A clinical syndrome characterized by inadequate organ perfusion and tissue oxygenation due to an imbalance between oxygen delivery and tissue oxygen demand.
Commonly diagnosed when signs of hypoperfusion are associated with low or declining BP.
It may result from a number of disease processes, including pump failure (cardiogenic), loss of intravascular volume (hypovolemic), failure of vasoregulation (distributive), or obstruction to blood flow (obstructive).
Initial treatment aims to optimize oxygen delivery and reverse hypoperfusion through volume resuscitation, vasopressors for refractory hypotension due to vasodilation, management of cardiac dysfunction, and treatment of the underlying cause.
Management of shock is best undertaken in a critical care environment.
Shock is most commonly defined as the life-threatening failure of adequate oxygen delivery to the tissues and may be due to decreased blood perfusion of tissues, inadequate blood oxygen saturation, or increased oxygen demand from the tissues that results in decreased end-organ oxygenation and dysfunction. If left untreated, shock results in sustained multiple organ dysfunction, and end-organ damage with possible death. Tissue hypoperfusion may be present without systemic hypotension, but at the bedside shock is commonly diagnosed when both are present (arterial hypotension and organ dysfunction).    
Fielding School of Public Health
David Geffen School of Medicine at UCLA
Deputy Health Officer
Orange County Health Care Agency
Health Disaster Management/Emergency Medical Services
SJS declares that he has no competing interests.
Dr Samuel J. Stratton would like to gratefully acknowledge Dr Christoph Pechlaner and Dr Christian Wiedermann, previous contributors to this monograph. CP and CW declare that they have no competing interests.
Consultant in Accident & Emergency Medicine
St Helens & Knowsley Hospitals NHS Trust
PN declares that he has no competing interests.
Vice-Chair and Program Director
Wright State University Department of Emergency Medicine
JB declares that he has no competing interests.
Use of this content is subject to our disclaimer