Evaluation of Postocclusive Reactive Hyperemia in Rat Paw Skin Using Laser Speckle Contrast Imaging.

Laser Speckle Contrast Imaging (LSCI) is a modern, non-invasive technique for assessing microvascular perfusion in humans and laboratory animals. The combination of LSCI with invasive blood pressure (BP) measurement and a vascular occlusion test allows the study of postocclusive reactive hyperemia (PORH), providing an assessment of microvascular blood flow reserve and the vascular reactivity. This article demonstrates the technique of using the LSCI to record and visualize PORH in the hind paw of a rat under general anesthesia. A special pneumatic cuff is inflated to create a temporary (180 s) vascular occlusion at the level of the tibia. Evaluation of the subsequent PORH (peak hyperemia and kinetic indices) can provide additional information on the mechanisms and severity of the pathological process under study (circulatory shock, heart failure, hypertension, etc.) or identify vascular effects of a new drug that are not apparent when assessing perfusion at rest. Invasive BP monitoring allows calculation of cutaneous vascular conductance and consideration of changes in systemic hemodynamics, which is particularly important in experimental models of critical illness. The use of this approach to identify microvascular dysfunction in a rat model of hemorrhagic shock will also be demonstrated.