While ischemia alone results in tissue damage, reperfusion of ischemic tissue results in further damage both to the tissue and systemically to other organs.
The concept of reperfusion accelerating damage in local tissues may be true in the sense that damage is increased or it may simply represent acceleration in normal patho-physiological processes with restoration of blood flow. For instance, patients with occlusive arterial disease of the lower limbs with critical ischemia, who undergo limb saving arterial reconstructive surgery, will usually demonstrate rapid demarcation of ischaemic tissues that may not have been so obvious prior to surgery. The appearance of the tissues would eventually take on the same appearance if time permitted.
Examination of tissues with ischemia-reperfusion injury show evidence of endothelial cell dysfunction with respect to oedema, and an infiltration of leucocytes.
Ischemic tissues however must, be exposed to molecular oxygen on reperfusion to manifest tissue injury. This suggests that reperfusion with higher than normal (for the tissue in question) oxygen results in generation of reactive oxygen species that cause further tissue injury. Further research suggests that activated leucocytes also contribute to the damage. `Spilling over' of soluble mediators and activated leucocytes results in remote systemic damage.