Editing Shock (circulatory) (section)

===Refractory===
At Refractory stage (stage 4), the vital [[organ failure|organs have failed]] and the shock can no longer be reversed. [[Brain damage]] and cell death are occurring, and death will occur imminently. One of the primary reasons that shock is irreversible at this point is that much of the cellular [[Adenosine triphosphate|ATP]] (the basic energy source for cells) has been degraded into [[adenosine]] in the absence of oxygen as an electron receptor in the [[mitochondrial matrix]]. Adenosine easily perfuses out of cellular membranes into extracellular fluid, furthering capillary [[vasodilation]], and then is transformed into [[uric acid]]. Because cells can only produce adenosine at a rate of about 2% of the cell's total need per hour, even restoring oxygen is futile at this point because there is no adenosine to [[phosphorylate]] into ATP.<ref name=Guyton/>