What is the approach for correcting hyponatremia?

Approach to Correcting Hyponatremia

The correction of hyponatremia should be guided by symptom severity, onset timing, and underlying cause, with a maximum increase of 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome. 1

Initial Assessment

• Evaluate hyponatremia based on volume status (hypovolemic, euvolemic, hypervolemic) and serum osmolality 1
• Obtain serum and urine osmolarity, urine electrolytes, and uric acid to determine the underlying cause 1
• Assess symptom severity to guide treatment approach and correction rate 2, 1

Correction Rate Guidelines

Severe Symptomatic Hyponatremia (seizures, coma, altered mental status)

• Correct by 6 mmol/L over 6 hours or until severe symptoms improve using 3% hypertonic saline 2, 1
• Do not exceed total correction of 8 mmol/L over 24 hours (if 6 mmol/L is corrected in first 6 hours, limit to only 2 mmol/L in the following 18 hours) 2, 1
• Monitor serum sodium every 2 hours initially in ICU setting 3
• Calculate sodium deficit using formula: Desired increase in Na (mEq/L) × (0.5 × ideal body weight in kg) 1

Mild Symptomatic Hyponatremia (nausea, vomiting, headache)

• Implement fluid restriction to 1 L/day 2, 1
• Monitor serum sodium every 4 hours 3
• Consider oral sodium supplementation if no response to fluid restriction 1

Asymptomatic Hyponatremia

• For chronic asymptomatic hyponatremia, avoid rapid correction exceeding 1 mmol/L/hour 2
• Implement fluid restriction with adequate solute intake (salt and protein) 1, 4
• For patients with advanced liver disease, use more conservative correction rates (4-6 mmol/L per day) 1

Treatment Based on Underlying Cause

SIADH (Syndrome of Inappropriate ADH)

• First-line treatment: Fluid restriction to 1 L/day for mild/asymptomatic cases 1, 3
• For severe symptoms: 3% hypertonic saline with careful monitoring 3
• If no response to fluid restriction, add oral sodium chloride 100 mEq three times daily 1
• Consider tolvaptan for refractory cases, but must be initiated in hospital setting 5

Cerebral Salt Wasting (CSW)

• Focus on volume and sodium replacement rather than fluid restriction 1
• For severe symptoms: ICU admission with 3% hypertonic saline and fludrocortisone 2, 1
• When symptoms resolve, transition to mild symptom or asymptomatic protocol 6

Hypovolemic Hyponatremia

• Discontinue diuretics if applicable 1
• Administer isotonic saline (0.9% NaCl) for volume repletion 1

Hypervolemic Hyponatremia (cirrhosis, heart failure)

• Implement fluid restriction to 1000-1500 mL/day 1
• Consider albumin infusion for patients with cirrhosis 1
• Avoid hypertonic saline unless life-threatening symptoms are present 1

Monitoring and Safety

• Discontinue 3% normal saline when severe symptoms resolve 6
• After discontinuation, switch to mild symptom protocol or asymptomatic protocol 6
• Continue treatment until sodium reaches 131 mmol/L (exception: subarachnoid hemorrhage patients receive treatment even for sodium levels of 131-135 mmol/L) 6
• For tolvaptan, initiate only in hospital setting where serum sodium can be closely monitored 5

Common Pitfalls to Avoid

• Overly rapid correction of chronic hyponatremia leading to osmotic demyelination syndrome 1, 5
• Inadequate monitoring during active correction 1
• Using fluid restriction in cerebral salt wasting (can worsen outcomes) 1
• Failing to recognize and treat the underlying cause 1
• Using hypertonic saline in hypervolemic hyponatremia without life-threatening symptoms 1

Special Considerations

• Patients with malnutrition, alcoholism, or advanced liver disease require more cautious correction rates (4-6 mmol/L per day) 1, 5
• A retrospective study showed higher mortality in patients with severe hyponatremia (<115 mmol/L) who had slower correction rates 7
• Tolvaptan should not be administered for more than 30 days to minimize risk of liver injury 5