How to manage a patient with severe hyponatremia, serum sodium level of 118 mmol/L, and potential for neurological complications?

Management of Severe Hyponatremia (Sodium 118 mmol/L)

A serum sodium of 118 mmol/L represents severe hyponatremia requiring immediate hospital admission with urgent intervention, particularly if the patient has any neurological symptoms. 1

Immediate Assessment and Risk Stratification

Determine symptom severity first—this dictates your entire treatment approach. 1

Severe Symptoms (Medical Emergency)

• Seizures, coma, altered mental status, confusion, somnolence, obtundation, or cardiorespiratory distress 1, 2
• These patients require immediate 3% hypertonic saline—do not delay for diagnostic workup 1, 3

Mild/Moderate Symptoms

• Nausea, vomiting, headache, weakness, gait instability 1, 4
• These patients need urgent but more measured correction 1

Asymptomatic

• Rare at sodium 118 mmol/L, but if truly asymptomatic, slower correction is safer 1

Emergency Treatment for Severe Symptoms

Administer 100 mL of 3% hypertonic saline IV over 10 minutes immediately. 3

• Repeat the 100 mL bolus every 10 minutes if severe symptoms persist, up to three total boluses 3
• Target: Increase sodium by 4-6 mEq/L in the first 1-2 hours or until severe symptoms resolve 3, 2
• Critical safety limit: Total correction must NOT exceed 8 mmol/L in 24 hours 1, 5, 3

Monitoring During Acute Correction

• Check serum sodium every 2 hours during initial correction phase 1, 3
• Monitor strict intake/output and daily weights 3
• Watch for signs of osmotic demyelination syndrome (dysarthria, dysphagia, oculomotor dysfunction, quadriparesis) 1, 6

When to Stop 3% Saline

Discontinue 3% saline when: 5

• Severe symptoms resolve, OR
• Sodium increases by 6 mmol/L over 6 hours, OR
• Sodium reaches 125-130 mmol/L 5

After initial 6 mmol/L correction, limit additional correction to only 2 mmol/L in the following 18 hours. 5, 3

Determining the Underlying Cause

While treating, simultaneously assess volume status and obtain key labs—but never delay treatment. 1, 4

Volume Status Assessment

• Hypovolemic: Orthostatic hypotension, dry mucous membranes, decreased skin turgor, flat neck veins 1
• Euvolemic: No edema, normal blood pressure, normal skin turgor 1
• Hypervolemic: Peripheral edema, ascites, jugular venous distention, pulmonary congestion 1

Essential Laboratory Tests

• Serum osmolality (should be low, <275 mOsm/kg) 1
• Urine osmolality and urine sodium 1
• Serum uric acid (<4 mg/dL suggests SIADH with 73-100% positive predictive value) 1
• TSH and cortisol to rule out hypothyroidism/adrenal insufficiency 1

Treatment Based on Volume Status (After Acute Phase)

Hypovolemic Hyponatremia

• Discontinue diuretics immediately 1
• Administer isotonic saline (0.9% NaCl) for volume repletion 1
• Urine sodium <30 mmol/L predicts good response to saline (71-100% positive predictive value) 1

Euvolemic Hyponatremia (SIADH)

• Fluid restriction to 1 L/day is the cornerstone of treatment 1, 5
• If no response to fluid restriction, add oral sodium chloride 100 mEq three times daily 1
• For resistant cases, consider vaptans (tolvaptan 15 mg once daily, titrate to 30-60 mg) 1, 6
  • Warning: Tolvaptan should only be initiated in hospital with close sodium monitoring 6
  • Limit tolvaptan use to 30 days maximum due to hepatotoxicity risk 6

Hypervolemic Hyponatremia (Heart Failure, Cirrhosis)

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

Critical Correction Rate Guidelines

The single most important safety principle: Never exceed 8 mmol/L correction in 24 hours. 1, 5, 3, 7

Standard Patients

• Target: 4-8 mmol/L per day, maximum 10-12 mmol/L in 24 hours 1

High-Risk Patients (Require Slower Correction)

Patients with advanced liver disease, alcoholism, malnutrition, or prior encephalopathy require even more cautious correction: 4-6 mmol/L per day, maximum 8 mmol/L in 24 hours. 1, 6, 8

Why This Matters

• Overcorrection >12 mmol/L per 24 hours causes osmotic demyelination syndrome 6, 8
• This results in dysarthria, mutism, dysphagia, lethargy, spastic quadriparesis, seizures, coma, or death 6
• Symptoms typically appear 2-7 days after rapid correction 1

Special Considerations for Neurosurgical Patients

In patients with CNS pathology, distinguish SIADH from cerebral salt wasting (CSW)—they require opposite treatments. 1

SIADH Characteristics

• Euvolemic state, urine sodium >20-40 mmol/L, urine osmolality >300 mOsm/kg 1
• Treatment: Fluid restriction 1

Cerebral Salt Wasting Characteristics

• True hypovolemia (low CVP <6 cm H₂O), urine sodium >20 mmol/L despite volume depletion 1
• Treatment: Volume and sodium replacement with isotonic or hypertonic saline 1
• For severe symptoms: 3% hypertonic saline plus fludrocortisone 0.1-0.2 mg daily 1
• Never use fluid restriction in CSW—this worsens outcomes 1, 3

Management of Overcorrection

If sodium correction exceeds 8 mmol/L in 24 hours, act immediately: 1

• Discontinue current fluids and switch to D5W (5% dextrose in water) 1
• Consider administering desmopressin to slow or reverse the rapid rise 1, 8
• Goal: Bring total 24-hour correction to no more than 8 mmol/L from starting point 1

Common Pitfalls to Avoid

• Never use fluid restriction as initial treatment for severe symptomatic hyponatremia—this is a medical emergency requiring hypertonic saline 3
• Never correct chronic hyponatremia faster than 8 mmol/L in 24 hours 1, 7
• Never use fluid restriction in subarachnoid hemorrhage patients at risk of vasospasm 1, 3
• Never use hypertonic saline in hypervolemic hyponatremia without life-threatening symptoms 1
• Never ignore mild hyponatremia (130-135 mmol/L) as clinically insignificant—it increases fall risk and mortality 1, 2
• Inadequate monitoring during active correction leads to osmotic demyelination syndrome 1

Post-Acute Monitoring

• After severe symptoms resolve, check sodium every 4 hours instead of every 2 hours 5
• Continue monitoring daily until sodium stabilizes above 130 mmol/L 1
• Watch for biphasic neurologic deterioration (improvement followed by worsening on days 2-6) 7