Grades of Hyponatremia and Treatment in Children
Classification by Severity
Hyponatremia in children is classified into three grades based on serum sodium concentration: mild (130-134 mmol/L), moderate (125-129 mmol/L), and severe (<125 mmol/L), with treatment intensity escalating according to both the sodium level and symptom severity. 1, 2
Mild Hyponatremia (130-134 mmol/L)
- Serum sodium 130-134 mmol/L with minimal or no symptoms 1, 2
- May present with subtle findings: nausea, mild weakness, headache, or minor neurocognitive deficits 2
- Often discovered incidentally on laboratory testing 3
Moderate Hyponatremia (125-129 mmol/L)
- Serum sodium 125-129 mmol/L with more pronounced symptoms 1, 2
- Clinical features include lack of concentration, nausea, forgetfulness, apathy, and loss of balance 3
- Increased risk of falls and attention deficits 1
Severe Hyponatremia (<125 mmol/L)
- Serum sodium <125 mmol/L or <120 mmol/L depending on classification system 1, 2, 3
- Life-threatening symptoms: delirium, confusion, impaired consciousness, ataxia, seizures, coma, and rarely brain herniation 2, 3
- Requires emergency intervention regardless of symptom presence 2
Critical Distinction: Acute vs. Chronic
The rate of sodium decline determines symptom severity more than the absolute sodium value—acute hyponatremia (<48 hours) causes cerebral edema and severe neurological symptoms, while chronic hyponatremia (>48 hours) allows brain adaptation with fewer symptoms but higher risk of osmotic demyelination if corrected rapidly. 4, 5, 3
- Acute hyponatremia (<48 hours): Brain water increases, causing encephalopathy of varying severity 4
- Chronic hyponatremia (>48 hours): Osmoregulatory mechanisms normalize brain water content, reducing symptoms 4
- Rapid correction of chronic hyponatremia risks osmotic demyelination syndrome 4, 6
Treatment Algorithm by Grade and Symptoms
Severe Symptomatic Hyponatremia (Emergency)
For children with seizures, altered consciousness, or coma, immediately administer 3% hypertonic saline as a 100 mL bolus (or 2 mL/kg) over 10-15 minutes, repeatable up to 3 times at 10-minute intervals, targeting a 6 mmol/L increase over the first 6 hours. 7, 2, 6
- Initial bolus: 3% hypertonic saline 2 mL/kg over 10-15 minutes intravenously 6
- Repeat dosing: Up to 2 additional boluses if no improvement 6
- Target correction: Increase sodium by 4-6 mmol/L over 10-15 minutes in symptomatic patients 4
- Maximum limit: Never exceed 8 mmol/L correction in any 24-hour period 7, 2
- Monitoring: Check serum sodium every 2 hours during active correction 7
Moderate Hyponatremia (125-129 mmol/L) Without Severe Symptoms
Treatment depends on volume status assessment—look for dry mucous membranes, decreased skin turgor, and orthostatic changes (hypovolemic), versus edema and ascites (hypervolemic), versus normal examination (euvolemic). 7, 5
Hypovolemic Hyponatremia
- Administer isotonic saline (0.9% NaCl) for volume repletion 7, 2
- Initial rate: 15-20 mL/kg/h, then 4-14 mL/kg/h based on response 7
- Never use hypotonic fluids (0.45% saline, D5W) as they worsen hyponatremia 7, 6
Euvolemic Hyponatremia (SIADH)
- Fluid restriction to 80-100 mL/kg/day for ages 1-3 years 7
- Ensure adequate sodium intake: 1,000 mg/day (43 mmol/day) for ages 1-3 years 7
- Increase dietary protein to boost solute load and promote free water excretion 7
Hypervolemic Hyponatremia (Heart Failure, Cirrhosis)
- Fluid restriction to 80-100 mL/kg/day 7
- Treat underlying condition (heart failure management, diuretic adjustment) 2
- Avoid hypertonic saline unless life-threatening symptoms present 1
Mild Hyponatremia (130-134 mmol/L)
For asymptomatic children with sodium 130-134 mmol/L, reassess fluid therapy appropriateness and monitor sodium levels without aggressive intervention, as most cases resolve with correction of underlying causes. 8, 7
- No emergency treatment required for asymptomatic mild hyponatremia 8
- Use isotonic maintenance fluids (0.9% NaCl) in hospitalized children to prevent worsening 8, 7
- Monitor sodium every 24-48 hours initially 7
- Identify and address underlying causes: medications (diuretics, SSRIs), excessive free water intake, or underlying illness 5, 2
Universal Correction Rate Guidelines
The absolute maximum sodium correction is 8 mmol/L in any 24-hour period for all children, with a safer target of 4-6 mmol/L per day to prevent osmotic demyelination syndrome, which causes devastating neurological injury. 7, 4, 2
- Standard correction rate: 4-8 mmol/L per 24 hours 7
- Absolute maximum: 8 mmol/L in 24 hours—never exceed this limit 7, 4, 2
- High-risk populations (neonates, preterm infants <34 weeks): Slower correction over 48-72 hours 7
- Osmotic demyelination syndrome presents 2-7 days after rapid correction with dysarthria, dysphagia, quadriparesis 1
Maintenance Fluid Selection in Hospitalized Children
All hospitalized children ages 28 days to 18 years requiring maintenance IV fluids should receive isotonic solutions (0.9% NaCl) with appropriate KCl and dextrose to prevent hospital-acquired hyponatremia, which affects 15-30% of children receiving hypotonic fluids. 8, 7
- Isotonic fluids prevent hyponatremia: Number needed to treat = 7.5 to prevent any hyponatremia, 27.8 to prevent moderate hyponatremia 8
- Never use hypotonic fluids (0.45% saline, 0.18% saline, lactated Ringer's) for maintenance 8, 7
- Hypotonic fluids increase risk >5-fold in children with elevated ADH (postoperative, pneumonia, CNS disorders) 9
Monitoring Requirements
During active sodium correction, check serum sodium every 2 hours initially, then every 4-6 hours once stable, while tracking daily weight, urine output, and specific gravity to assess fluid balance and prevent overcorrection. 7
- Severe symptoms: Serum sodium every 2 hours during initial correction 7
- After stabilization: Every 4-6 hours 7
- Daily monitoring: Weight, urine output, urine specific gravity 7
- Watch for overcorrection: If sodium rises >8 mmol/L in 24 hours, stop current fluids and consider D5W or desmopressin 1
Common Pitfalls to Avoid
- Never correct chronic hyponatremia faster than 8 mmol/L in 24 hours—this causes irreversible osmotic demyelination 7, 4
- Never use hypotonic maintenance fluids in hospitalized children—isotonic fluids prevent hyponatremia without causing hypernatremia 8, 7
- Never delay emergency treatment while pursuing diagnostic workup in symptomatic patients 2
- Never assume mild hyponatremia is benign—even sodium 130-134 mmol/L increases fall risk and mortality in certain populations 1
- Never rely on physical examination alone to assess volume status—sensitivity only 41%, specificity 80% 1