Inadequate Delivery

In very simple terms, cells run on adenosine triphosphate (ATP). ATP is produced by respiration, either aerobic or anaerobic. Anaerobic respiration is about 18 times less efficient than aerobic. In the absence of adequate oxygen delivery, cells run out of energy and cease to function effectively and, if the situation is not corrected, die. On the macroscopic level this is apparent in organ dysfunction and failure.

Compensation and decompensation

The body has a range of compensatory mechanisms to cope with a reduction in oxygen delivery as a result of circulatory compromise. These include the ability to dramatically increase the amount of oxygen extracted from the blood – the oxygen extraction ratio (OER). The initial clinical signs and symptoms that suggest shock is developing are the result of the compensatory mechanisms; the later features are those of organ dysfunction as the compensatory mechanisms fail. If the causative pathology is not identified and corrected quickly enough the uncompensated shock state will progress to a situation of irreversible damage.

Learning bite

There is a window of opportunity in which to identify and treat a shock state after which the damage will become irreversible.