Shock is a cyclic, self-perpetuating problem with numerous causes, all of which have in common poor perfusion, anaerobic metabolism and release of tissue damaging mediators.
Shock is a major critical illness that involves almost every organ system.
It is not simply a problem of decreased blood pressure. The reflex vasoconstrictive response, and increased vascular permeability in the shocked state leads to the loss of central intravascular volume. Cardiac function is compromised by the reduced oxygen availability at a time when the body has an increased demand due to the increased sympathetic tone and tachycardia. Conditions which alter any of these parameters significantly will, therefore, lead to inadequate tissue perfusion and severly effect subsequent delivery of metabolic substrates to tissue and finally cell level. There are a basically three different pathophysiological causes of shock.