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Ruikang K Wang - One of the best experts on this subject based on the ideXlab platform.

  • macular vascular Microcirculation in eyes with open angle glaucoma using different visual field severity classification systems
    Journal of Glaucoma, 2019
    Co-Authors: Karine D Bojikian, Joanne C Wen, Qinqin Zhang, Raghu C Mudumbai, Murray A Johnstone, Ruikang K Wang, Priscilla Nobrega, Philip P Chen
    Abstract:

    PRECIS We found significant differences in macular vascular Microcirculation between normal and glaucomatous eyes using optical coherence tomography angiography (OCTA). Macular vascular Microcirculation changes also showed significant correlations with visual field (VF) severity classification systems. PURPOSE To correlate VF severity defined by different classification systems and macular vascular Microcirculation in eyes with glaucoma using OCTA. PATIENTS AND METHODS Twenty normal and 58 open-angle glaucoma (OAG) eyes were scanned using a swept-source OCTA (Plex Elite 9000) and macular vascular Microcirculation was measured by calculating the overall blood flux index (BFI) and vessel area density (VAD) over the entire 6×6 mm area excluding the big retinal vessels. Glaucomatous eyes were staged into severity groups based on 4 VF severity classifications: Hodapp-Parrish-Anderson scale, Glaucoma Severity Staging system, ICD-10 glaucoma staging definitions, and VF mean deviation. Central 10-degree VF mean sensitivity (CMS) was calculated based on 24-2 VF. One-way analysis of variance was used to analyze the differences and correlation between macular vascular Microcirculation and other clinical parameters. RESULTS Glaucomatous eyes had significantly lower ganglion cell and inner plexiform layer BFI and VAD (P<0.0001) compared with normal eyes. In OAG patients, BFI and VAD were significantly higher in mild OAG compared with severe OAG with all VF disease severity classification systems (P<0.001). Glaucoma Severity Staging had the highest correlation with changes in macular vascular Microcirculation metrics (r=0.734 for BFI; r=0.647 for VAD) and VF CMS had highest correlation with macular vascular Microcirculation metrics (r=0.887 for BFI; r=0.903 for VAD). CONCLUSION Macular vascular Microcirculation metrics detected by OCTA correlate with disease severity in glaucomatous eyes. VF CMS, calculated from only 12 tested central 10-degree points, correlated best with macular OCTA.

  • peripapillary retinal nerve fiber layer vascular Microcirculation in glaucoma using optical coherence tomography based microangiography
    Investigative Ophthalmology & Visual Science, 2016
    Co-Authors: Chiehli Chen, Anqi Zhang, Karine D Bojikian, Joanne C Wen, Qinqin Zhang, Chen Xin, Raghu C Mudumbai, Murray A Johnstone, Philip P Chen, Ruikang K Wang
    Abstract:

    Purpose To investigate the vascular Microcirculation changes in the retinal nerve fiber layer (RNFL) in normal, glaucoma suspect, and open-angle glaucoma (OAG) groups using optical coherence tomography-based microangiography (OMAG). Methods One eye from each subject was scanned with a Cirrus HD-OCT 5000-based OMAG prototype system montage scanning protocol centered at the optic nerve head (ONH). Blood flow signals were extracted using OMAG algorithm. Retinal nerve fiber layer vascular Microcirculation was measured by calculating the blood flux index and vessel area density within a 1.2-mm width annulus centered at the ONH with exclusion of big retinal vessels. One-way ANOVA were performed to analyze the RNFL Microcirculation among groups. Linear-regression models were constructed to analyze the correlation between RNFL Microcirculation and clinical parameters. Discrimination capabilities of the flow metrics were assessed with the area under the receiver operating characteristic curve (AROC). Results Twenty normal, 26 glaucoma suspect, and 42 OAG subjects were enrolled. Eyes from OAG subjects and glaucoma suspects showed significantly lower blood flux index compared with normal eyes (P ≤ 0.0015). Retinal nerve fiber layer blood flow metrics showed significant correlations with visual field indices and structural changes in glaucomatous eyes (P ≤ 0.0123). Similar discrimination capability of blood flux index compared with RNFL thickness was found in both disease groups. Conclusions Peripapillary RNFL vascular Microcirculation measured as blood flux index by OMAG showed significant differences among OAG, glaucoma suspect, and normal controls and was significantly correlated with functional and structural defects. Retinal nerve fiber layer Microcirculation measurement using OMAG may help physicians monitor glaucoma.

