What adjustments should be made to the medication regimen for a toddler with classical CAH on hydrocortisone (cortisol) and fludrocortisone (Florinef) with hyperkalemia and hyponatremia?

Management of Electrolyte Abnormalities in Classical CAH Toddler

This child requires immediate increase in fludrocortisone dose to address the hyperkalemia (K+ 6.0) and hyponatremia (Na 132), as these electrolyte abnormalities indicate inadequate mineralocorticoid replacement despite being on 50 micrograms daily. 1

Immediate Fludrocortisone Adjustment

• Increase fludrocortisone from 50 to 100 micrograms daily as the current dose is clearly insufficient given the electrolyte derangements 1, 2
• Most children and younger patients with primary adrenal insufficiency require 50-200 µg fludrocortisone daily, with children often needing higher doses than adults 1
• The FDA-approved dosing for salt-losing adrenogenital syndrome is 0.1-0.2 mg (100-200 micrograms) daily 2
• Monitor serum electrolytes within 3-5 days after dose adjustment to assess response 1, 2

Hydrocortisone Dose Assessment

• Current total hydrocortisone dose is 10 mg/day (approximately 11 mg/m² for a 9 kg toddler with BSA ~0.45 m²)
• This glucocorticoid dose is appropriate as guidelines recommend 6-10 mg/m² body surface area for children with CAH 1
• The three-times-daily dosing schedule (5 mg, 2.5 mg, 2.5 mg) is acceptable, though ensure the first dose is given immediately upon waking and the last dose at least 6 hours before bedtime 1

Acute Hyperkalemia Management

• K+ of 6.0 mmol/L requires urgent treatment while awaiting fludrocortisone effect 1
• Consider oral sodium bicarbonate if concurrent metabolic acidosis is present, as this promotes potassium excretion 1
• Ensure adequate sodium intake through diet while increasing fludrocortisone dose 1, 3
• Potassium-binding agents (patiromer or sodium zirconium cyclosilicate) may be considered if hyperkalemia persists despite fludrocortisone adjustment, though these are typically used in chronic kidney disease 1

Monitoring Parameters

• Recheck electrolytes (sodium, potassium) within 3-5 days after fludrocortisone increase 1, 2
• Monitor blood pressure at each visit, as excessive fludrocortisone can cause hypertension 1, 2
• If hypertension develops, reduce fludrocortisone dose but do not discontinue 1
• Periodic checking of serum electrolytes is advisable during prolonged therapy 2
• Potassium supplementation may be needed paradoxically once fludrocortisone is optimized, as the medication can cause hypokalemia 4, 2

Expected Response

• Plasma renin correlates with mineralocorticoid adequacy; if available, target renin 20-60 mIU/L indicates appropriate replacement 5
• Sodium should normalize to >135 mmol/L and potassium should decrease to 3.5-5.0 mmol/L within days of appropriate fludrocortisone dosing 1, 6
• Growth velocity should remain appropriate (approximately 18 cm/year in first year) with proper treatment 7, 8

Common Pitfalls to Avoid

• Do not attribute electrolyte abnormalities to inadequate glucocorticoid dosing alone—this is a mineralocorticoid deficiency requiring fludrocortisone adjustment 1, 6
• Do not add sodium chloride supplementation as first-line therapy; fludrocortisone dose adjustment is more effective 9
• Avoid reducing fludrocortisone dose if mild hypertension develops; instead, restrict dietary salt intake first 1
• Do not delay treatment while waiting for confirmatory tests; electrolyte abnormalities in known CAH require immediate intervention 6