Cellular metabolic alterations in shock.

Circulatory shock is considered one of the most severe stimulus of the pituitary adrenal axis, therefore causing profound physiologic and metabolic sequelae. It is defined as inadequate circulating blood volume producing decreased perfusion first to nonvital tissues (skin, connective tissue, bone, and muscle), and subsequently to vital organs (brain, heart, lungs, liver, and kidney). Decreased perfusion of nonvital tissues results in anaerobic metabolism because the nonvital tissue cell mass is significantly larger than the vital tissue cell mass. As circulating blood volume decreases, catecholamines and angiotensin are secreted which increases peripheral resistance thus producing low flow in the periphery. Later, baroreceptors in the auricles and carotid and aortic bodies stimulate the vasomotor center in the medulla oblongata via the sympathetic nerves. The vasomotor center compounds sympathetic vasoconstriction further, increasing peripheral resistance.