Ischemia-reperfusion injury in the lung: quantitation using electron microscopy

The primary objectives of this study were to determine the time course of ischemia-reperfusion injury in an isolated rabbit lung model and to quantify this damage using electron microscopic methodology coupled with statistical analyses.

Eight groups of isolated rabbit lungs (n = 5 per group) were subjected to predetermined periods of ischemia-reperfusion. Two hours of ischemia and 4 hours of reperfusion were concluded to be necessary to induce optimal ischemia-reperfusion injury in this model. Four other groups were subjected to 2 hours of ischemia followed by selected periods of reperfusion. These groups were compared to 4 control groups that were perfused for comparable time periods but without the initial ischemia. New quantitative methods were developed based on the average surface area of the alveoli and average number of alveoli per unit surface area, using scanning electron microscopic examination.

Ischemia per se caused substantial damage. Restoration of volume and nutrients reversed this damage at 1 hour of reperfusion, but severe damage was evident at 4 hours of reperfusion, as reported by subjective and blinded examination. By using the new quantitative methods, there was a significant difference between the groups (P < .005) according to the time of post-ischemia-reperfusion, which correlated with the subjective evaluation of damage.

These 2 new quantitative techniques provide an objective assessment of damage in the isolated rabbit lung model, suggesting that they warrant further consideration in similar studies of ischemia reperfusion injury.