What is the essential practice for managing hyponatremia?

Essential Practice for Managing Hyponatremia

The management of hyponatremia should be guided by the patient's volume status, symptom severity, and the rate of sodium decline, with correction rates not exceeding 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome. 1

Initial Assessment

• Classify hyponatremia (serum sodium <135 mmol/L) based on volume status (hypovolemic, euvolemic, or hypervolemic) and serum osmolality 1
• Obtain serum and urine osmolality, urine electrolytes, and uric acid to determine the underlying cause 1
• Assess symptom severity: mild (nausea, headache, weakness), moderate (confusion), or severe (seizures, coma) 2, 3
• Determine acuity of onset: acute (<48 hours) versus chronic (>48 hours) 1

Treatment Based on Symptom Severity

Severe Symptomatic Hyponatremia (Medical Emergency)

• For severe symptoms (seizures, coma), administer 3% hypertonic saline with an initial goal to correct 6 mmol/L over 6 hours or until symptoms resolve 1
• Maximum correction should not exceed 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome 1, 2
• Monitor serum sodium every 2 hours during initial correction 1
• Calculate sodium deficit using formula: Desired increase in Na (mEq/L) × (0.5 × ideal body weight in kg) 1

Mild to Moderate Symptomatic Hyponatremia

• For chronic hyponatremia, limit correction to <8 mmol/L per 24 hours 1
• Patients with advanced liver disease, alcoholism, malnutrition require more cautious correction (4-6 mmol/L per day) 1

Treatment Based on Volume Status

Hypovolemic Hyponatremia

• Discontinue diuretics and administer isotonic saline (0.9% NaCl) for volume repletion 1, 4
• A urinary sodium <30 mmol/L suggests hypovolemic hyponatremia and predicts response to 0.9% saline infusion 1

Euvolemic Hyponatremia (SIADH)

• Implement fluid restriction to 1L/day as first-line treatment 1, 2
• For resistant cases, consider:
  • Oral sodium chloride (100 mEq three times daily) 1
  • Urea 1, 2
  • Vasopressin receptor antagonists (tolvaptan, conivaptan) for short-term use 1, 5
  • Diuretics, lithium, or demeclocycline in selected cases 1
• Identify and treat underlying causes (medications, malignancy, pulmonary disorders) 1

Hypervolemic Hyponatremia (Heart Failure, Cirrhosis)

• Implement fluid restriction to 1-1.5 L/day for serum sodium <125 mmol/L 1
• For cirrhotic patients, consider albumin infusion alongside fluid restriction 1
• In heart failure with persistent severe hyponatremia despite water restriction and maximization of guideline-directed medical therapy, vasopressin antagonists may be considered in the short term 6
• Avoid hypertonic saline unless life-threatening symptoms are present 1

Special Considerations

Neurosurgical Patients

• Distinguish between SIADH and cerebral salt wasting (CSW), as treatment approaches differ significantly 1
• For CSW, focus on volume and sodium replacement, not fluid restriction 1
• Consider fludrocortisone for hyponatremia in subarachnoid hemorrhage patients 1
• Avoid fluid restriction in subarachnoid hemorrhage patients at risk of vasospasm 1

Cirrhotic Patients

• Hyponatremia reflects worsening hemodynamic status 1
• Serum Na ≤130 mEq/L increases risk for hepatic encephalopathy, hepatorenal syndrome, and spontaneous bacterial peritonitis 1
• Careful correction is needed to avoid osmotic demyelination syndrome 1

Managing Overcorrection

• If overcorrection occurs, consider relowering with electrolyte-free water or desmopressin 1
• Watch for signs of osmotic demyelination syndrome (dysarthria, dysphagia, oculomotor dysfunction, quadriparesis) typically occurring 2-7 days after rapid correction 1

Pharmacological Considerations

• Vasopressin antagonists (tolvaptan, conivaptan) can increase serum sodium levels but require careful monitoring 5, 2
• Common side effects include thirst (12%), dry mouth (7%), and polyuria (4%) 5
• Gastrointestinal bleeding was reported in 10% of cirrhotic patients treated with tolvaptan versus 2% with placebo 5
• Hypernatremia occurred in 1.7% of patients receiving tolvaptan versus 0.8% receiving placebo 5
• Osmotic demyelination syndrome has been reported with tolvaptan use 5

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
• Ignoring mild hyponatremia (130-135 mmol/L) as clinically insignificant 1, 2