  • optical microangiography provides an ability to monitor responses of cerebral Microcirculation to hypoxia and hyperoxia in mice
    Journal of Biomedical Optics, 2011
    Co-Authors: Yali Jia, Ruikang K Wang
    Abstract:

    In vivo imaging of Microcirculation can improve our fundamental understanding of cerebral microhemodynamics under various physiological challenges, such as hypoxia and hyperoxia. However, existing techniques often involve the use of invasive procedures or exogenous contrast agents, which would inevitably perturb the intrinsic physiologic responses of Microcirculation being investigated. We report ultrahigh sensitive optical microangiography (OMAG) for label-free monitoring of Microcirculation responses challenged by oxygen inhalation. For the first time, we demonstrate that OMAG is capable of showing the impact of acute hypoxia and hyperoxia on microhemodynamic activities, including the passive and active modulation of microvascular density and flux regulation, within capillary and noncapillary vessels in rodents in vivo. The ability of OMAG to functionally image the intact Microcirculation promises future applications for studying cerebral diseases.

  • highly sensitive imaging of renal Microcirculation in vivo using ultrahigh sensitive optical microangiography
    Biomedical Optics Express, 2011
    Co-Authors: Zhongwei Zhi, Yeongri Jung, Yali Jia, Ruikang K Wang
    Abstract:

    Studying renal Microcirculation and its dynamics is of great importance for understanding the renal function and further aiding the diagnosis, prevention and treatment of renal pathologies. In this paper, we present a potentially useful method to provide high-sensitive volumetric imaging of renal Microcirculations using ultrahigh-sensitive optical microangiography (UHS-OMAG). The UHS-OMAG image system used here is based on spectral domain optical coherence tomography, which uses a broadband light source centered at 1300 nm with an imaging speed of 150 frames per second that requires ~6.7 sec to complete one 3D scan of ~2.5 × 2.5 mm2 area. The technique is sensitive enough to image capillary networks, such as peritubular capillaries within renal cortex. We show the ability of UHS-OMAG to provide depth-resolved volumetric images of capillary level renal Microcirculation. We also show that UHS-OMAG is capable of monitoring the changes of renal Microcirculation in response to renal ischemia and reperfusion. Finally, we attempt to show the capability of OMAG to provide quantitative analysis about velocity changes in a single capillary vessel (down to tens of microns per second) in response to the ischemic event.

  • label free in vivo optical micro angiography imaging of cerebral capillary blood flow within meninges and cortex in mice with the skull left intact
    Proceedings of SPIE, 2011
    Co-Authors: Yali Jia, Ruikang K Wang
    Abstract:

    Abnormal Microcirculation within meninges is common in many neurological diseases. There is a need for an imaging method that is capable of visualizing functional meningeal Microcirculations alone, preferably decoupled from the cortical blood flow. Optical microangiography (OMAG) is a recently developed label-free imaging method capable of producing 3D images of dynamic blood perfusion within micro-circulatory tissue beds at an imaging depth up to ~2 mm, with an unprecedented imaging sensitivity to the blood flow at ~4 μm/s. In this study, we demonstrate the utility of ultra-high sensitive OMAG in imaging the detailed blood flow distributions, at a capillary level resolution, within meninges and cortex in mice with the cranium left intact. The results indicate that OMAG can be a valuable tool for the study of meningeal circulations.

Maarten L. Simoons - One of the best experts on this subject based on the ideXlab platform.

Aristidis Veves - One of the best experts on this subject based on the ideXlab platform.

  • micro and macrovascular disease in diabetic neuropathy
    2007
    Co-Authors: Aristidis Veves, Antonella Caselli
    Abstract:

    Diabetes is often defined a “vascular disease” because of the early and extensive involvement of the vascular-tree observed in patients with diabetes and even in those at risk of developing diabetes. Both the micro- and macrocirculation are affected. Changes in the micro- and macrocirculation, both anatomical and functional, contribute to the development of diabetic neuropathy. On the other hand, the development of diabetic neuropathy also affects the vasodilatory capacity of the Microcirculation. Thus, the interaction between changes in the vasculature and peripheral nerves is bidirectional and results in changes in both blood flow and neuronal function. The possible links between diabetic micro- and macrovascular alterations and nerve damage will be the focus of this chapter.

