Dynamic pituitary–adrenal interactions in the critically ill after cardiac surgery

Abstract

Context: Patients with critical illness are thought to be at risk of adrenal insufficiency. There are no models of dynamic hypothalamic–pituitary–adrenal (HPA) axis function in this group of patients and thus current methods of diagnosis are based on aggregated, static models. Objective: To characterize the secretory dynamics of the HPA axis in the critically ill (CI) after cardiac surgery. Design: Mathematical modeling of cohorts. Setting: Cardiac critical care unit. Patients: 20 male patients CI at least 48 hours after cardiac surgery and 19 healthy (H) male volunteers. Interventions: None. Main Outcome Measures: Measures of hormone secretory dynamics were generated from serum adrenocorticotrophic hormone (ACTH) sampled every hour and total cortisol every 10 min for 24 h. Results: All CI patients had pulsatile ACTH and cortisol profiles. CI patients had similar ACTH secretion (1036.4 [737.6] pg/mL/24 h) compared to the H volunteers (1502.3 [1152.2] pg/mL/24 h; P = .20), but increased cortisol secretion (CI: 14 447.0 [5709.3] vs H: 5915.5 [1686.7)] nmol/L/24 h; P