Physiology · Cardiovascular System

Circulatory shock: physiological basis

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Definition

  • Shock is a syndrome of inadequate tissue perfusion with a relative or absolute decrease in cardiac output.
  • Acute hemorrhage of more than 15 mL/kg body weight results in shock.

Classification of Shock

Classification of shock by mechanism

Type

Hypovolemic

Mechanism
Decreased volume of fluid in the vascular system
Examples
Hemorrhagic, traumatic, surgical, burn shock

Distributive

Mechanism
Increased vascular capacity from acute marked vasodilation
Examples
Neurogenic, anaphylactic, septic shock

Cardiogenic

Mechanism
Decreased ability of the heart to pump blood
Examples
Acute myocardial infarction, heart failure, arrhythmias

Obstructive

Mechanism
Obstruction to ejection of blood from the ventricle
Examples
Cardiac tamponade, constrictive pericarditis, cardiac tumor, tension pneumothorax