What is the management of acute hyponatremia?

Management of Acute Hyponatremia

The treatment of acute hyponatremia should be based on symptom severity, with hypertonic saline (3%) as the first-line treatment for severe symptomatic cases, aiming for a correction of 6 mmol/L over 6 hours or until symptoms improve, while limiting total correction to 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome. 1

Initial Assessment and Classification

• Determine acuity of onset: acute (<48 hours) versus chronic (>48 hours) 1, 2
• Assess volume status to classify as hypovolemic, euvolemic, or hypervolemic hyponatremia 1, 3
• Evaluate symptom severity: mild (nausea, weakness, headache) versus severe (seizures, coma, respiratory distress) 1, 4
• Check serum and urine osmolality, urine electrolytes, and uric acid to determine underlying cause 1

Treatment Based on Symptom Severity

Severe Symptomatic Hyponatremia (seizures, coma)

• Administer 3% hypertonic saline with an initial goal to correct 6 mmol/L over 6 hours or until severe symptoms resolve 1
• Consider ICU admission for close monitoring during treatment 1
• Do not exceed total correction of 8 mmol/L over 24 hours to prevent osmotic demyelination syndrome 1, 3
• Monitor serum sodium every 2 hours during initial correction 1

Mild to Moderate Symptomatic Hyponatremia

• For chronic hyponatremia, avoid rapid correction exceeding 1 mmol/L/hour 1
• Patients with advanced liver disease, alcoholism, or malnutrition require more cautious correction (4-6 mmol/L per day) due to higher risk of osmotic demyelination 1, 2

Treatment Based on Volume Status and Etiology

Hypovolemic Hyponatremia

• Discontinue diuretics and administer isotonic saline (0.9% NaCl) for volume repletion 1, 4
• For severe dehydration with neurological symptoms, consider hypertonic saline with careful monitoring 1

Euvolemic Hyponatremia (SIADH)

• Fluid restriction to 1L/day for mild/asymptomatic cases 1, 3
• 3% hypertonic saline with careful monitoring for severe symptomatic cases 1
• Consider vasopressin receptor antagonists (tolvaptan) for resistant cases, starting at 15 mg once daily 1, 5
• Monitor for hypernatremia when using tolvaptan, as it occurred in 1.7% of patients in clinical trials 5

Hypervolemic Hyponatremia (cirrhosis, heart failure)

• Fluid restriction to 1000-1500 mL/day for moderate hyponatremia (Na 120-125 mmol/L) 1, 4
• More severe fluid restriction plus albumin infusion for severe hyponatremia (<120 mmol/L) 1
• Avoid hypertonic saline unless life-threatening symptoms are present, as it may worsen edema and ascites 1

Cerebral Salt Wasting (CSW)

• Focus on volume and sodium replacement rather than fluid restriction 1
• For severe symptoms, administer 3% hypertonic saline and consider fludrocortisone 1

Monitoring and Prevention of Complications

• Calculate sodium deficit using formula: Desired increase in Na (mEq/L) × (0.5 × ideal body weight in kg) 1
• For severe symptoms: monitor serum sodium every 2 hours during initial correction 1
• After resolution of severe symptoms, monitor every 4 hours 1
• If overcorrection occurs, consider relowering with electrolyte-free water or desmopressin 1, 2
• Watch for signs of osmotic demyelination syndrome (dysarthria, dysphagia, oculomotor dysfunction, quadriparesis) typically occurring 2-7 days after rapid correction 1, 6

Special Considerations

• In hyperglycemia-induced hyponatremia, calculate corrected sodium by adding 1.6 mEq/L to measured sodium for every 100 mg/dL of glucose above 100 mg/dL 7
• Patients with cirrhosis, serum Na ≤130 mEq/L have increased risk of hepatic encephalopathy, hepatorenal syndrome, and spontaneous bacterial peritonitis 1
• When using tolvaptan, avoid grapefruit juice and strong CYP3A inhibitors as they significantly increase tolvaptan exposure 5
• Tolvaptan is contraindicated with strong CYP3A inhibitors and should be avoided with moderate CYP3A inhibitors 5

Common Pitfalls to Avoid

• Overly rapid correction of chronic hyponatremia leading to osmotic demyelination syndrome 1, 2
• Inadequate monitoring during active correction 1
• Using fluid restriction in cerebral salt wasting, which can worsen outcomes 1
• Failing to recognize and treat the underlying cause 1, 8
• Using hypertonic saline in hypervolemic hyponatremia without life-threatening symptoms 1
• Failing to calculate corrected sodium in hyperglycemic states, leading to inappropriate fluid selection 7