5.2 Febrile Seizures & Childhood Dehydration

Febrile Seizures and Pediatric Fluid Management

Febrile seizures and acute dehydration are two of the most frequent challenges encountered in pediatric emergency medicine. Both conditions demand a precise clinical approach: distinguishing benign febrile episodes from life-threatening neurological infections, and accurately grading volume depletion to calculate fluid resuscitation and maintenance rates. Because infants and young children have a high surface-area-to-mass ratio, a high metabolic rate, and an immature renal concentrating capacity, they are exceptionally vulnerable to rapid fluid losses.

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Febrile Seizures: Classification and Diagnostics

A febrile seizure is defined as a seizure occurring in infancy or childhood (typically between 6 and 60 months of age), associated with a fever (>38.0°C or 100.4°F), in the absence of a central nervous system (CNS) infection, systemic metabolic derangement, or a history of prior afebrile seizures. They occur in 2–5% of children in North America and Europe, and up to 10% in Asian countries.

Simple vs. Complex Febrile Seizures

Clinicians must categorize febrile seizures as either simple or complex, as this classification guides diagnostic workup, treatment, and prognosis.

Diagnostic Evaluation

The primary clinical objective is to identify the source of the fever and exclude CNS infections.

• Lumbar Puncture (LP): An LP is not routinely indicated for simple febrile seizures. It should be performed immediately if there are clinical signs of meningitis or encephalitis (e.g., neck stiffness, Kernig's or Brudzinski's signs, bulging fontanelle, persistent altered mental status, or toxic appearance). An LP is also strongly considered in infants aged 6–12 months if their immunization status for Haemophilus influenzae type B (Hib) or Streptococcus pneumoniae is incomplete or unknown.
• Laboratory and Imaging: Routine blood tests, electroencephalograms (EEGs), and neuroimaging (CT/MRI) are not indicated for a child with a simple febrile seizure who has returned to baseline.

Management and Prognosis

• Acute Seizure Control: Most febrile seizures terminate before medical attention is received. If a seizure lasts longer than 5 minutes, administer a rescue benzodiazepine: intravenous diazepam (0.2 mg/kg), rectal diazepam (0.2–0.5 mg/kg), or intranasal midazolam (0.2 mg/kg).
• Antipyretics: Acetaminophen (10–15 mg/kg every 4–6 hours) or Ibuprofen (5–10 mg/kg every 6 hours) reduce fever and improve comfort. Crucial Exam Concept: Antipyretics do not prevent the recurrence of febrile seizures, as the seizure is triggered by the rapid rise or presence of fever rather than the absolute peak.
• Counseling: Reassure parents that simple febrile seizures are benign, do not cause brain damage or cognitive decline, and carry only a minor increase in the risk of developing epilepsy (1–2% compared to 1% in the general population). The recurrence rate of another febrile seizure is approximately 30–35%.

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Clinical Assessment of Dehydration

Pediatric dehydration is categorized based on the estimated percentage of fluid volume loss:

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Rehydration Strategies and Calculations

Oral Rehydration Therapy (ORT)

ORT is the first-line treatment for mild-to-moderate dehydration, as it is safer, cheaper, and less invasive than intravenous therapy.

• Mechanism: Utilizes a low-osmolarity Oral Rehydration Salt (ORS) solution (75 mEq/L sodium, 75 mmol/L glucose). The active cotransport of sodium and glucose across the brush border membrane of the small intestine remains functional during viral gastroenteritis. Sodium absorption carries water passively with it into the enterocytes.
• Protocol: Administer 50–100 mL/kg of ORS over 4 hours. Give small, frequent volumes—such as 5 mL (1 teaspoon) every 2–5 minutes via syringe or spoon. If the child vomits, pause for 10–15 minutes, then resume ORS at a slower rate (e.g., 2 mL every 5 minutes). Replace ongoing losses: 10 mL/kg for each diarrheal stool, and 2 mL/kg for each emesis episode.

Intravenous Fluid Resuscitation

Indications for IV fluids include severe dehydration, altered mental status, hemodynamic instability (shock), failure of ORT, or persistent vomiting.

Phase 1: Emergent Resuscitation

• Goal: Restore intravascular volume and prevent organ ischemia.
• Fluid Choice: Isotonic crystalloids only (0.9% Normal Saline or Ringer's Lactate). Never use hypotonic solutions (e.g., D5W, 0.45% NaCl) for resuscitation as they can cause rapid hyponatremia and cerebral edema.
• Dosing: Administer a 20 mL/kg bolus intravenously over 10–20 minutes. Re-assess perfusion after the bolus. If signs of shock persist, repeat the bolus up to a total of 3 times (60 mL/kg) before investigating other causes of shock.

Phase 2: Maintenance Therapy (Holliday-Segar Method)

Once intravascular volume is restored, maintenance fluids are calculated to meet baseline metabolic demands. The hourly rate is determined using the 4-2-1 rule:

• For the first 10 kg of body weight: 4 mL/kg/hour

• For the second 10 kg (11–20 kg): 2 mL/kg/hour

• For each kg above 20 kg: 1 mL/kg/hour

• Calculation Example (12 kg child):

  • First 10 kg: 10 * 4 mL/hr = 40 mL/hr
  • Next 2 kg: 2 * 2 mL/hr = 4 mL/hr
  • Total hourly rate = 40 + 4 = 44 mL/hour.

• Calculation Example (25 kg child):

  • First 10 kg: 10 * 4 mL/hr = 40 mL/hr
  • Next 10 kg: 10 * 2 mL/hr = 20 mL/hr
  • Remaining 5 kg: 5 * 1 mL/hr = 5 mL/hr
  • Total hourly rate = 40 + 20 + 5 = 65 mL/hour.

• Fluid Composition: Maintenance fluid is typically a hypotonic solution with dextrose, such as 5% Dextrose in 0.45% Normal Saline (D5 0.45% NaCl) or D5 0.9% NaCl, with 20 mEq/L Potassium Chloride (KCl). Caution: Do not add potassium to intravenous fluids until the child has voided (documented urine output), to prevent hyperkalemic cardiac arrhythmias.