  • valsartan improves resting skin blood flow in type 2 diabetic patients and reduces poly adenosine diphosphate ribose polymerase activation
    Journal of Vascular Surgery, 2006
    Co-Authors: Gautam V Shrikhande, Lalita Khaodhiar, Salvatore T Scali, Christina Lima, Matthew Hubbard, Katherine A Dudley, Om P Ganda, Christiane Ferran, Aristidis Veves
    Abstract:

    Objective To examine the effect of a 12-week daily treatment with 160 mg of valsartan, an angiotensin II receptor blocker, on the Microcirculation and macrocirculation of type 2 diabetic patients (T2DM) and healthy subjects. Methods This was a prospective, randomized, double-blind, placebo-controlled crossover study. Thirteen T2DM with no severe complications and 13 healthy subjects completed the trial. Results Treatment with valsartan in T2DM improved the resting forearm skin blood flow and increased the resting brachial artery diameter but had no effects on arterial blood pressure, large vessel vascular reactivity, or carotid intima-media thickness. Resting skin blood flow increased by 60% (2%-90%; median and 25th-75th percentiles) during valsartan treatment and by only 2% (−22% to 27%) during placebo treatment ( P P P = .057). Valsartan had no effect on the biochemical markers of endothelial cell activation and other cytokines, including CAMs, interleukin 6, tumor necrosis factor α, C-reactive protein, adiponectin, and plasma activator inhibitor 1. Conclusions Valsartan increases the resting skin blood flow in T2DM, likely through reduction of PARP activity.

  • endothelium dependent vasodilatation is impaired in both Microcirculation and macrocirculation during acute hyperglycemia
    Journal of Vascular Surgery, 1998
    Co-Authors: Camero M Akbari, Rola Saouaf, Deborah F Arnhill, Peggy A Newma, Frank W Logerfo, Aristidis Veves
    Abstract:

    Abstract Purpose: Endothelial dysfunction is associated with atheromatosis and is a common finding with diabetes. We have studied the effects of acute hyperglycemia on the endothelium-dependent vasodilatation of both the Microcirculation and the macrocirculation of healthy subjects. Because of the presence of endothelial dysfunction with diabetes, we hypothesize that acute hyperglycemia causes impaired endothelial-dependent responses. Methods: Twenty healthy subjects (15 men, 5 women) with a mean age of 32.3 years (range, 23 to 49 years) were examined during fasting conditions and at 1 hour after the ingestion of 75 g of glucose. The endothelium-dependent vasodilatation of the brachial artery, a conduit vessel, was evaluated with high-resolution ultrasound scan to measure the changes in the vessel diameter induced with reactive hyperemia. In the Microcirculation, the endothelial function was assessed by measuring the changes in the erythrocyte flux after the acetylcholine iontophoresis. Results: The brachial artery endothelium-dependent dilatation was greater during fasting as compared with the response after the glucose load was administered (11.7% [8.3 to 14.3] vs 4.2% [1.5 to 9.6]; P P P Conclusions: In healthy subjects, the ingestion of a glucose load impairs the endothelial-dependent vasodilation in both the Microcirculation and the macrocirculation. Because impairment of endothelial responses is associated with the early changes of atherosclerosis, it is possible that prolonged hyperglycemia and endothelial dysfunction may lead to the early and accelerated atherosclerosis of diabetes. Further studies are necessary to examine the long-term effects of hyperglycemia. (J Vasc Surg 1998;28:687-94.)

Pascal Leprince - One of the best experts on this subject based on the ideXlab platform.

Can Ince - One of the best experts on this subject based on the ideXlab platform.

  • Kidney Microcirculation as a Target for Innovative Therapies in AKI
    'MDPI AG', 2021
    Co-Authors: Bülent Ergin, Sakir Akin, Can Ince
    Abstract:

    Acute kidney injury (AKI) is a serious multifactorial conditions accompanied by the loss of function and damage. The renal Microcirculation plays a crucial role in maintaining the kidney’s functional and structural integrity for oxygen and nutrient supply and waste product removal. However, alterations in Microcirculation and oxygenation due to renal perfusion defects, hypoxia, renal tubular, and endothelial damage can result in AKI and the loss of renal function regardless of systemic hemodynamic changes. The unique structural organization of the renal microvasculature and the presence of autoregulation make it difficult to understand the mechanisms and the occurrence of AKI following disorders such as septic, hemorrhagic, or cardiogenic shock; ischemia/reperfusion; chronic heart failure; cardiorenal syndrome; and hemodilution. In this review, we describe the organization of Microcirculation, autoregulation, and pathophysiological alterations leading to AKI. We then suggest innovative therapies focused on the protection of the renal Microcirculation and oxygenation to prevent AKI

  • effect of pneumoperitoneum and steep reverse trendelenburg position on mean systemic filling pressure venous return and Microcirculation during esophagectomy
    Journal of Thoracic Disease, 2018
    Co-Authors: Huaiwu He, Bart F Geerts, G Gruartmoner, Yilmaz Ince, Suzanne S Gisbertz, Can Ince, Mark I Van Berge Henegouwen, Markus W Hollmann, Denise P Veelo
    Abstract:

