Shock Syndromes Shock is defined as an alteration in tissue perfusion that occurs at the cellular level.

Shock Syndromes

Shock is defined as an alteration in tissue perfusion that occurs at the cellular level.

Shock is a process that causes the eventual shutdown of all body systems in a systematic order.

The final common pathway in all types of shock is the switching of cellular metabolism from aerobic to anaerobic.

Anaerobic metabolism results in activation of the inflammatory response, decreased circulatory volume and decreasing pH.

Three major classifications:

-anaphylactic shock

-neurogenic shock

-septic shock

Hypovolemic Shock

Occurs when there is a significant loss of circulating blood or fluid, either by direct loss, or redistribution (third-spacing)
Most common causes are hemorrhage, burns and dehydration
May be seen when the total circulating blood volume has been decreased by 15-20% (approx. 500-1500 ml)

Cardiogenic Shock

Occurs when the pumping action of the heart fails
Most common causes are myocardial infarction, cardiac trauma, cardiomyopathy and congestive heart failure

Distributive Shock

Occurs when blood vessels dilate without a subsequent increase in circulating ...

-septic shock

Hypovolemic Shock

Occurs when there is a significant loss of circulating blood or fluid, either by direct loss, or redistribution (third-spacing)
Most common causes are hemorrhage, burns and dehydration
May be seen when the total circulating blood volume has been decreased by 15-20% (approx. 500-1500 ml)

Cardiogenic Shock

Occurs when the pumping action of the heart fails
Most common causes are myocardial infarction, cardiac trauma, cardiomyopathy and congestive heart failure

Distributive Shock

Occurs when blood vessels dilate without a subsequent increase in circulating blood volume
Blood volume is normal, but the vascular bed is greater in size

Anaphylactic Shock

A profound hypersensitivity reaction with a systemic antigen-antibody response
The antigen triggers release of vasoactive mediators that act on the vascular and pulmonary systems
Mediators cause smooth muscle contraction, vasodilation, increased capillary and bronchoconstriction
Redistribution of fluid intersitially, and vasodilation decreases intravascular volume

Neurogenic Shock

Most commonly caused by cervical spinal cord injury secondary to trauma, but can also occur as a result of severe head injuries
Sympathetic nervous system is blocked, and the parasympathetic system is unchallenged resulting in massive vasodilation
Rare form of shock and is usually transient

Septic Shock

Most common cause is untreated infection, mortality rate 40-90%
Triggering of the inflammatory and systemic inflammatory response by endotoxins of infecting organism, most commonly gram negative bacilli.
Immune response leads to vasodilation, increased capillary permeability and vascular redistribution into the interstitial spaces.
2 phases-initially “warm” phase- pt. febrile with high CO and decreased SVR, tachycardia, tachypnea, and facial flushing, followed by “cold” phase- with decreased CO and vasocontstriction, skin pale and cool, hypotensive

Shock Progression:

Compensatory Shock

Body responses initiated to increase cardiac output, tissue and cellular perfusion and vital organ perfusion

Progressive Shock

Body responses become inadequate to maintain perfusion and multisystem failure ensues

Irreversible Shock

Pervasive cellular destruction, death imminent

Compensatory Mechanisms

Initiated to restore CO and tissue perfusion

Blood shunted away from kidneys, GI tract, liver and skin to heart, lungs and brain
Compensation achieved by baroreceptors stimulating peripheral vasoconstriction, stimulation of sympathetic NS, and release of renin, aldosterone and ADH in an attempt to increase blood volume

McCance, H., & Huether, S. (2002). Pathophysiology: The biologic basis for disease in adults & children (4th ed.). St. Louis MO: Mosby.

Newberry, L. (2003). Sheehy’s emergency nursing: Principles and practice (5th ed.). St. Louis MO: Mosby.