Figure 2.

Differing effects of hyperglycemia on ischemic core, penumbra, and reperfusion. Complete or near-complete ischemia in core regions with poor collateral circulation leads to glucose and oxygen depletion, accompanied by ATP depletion and mild acidosis.

Hyperglycemia supports metabolism and exacerbates the acidosis to only a minor degree in core regions, because only the glucose present at onset of ischemia is metabolized. Penumbral regions with residual blood flow through collateral circulation receive continued glucose but not oxygen delivery, due to the molar excess of glucose in arterial blood. Glycolysis fueled by the continued glucose delivery can attenuate ATP depletion, but also generates lactic acidosis in proportion to blood glucose levels. During reperfusion pH is normalized and ATP recovers where tissue is still viable, but with increased glucose delivery there is increased production of reactive oxygen species.