How do I manage a patient with symptomatic hyponatremia?

Management of Symptomatic Hyponatremia

For symptomatic hyponatremia, immediately administer 3% hypertonic saline with a target correction of 6 mmol/L over 6 hours or until symptoms resolve, but never exceed 8 mmol/L total correction in 24 hours to prevent osmotic demyelination syndrome. 1

Immediate Assessment and Classification

Determine symptom severity first—this dictates urgency:

• Severe symptoms (seizures, coma, altered mental status, respiratory distress) require emergency hypertonic saline 1, 2
• Moderate symptoms (confusion, nausea, vomiting, headache, gait instability) warrant hospital admission with monitored correction 1, 3
• Mild symptoms (weakness, mild cognitive changes) can be managed more conservatively 3

Assess acuity of onset:

• Acute hyponatremia (<48 hours) can be corrected more rapidly without risk of osmotic demyelination 1, 4
• Chronic hyponatremia (>48 hours) requires slower, more cautious correction due to brain adaptation 1, 4

Emergency Treatment Protocol for Severe Symptoms

Administer 3% hypertonic saline immediately:

• Give 100-150 mL bolus over 10 minutes, which can be repeated up to 3 times at 10-minute intervals until symptoms improve 1
• Alternative: continuous infusion with initial rate calculated as body weight (kg) × desired rate of increase (mmol/L/hour) 5
• Target: 6 mmol/L correction over first 6 hours or until severe symptoms resolve 1, 6

Critical safety limit: Never exceed 8 mmol/L correction in 24 hours 1, 6, 2

• For high-risk patients (cirrhosis, alcoholism, malnutrition, prior encephalopathy), limit to 4-6 mmol/L per day 1, 6
• Monitor serum sodium every 2 hours during initial correction 1

Volume Status Assessment and Etiology-Based Management

After stabilizing severe symptoms, determine volume status to guide ongoing treatment:

Hypovolemic Hyponatremia

• Clinical signs: orthostatic hypotension, dry mucous membranes, decreased skin turgor, flat neck veins 1
• Urine sodium <30 mmol/L suggests extrarenal losses 1
• Treatment: Isotonic saline (0.9% NaCl) for volume repletion at 15-20 mL/kg/h initially, then 4-14 mL/kg/h based on response 1, 3
• Discontinue diuretics immediately 1

Euvolemic Hyponatremia (SIADH)

• Clinical signs: no edema, normal blood pressure, normal skin turgor 1
• Urine sodium >20-40 mmol/L with urine osmolality >300 mOsm/kg 1
• Treatment after acute phase:
  • Fluid restriction to 1 L/day as cornerstone 1, 2
  • If no response, add oral sodium chloride 100 mEq three times daily 1, 6
  • Consider urea or vaptans for resistant cases 1, 2, 7

Hypervolemic Hyponatremia (Heart Failure, Cirrhosis)

• Clinical signs: peripheral edema, ascites, jugular venous distention 1
• Treatment:
  • Fluid restriction to 1-1.5 L/day for sodium <125 mmol/L 1, 3
  • Discontinue diuretics temporarily if sodium <125 mmol/L 1
  • Consider albumin infusion in cirrhotic patients 1
  • Avoid hypertonic saline unless life-threatening symptoms as it worsens fluid overload 1

Special Considerations for Neurosurgical Patients

Distinguish between SIADH and Cerebral Salt Wasting (CSW)—they require opposite treatments:

• CSW characteristics: true hypovolemia, low CVP (<6 cm H₂O), urine sodium >20 mmol/L despite volume depletion 1
• CSW treatment: Volume and sodium replacement with isotonic or hypertonic saline, plus fludrocortisone 0.1-0.2 mg daily for severe cases 1
• Never use fluid restriction in CSW or subarachnoid hemorrhage patients at risk of vasospasm—this worsens outcomes 1

Monitoring Protocol

Intensive monitoring during active correction:

• Check serum sodium every 2 hours for severe symptoms 1
• Every 4 hours after symptom resolution 1
• Calculate sodium deficit: Desired increase (mEq/L) × (0.5 × ideal body weight in kg) 1, 6

Watch for osmotic demyelination syndrome (typically 2-7 days post-correction):

• Dysarthria, dysphagia, oculomotor dysfunction, quadriparesis 1
• If overcorrection occurs (>8 mmol/L in 24 hours), immediately switch to D5W and consider desmopressin to relower sodium 1, 8

Common Pitfalls to Avoid

• Never use fluid restriction as initial treatment for severely symptomatic hyponatremia—this is a medical emergency requiring hypertonic saline 1
• Never exceed 8 mmol/L correction in 24 hours for chronic hyponatremia—overcorrection causes osmotic demyelination 1, 2, 7
• Never use hypertonic saline in hypervolemic hyponatremia without life-threatening symptoms—it worsens fluid overload 1
• Never ignore mild hyponatremia (130-135 mmol/L)—it increases fall risk (21% vs 5%) and mortality (60-fold increase when <130 mmol/L) 1, 2
• Inadequate monitoring during active correction leads to overcorrection 1
• Using fluid restriction in cerebral salt wasting worsens outcomes 1