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Vicious circles in shock. Initiation of shock can occur at any point, but the endpoint is often the same. Source: Reprinted, with permission, from Davis et al., (1995, p. 145). Copyright 1995 by Mosby-Year Book, Inc.
fusion. Increased cardiac work may lead to failing myocardial function and decreased coronary perfusion. Decreased tissue perfusion at the cellular level leads to microcirculatory damage, cellular aggregation, and microcirculatory obstruction, followed by cell hypoxia, transfer of salts and fluid into the cells, and decreased venous return. These events lead to metabolic acidosis, which, if it becomes deep, can result in decreased myocardial contraction. There are time-honored classifications of shock, many of which were initiated by definitions described by Alfred Blalock in the late 1930s. They are:
Hypovolemic shock: shock secondary to inadequate circulating volume.
Traumatic shock: shock secondary to inadequate circulatory volume plus soft-tissue injury.
Cardiogenic shock: failure of the heart to provide circulation.
Neurogenic shock: failure of the nervous system to provide peripheral vascular resistance.
Septic shock: hemodynamic instability that may arise as a result of septicemia.