Blood Rheology: Key Parameters, Impact on Blood Flow, Role in Sickle Cell Disease and Effects of Exercise

Blood viscosity is an important determinant of local flow characteristics, which exhibits shear thinning behavior: it decreases exponentially with increasing shear rates. Both hematocrit and plasma viscosity influence blood viscosity. The shear thinning property of blood is mainly attributed to red blood cell (RBC) rheological properties. RBC aggregation occurs at low shear rates, and increases blood viscosity and depends on both cellular (RBC aggregability) and plasma factors. Blood flow in the microcirculation is highly dependent on the ability of RBC to deform, but RBC deformability also affects blood flow in the macrocirculation since a loss of deformability causes a rise in blood viscosity. Indeed, any changes in one or several of these parameters may affect blood viscosity differently. Poiseuille’s Law predicts that any increase in blood viscosity should cause a rise in vascular resistance. However, blood viscosity, through its effects on wall shear stress, is a key modulator of nitric oxide (NO) production by the endothelial NO-synthase. Indeed, any increase in blood viscosity should promote vasodilation. This is the case in healthy individuals when vascular function is intact and able to adapt to blood rheological strains. However, in sickle cell disease (SCD) vascular function is impaired. In this context, any increase in blood viscosity can promote vaso-occlusive like events. We previously showed that sickle cell patients with high blood viscosity usually have...
Source: Frontiers in Physiology - Category: Physiology Source Type: research

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Conclusion: Optical coherence tomography angiography may reflect the extent of functional compromise even before it being evident on fluorescein angiography. The area vascular compromise was larger in the deep plexus compared with the superficial plexus. The area of complete loss of retinal sensitivity corresponds to loss of vasculature in both the superficial and deep plexuses, whereas the area of decreased sensitivities corresponds to compromise only in the deep plexus.
Source: Retinal Cases and Brief Reports - Category: Opthalmology Tags: Case Report Source Type: research
Abstract It is well established that patients with sickle cell disease (SCD) are at substantial risk of neurological complications, including overt and silent stroke, diffuse structural injury, and cognitive difficulties. Yet the underlying mechanisms remain poorly understood, partly because findings have largely been considered in isolation. Here, we review mechanistic pathways for which there is accumulating evidence and propose an integrative systems-biology framework for understanding neurological risk. Drawing upon work from other vascular beds in SCD, as well as the wider stroke literature, we propose that macro-cir...
Source: Frontiers in Neurology - Category: Neurology Source Type: research
CONCLUSIONS: Abnormal FAZ morphology and altered parafoveal capillary perfusion were found in patients with SCR. Our customised OCT-A image analysis method uniquely highlights significant quantitative alterations in perfusion density mapping in a qualitative display, with minimal obscuration of OCT-A image detail. PMID: 31337609 [PubMed - as supplied by publisher]
Source: The British Journal of Ophthalmology - Category: Opthalmology Authors: Tags: Br J Ophthalmol Source Type: research
Conclusion: 5-HMF treatment decreased P50, improved SaO2, and mitigated increases in PAP in this swine model of NH. Introduction The reduction of barometric pressure at altitude is associated with reduced partial pressure of ambient Oxygen (PO2). With lower ambient PO2, it can be anticipated that alveolar (PAO2), arterial O2 (PaO2) and blood O2 content (CaO2) will decrease accordingly, resulting in a widely recognized decrease in maximal O2 consumption (VO2) (Dill and Adams, 1972; Lucas et al., 2011). In humans, with acute exposure to altitude, maximal VO2 decrements are measurable at elevations even as low as 580 ...
Source: Frontiers in Physiology - Category: Physiology Source Type: research
Conclusion: There is a wide heterogeneity of postoperative cerebral hemodynamic findings among TBI patients who underwent DC, including hemodynamic heterogeneity between their cerebral hemispheres. DC was proved to be effective for the treatment of cerebral oligoemia. Our data support the concept of heterogeneous nature of the pathophysiology of the TBI and suggest that DC as the sole treatment modality is insufficient. Introduction Decompressive craniectomy (DC) may effectively decrease intracranial pressure (ICP) and increase cerebral perfusion pressure (CPP) in traumatic brain injury (TBI) patients with refracto...
Source: Frontiers in Neurology - Category: Neurology Source Type: research
Conclusion: There is a wide heterogeneity of postoperative cerebral hemodynamic findings among TBI patients who underwent DC, including hemodynamic heterogeneity between their cerebral hemispheres. DC was proved to be effective for the treatment of cerebral oligoemia. Our data support the concept of heterogeneous nature of the pathophysiology of the TBI and suggest that DC as the sole treatment modality is insufficient. Introduction Decompressive craniectomy (DC) may effectively decrease intracranial pressure (ICP) and increase cerebral perfusion pressure (CPP) in traumatic brain injury (TBI) patients with refracto...
Source: Frontiers in Neurology - Category: Neurology Source Type: research
Abstract Sickle cell disease (SCD) is one of the most common hereditary hemoglobinopathies worldwide, affecting almost 400,000 newborns globally each year. It is characterized by chronic hemolytic anemia and endothelial dysfunction, resulting in a constant state of disruption of the vascular system and leading to recurrent episodes of ischemia-reperfusion injury (I/RI) to multiple organ systems. I/RI is a fundamental vascular pathobiological paradigm and contributes to morbidity and mortality in a wide range of conditions, including myocardial infarction, stroke, acute kidney injury, and transplantation. I/RI is c...
Source: The American Journal of Pathology - Category: Pathology Authors: Tags: Am J Pathol Source Type: research
Abstract Sickle cell anaemia results from homozygosity of an A-T point mutation leading to a substitution of glutamic acid for valine at point 6 of the β-globin gene. A person with sickle cell trait inherits one normal and one mutated allele. Patients with sickle cell anaemia, and to a lesser extent sickle cell trait, have a wide spectrum of haemostatic abnormalities. Here we describe the problems faced in obtaining an accurate activated clotting time measurement, in a patient with sickle cell trait, prior to commencement of cardiopulmonary bypass for decannulation of Berlin Heart. PMID: 30628549 [PubMed...
Source: Perfusion - Category: Cardiovascular & Thoracic Surgery Authors: Tags: Perfusion Source Type: research
Pulmonary hypertension (PH) in adults with sickle cell disease (SCD) is associated with early mortality. Chronic thromboembolic PH (CTEPH) is an important complication and contributor to PH in SCD but is likely underappreciated. Guidelines recommend ventilation–perfusion (V/Q) scintigraphy as the imaging modality of choice to exclude CTEPH. Data on V/Q scanning are limited in SCD. Our objective was to compare the performance of V/Q scanning with that of CT pulmonary angiography (CTPA) and to report clinical outcomes associated with abnormal V/Q findings. Methods: Laboratory data, echocardiography, 6-min-walk testing,...
Source: Journal of Nuclear Medicine - Category: Nuclear Medicine Authors: Tags: Clinical Source Type: research
CONCLUSIONS: Although SS and MerKO mice demonstrated elevated numbers of aged neutrophils, our data suggest that oxidant stress causes aged CXCR4HiCD62Llo neutrophils in SS to impede vascular repair after ischemia. This specialized subset of neutrophils may be targeted to improve vascular health in SCD.DisclosuresNo relevant conflicts of interest to declare.
Source: Blood - Category: Hematology Authors: Tags: 201. Granulocytes, Monocytes, and Macrophages: Poster III Source Type: research
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