This study was undertaken in an effort to examine the effects of selective variations in systemic hematocrit on the preglomerular. glomerular. and postglomerular microcirculation in the rat. By isovolemic exchange transfusions, systemic hematocrit (control 51 ml/ 100 ml) was either reduced (21 ml/100 ml, N = 7 rats) or elevated (62 ml/100 ml, N = 7). Single nephron glomerular filtration rate va...

Since the original publications by Martini et al. (Dtsch. Arch. Klin. Med. 169: 212-222, 1930) and Fahraeus and Lindqvist (Am. J. Physiol. 96: 562-568, 1931), it has been known that the relative apparent viscosity of blood in tube flow depends on tube diameter. Quantitative descriptions of this effect and of the dependence of blood viscosity on hematocrit in the different diameter tubes are req...

Physiological studies on fetal blood in narrow glass tubes have suggested that fetal optimal hematocrit (hct) might be as high as 60%. A theoretical 'ideal' hct can also be predicted with a theoretical curve of hematocrit/viscosity (h/η) ratio vs hct constructed with Quemada's model. We used the database of one of our previous papers on fetal hemorheology to reinterpret its results with this co...

This study was undertaken in an effort to examine the effects of selective variations in systemic hematocrit on the preglomerular. glomerular. and postglomerular microcirculation in the rat. By isovolemic exchange transfusions, systemic hematocrit (control 51 ml/ 100 ml) was either reduced (21 ml/100 ml, N = 7 rats) or elevated (62 ml/100 ml, N = 7). Single nephron glomerular filtration rate va...

To investigate the effect of hematocrit and serum fibrinogen on transcranial Doppler ultrasound (TCD) measurements, we performed, TCD tests and measured hematocrit and serum fibrinogen concentrations in 112 healthy adult volunteers. The mean velocities of the middle cerebral (r = -.37, p < .0001), internal carotid at siphon (r = -.14, p < .05) and cervical level (r = -.14, p < .05), vertebral (...

The cut off for hemoglobin or hematocrit that indicates the need for an isotopic red cell mass study was investigated in 179 patients with a presumptive diagnosis of polycythemia vera or essential thrombocythemia. Hematocrit showed better diagnostic accuracy than hemoglobin. Hemoglobin over 18.5 g/dL in males or over 16.5 g/dL in females showed a high specificity indicating that red cell mass s...

The flow of blood through a stenosed catheterized artery has been studied. To observe the effects of hematocrit, blood has been represented by a two-phase macroscopic model (i.e., a suspension of red cells in plasma). It is found that for any given catheter size, the impedance increases with hematocrit and also for a given hematocrit, the same increases with the catheter size. In the stenotic r...

S everal prospective studies have shown that a high hematocrit (or hemoglobin) predicts type 2 diabetes (1–6). However, the reasons for this association have not been fully explored. Hematocrit has been positively correlated with hyperinsulinemia and conditions associated with insulin resistance such as high blood pressure, elevated serum triglycerides, low HDL cholesterol, and central obesity ...