Hypothalamic–pituitary–adrenal function: anaesthetic implications

The hypothalamic–pituitary–adrenal axis is activated by surgery, trauma and critical illness. Anaesthesia can suppress adrenocortical secretion either by an effect at the hypothalamus (e.g. by a decrease in neural input with regional anaesthesia) or by a direct effect on the adrenal cortex (e.g. by etomidate). For patients undergoing routine surgery an increase in cortisol secretion is unnecessary; uneventful recovery occurs in the presence of circulating cortisol concentrations within the normal range. Patients taking corticosteroids for many medical conditions often present for surgery. A rationale for steroid supplementation based on physiological principles and clinical evidence is presented in this article. The use of steroids in critically ill patients remains contentious, with little agreement about what is an appropriate circulating cortisol concentration and the interpretation of the results of the short Synacthen test.