Congenital Adrenal Hyperplasia (CAH)

Know which CAH - Ask which enzyme and which phenotype. Classic salt-wasting 21-hydroxylase patients are the ones who decompensate under stress. 17-hydroxylase deficiency runs the other direction — mineralocorticoid excess from accumulated 11-deoxycorticosterone, so hypertension and hypokalemia, and these patients rarely have adrenal crisis.

Preop labs - Serum sodium, potassium, and glucose before the case, plus a creatinine. Salt-wasting CAH runs hyponatremic, hyperkalemic, and hypoglycemic, and cortisol deficiency also drops GFR and increases ADH secretion. In an infant with a positive newborn screen, confirmation is a repeat plasma 17-hydroxyprogesterone with serum electrolytes.

Adrenal crisis is the headline risk - Surgery is exactly the stress these patients cannot mount cortisol for. Have hydrocortisone drawn up before induction. Stress dosing for acute crisis is hydrocortisone 50 to 100 mg/m², which can be run as a continuous infusion.

Don't interrupt replacement - Maintenance is oral hydrocortisone, roughly 10 to 15 mg/m²/day divided in adults and about 8 mg/m²/day divided in children, plus fludrocortisone 0.05 to 0.2 mg/day. NPO status doesn't pause the requirement — the IV stress dose covers it. Fever or intercurrent illness alone doubles their home dose, so a sick child arriving for surgery may already be behind.

Hemodynamics - Expect a blunted pressor response until steroid is on board. Cortisol deficiency means poor cardiac function and poor vascular responsiveness to catecholamines, so treat refractory hypotension as under-replacement rather than escalating vasopressor alone.

Volume in infants - Salt-wasting infants arrive volume-depleted after days of vomiting and poor feeding. Resuscitate and correct sodium and potassium before elective induction.

Fludrocortisone effects - It drives sodium and water retention and potassium and hydrogen excretion, so watch for iatrogenic hypertension, hypokalemia, metabolic alkalosis, edema, and rapid weight gain. A blood pressure and a potassium tell you whether the dose is right. Plasma renin activity is what the endocrinologist titrates against.

Cases you'll see - Genitoplasty, vaginoplasty, and urogenital sinus repair, usually before one year of age in significantly virilized girls, done at centers that specialize in it. Bilateral adrenalectomy is now rare. Adult women may return for vaginal stenosis and dyspareunia, so preop questions about prior genital surgery are relevant to positioning and to consent.

Growth and airway - Children with CAH are tall early but short as adults from androgen-driven early epiphyseal fusion. Size the airway and drug doses to actual weight and length, not to the age on the chart.

17-hydroxylase management - These patients take dexamethasone 0.25 to 1.0 mg/day or prednisone 2 to 5 mg/day to suppress ACTH, often with spironolactone for the mineralocorticoid-driven hypertension. Check the potassium and the blood pressure preop; severe cases stay hypertensive and hypokalemic even on glucocorticoid.

Congenital adrenal hyperplasia (CAH) is a group of autosomal recessive defects in adrenal steroid synthesis. 21-hydroxylase deficiency accounts for more than 90% of cases. Without it, 17-hydroxyprogesterone cannot become 11-deoxycortisol and progesterone cannot become deoxycorticosterone, so cortisol — and in the severe form aldosterone — run short.

Low cortisol releases the feedback brake on ACTH, the cortex hyperplases, and precursor steroid is shunted into androgen, producing virilization and ambiguous genitalia in newborn girls. Roughly 75% of classic 21-hydroxylase patients are salt-wasting: they cannot hold sodium or excrete potassium, and present in the first weeks of life with vomiting, poor feeding, dehydration, hypovolemia, and shock. Cortisol deficiency itself blunts cardiac function and the vascular response to catecholamines.