Official reprint from UpToDate ® www.uptodate.com Print | Back Shock in adults: Types, presentation, and diagnostic approach Author David Gaieski, MD Section Editor Polly E Parsons, MD Deputy Editor Kevin C Wilson, MD Last literature review for version 17.1: January 1, 2009 | This topic last updated: August 6, 2008 INTRODUCTION — Shock is the physiologic state characterized by significant reduction of systemic tissue perfusion, resulting in decreased tissue oxygen delivery. This creates an imbalance between oxygen delivery and oxygen consumption. Prolonged oxygen deprivation leads to cellular hypoxia and derangement of critical biochemical processes at the cellular level, which can progress to the systemic level [1,2 ]: Cellular effects include cell membrane ion pump dysfunction, intracellular edema, leakage of intracellular contents into the extracellular space, and inadequate regulation of intracellular pH Systemic effects include alterations in the serum pH, endothelial dysfunction, and further stimulation of inflammatory and antiinflammatory cascades The effects of oxygen deprivation are initially reversible, but rapidly become irreversible. The result is sequential cell death, end-organ damage, multi-system organ failure, and death. This highlights the importance of prompt recognition and reversal of shock [3 ]. The types and stages of shock are discussed in this topic review, as well as the clinical presentation and differential diagnosis of shock. A recommended diagnostic approach is also presented. Treatment of specific types of shock is discussed separately. (See "Management of severe sepsis and septic shock in adults" and see "Treatment and prognosis of cardiogenic shock complicating acute myocardial infarction" and see "Treatment of severe hypovolemia or hypovolemic shock in adults" ). PHYSIOLOGY — Systemic tissue perfusion is determined by the cardiac output (CO) and systemic vascular resistance (SVR):