Corticosteroid therapy and adverse effects — branching viva

Opening — the weaning plan on the ward

Examiner: A four-year-old on daily prednisolone for frequently relapsing nephrotic syndrome has been on a pharmacologic dose for three months. Walk me through the corticosteroid pharmacology and how you would wean her. [9]

Candidate (model): Prednisolone is about four times as glucocorticoid-potent as hydrocortisone, with slight mineralocorticoid activity. The equivalent-dose anchor I keep at the bedside is hydrocortisone 20 mg equals prednisolone 5 mg equals methylprednisolone 4 mg equals dexamethasone 0.75 mg. Because she has been on a pharmacologic dose well beyond two to three weeks, her hypothalamic-pituitary-adrenal axis is suppressed and she cannot mount a cortisol response to stress. I would not stop abruptly. I would taper the prednisolone to a physiological equivalent — about hydrocortisone 8 to 10 mg per square metre per day — then step it down every one to two weeks while she stays well. Before I stop, I would test the axis with a morning cortisol or a short Synacthen test, and I would keep the sick-day rules and emergency hydrocortisone in place through the recovery window, because full adrenal responsiveness lags behind the wean. [9]

Branch 1 — the child collapses with hypoglycaemia

Examiner: The same child presents to the emergency department vomiting and drowsy with a fever, hypotensive, with a bedside glucose of 2.1 mmol/L. What is going on, and what do you do first? [9] [7]

Candidate (model): This is adrenal crisis until proven otherwise. She has the three ingredients — long-term corticosteroid exposure with HPA suppression, a febrile precipitant, and the classic collapse with hypotension and hypoglycaemia. Hypoglycaemia is prominent in younger children because their glycogen reserves are small. My first action is to replace the cortisol she cannot make: intravenous or intramuscular hydrocortisone immediately at the age-banded stress dose — 50 mg for this four-year-old — followed by a continuous infusion around 2 to 3 mg/kg per 24 hours or repeated six-hourly doses. In parallel I give a 10 to 20 mL/kg saline bolus, correct the glucose with dextrose, take cultures and start antibiotics because sepsis is both a precipitant and a differential, and draw a cortisol and ACTH sample without delaying the steroid. [9]

Branch 2 — why hydrocortisone and not dexamethasone

Examiner: Why hydrocortisone specifically, and not dexamethasone, which is more potent? [7]

Candidate (model): Because glucocorticoid potency and mineralocorticoid activity are independent. Dexamethasone is twenty-five to thirty times as glucocorticoid-potent as hydrocortisone, but it has negligible mineralocorticoid activity, so a child given dexamethasone alone may continue to salt-waste. Hydrocortisone, at stress doses, carries enough mineralocorticoid activity to cover both the glucocorticoid and the mineralocorticoid deficit, which is why it is the crisis drug. If I were forced to use a high-potency agent in crisis, I would have to add a mineralocorticcoid — so I reach for hydrocortisone in the first place. [7] [9]

Branch 3 — perioperative stress cover

Examiner: Now a different child: a steroid-dependent teenager on long-term hydrocortisone replacement for autoimmune Addison's disease is admitted for elective orthopaedic surgery. What is your perioperative corticosteroid plan? [10]

Candidate (model): A child with known adrenal insufficiency needs additional parenteral hydrocortisone around surgery, because the surgical stress raises the cortisol demand beyond the maintenance dose. At induction I give the age-banded stress hydrocortisone — 100 mg for an adolescent — and continue a continuous infusion or regular intravenous doses through the perioperative period, stepping down as the child recovers and tolerates oral intake. The Association of Anaesthetists, Royal College of Physicians and Society for Endocrinology guidance sets this approach, and the modern practice is more restrained than the large historical doses, but the principle is unchanged: the suppressed or absent axis must be supported through major stress. [10]

Closing — the one-liners examiners reward

Examiner: Give me the three principles you would want every registrar to remember. [7] [9]

Candidate (model): First, know the equivalent-dose ladder — hydrocortisone 20 mg equals prednisolone 5 mg equals methylprednisolone 4 mg equals dexamethasone 0.75 mg — and know that dexamethasone is twenty-five to thirty times as potent as hydrocortisone. Second, any course beyond two to three weeks suppresses the axis and must be weaned, because recovery takes weeks to months. Third, in a steroid-dependent collapse, give empirical age-banded hydrocortisone — infant 25 mg, child 50 mg, adolescent 100 mg — before you have the cortisol result, and use hydrocortisone, not dexamethasone, because the mineralocorticoid activity matters. [7] [9]