Scanning electron microscopic changes in the morphology of rabbit pulmonary tissue biopsied following ischemia and reperfusion: a window of opportunity?

Reperfusion is known to cause tissue damage in ischemic pulmonary tissue. W e investigated the time frame of this occurrence by examining electron micr oscopic changes in lung tissue. Isolated, perfused, and ventilated rabbit l ungs land heart) were placed en bloc in a 37 degrees C chamber and perfused through the pulmonary artery at 15 mm Hg pressure with oxygenated Krebs-He nseleit buffer, pH 7.4, 70 ml min(-1), for 20 min and the pulmonary pump an d ventilator were stopped. The resultant ischemic state was maintained for 2 h, and reperfusion resumed with the same buffer. The lungs of four groups of rabbits (n = 5 per group) were each subjected to 30 min, 1, 2, and 4 h of reperfusion respectively. Upon completion, lungs were biopsied for scann ing electron microscopy. Ischemic damage including the loss of lung archite cture, and edema were seen. Reperfusion restored some of the tissue anatomy and the return to normalcy increased up to 1 h of reperfusion after which the damage increased with time. Results suggest that damage due to ischemia alone may be reversible. Initial recovery is due to the re-establishment o f circulation. However with time, the damage seen may be due to free radica ls and with 4 h of reperfusion, cell death may have occurred.