Hypothalamic–Pituitary–Adrenal Axis Response to Sustained Stress after Major Burn Injury in Children

Abstract

The hypothalamic-pituitary-adrenal (HPA) axis is responsible for stress response after injury, yet its function after severe burn injury in children is unclear. The purpose of this study was to define the effects of burn injury on the HPA axis and to evaluate the utility of total serum cortisol in measuring adrenal function in children with major burns in the 2 months after injury. Children ages 0 to 17 years who were admitted within 72 hours to our pediatric burn center with 20% TBSA or greater full-thickness burns were eligible for the study. Serum total cortisol, adrenocorticotropic hormone (ACTH), dehydroepiandrosterone, vasopressin, Pediatric Risk of Mortality (PRISM) score, serum albumin level, and electrolytes were obtained on admission and weekly for 8 weeks. An ACTH stimulation test (250 microg for children >2 years, 125 microg for children < or =2 years) was administered weekly at 8:00 am. Total serum cortisol was measured before and 60 minutes after the administration of ACTH. Twenty-five children with mean age 7.6 +/- 1.1 years and TBSA burn 41.8 +/- 3.8% were enrolled in the study. Baseline total serum cortisol was 12.4 +/- 0.7 microg/dl in the 8 weeks after injury and increased to 24.4 +/- 0.8 microg/dl after the administration of ACTH. Cortisol level did not correlate with PRISM score, albumin, vasopressin, ACTH, or mortality. Although the adrenal response to acute and chronic stress is intact after severe burn injury, the ACTH/adrenal feedback loop is disrupted. Random total serum cortisol measurements overestimate adrenal dysfunction; thus, ACTH stimulation testing should be used to assess adrenal function before the administration of exogenous steroids.