Hemorheology and hemodynamics: Dove andare?

The rheologic characteristics of blood and its formed elements continue to be of basic science and clinical interest, with numerous publications dealing with topics such as blood and plasma viscosity, RBC aggregation and cell deformability. Alterations of blood's rheologic behavior in pathologic states have been extensively studied, with the findings usually indicating changes assumed to be detrimental to tissue perfusion (e.g., increased RBC aggregation). However, the current literature contains relatively few studies dealing with two important areas: (1) relations between altered rheologic behavior and in vivo hemodynamics; (2) the effects of therapy in those clinical states associated with altered rheologic behavior. This paper presents brief and selective comments on the assumed importance of two rheologic "abnormalities" (i.e., increased plasma viscosity, increased RBC aggregation), and on whether clinical therapy in diabetes, hypertension and sepsis leads to normalization of the "abnormalities". Finally, a few gratuitous comments are presented regarding possible future directions in the field of hemorheology and hemodynamics.