How to manage hyponatremia in a child with Chronic Kidney Disease (CKD)?

Management of Hyponatremia in Children with CKD

Sodium supplementation, not restriction, is the primary intervention for hyponatremic children with CKD, as most pediatric CKD results from salt-wasting nephropathies that cause chronic sodium depletion despite normal or even low serum sodium levels. 1

Critical First Step: Identify the Underlying Mechanism

The management approach depends entirely on whether the child has:

Salt-Wasting CKD (Most Common in Pediatrics)

• Infants and children with polyuric salt-wasting forms of CKD (the most common pediatric CKD etiologies) develop hyponatremia from chronic sodium losses, not water retention. 1, 2
• These children present with vomiting, constipation, growth retardation, polyuria, and polydipsia due to chronic intravascular volume depletion. 2
• Normal serum sodium does NOT exclude sodium depletion—supplementation may still be required. 2

Non-Salt-Wasting CKD with True Hyponatremia

• Less common in children but can occur with advanced CKD stages or specific conditions
• Requires different management focused on water balance

Management Algorithm

For Salt-Wasting CKD (Primary Approach)

Sodium supplementation is indicated based on clinical symptoms (hypotension, hyponatremia, abnormal chloride) rather than serum sodium alone. 1

Dosing Guidelines:

• Provide 2-4 mmol sodium/100 mL formula (adjusted to 180-240 mL/kg/day) OR 1-5 mmol Na/kg body weight/day 1, 2
• Average effective dose: 3.2 ± 1.04 mmol/kg 1
• Adjust based on blood biochemistry results 1

Route of Administration:

• Nasogastric or gastrostomy tube feedings may be necessary during critical periods 1
• Home preparation using table salt is NOT recommended due to risk of formulation errors causing hypo- or hypernatremia 1
• Use commercially prepared sodium supplements 1

Special Considerations for Infants on Peritoneal Dialysis:

• All infants with CKD stage 5D on PD therapy should receive sodium supplements 1
• High ultrafiltration requirements remove significant sodium that cannot be replaced by breast milk (7 mmol/L) or standard formulas (7-8 mmol/L) 1
• Consequences of untreated hyponatremia include cerebral edema and blindness—neutral sodium balance must be maintained 1

Monitoring:

• Measure sodium balance (dietary/medication intake minus dialysate losses) every 6 months with dialysis adequacy assessments 1
• More frequent monitoring after significant dialysis prescription changes or clinical status changes 1
• Individualize therapy based on clinical symptoms, serum sodium, and chloride levels 1

For Non-Salt-Wasting CKD with True Water-Excess Hyponatremia

This scenario is less common but requires different management:

Fluid Management:

• Children with CKD stages 3-5 and 5D who are oligoanuric require fluid restriction to prevent complications 3
• Daily fluid allowance = insensible losses (20 mL/kg/day for children/adolescents OR 400 mL/m² body surface area) + urine output + replacement for additional losses 3
• Severe fluid restriction should be discouraged as it fosters malnutrition 3

Acute Symptomatic Hyponatremia:

• For severely symptomatic hyponatremia (seizures, coma, obtundation), administer 3% hypertonic saline bolus to increase serum sodium by 4-6 mEq/L within 1-2 hours 4
• Initial infusion rate (mL/kg/hour) = body weight (kg) × desired rate of sodium increase (mmol/L/hour) 5
• Maximum correction: 10-12 mEq/L in first 24 hours to avoid osmotic demyelination syndrome 4, 6
• In children with risk factors (hypokalemia, liver disease, malnutrition), limit correction to 10 mEq/L/24 hours 6

Chronic Asymptomatic Hyponatremia:

• Adequate solute intake (salt and protein) with initial fluid restriction of 500 mL/day adjusted to serum sodium levels 7
• Nearly half of SIADH patients do not respond to fluid restriction as first-line therapy 7
• Second-line options include oral urea or vaptans, though evidence in pediatrics is limited 7

Critical Pitfalls to Avoid

1. Assuming normal serum sodium excludes sodium depletion in polyuric CKD children—supplementation may still be needed 2
2. Failing to recognize that most pediatric CKD etiologies are salt-wasting conditions requiring supplementation, not restriction 2
3. Using home-prepared table salt supplements—formulation errors can cause dangerous hypo- or hypernatremia 1
4. Instituting sodium restriction too abruptly—this causes appetite loss and malnutrition 3
5. Overly rapid correction (>12 mEq/L/24 hours) in chronic hyponatremia—this causes osmotic demyelination syndrome 4, 6
6. Fluid restriction in salt-wasting nephropathy—this worsens outcomes 1

Sodium Restriction: Only for Hypertensive Children

Sodium restriction should ONLY be considered for children with CKD stages 2-5 and 5D who have hypertension (BP >95th percentile) or prehypertension 1

• Follow age-based Recommended Daily Intake for children with BP >90th percentile 1
• Target: 1-2 mmol/kg/day (equivalent to 1,500-2,400 mg/day for adults, scaled to child size) 1
• Dietary sodium restriction is NOT appropriate for patients with sodium-wasting nephropathy 1

Age-Appropriate Sodium Requirements for Reference

For children WITHOUT salt-wasting conditions 1, 8:

• 0-6 months: 120 mg/day
• 7-12 months: 370 mg/day
• 1-3 years: 1,000 mg/day
• 4-8 years: 1,200 mg/day
• 9-13 years: 1,500 mg/day
• 14-18 years: 1,500 mg/day

These targets are reversed in salt-wasting CKD—supplementation to the upper limits or beyond is required. 1