A 3-year-old child presents to the emergency department with continuous seizure activity lasting 25 minutes. The child has a history of febrile seizures. After securing the airway and administering first-line anticonvulsants (lorazepam), what is the most appropriate next investigation to identify the underlying etiology?

## Investigation of Choice in Status Epilepticus ### Clinical Context A 3-year-old with febrile seizure history presenting with status epilepticus requires urgent identification of the precipitating cause. While seizure control is the immediate priority, determining etiology guides definitive management. ### Why Blood Glucose and Serum Electrolytes Come First **Key Point:** In any child presenting with status epilepticus, the **first and most immediate investigation** is bedside blood glucose and serum electrolytes (including sodium, calcium, and magnesium). Hypoglycemia and electrolyte disturbances (hyponatremia, hypocalcemia) are rapidly reversible, life-threatening causes of seizures that must be excluded before proceeding to invasive investigations. **High-Yield:** Per Nelson Textbook of Pediatrics (21e, Ch. 608), the initial workup in status epilepticus mandates **immediate bedside glucose testing** and serum electrolytes as the first-line investigation. These are non-invasive, rapid, and directly actionable — hypoglycemia can be corrected within minutes with dextrose. **Clinical Pearl:** Even in a child with a known history of febrile seizures, metabolic derangements must be excluded first. A child with hyponatremia (e.g., from gastroenteritis) can present identically to febrile status epilepticus. Treating the metabolic cause may abort the seizure without further intervention. ### Investigation Hierarchy in Status Epilepticus | Investigation | Timing | Purpose | Priority | |---|---|---|---| | Blood glucose, electrolytes, calcium | Immediate (bedside) | Rule out metabolic causes | **1st** | | Lumbar puncture + CSF | Urgent (after stabilization) | Rule out meningitis/encephalitis | 2nd | | Non-contrast CT head | After LP (if no contraindication) | Rule out structural lesion | 3rd | | EEG | During/after seizure control | Confirm seizure activity, guide management | 4th | **Mnemonic: BLESS** — **B**lood work, **L**umbar puncture, **E**lectroencephalography, **S**tructure (CT/MRI), **S**erum anticonvulsant levels ### Why Not Lumbar Puncture First? - LP is invasive and requires prior stabilization and assessment for contraindications (raised ICP, coagulopathy) - Metabolic causes must be excluded before proceeding to LP - In a febrile child where meningitis is suspected, empiric antibiotics can be started while awaiting LP — but blood glucose/electrolytes must be checked immediately regardless - The stem asks for the "next investigation after securing airway and administering lorazepam" — at this point, bedside metabolic workup is the standard of care **Warning:** Do not delay glucose and electrolyte testing in any seizing child. Untreated hypoglycemia causes irreversible neuronal injury within minutes. [cite: Nelson Textbook of Pediatrics 21e Ch 608; IAP Guidelines on Status Epilepticus]