Acute Blood Loss: Regional Blood Flow and Microcirculation (Review, Part I)
The first part of the review highlights the data on the structural and functional organization of the microvas culature; regulation of vascular tone including local (metabolic and myogenic mechanisms, role of endothelium and red blood cells) and systemic (nervous, humoral) factors; general issues of microcirculatory alterations in blood loss and shock. Acute blood loss is considered as a phasic development of compensatory and adaptive processes involving the blood system, cardiovascular, nervous and endocrine systems. Changes in oxygen transport, the pathogenesis of hypoxia and metabolic abnormalities in blood loss and hemorrhagic shock are described. Examples of the vicious circles contributing to acute blood loss pathogenesis are considered as a base for developing decompensated hemorrhagic shock in which the role of hemostasis and blood rheology alterations are also considered.