 27-50% of cirrhotic patients but high dropout rate (12/32) due to dehydration and hypotension 4
Special Considerations for Cirrhosis
- Hyponatremia in cirrhosis increases risk of spontaneous bacterial peritonitis (OR 3.40), hepatorenal syndrome (OR 3.45), and hepatic encephalopathy (OR 2.36) 3
- Patients with cirrhosis require more cautious correction (4-6 mmol/L per day) 3
- Hypertonic sodium chloride allows temporary elevation but worsens edema and ascites 4
ISOTONIC HYPONATREMIA (PSEUDOHYPONATREMIA)
Isotonic hyponatremia is caused by hyperproteinemia, hyperlipidemia, or hyperglycemia and does not require sodium correction—treat the underlying cause. 8
- This is a laboratory artifact, not true hyponatremia 8
- Serum osmolality is normal 8
- No specific sodium treatment needed 8
HYPERTONIC HYPONATREMIA
Hypertonic hyponatremia is most commonly caused by hyperglycemia; correct the underlying hyperglycemia and the sodium will normalize as glucose is corrected (sodium increases ~1.6 mEq/L for every 100 mg/dL decrease in glucose). 8
- Serum osmolality is elevated 8
- Treat the underlying cause (typically hyperglycemia) 8
- Sodium corrects as glucose normalizes 8
SEVERE SYMPTOMATIC HYPONATREMIA (EMERGENCY)
For severe symptoms (seizures, coma, altered mental status), immediately administer 3% hypertonic saline as 100 mL boluses over 10 minutes, repeatable up to three times at 10-minute intervals, with target correction of 6 mEq/L over 6 hours and maximum 8 mEq/L in 24 hours. 3, 1, 6
Administration Protocol
- Give 3% hypertonic saline: 100 mL over 10 minutes 3
- Can repeat up to three times at 10-minute intervals until symptoms improve 3
- Target: increase sodium by 4-6 mEq/L within 1-2 hours 6
- Maximum correction: 8 mEq/L in 24 hours (10 mEq/L absolute maximum) 3, 6
Monitoring Requirements
- Check sodium every 2 hours during initial correction 3
- ICU admission for close monitoring 3
- Watch for osmotic demyelination syndrome signs: dysarthria, dysphagia, oculomotor dysfunction, quadriparesis (typically 2-7 days post-correction) 3, 7
Contraindications to Hypertonic Saline
- Hypervolemic hyponatremia without life-threatening symptoms 3
- Heart failure with volume overload (relative contraindication) 3
CEREBRAL SALT WASTING (CSW) vs SIADH
Cerebral salt wasting requires volume and sodium replacement with isotonic or hypertonic saline plus fludrocortisone—NEVER fluid restriction—while SIADH requires fluid restriction; distinguish by volume status assessment. 3
Diagnostic Differentiation
- CSW: Evidence of volume depletion (hypotension, tachycardia, dry mucous membranes), urine sodium >20 mmol/L 3
- SIADH: Euvolemic (no edema, normal BP, normal skin turgor), urine sodium >20-40 mmol/L 3
- Both have high urine osmolality relative to serum 3
CSW Treatment
- Volume and sodium replacement (NOT fluid restriction) 3
- Isotonic or hypertonic saline based on severity 3
- Fludrocortisone for subarachnoid hemorrhage patients at risk of vasospasm 3
- Hydrocortisone to prevent natriuresis 3
Critical Pitfall
Using fluid restriction in CSW worsens outcomes and can lead to cerebral ischemia 3
MANAGEMENT OF OVERCORRECTION
If sodium correction exceeds 8 mmol/L in 24 hours, immediately discontinue current fluids, switch to D5W, and administer desmopressin to relower sodium levels. 3
Immediate Actions
- Stop all sodium-containing fluids 3
- Switch to D5W (5% dextrose in water) 3
- Administer desmopressin to slow/reverse rapid rise 3
- Target: bring total 24-hour correction to ≤8 mEq/L from starting point 3
High-Risk Populations for Osmotic Demyelination
- Advanced liver disease 3, 7
- Alcoholism 3, 7
- Malnutrition 3, 7
- Severe hyponatremia 3
- Hypophosphatemia, hypokalemia, hypoglycemia 3
PEDIATRIC CONSIDERATIONS
For hospitalized children 28 days to 18 years requiring maintenance IV fluids, use isotonic solutions with appropriate KCl and dextrose to prevent hyponatremia (AAP strong recommendation, evidence quality A). 4
Key Recommendations
- Isotonic fluids significantly decrease risk of developing hyponatremia 4
- Hypotonic fluids may be required for severe burns, voluminous diarrhea, or correcting hypernatremia 4
- Monitor electrolytes frequently in high-risk patients (post-major surgery, ICU, large GI losses, diuretic use) 4
Warning Signs Requiring Electrolyte Check
- Unexplained nausea, vomiting, headache 4
- Confusion or lethargy 4
- Any neurologic symptoms consistent with hyponatremic encephalopathy 4
COMMON PITFALLS TO AVOID
- Overly rapid correction (>8 mmol/L in 24 hours) causing osmotic demyelination syndrome 3
- Using fluid restriction in cerebral salt wasting instead of volume replacement 3
- Inadequate monitoring during active correction 3
- Using hypertonic saline in hypervolemic hyponatremia without life-threatening symptoms 3
- Ignoring mild hyponatremia (130-135 mmol/L) as clinically insignificant 3
- Failing to recognize and treat the underlying cause 3
- Administering isotonic fluids to patients with nephrogenic diabetes insipidus (causes hypernatremia) 4