A 3-year-old girl with congenital adrenal hyperplasia due to 21-hydroxylase deficiency presents to the emergency department with lethargy, vomiting, and poor perfusion. Her parents report she has not received her hydrocortisone or fludrocortisone for the past 10 days due to a missed pharmacy refill. On examination: BP 82/48 mmHg, HR 142 bpm, RR 26/min, temperature 37.5°C. Skin turgor is decreased. Laboratory results show serum sodium 118 mEq/L, potassium 7.2 mEq/L, chloride 92 mEq/L, bicarbonate 24 mEq/L, BUN 34 mg/dL, creatinine 1.1 mg/dL, and ACTH 156 pg/mL (markedly elevated). Urine sodium is low. Which of the following is the most appropriate initial management?

1. A)Hypertonic saline (3%) at 2-4 mL/kg/hour to raise serum sodium by 10-12 mEq/L over 2 hours, followed by fludrocortisone
2. B)Isotonic saline bolus (20 mL/kg over 30 minutes) concurrent with intravenous hydrocortisone (50 mg/m² every 6 hours), followed by fludrocortisone replacementGABARITO
3. C)Insulin (0.1 unit/kg IV) with dextrose (0.5 g/kg IV) and sodium polystyrene sulfonate to address hyperkalemia, then fluid resuscitation
4. D)Slow isotonic saline infusion (5 mL/kg/hour) with oral hydrocortisone and observation for gradual electrolyte correction over 48 hours
5. E)Spironolactone to block aldosterone effects and correction of hyponatremia with fluid restriction and hypertonic saline