522 Low and Stardard Doses of Synthetic Acth in the Assessment of Adrenal Function of Children with Septic Shock

Background and method: ACTH stimulation test is used for the diagnosis of adrenal insufficiency in sepsis, but the optimal dosage of ACTH is still debatable. We, therefore, compared the efficacy of low (1μg/1.73m 2 ) and standard (250µg/1.73m 2 ) dosages of ACTH in identifying adrenal insufficiency in children with septic shock. Method: We evaluated 25 children admitted to PICU with catecholamine-dependent septic shock. Upon recruitment, a blood sample was collected for baseline cortisol determination. After an intravenous administration of low dose ACTH another blood sample was collected in 30 minutes for determination of cortisol response. Four hours after, a second intravenous ACTH stimulation test was performed, now using standard dose. Children were followed until PICU discharge. Results: The mean baseline cortisol was 773±421nmol/L. Baseline cortisol was not different between survivors and non-survivors (724±443 vs 795±241, p=0.16). Mean peak cortisol after low dose ACTH stimulation was 1157±451nmol/L, with mean change from baseline of 458nmol/L. Both mean peak cortisol (1160±445nmol/L) and mean change from baseline (746±458nmol/L) were higher after standard dose ACTH stimulation (p=0.045 and p< 0.01, respectively). There was a good correlation between peak cortisol after low and standard dose ACTH stimulation tests (r 2 =0.58). Out of the 25 children in the study, 7(28%) had AI. All of these children could be identified using the low dose ACTH stimulation test, but only 3(43%) could be identified using the standard dose ACTH stimulation test (p = 0.01) alone. Conclusion: Low dose ACTH for adrenal stimulation identifies more children with AI when compared with the standard dose test.