Evaluation of the HPA Axis in Patients With Vasoplegic Syndrome After Cardiac Surgery

Overview

Vasoplegic syndrome after cardiac surgery is common and is associated with increased morbidity and mortality. It is characterized by early and prolonged arterial hypotension, with preserved cardiac output and low systemic vascular resistance. Vasoplegic syndrome therefore shares pathophysiological features with septic shock. There are no data in the literature on the function of the hypothalamic-pituitary-adrenal (HPA) axis during vasoplegic syndrome after cardiac surgery. In situations of acute stress and systemic inflammation, relative adrenal insufficiency has been reported in the most severe patients, particularly those in septic shock. The term ""CIRCI"" (Critical Illness-Related Corticosteroid Insufficiency) is currently defined as an increase in total plasma cortisol of less than 9 µg/dl after stimulation with 250 µg tetracosactide (synthetic ACTH), or a basal total plasma cortisol level of less than 10 µg/dl. However, recent studies have called into question the usefulness of the cosyntropin stimulation test for exploring the HPA axis in intensive care patients. Tandem mass spectrometry (LC-MS/MS) assays can be used to measure steroid metabolites (steroidome), enabling more precise exploration of the corticotropic axis. The aim of this study is to evaluate, on an exploratory basis, the impact of the presence of a post-cardiac surgery vasoplegic syndrome on adrenal function by steroidome mapping (LC-MS/MS).

Vasoplegic syndrome after cardiac surgery is common (incidence 5-44%) and is associated with increased morbidity and mortality. It is characterized by early (immediately or within the first 24 hours post-operatively) and prolonged (more than 4 hours) arterial hypotension, with preserved cardiac output and low systemic vascular resistance. Vasoplegic syndrome therefore shares pathophysiological features with septic shock. There are no data in the literature on the function of the hypothalamic-pituitary-adrenal (HPA) during vasoplegic syndrome after cardiac surgery. In situations of acute stress and systemic inflammation, relative adrenal insufficiency has been reported in the most severe patients, particularly those in septic shock. The term ""CIRCI"" (Critical Illness-Related Corticosteroid Insufficiency) is currently defined as an increase in total plasma cortisol of less than 9 µg/dl after stimulation with 250 µg tetracosactide (synthetic ACTH), or a basal total plasma cortisol level of less than 10 µg/dl. However, recent studies have called into question the usefulness of the cosyntropin stimulation test for exploring the HPA axis in intensive care patients. An increase in the volume of cortisol distribution, a decrease in cortisol-binding protein and cortisol clearance (notably via an increase in bile acids) could distort test interpretation: the slight increase in total plasma cortisol would contrast with a normal increase in free cortisol. Tandem mass spectrometry (LC-MS/MS) assays can be used to measure steroid metabolites (steroidome), enabling more precise exploration of the corticotropic axis. Another study, has shown that steroidome analysis by LC-MS/MS enables the diagnosis of adrenal insufficiency with excellent sensitivity and specificity in a population of women with hyperandrogenism. The aim of this study is to evaluate, on an exploratory basis, the impact of the presence of a post-cardiac surgery vasoplegic syndrome on adrenal function by steroidome.