Red blood cell flow dynamics at bifurcations of the brain capillaries

2021 ◽  
Author(s):  
Kazuto Masamoto ◽  
Ruka Sakuraba ◽  
Tomoya Niizawa
Keyword(s):  
Blood Cell ◽  
Red Blood Cell ◽  
Flow Dynamics ◽  
Brain Capillaries ◽  
The Brain

In vivo microvascular structural and functional consequences of muscle length changes

1997 ◽  
Vol 272 (5) ◽  
pp. H2107-H2114 ◽  
Author(s):  
D. C. Poole ◽  
T. I. Musch ◽  
C. A. Kindig
Keyword(s):  
Blood Flow ◽  
Blood Cell ◽  
Red Blood Cell ◽  
Oxygen Delivery ◽  
Sarcomere Length ◽  
Flow Dynamics ◽  
Capillary Diameter ◽  
Luminal Diameter ◽  
Length Changes

As muscles are stretched, blood flow and oxygen delivery are compromised, and consequently muscle function is impaired. We tested the hypothesis that the structural microvascular sequellae associated with muscle extension in vivo would impair capillary red blood cell hemodynamics. We developed an intravital spinotrapezius preparation that facilitated direct on-line measurement and alteration of sarcomere length simultaneously with determination of capillary geometry and red blood cell flow dynamics. The range of spinotrapezius sarcomere lengths achievable in vivo was 2.17 +/- 0.05 to 3.13 +/- 0.11 microns. Capillary tortuosity decreased systematically with increases of sarcomere length up to 2.6 microns, at which point most capillaries appeared to be highly oriented along the fiber longitudinal axis. Further increases in sarcomere length above this value reduced mean capillary diameter from 5.61 +/- 0.03 microns at 2.4-2.6 microns sarcomere length to 4.12 +/- 0.05 microns at 3.2-3.4 microns sarcomere length. Over the range of physiological sarcomere lengths, bulk blood flow (radioactive microspheres) decreased approximately 40% from 24.3 +/- 7.5 to 14.5 +/- 4.6 ml.100 g-1.min-1. The proportion of continuously perfused capillaries, i.e., those with continuous flow throughout the 60-s observation period, decreased from 95.9 +/- 0.6% at the shortest sarcomere lengths to 56.5 +/- 0.7% at the longest sarcomere lengths and was correlated significantly with the reduced capillary diameter (r = 0.711, P < 0.01; n = 18). We conclude that alterations in capillary geometry and luminal diameter consequent to increased muscle sarcomere length are associated with a reduction in mean capillary red blood cell velocity and a greater proportion of capillaries in which red blood cell flow is stopped or intermittent. Thus not only does muscle stretching reduce bulk blood (and oxygen) delivery, it also alters capillary red blood cell flow dynamics, which may further impair blood-tissue oxygen exchange.

scholarly journals Red Blood Cell Transfusion Practices in the Neurointensive Care Unit: A Narrative Review

2019 ◽  
Vol 06 (02) ◽  
pp. 072-079
Author(s):  
Rohini M. Surve ◽  
Sonia Bansal ◽  
Radhakrishnan Muthuchellappan
Keyword(s):  
Blood Transfusion ◽  
Blood Cell ◽  
Red Blood Cell ◽  
Narrative Review ◽  
Neurointensive Care ◽  
Red Blood Cell Transfusion ◽  
Compensatory Mechanism ◽  
Neurointensive Care Unit ◽  
The Impact ◽  
The Brain

AbstractAnemia is common in neurointensive care unit (NICU) patients and is one of the common causes of systemic insults to the brain. Though the recent literature favors restrictive blood transfusion practices over liberal transfusion to correct anemia in the general ICU, whether a similar practice can be adopted in NICU patients is doubtful due to lack of strong evidence. Impairment of cerebral autoregulation and cardiac function following acute brain injury affects the body's compensatory mechanism to anemia and renders the brain susceptible to anemic hypoxia at different hemoglobin (Hb) thresholds. Hence, red blood cell transfusion (RBCT) practice based on a single Hb threshold value might be inappropriate. On the other hand, allogenic RBCT has its own risks, both in short and in long run, leading to adverse outcomes. Thus, instead of relying only on arbitrary Hb values, a better way to decide the need for RBCT in NICU patients is to target parameters based on systemic and regional cerebral oxygenation. This approach will help us to individualize RBCT practices. In this narrative review, based on the available literature, authors have discussed the impact of anemia and blood transfusion on the immediate and late neurological outcomes and the current role of regional brain monitoring in guiding blood transfusion practices. In the end, authors have tried to update on the current RBCT practices in neurosurgical and neuromedical patients admitted to the NICU.

scholarly journals Multiple-Capillary Measurement of RBC Speed, Flux, and Density with Optical Coherence Tomography

2013 ◽  
Vol 33 (11) ◽  
pp. 1707-1710 ◽  
Author(s):  
Jonghwan Lee ◽  
Weicheng Wu ◽  
Frederic Lesage ◽  
David A Boas
Keyword(s):  
Optical Coherence Tomography ◽  
Blood Cell ◽  
Red Blood Cell ◽  
Linear Density ◽  
Flow Dynamics ◽  
Optical Coherence ◽  
Microvascular Flow ◽  
Different Depths

As capillaries exhibit heterogeneous and fluctuating dynamics even during baseline, a technique measuring red blood cell (RBC) speed and flux over many capillaries at the same time is needed. Here, we report that optical coherence tomography can capture individual RBC passage simultaneously over many capillaries located at different depths. Further, we demonstrate the ability to quantify RBC speed, flux, and linear density. This technique will provide a means to monitor microvascular flow dynamics over many capillaries at different depths at the same time.

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