Critical illness, anesthesia, surgery, trauma, burns, hemorrhage, infection, pain, cold, fever, and emotional disorders are stressors that activate the hypothalamic-pituitary-adrenal (HPA) axis. 1,2 The HPA axis is an essential component of the general adaptation to stress and plays a crucial role in cardiovascular, metabolic, and immunologic homeostasis. As noted in Figure 1 , when faced with a stressor, the hypothalamus releases corticotropin-releasing hormone (CRH), which elicits a series of events. The initial event involves the stimulation of the sympathetic nervous system to release norepinephrine and epinephrine, which causes vascular smooth muscle vasoconstriction and enhances inotropic response. Secondly, the posterior pituitary is stimulated to release anti-diuretic hormone (ADH) to promote intravascular fluid retention. Lastly, stimulation of the anterior pituitary leads to the release of corticotropin (ACTH), which stimulates the adrenal cortex to release the minera...