How to manage acute hyponatremia (low sodium levels) of 126 mmol/L?

Management of Acute Hyponatremia at 126 mmol/L

For acute hyponatremia at 126 mmol/L, immediately assess symptom severity and volume status to determine treatment urgency—if severe symptoms (seizures, altered mental status, coma) are present, administer 3% hypertonic saline targeting 6 mmol/L correction over 6 hours; if asymptomatic or mildly symptomatic, treatment depends on whether the patient is hypovolemic, euvolemic, or hypervolemic. 1

Immediate Assessment Required

Determine if symptoms are severe:

• Severe symptoms include seizures, coma, altered mental status, confusion, or cardiorespiratory distress 1, 2
• Mild symptoms include nausea, vomiting, headache, weakness, or mild cognitive changes 2, 3
• Even at 126 mmol/L, this represents moderate hyponatremia requiring intervention 1, 2

Assess volume status through physical examination:

• Hypovolemic signs: orthostatic hypotension, dry mucous membranes, decreased skin turgor, flat neck veins 1
• Euvolemic signs: normal blood pressure, no edema, normal skin turgor 1
• Hypervolemic signs: peripheral edema, ascites, jugular venous distention 1

Treatment Based on Symptom Severity

For Severe Symptomatic Hyponatremia (Medical Emergency)

Administer 3% hypertonic saline immediately:

• Give 100 mL bolus over 10 minutes, can repeat up to 3 times at 10-minute intervals until symptoms improve 1
• Target correction of 6 mmol/L over first 6 hours or until severe symptoms resolve 1, 2
• Critical safety limit: Never exceed 8 mmol/L correction in 24 hours to prevent osmotic demyelination syndrome 1, 3

Monitoring during acute correction:

• Check serum sodium every 2 hours during initial correction phase 1
• Once severe symptoms resolve, check every 4 hours 1
• ICU admission is recommended for close monitoring 1

For Asymptomatic or Mildly Symptomatic Hyponatremia

Treatment depends on volume status:

Hypovolemic hyponatremia (volume depletion):

• Discontinue diuretics immediately 1
• Administer isotonic saline (0.9% NaCl) for volume repletion 1, 2
• Initial infusion rate: 15-20 mL/kg/h, then 4-14 mL/kg/h based on response 1
• Urine sodium <30 mmol/L predicts good response to saline (71-100% positive predictive value) 1

Euvolemic hyponatremia (likely SIADH):

• Fluid restriction to 1 L/day is cornerstone of treatment 1, 2
• If no response to fluid restriction, add oral sodium chloride 100 mEq three times daily 1
• Consider vasopressin receptor antagonists (tolvaptan 15 mg daily) for resistant cases 1, 4
• Avoid hypotonic fluids which will worsen hyponatremia 1

Hypervolemic hyponatremia (heart failure, cirrhosis):

• Implement fluid restriction to 1-1.5 L/day 1, 2
• Discontinue diuretics temporarily if sodium <125 mmol/L 1
• For cirrhotic patients, consider albumin infusion alongside fluid restriction 1
• Avoid hypertonic saline unless life-threatening symptoms present, as it worsens edema and ascites 1

Critical Correction Rate Guidelines

Standard correction rates to prevent osmotic demyelination syndrome:

• Maximum 8 mmol/L in 24 hours for most patients 1, 3
• For high-risk patients (advanced liver disease, alcoholism, malnutrition, prior encephalopathy): limit to 4-6 mmol/L per day 1
• Acute hyponatremia (<48 hours) can be corrected more rapidly than chronic 1
• Chronic hyponatremia (>48 hours or unknown duration) requires slower correction 1, 5

Calculating Sodium Deficit

Use this formula to guide replacement:

• Sodium deficit = Desired increase in Na (mEq/L) × (0.5 × ideal body weight in kg) 1
• This helps determine appropriate volume of hypertonic saline needed 1

Common Pitfalls to Avoid

Never correct too rapidly:

• Overcorrection exceeding 8 mmol/L in 24 hours causes osmotic demyelination syndrome 1, 3
• Symptoms of osmotic demyelination (dysarthria, dysphagia, oculomotor dysfunction, quadriparesis) typically occur 2-7 days after rapid correction 1

If overcorrection occurs:

• Immediately discontinue current fluids and switch to D5W (5% dextrose in water) 1
• Consider administering desmopressin to slow or reverse rapid sodium rise 1

Do not use fluid restriction in certain situations:

• Never use fluid restriction in cerebral salt wasting—this worsens outcomes 1
• Avoid fluid restriction in subarachnoid hemorrhage patients at risk of vasospasm 1

Distinguish SIADH from cerebral salt wasting in neurosurgical patients:

• SIADH: euvolemic, treat with fluid restriction 1
• Cerebral salt wasting: hypovolemic, treat with volume and sodium replacement 1
• Using wrong treatment approach can be harmful 1

Special Populations

Patients with cirrhosis:

• Require more cautious correction (4-6 mmol/L per day maximum) 1
• Hyponatremia increases risk of spontaneous bacterial peritonitis (OR 3.40), hepatorenal syndrome (OR 3.45), and hepatic encephalopathy (OR 2.36) 1
• Tolvaptan carries higher risk of gastrointestinal bleeding in cirrhosis (10% vs 2% placebo) 4

Patients with advanced liver disease, alcoholism, or malnutrition:

• Higher risk for osmotic demyelination syndrome 1
• Limit correction to 4-6 mmol/L per day, maximum 8 mmol/L in 24 hours 1