How to correct sodium imbalance in patients with hyponatremia or hypernatremia?

Sodium Correction in Hyponatremia and Hypernatremia

Hyponatremia Management

The correction of hyponatremia must be guided by symptom severity, volume status, and chronicity, with the absolute rule that correction should never exceed 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome. 1

Initial Assessment

Determine three critical factors before initiating treatment:

• Symptom severity: Severe symptoms (seizures, coma, altered mental status) require immediate hypertonic saline, while mild symptoms or asymptomatic cases allow for more conservative approaches 1, 2
• Volume status: Classify as hypovolemic (dehydration, orthostatic hypotension), euvolemic (SIADH), or hypervolemic (heart failure, cirrhosis) through physical examination and urine studies 1, 3
• Chronicity: Acute (<48 hours) vs. chronic (>48 hours) determines safe correction rates, with chronic cases requiring slower correction 1, 4

Severe Symptomatic Hyponatremia (Medical Emergency)

For patients with seizures, coma, or severe neurological symptoms, immediately administer 3% hypertonic saline with a target correction of 6 mmol/L over 6 hours or until symptoms resolve. 1, 5

• Administer 100 mL boluses of 3% saline over 10 minutes, repeatable up to three times 1
• Monitor serum sodium every 2 hours during active correction 1
• Critical safety limit: Total correction must not exceed 8 mmol/L in 24 hours 1, 5, 6
• Once severe symptoms resolve, discontinue 3% saline and transition to protocols for mild symptoms 5
• After initial 6 mmol/L correction, limit additional correction to only 2 mmol/L in the following 18 hours 5

Treatment Based on Volume Status

Hypovolemic Hyponatremia

• Administer isotonic saline (0.9% NaCl) for volume repletion 1, 3
• Initial infusion rate: 15-20 mL/kg/hour, then 4-14 mL/kg/hour based on response 1
• Discontinue diuretics immediately if sodium <125 mmol/L 1
• Urine sodium <30 mmol/L predicts good response to saline (71-100% positive predictive value) 1

Euvolemic Hyponatremia (SIADH)

• First-line treatment: Fluid restriction to 1 L/day 1, 3
• If no response to fluid restriction, add oral sodium chloride 100 mEq three times daily 1, 7
• For persistent cases, consider vasopressin receptor antagonists (tolvaptan 15 mg daily, titrate to 30-60 mg) 1, 6
• Never use fluid restriction in subarachnoid hemorrhage patients at risk of vasospasm 1

Hypervolemic Hyponatremia (Heart Failure, Cirrhosis)

• Implement fluid restriction to 1-1.5 L/day for sodium <125 mmol/L 1, 3
• Temporarily discontinue diuretics if sodium <125 mmol/L 1
• For cirrhotic patients, consider albumin infusion alongside fluid restriction 1
• Avoid hypertonic saline unless life-threatening symptoms are present, as it worsens ascites and edema 1

Special Consideration: Cerebral Salt Wasting (CSW)

In neurosurgical patients, distinguish CSW from SIADH as they require opposite treatments. 1

• CSW requires volume and sodium replacement with isotonic or hypertonic saline, NOT fluid restriction 1
• For severe symptoms, use 3% hypertonic saline plus fludrocortisone (0.1-0.2 mg daily) in ICU 1
• Fluid restriction in CSW worsens outcomes 1

High-Risk Populations Requiring Slower Correction

Patients with advanced liver disease, alcoholism, malnutrition, or prior encephalopathy require even more cautious correction at 4-6 mmol/L per day, maximum 8 mmol/L in 24 hours. 1, 2

Management of Overcorrection

If sodium correction exceeds 8 mmol/L in 24 hours:

• Immediately discontinue current fluids and switch to D5W (5% dextrose in water) 1
• Consider administering desmopressin to slow or reverse the rapid rise 1
• Monitor closely for signs of osmotic demyelination syndrome (dysarthria, dysphagia, quadriparesis) typically occurring 2-7 days after rapid correction 1, 6

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Hypernatremia Management

Hypernatremia correction requires hypotonic fluids with a maximum correction rate of 10 mmol/L per 24 hours to prevent cerebral edema. 1

Fluid Selection

• Preferred fluid: 5% dextrose (D5W) as it delivers no renal osmotic load and allows controlled decrease in plasma osmolality 1
• Alternative: 0.45% NaCl (half-normal saline) for moderate hypernatremia 1
• Avoid isotonic saline (0.9% NaCl) in hypernatremia as it delivers excessive osmotic load and worsens the condition 1

Correction Rate

• Maximum correction: 0.4 mmol/L/hour or 10 mmol/L per 24 hours 1
• For severe hypernatremia, reduce sodium at 10-15 mmol/L per 24 hours 1
• Correction rates faster than 48-72 hours increase risk of pontine myelinolysis 1

Initial Fluid Administration

• Adults: 25-30 mL/kg/24 hours 1
• Children: 100 mL/kg/24 hours for first 10 kg, 50 mL/kg/24 hours for 10-20 kg, 20 mL/kg/24 hours for remaining weight 1

Special Considerations

• In nephrogenic diabetes insipidus, ongoing hypotonic fluid administration is required to match excessive free water losses 1
• Address underlying causes: replace ongoing losses from diarrhea/vomiting, ensure access to free water 1

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Common Pitfalls to Avoid

• Never correct chronic hyponatremia faster than 8 mmol/L in 24 hours - this causes osmotic demyelination syndrome 1, 2
• Inadequate monitoring during active correction leads to overcorrection 1
• Using fluid restriction in cerebral salt wasting worsens outcomes 1
• Failing to recognize and treat the underlying cause 1
• Using hypertonic saline in hypervolemic hyponatremia without life-threatening symptoms 1
• Ignoring mild hyponatremia (130-135 mmol/L) as clinically insignificant - even mild hyponatremia increases fall risk and mortality 1, 2