Differences in peripheral arterial and venous hemorheologic parameters.

To evaluate the comparability of hemorheologic parameters in arterial and venous blood, we measured hematocrit, whole blood viscosity, plasma viscosity, erythrocyte deformability, erythrocyte aggregation, and erythrocyte indices in both arterial and venous blood from 20 consecutive patients scheduled for coronary artery surgery and/or valve replacement surgery. Hematocrit, whole blood viscosity at three shear rates (0.05 s-1, 0.5 s-1, and 70 s-1), plasma viscosity, and erythrocyte aggregation factor were statistically significantly higher in venous blood than in arterial blood. The differences may be explained by the difference in hematocrit. Erythrocyte deformability did not differ significantly. With the availability of more precise rheological measurement techniques, differences such as those encountered in this study may be of importance in clinical studies. It is concluded that arterial and venous blood samples are not entirely rheologically comparable.

Hemorrheological changes associated with brain death and their implications for potential organ donors.

Successful transplantation of donor organs from brain-dead patients requires adequate maintenance of hemodynamic parameters. Blood flow and tissue perfusion are highly dependent upon hemorrheology. The aim of the present study was to evaluate hemorrheological parameters in potential organ donors compared to healthy volunteers. Whole blood-, plasma- and corrected blood viscosity, hematocrit, erythrocyte deformability, and erythrocyte aggregation were obtained in ten consecutive brain-dead patients and ten matched volunteers. Compared to controls, hematocrit and whole blood viscosity at high and medium shear rates and erythrocyte deformability were significantly decreased. Plasma viscosity was significantly increased in all patients. In the same group, a highly significant increase was observed at all shear rates when viscosity was corrected for hematocrit. Definite rheological abnormalities were found in the blood of brain-dead patients, something which might lead to impaired organ function after transplantation. Therefore, optimizing such parameters by special fluid management may be of importance in potential organ donors.

The effects of propofol compared to high-dose fentanyl anesthesia on rheologic parameters in coronary artery surgery.

Propofol has previously been found to decrease hematocrit values. Because hematocrit is an important determinant of blood viscosity, lower hematocrits may cause a decrease in blood viscosity, improving blood flow and oxygen delivery. This phenomenon may be beneficial in certain intraoperative situations. To study the influence of two anesthetic techniques on a variety of rheologic parameters, 32 patients scheduled for coronary artery bypass grafting (CABG) were divided into two groups. Group I (n = 18) was induced with high-dose fentanyl anesthesia (100 micrograms/kg), and group II (n = 16) with a combination of propofol and fentanyl anesthesia (1 to 1.5 mg/kg and 35 to 50 micrograms/kg, respectively). Maintenance anesthesia continued with infusions of the same drugs. Blood and plasma viscosity, hematocrit, erythrocyte aggregation factor, and erythrocyte deformability were measured preoperatively, intraoperatively, and up to 48 hours postoperatively. Whole blood viscosity was corrected to a standard hematocrit of 0.45. The two groups were comparable with respect to age, bypass duration, blood loss, urine output, transfusions, and fluid management. Erythrocyte deformability did not decrease during or after cardiopulmonary bypass (CPB). In both groups, hematocrit and blood and plasma were decreased significantly during and after CPB (P < 0.01) and returned to baseline levels 48 hours after surgery. After induction and before CPB, blood viscosity was only decreased in group II. However, the corrected blood viscosity was significantly elevated at all shear rates in group II compared to group I at 24 and 48 hours postoperatively (P < 0.01). In group II at these sampling times, this parameter was also significantly elevated compared to preoperative values.(ABSTRACT TRUNCATED AT 250 WORDS)

The clinical importance of erythrocyte deformability, a hemorrheological parameter.

Hemorheology, the science of the flow behavior of blood, has become increasingly important in clinical situations. The rheology of blood is dependent on its viscosity, which in turn is influenced by plasma viscosity, hematocrit, erythrocyte aggregation, and erythrocyte deformability. In recent years it has become apparent that the shape and elasticity of erythrocytes may be important in explaining the etiology of certain pathological situations. Thus, clinicians have become increasingly interested in hemorheology in general and erythrocyte deformability in particular. In the course of time, many clinical studies have been performed, but no concise review has thus far been published. This article encompasses a review of the clinically based literature on this subject.