Is there a relationship between the hematocrit-to-viscosity ratio and microvascular oxygenation in brain and muscle?

Waltz, Xavier; Hardy‐Dessources, Marie‐Dominique; Lemonne, Nathalie; Mougenel, Danièle; Lalanne-Mistrih, Marie Laure; Lamarre, Yann; Tarer, Vanessa; Tressières, Benoît; Etienne‐Julan, Maryse; Hue, Olivier; Connes, Philippe

doi:10.3233/ch-131742

Cited by 46 publications

(30 citation statements)

References 22 publications

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“…This might be explained by the absence of differences in Hb levels before and after HD; however, it was recently reported that cerebral oxygenation did not improve even with the significant increase in Hb levels induced by ultrafiltration during HD [7, 8]. Regarding the differences in changes in cerebral oxygenation between Hb increases by intradialytic blood transfusion and those by ultrafiltration during HD, the reasons might be explained by the changes in hematocrit-to-viscosity ratios [20] during HD. However, in this study, plasma viscosity was not measured; therefore, we cannot conclude an association between its ratio and changes in cerebral oxygenation.…”

Section: Discussionmentioning

confidence: 99%

Changes in Cerebral Oxygenation Associated with Intradialytic Blood Transfusion in Patients with Severe Anemia Undergoing Hemodialysis

Ookawara

Ueda

et al. 2017

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Background: Hemodialysis (HD) patients frequently suffer from severe anemia caused by various hemorrhagic disorders in addition to renal anemia. Intradialytic blood transfusion is sometimes performed; however, the cerebral oxygenation changes associated with this procedure remain unclear. Methods: Sixteen HD patients with severe anemia who required intradialytic blood transfusion were included (12 men and 4 women; mean age, 64.8 ± 9.8 years). Cerebral regional oxygen saturation (rSO₂) was monitored using near-infrared spectroscopy, and cerebral fractional oxygen extraction (FOE) was calculated before and after HD. Twenty-five HD patients with well-maintained hemoglobin (Hb) levels were included as a control group. Results: Cerebral rSO₂ values were significantly lower in HD patients with severe anemia than in the control group (42.4 ± 9.9 vs. 52.5 ± 8.5%, p = 0.001). Following intradialytic blood transfusion (385 ± 140 mL of concentrated red blood cells), Hb levels significantly increased (from 7.2 ± 0.9 to 9.1 ± 1.1 g/dL, p < 0.001), and cerebral rSO₂ values significantly improved after HD (from 42.4 ± 9.9 to 46.3 ± 9.0%, p < 0.001). Cerebral FOE values before HD in patients with severe anemia were significantly higher than those in the control group (severe anemia, 0.56 ± 0.10; controls, 0.45 ± 0.08; p < 0.001). After HD with intradialytic blood transfusion, these values significantly decreased (0.52 ± 0.09 after HD versus 0.56 ± 0.10 before HD, p = 0.002). Conclusion: HD patients with severe anemia represented cerebral oxygen metabolism deterioration, which could be significantly improved by intradialytic blood transfusion.

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Section: Discussionmentioning

confidence: 99%

Changes in Cerebral Oxygenation Associated with Intradialytic Blood Transfusion in Patients with Severe Anemia Undergoing Hemodialysis

Ookawara

Ueda

et al. 2017

Nephron Extra

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“…35 Oxygen transport effectiveness has been analyzed in recent years theoretically, 37 experimentally ex vivo [38][39][40] and in vivo. 41 We have previously calculated theoretical oxygen transport effectiveness to assess optimal Hct values viscometrically and with the AMVN device. 42 In the present study, estimated oxygen transport effectiveness was highest at a Hct feeding of approximately 60% in all capillary microchannels studied ( Figure 6).…”

Section: Discussionmentioning

confidence: 99%

Influence of feeding hematocrit and perfusion pressure on hematocrit reduction (Fåhræus effect) in an artificial microvascular network

2017

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Objective Hematocrit in narrow vessels is reduced due to concentration of fast flowing red blood cells (RBC) in the center, and of slower flowing plasma along the wall of the vessel, which in combination with plasma skimming at bifurcations leads to the striking heterogeneity of local hematocrit in branching capillary networks known as the network Fåhræus effect. We analyzed the influence of feeding hematocrit and perfusion pressure on the Fåhræus effect in an artificial microvascular network (AMVN). Methods RBC suspensions in plasma with hematocrits between 20–70% were perfused at pressures of 5–60 cmH2O through the AMVN. A microscope and high-speed camera were used to measure RBC velocity and hematocrit in microchannels of height of 5 μm and widths of 5–19 μm. Results Channel hematocrits were reduced compared with feeding hematocrits in 5 μm and 7 μm, but not in larger microchannels. The magnitude of hematocrit reduction increased with decreasing feeding hematocrit and decreasing perfusion pressure (flow velocity), showing an about 7-fold higher effect for 40% feeding hematocrit and low pressure/flow velocity than for 60% feeding hematocrit and high pressure/flow velocity. Conclusions The magnitude of the network Fåhræus effect in an AMVN is inversely related to feeding hematocrit and perfusion pressure.

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“…Although vascular function seems to be better preserved in children with SC, both sickle cell groups had a decreased exercise capacity compared to healthy children. In SC, mild anaemia and blood hyperviscosity could be responsible for decreased physical fitness, due to their known adverse effects on tissue oxygenation [64].…”

Section: Physical Activity Level and Fitnessmentioning

confidence: 99%

Micro- and macrovascular function in children with sickle cell anaemia and sickle cell haemoglobin C disease

Möckesch

Charlot

Jumet

et al. 2017

Blood Cells, Molecules, and Diseases

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It is unclear whether vascular function is affected similarly in children with sickle cell anaemia (SS) and children with sickle haemoglobin C (SC) disease. Therefore, we compared micro and macrovascular functions in healthy (AA) children, children with SS and SC disease, and assessed their association with physical activity. Participants (24 SS, 22 SC and 16 AA), were compared in terms of 1) thermal hyperaemic response (finger pad warming to 42°C) measured by Laser Doppler techniques, 2) arterial stiffness determined by pulse wave velocity, 3) daily energy expenditure related to moderate and intense physical activities estimated by questionnaire and 4) fitness level, evaluated by the six-minute walk test. Response to heating differed between SS, SC and controls. Peripheral microvascular reactivity was lower and pulse wave velocity higher in SS compared to AA. SC had blunted microvascular reactivity in response to heating compared to AA but pulse wave velocity was not different within the two groups. Physical activity and fitness levels were markedly lower in sickle cell patients compared to healthy controls but no association was observed with vascular function. Microvasodilatory reserve is decreased in both SS and SC patients but only SS patients were also characterised by impaired macrovascular function.

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Is there a relationship between the hematocrit-to-viscosity ratio and microvascular oxygenation in brain and muscle?

Cited by 46 publications

References 22 publications

Changes in Cerebral Oxygenation Associated with Intradialytic Blood Transfusion in Patients with Severe Anemia Undergoing Hemodialysis

Changes in Cerebral Oxygenation Associated with Intradialytic Blood Transfusion in Patients with Severe Anemia Undergoing Hemodialysis

Influence of feeding hematocrit and perfusion pressure on hematocrit reduction (Fåhræus effect) in an artificial microvascular network

Micro- and macrovascular function in children with sickle cell anaemia and sickle cell haemoglobin C disease

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