Serum Electrolytes in Pediatric Practice
Serum Electrolytes in Pediatric Practice
Serum electrolytes are essential ions in body fluids that maintain proper hydration, blood pH, nerve conduction, and muscle contraction. Regular monitoring is crucial in pediatric practice.
Key Points
- Critical for homeostasis and cellular function
- Age-specific reference ranges differ from adults
- Essential for assessment of dehydration and acid-base disorders
- Regular monitoring needed in chronic conditions
Common Indications
- Acute gastroenteritis with dehydration
- Diabetic ketoacidosis
- Seizure disorders
- Renal disorders
- Medication monitoring (diuretics, steroids)
Reference Ranges by Age
Newborns (0-30 days)
- Sodium: 134-144 mEq/L
- Potassium: 3.5-5.5 mEq/L
- Chloride: 96-106 mEq/L
- Bicarbonate: 20-28 mEq/L
Infants (1-12 months)
- Sodium: 135-145 mEq/L
- Potassium: 3.5-6.0 mEq/L
- Chloride: 98-108 mEq/L
- Bicarbonate: 18-26 mEq/L
Children (1-18 years)
- Sodium: 135-145 mEq/L
- Potassium: 3.5-5.0 mEq/L
- Chloride: 98-108 mEq/L
- Bicarbonate: 22-28 mEq/L
Sodium (Na+)
Clinical Significance
Primary extracellular cation essential for maintaining fluid balance, nerve conduction, and muscle contraction.
Hypernatremia (>145 mEq/L)
- Common Causes:
- Dehydration
- Diabetes insipidus
- Excessive sodium intake
- Hyperaldosteronism
- Clinical Features:
- Irritability
- Hyperthermia
- Seizures
- Altered consciousness
- Management Principles:
- Gradual correction (≤10 mEq/L/24h)
- Calculate free water deficit
- Monitor neurological status
Hyponatremia (<135 mEq/L)
- Common Causes:
- SIADH
- Gastroenteritis
- Adrenal insufficiency
- Excessive water intake
- Clinical Features:
- Lethargy
- Headache
- Nausea
- Seizures in severe cases
- Management Principles:
- Assess volume status
- Correct underlying cause
- 3% saline for severe symptomatic cases
Potassium (K+)
Clinical Significance
Primary intracellular cation crucial for cardiac conduction, muscle function, and cellular metabolism.
Hyperkalemia (>5.5 mEq/L)
- Common Causes:
- Renal failure
- Acidosis
- Tissue breakdown
- Medications (ACE inhibitors, K-sparing diuretics)
- Clinical Features:
- Muscle weakness
- Cardiac arrhythmias
- ECG changes (peaked T waves, prolonged PR)
- Emergency Management:
- Calcium gluconate for cardiac protection
- Insulin with glucose
- Beta-agonists
- Kayexalate in non-urgent cases
Hypokalemia (<3.5 mEq/L)
- Common Causes:
- Gastrointestinal losses
- Diuretic therapy
- Metabolic alkalosis
- Poor intake
- Clinical Features:
- Muscle weakness
- Cardiac arrhythmias
- ECG changes (U waves, ST depression)
- Management:
- Oral replacement preferred when possible
- IV replacement in severe cases
- Maximum rate 0.5 mEq/kg/hr
Chloride (Cl-)
Clinical Significance
Major extracellular anion important for acid-base balance and osmotic pressure regulation.
Key Aspects
- Usually follows sodium concentration
- Critical for assessment of acid-base disorders
- Important in calculating anion gap
High Chloride (>108 mEq/L)
- Causes:
- Dehydration
- Renal tubular acidosis
- Excessive saline administration
- Clinical Implications:
- Hyperchloremic metabolic acidosis
- Respiratory compensation
- May affect renal function
Low Chloride (<98 mEq/L)
- Causes:
- Vomiting
- Diuretic use
- Metabolic alkalosis
- Clinical Implications:
- May indicate volume depletion
- Associated with metabolic alkalosis
- Check urine chloride for differentiation
Bicarbonate (HCO3-)
Clinical Significance
Major buffer in blood pH regulation and critical component in acid-base balance assessment.
High Bicarbonate (>28 mEq/L)
- Causes:
- Metabolic alkalosis
- Respiratory acidosis compensation
- Vomiting
- Diuretic use
- Evaluation:
- Check blood pH
- Assess respiratory rate
- Calculate anion gap
Low Bicarbonate (<22 mEq/L)
- Causes:
- Metabolic acidosis
- Respiratory alkalosis compensation
- Diarrhea
- Renal tubular acidosis
- Evaluation:
- Calculate anion gap
- Assess respiratory compensation
- Check urine pH
Clinical Cases and Pearls
Case Studies
Case 1: Diabetic Ketoacidosis
- Typical Findings:
- ↓ HCO3- (metabolic acidosis)
- ↑ K+ (despite total body deficit)
- ↑ Na+ (hyperglycemia correction)
Case 2: Severe Gastroenteritis
- Common Pattern:
- ↓ HCO3- (bicarbonate loss)
- ↓ K+ (GI losses)
- ↑ Na+ (dehydration)
Clinical Pearls
- Always interpret electrolytes with clinical context
- Consider medication effects on electrolyte balance
- Serial monitoring often more valuable than single measurements
- Calculate corrected sodium in hyperglycemia
- Consider pseudo-hyponatremia in hyperlipidemia
