Neonatal Hyponatremia
Neonatal Hyponatremia
Neonatal hyponatremia is defined as serum sodium concentration <135 mEq/L in the newborn period. It represents one of the most common electrolyte disorders in neonates, particularly in premature infants.
Key Points
- Critical threshold: Severe hyponatremia is defined as <125 mEq/L
- Higher risk in premature infants (<34 weeks gestation)
- Can be acute (<48 hours) or chronic (>48 hours)
- Requires careful monitoring and gradual correction
Definition & Epidemiology
Classification based on severity:
- Mild: 130-134 mEq/L
- Moderate: 125-129 mEq/L
- Severe: <125 mEq/L
Epidemiology
- Incidence: 25-65% in NICU patients
- Risk factors:
- Prematurity
- Low birth weight
- Respiratory distress syndrome
- Patent ductus arteriosus
- Total parenteral nutrition
- Maternal hyponatremia
Pathophysiology
Common Mechanisms
- Excess water retention
- Sodium loss
- Inadequate sodium intake
Major Causes
- Non-osmotic ADH secretion
- Respiratory distress
- Mechanical ventilation
- Pain/stress
- CNS disorders
- Renal sodium losses
- Diuretic therapy
- Tubular dysfunction
- Salt-losing nephropathy
- Iatrogenic
- Hypotonic fluid administration
- Inadequate sodium supplementation
Diagnosis & Clinical Features
Clinical Presentation
- Neurological symptoms:
- Lethargy
- Hypotonia
- Seizures (in severe cases)
- Poor feeding
- Apnea
- Other features:
- Vomiting
- Temperature instability
- Respiratory distress
Diagnostic Workup
- Essential labs:
- Serum sodium
- Serum osmolality
- Urine sodium
- Urine osmolality
- Serum potassium
- Blood glucose
- Acid-base status
- Additional tests based on suspected etiology:
- Renal function tests
- Plasma ADH levels
- Head ultrasound
Management
General Principles
- Rate of correction:
- Maximum 8-10 mEq/L/24 hours
- Slower correction in chronic cases
- More rapid initial correction only if severe symptoms present
- Continuous monitoring of vital signs and neurological status
Specific Interventions
- Acute symptomatic hyponatremia:
- 3% hypertonic saline: 2-4 mL/kg over 15-30 minutes
- Target initial rise: 4-6 mEq/L
- Monitor sodium levels every 2-4 hours
- Chronic/asymptomatic hyponatremia:
- Fluid restriction if appropriate
- Sodium supplementation
- Treatment of underlying cause
Calculation Formulas
- Sodium deficit = (Desired Na - Current Na) × Weight in kg × 0.6
- 3% saline dose (mL) = (Desired increase in Na × Weight in kg × 0.6) ÷ 0.51
Complications & Monitoring
Potential Complications
- Acute complications:
- Cerebral edema
- Seizures
- Brainstem herniation
- Treatment-related complications:
- Central pontine myelinolysis (from rapid correction)
- Fluid overload
- Hypernatremia
Monitoring Parameters
- Frequent vital signs
- Neurological checks
- Serial electrolyte measurements
- Fluid balance
- Weight changes
Disclaimer
The notes provided on Pediatime are generated from online resources and AI sources and have been carefully checked for accuracy. However, these notes are not intended to replace standard textbooks. They are designed to serve as a quick review and revision tool for medical students and professionals, and to aid in theory exam preparation. For comprehensive learning, please refer to recommended textbooks and guidelines.
