The emerging role of the microcirculation in clinical medicine.

Although research on microcirculation has expanded rapidly in the last 20 years, clinical evaluation of microcirculation, as an entity, has not achieved any status in the United States. Three aspects of microcirculation are presented, wherein clinical applications exist or on the verge of existing. Biomicroscopy is the direct observation of, and measurements within, the microcirculation is superficial areas of the body. Not only can the pattern of the microcirculation be examined and related to microcirculatory function but also the intravascular relationships among red cells, leukocytes, and platelets can be studied. Rheology includes measurement of the interactions among plasma and cellular elements during flow within the microcirculation. Unfortunately, rheologic factors are generally ignored in thinking about hemodynamics. The concept of the optimal hematocrit has great clinical relevance in both acute and chronic disease. Transvascular fluid and solute exchange can be evaluated in the body as a whole and in individual organs by relatively noninvasive techniques. Such evaluations provide useful information about the natural progress and the effect of treatment of a variety of serious diseases. Microcirculation, as an entity, is a quantitative science in its own right and ought to be actively applied in clinical medicine.