Before starting corticosteroid treatment, it is worth confirming the diagnosis of adrenal insufficiency. Failure of plasma cortisol to rise after IM/IV tetracosactrin 250 μg indicates adrenocortical insufficiency.

Procedure:

1. • Contact lab first

2. • Take 5 ml blood in a plain tube for cortisol before and 30 min after IM/IV tetracosactrin 250 μg

Interpretation:

1. • A normal response requires an incremental rise of at least 200 nmol/l and a final result must be >500 nmol/l. In the critically ill, values should be much higher. We normally accept 1000 nmol/l anywhere in the test as being a level sufficient for a septic patient needing ventilatory support

The test is impossible to interpret once hydrocortisone has been started. If urgent treatment is required before test, use dexamethasone initially.