[Shock: a review. I: Pathophysiology]

In the present review, an attempt has been made to describe the modern concept of circulatory shock (Part I). The shock inducing insults (low circulatory volume/vascular capacity equation, heart failure, or disturbance of cellular metabolism induce physiological defense mechanisms, which result in peripheral vasoconstriction in order to maintain adequate blood pressure and perfusion of vital organs (compensatory phase). However, when the insult is too aggressive or too prolonged, deterioration of the cardiovascular system and cellular function ensues as a result of anaerobic metabolism, loss of vascular tone, reperfusion injury, depression of the reticuloendothelial system, disseminated intravascular coagulation, and myocardial failure (decompensatory phase). This leads to widespread cellular destruction, autodigestion, and finally death of the patient. Recent features of shock therapy will be discussed in part II of this review.