    Background: Keeping adequate tissue perfusion during high-risk abdominal surgery is of utmost importance to decrease postoperative complications. The objective was to investigate the alteration in mean systemic filling pressure (MSFP), venous return (VR) and sublingual Microcirculation during pneumoperitoneum and steep reverse-Trendelenburg position during thoracolaparoscopic esophagectomy. Methods: This is a single-center prospective observational study in operating room at a university hospital. Eleven consecutive patients undergoing minimally invasive esophagectomy. Intraoperative hemodynamic and sublingual microcirculatory variables were simultaneously measured within 5 minutes at the following time points: T1, baseline supine position before the start of surgery; T2, pneumoperitoneum in supine position; T3, steep reverse-Trendelenburg position after the pneumoperitoneum. The cardiac output (CO) was obtained with continuous pulse contour waveform-derived measurements, and the MSFP was estimated with the analogue method. Results: The pneumoperitoneum and reverse-Trendelenburg caused an increase in stroke volume variation (SVV), MSFP and central venous pressure (CVP), and a decrease in the microcirculatory perfusion index (MFI, 2. Using a CVP ≥23 mmHg to detect MFI ≤2 results in a sensitivity of 61.54% and a specificity of 100%. Conclusions: A high CVP is related to poor microcirculatory flow perfusion even if the macrocirculation has been maintained during pneumoperitoneum.

  • intravenous fluids in aki a mechanistically guided approach
    Seminars in Nephrology, 2016
    Co-Authors: Can Ince, Matthieu Legrand
    Abstract:

    Acute kidney injury (AKI) has been associated with an increased risk of death and morbidity in many clinical scenarios. The prevention and treatment of AKI therefore has been advocated as a high-priority research focus. However, nearly all strategies tested in this setting have failed to prevent or cure AKI and fluid loading remains a cornerstone of preventive and curative treatment of AKI. Concerns have been raised, however, regarding both the efficacy and safety of fluid loading to prevent or reverse AKI. In this review, we address the question of the best use of fluid loading based on current preclinical and clinical data in a mechanistically guided approach. Impacts of fluid resuscitation on renal hemodynamics, from macrocirculation to Microcirculation, with physiological end points as well as renal consequences of different fluids available are discussed. Finally, the complex relationship between renal hemodynamics is discussed.

  • hemodynamic coherence and the rationale for monitoring the Microcirculation
    Critical Care, 2015
    Co-Authors: Can Ince
    Abstract:

    This article presents a personal viewpoint of the shortcoming of conventional hemodynamic resuscitation procedures in achieving organ perfusion and tissue oxygenation following conditions of shock and cardiovascular compromise, and why it is important to monitor the Microcirculation in such conditions. The article emphasizes that if resuscitation procedures are based on the correction of systemic variables, there must be coherence between the macrocirculation and Microcirculation if systemic hemodynamic-driven resuscitation procedures are to be effective in correcting organ perfusion and oxygenation. However, in conditions of inflammation and infection, which often accompany states of shock, vascular regulation and compensatory mechanisms needed to sustain hemodynamic coherence are lost, and the regional circulation and Microcirculation remain in shock. We identify four types of microcirculatory alterations underlying the loss of hemodynamic coherence: type 1, heterogeneous microcirculatory flow; type 2, reduced capillary density induced by hemodilution and anemia; type 3, microcirculatory flow reduction caused by vasoconstriction or tamponade; and type 4, tissue edema. These microcirculatory alterations can be observed at the bedside using direct visualization of the sublingual Microcirculation with hand-held vital microscopes. Each of these alterations results in oxygen delivery limitation to the tissue cells despite the presence of normalized systemic hemodynamic variables. Based on these concepts, we propose how to optimize the volume of fluid to maximize the oxygen-carrying capacity of the Microcirculation to transport oxygen to the tissues.

  • elevated central venous pressure in septic patients is associated with impairment of microcirculatory blood flow
    Critical Care, 2012
    Co-Authors: N Vellinga, Can Ince, E C Boerma
    Abstract:

    The Microcirculation plays a pivotal role in oxygen delivery to the tissue. Microcirculatory alterations have been observed to occur independently of the major inflow variable for Microcirculation: mean arterial pressure. According to physiological theory, the Microcirculation is considered to be a low-pressure compartment. Maximum optimal central venous pressure (CVP) according to Surviving Sepsis Campaign (SSC) guidelines is 12 to 15 mmHg in mechanically ventilated patients. We hypothesized that a CVP >12 mmHg would hamper microcirculatory perfusion but not diffusion, by acting as outflow obstruction.