Pressure-induced ischemia. I. An experimental model for intravital microscopic studies in hamster cheek pouch

A model to study pressure-induced ischemia by intravital microscopy is presented. A hamster cheek pouch is prepared to get a single layer of epithelium, together with vessels and connective tissue. Pressure, which can be varied, is transmitted to the tissue by a pressure chamber with a rubber membrane. Microcirculatory reactions may be studied while the pressure is applied, when the pressure is released and as the tissue is regaining circulation. The local environment is controlled by irrigating the test tissue with a solution approximating the composition of interstitial fluid. Local oxygen and carbon dioxide tensions are controlled. There is a marked difference in restoration of blood flow to the tissue after 2- and 4-hour ischemia. After 2-hour ischemia the tissue regained circulation rapidly. Microbleedings developed during the postpressure observation time. After 4-hour ischemia, on the other hand, the tissue regained circulation slowly and only in one third of the microvessels. Extensive white blood cells sticking to the vessel walls were seen indicating endothelial damage. In the 4-hour experiments there were very few microbleedings compared to the 2-hour experiments.