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PubMedDate not supplied

Red blood cell aggregation and blood viscosity in an isolated heart preparation.

We studied the effects of moderate changes in red blood cell RBC aggregation on blood flow in the vasodilated vascular bed of an isolated rat heart. We compared a non-aggregating RBC suspension (in Krebs-albumin medium) with RBC suspensions in 1% and 2% Dextran 70 (MW 70000), exhibiting two different degrees of moderate aggregation. Degrees of aggregation were precisely estimated by in vitro laser aggregometry. Each heart was perfused by the non-aggregating RBC suspension and by one aggregating RBC suspensions. Blood flow was measured in a range of perfusion pressure from 40 to 80 mm Hg. For the three RBC suspensions, linear pressure/flow relationships were found. From the comparison between the pressure/flow relationships obtained with Krebs albumin medium and either 1% or 2% Dextran, it was possible to compare in vivo the contribution of RBC to the viscosity (i.e., the relative apparent viscosity) in the 2 aggregating RBC suspensions with that of the non-aggregating RBC suspension. The contribution of RBC to the viscosity was found to be 20% to 25% lower in the 1% RBC suspension than in the non-aggregating RBC suspension. With 2% Dextran which induced a higher degree of aggregation no differences were found between the relative apparent viscosities of the aggregating and the non-aggregating suspension. From the comparison between RBC in 1% Dextran and Krebs-albumin, we concluded that in vivo a moderate RBC aggregation reduces viscous resistance due to the presence of blood in a vascular network. Since no more effect of RBC aggregation per se was found when the degree of aggregation was higher (with RBC in 2% Dextran), this suggests that, in this case, aggregation induces opposite effects along the myocardial vascular network which cancel each other out, thus inducing a nil net balance.

Animals↗
PubMed1977

[The effect of low fibrinogen concentrations on human blood viscosity].

Simultaneous studies of viscosity, red cell aggregation and deformation were carried out on human blood with different fibrinogen concentrations using a Brookfield viscometer fitted with a reflection photometer. Fibrinogen progressively increased rouleaux formation, while decreasing viscosity at low and increasing it at higher concentrations. This antagonism is explained by the specific hemodynamic effects of the rouleaux formed under either condition.

Afibrinogenemia↗
PubMed1988

Effects of total hip replacement and bed rest on blood rheology and red cell metabolism.

In order to better understand the pathophysiologic changes in the immediate postoperative period after total hip replacement surgery and to distinguish alterations due to the surgical operation from those due to bed rest, we examined rheologic parameters and red cell metabolism of patients before, 1 day after, and 5 to 6 days after total hip replacement and compared the results to those obtained from normal volunteers placed at bed rest for 5 days. Bed rest in the control group led to increases in hematocrit, mean corpuscular hemoglobin concentration, red cell DPG and ATP levels, and plasma concentrations of total proteins, globulins, and fibrinogen, with attendant increases in whole blood viscosity, plasma viscosity, blood viscosity, relative blood viscosity with hematocrit adjusted to 45%, and viscometric aggregation index, and the viscosity of red cell suspensions in Ringer's solution at 45% hematocrit decreased at low shear rate. The patient group, despite the postoperative lowering of their hematocrit, mean corpuscular hemoglobin concentration, and total plasma proteins and a consequent decrease of whole blood viscosity, revealed disproportionate increases in blood viscosity, relative blood viscosity, and viscometric aggregation index. These rheologic changes, which reflect an enhanced red cell aggregability, may contribute to complications of thrombophlebitis. Enforced inactivity, when superimposed on the effects of trauma, blood loss, transfusion with bank blood, and the low-flow state, would exaggerate these rheologic problems. The results suggest that management of total hip replacement patients should include hemorrheologic considerations (e.g., preoperative intentional hemodilution) and early postoperative activity.

2,3-Diphosphoglycerate↗
PubMed1998

[Effect of blood viscosity on the function of isolated perfused porcine kidney after cold preservation].

With the new method of gas exchange and dialysis carried out simultaneously with a standard dialysis module, for the first time normothermic ex-vivo whole blood perfusion of pig kidneys becomes practicable under nearly physiological conditions. To show the possibility of animal experiment replacements we use slaughter house kidneys to investigate functional abilities of the perfusion method. Slaughter house kidneys show a state of acute ischemic renal failure due to the unavoidable time of ischemia and cold preservation. Nevertheless they show a specific functional metabolism up to 4 hours of perfusion time. For the future, the new perfusion model seems suitable to investigate acute organ rejection and perfusion phenomena on pig kidneys, which are most interesting for xenotransplantation.

Animals↗