1. Shock is defined as a failure to meet the metabolic demands
of cells and tissues and the consequences that ensue.
2. A central component of shock is decreased tissue perfusion. This
may be a direct consequence of the etiology of shock, such as in
hypovolemic/hemorrhagic, cardiogenic, or neurogenic etiologies,
or may be secondary to elaborated or released molecules or cellular
products that result in endothelial/cellular activation,
such as in septic shock or traumatic shock.
3. Physiologic responses to shock are based upon a series of afferent
(sensing) signals and efferent responses that include neuroendocrine,
metabolic, and immune/inflammatory signaling.
4. The mainstay of treatment of hemorrhagic/hypovolemic
shock includes volume resuscitation with blood products and fluids.
In the case of hemorrhagic shock, timely control of bleeding is
essential and influences outcome.
5. Prevention of hypothermia, acidemia, and coagulopathy are essential
in the management of patients in hemorrhagic shock.
6. The mainstay of treatment of septic shock is fluid resuscitation,
initiation of appropriate antibiotic therapy, and control of the
source of infection. This includes drainage of infected fluid collections, removal
of infected foreign bodies, and débridement of devitalized
7. A combination of physiologic parameters and markers of organ
perfusion/tissue oxygenation are used to determine if patients
are in shock and to follow the efficacy of resuscitation.
“Shock is the manifestation
of the rude unhinging of the machinery of life.”1
Shock, at its most rudimentary definition and regardless of the etiology,
is the failure to meet the metabolic needs of the cell and the consequences
that ensue. The initial cellular injury that occurs is reversible;
however, the injury will become irreversible if tissue perfusion
is prolonged or severe enough such that, at the cellular level,
compensation is no longer possible. Our evolution in the understanding
of shock and the disease processes that result in shock made its
most significant advances throughout the twentieth century as our
appreciation for the physiology and pathophysiology of shock matured.
Most notably, this includes the sympathetic and neuroendocrine stress
responses on the cardiovascular system. The clinical manifestations
of these physiologic responses are most often what lead practitioners
to the diagnosis of shock as well as guide the management of patients
in shock. However, hemodynamic parameters such as blood pressure
and heart rate are relatively insensitive measures of shock, and
additional considerations must be used to help aid in early diagnosis
and treatment of patients in shock. The general approach to the
management of patients in shock has been empiric: assuring a secure
airway with adequate ventilation and restoration of vascular volume
and tissue perfusion.
Integral to our understanding of shock is the appreciation that
our bodies attempt to maintain a state of homeostasis. Claude Bernard suggested
in the ...