A method to evaluate microcirculatory vascular patency of full thickness burn in an animal model

Background. In cases of thermal injuries it is always difficult to predict the extent of necrosis to the peripheral ischemic zone. Practically, full-t hickness skin burn also affects the underlying muscle, panniculus carnosus, which adheres tightly to the skin. In this proposed model, the muscle whic h was always partly damaged also covers the ischemic zone of full-thickness burn injury. To evaluate the deeper Levels of injury, the status of the mi cro circulation of thermally affected muscle was evaluated by counting the accumulated radioactive agent, Tc-99m methoxyisobutylisonitril (MIBI) in th e muscle cells. Methods. 370 MBq/kg (10 mCi/kg) MIBI was administered intravenously to the animals having burn injuries by a comb device as described in previous lite rature. Then, 20 minutes after injection, whole burned areas were excised a nd placed under a gamma camera. Each thermally injured area showed four rec tangular defects with lower tracer uptakes than the three adjacent interspa ces. The tracer uptake of the burned sites and interspaces was analyzed fro m the acquired images on a computer, and the degree of injury could be asse ssed quantitatively. Additionally, specimen counts were obtained from selec ted burned stripes, interspaces and normal tissue for comparison, Results. Burned sites were evident with lower tracer uptakes whereas inters paces with higher uptakes. Captured activity in interspaces indicated that capillary patency mostly maintained and it permitted the arrival of the rad iopharmaceutical to the muscle cells. Conclusions. Muscle layer, where just below the burn area and tightly attac hed to the skin, could be assessed as a representative of the extension of the injury.