D5 0.3 NaCl vs D5 NSS: Composition and Clinical Implications
D5 0.3 NaCl contains 5% dextrose with 0.3% (51 mEq/L) sodium chloride, while D5 NSS contains 5% dextrose with 0.9% (154 mEq/L) sodium chloride—the key difference is the sodium concentration, which is critically important in a 2-year-old with complex febrile seizures given the association between hyponatremia and seizure recurrence.
Fluid Composition Differences
D5 0.3 NaCl (D5 1/3 NS)
- Contains 5% dextrose (50 g/L glucose)
- Contains 0.3% sodium chloride = 51 mEq/L sodium and 51 mEq/L chloride
- Osmolality approximately 320 mOsm/L
- Considered a hypotonic maintenance fluid
D5 NSS (D5 0.9% NaCl / D5 Normal Saline)
- Contains 5% dextrose (50 g/L glucose)
- Contains 0.9% sodium chloride = 154 mEq/L sodium and 154 mEq/L chloride
- Osmolality approximately 560 mOsm/L
- Considered an isotonic fluid
Critical Clinical Relevance for Complex Febrile Seizures
Hyponatremia and Seizure Risk
Hyponatremia significantly increases the risk of multiple convulsions during febrile illness, with children experiencing repeated seizures having the lowest sodium levels (134.20 ± 2.30 mmol/L) compared to those with simple febrile seizures (137.62 ± 2.63 mmol/L) 1
Children with complicated febrile convulsions have significantly lower sodium levels (136.07 ± 3.06 mmol/L) compared to those with simple convulsions (p < 0.01) 1
Fluid Selection in Complex Febrile Seizures
For a 2-year-old with complex febrile seizures, D5 NSS (isotonic fluid) is preferred over D5 0.3 NaCl to avoid exacerbating or inducing hyponatremia, which could lower seizure threshold and increase risk of recurrent seizures 1
The use of hypotonic fluids (like D5 0.3 NaCl) in children with active seizures or at risk for recurrent seizures should be avoided, as fever-related fluid and electrolyte disturbances already predispose to hyponatremia 1
Clinical Management Context
Immediate Assessment Requirements
Serum electrolytes, particularly sodium, should be measured in children with complex febrile seizures to guide fluid selection 1
Children with complex febrile seizures require hospital admission for complete evaluation, close observation, and appropriate fluid management 2
Seizure Management Priorities
Position the child laterally, protect the head, and remove dangerous objects during active seizure 3, 2
Administer benzodiazepines (lorazepam 0.05-0.1 mg/kg IV, maximum 4 mg) for seizures lasting >5 minutes 3, 2
Bacterial meningitis must be ruled out through lumbar puncture if there are meningeal signs, septic appearance, or behavioral disturbances, particularly in children under 12 months 2, 4
Common Pitfall to Avoid
The most critical error would be administering hypotonic fluids (D5 0.3 NaCl) to a child with complex febrile seizures without checking serum sodium levels, as this could precipitate further seizures by worsening hyponatremia 1. Always verify electrolyte status before selecting maintenance fluids in children with seizures.