Microculatory reactions to controlled tissue ischaemia and temperature: a vital microscopic study on the hamster's...

An ischaemic insult is produced on a hamster's cheek pouch under intravital-microscopic control. Recirculation and the condition of the nutritive flow is studied. Three hours ischaemia at 36 degrees C will produce only a slight immediate reaction. Microbleedings, thrombus formation and oedema are recorded later. The nutritive blood flow is unevenly distributed. Eight hours ischaemia at 22 degrees C will produce less disturbed microcirculation than a shorter period at body temperature. Tissue viability after an ischaemic insult is dependent on mainly two factors. First, the ability of parenchymal cells to withstand hypoxic injury and secondly the ability of the microvasculature to resume blood flow. Tissue temperature has been found to be a major determinant of the balance between metabolic rate and nutritive blood flow. Studies in the past have utilised the skin of the rat and the ear of the rabbit as tissue models for ischaemic injury (Lindan, 1961; Willms-Kretschmer and Majno, 1969). The aim of our studies is to elucidate the early phase of recovery after an ischaemic insult in the cheek pouch. This tissue is thin and well suited for vital microscopic studies. and pressure may be applied with little shear stress. We have chosen a tissue without parenchymal elements, thus it is to a large extent composed only of a vascular network with its accompanying connective tissue. Our study of microcirculatory events will thus show the effect of ischaemic insults on the microvasculature.