Search Results (29)

Gas-inducing reactors (GIRs) are widely used in applications where external gas recycling is unsafe or operationally restricted, yet quantitative design guidelines for impeller–stator geometry remain scarce, despite its strong influence on gas dispersion and retention. This study investigates the effects of stator blade number and blade thickness on gas holdup in a double-impeller GIR using a three-dimensional Euler–Euler CFD framework. Stator configurations with 12–48 blades and blade thicknesses of 1.5–45 mm were examined and validated against experimental data, with gas holdup predictions agreeing within 5–10%. The results show that the stator open-area fraction (ϕ_A) is the dominant geometric parameter governing the balance between radial dispersion and axial confinement. High-ϕ_A stators (fewer, thinner blades) enhance bulk recirculation and bubble residence time, increasing gas holdup by up to ~20% relative to dense stator designs, whereas low-ϕ_A stators suppress macro-circulation, promote axial gas transport, and reduce holdup despite higher local dissipation near the rotor–stator gap. A modified gas-holdup correlation incorporating ϕ_A is proposed, yielding strong agreement with CFD and experimental data (R² = 0.96). Torque analysis further reveals competing effects between impeller gassing, which lowers hydraulic loading, and increased flow resistance at low ϕ_A, which elevates torque. Overall, the results provide quantitative guidance on how stator blade number and thickness influence gas holdup, enabling informed stator design and optimization in GIRs to improve gas dispersion through rational geometric selection rather than trial and error approaches. Full article

Introduction: Blood gas analysis is utilized to assess parameters of oxygenation and ventilation, including acid–base status [pH value, base excess (BE) or base deficit (BD), and bicarbonate (HCO₃)], to evaluate systemic metabolism status. Acid–base imbalances can have complex effects on the organism, potentially impacting oxygen delivery to tissue. Cerebral oximetry is a non-invasive monitoring technique using near-infrared spectroscopy (NIRS) for the continuous measurement of cerebral tissue oxygenation. The relationship between the acid–base status and cerebral tissue oxygenation in neonates remains unclear. This systematic qualitative review aims to analyze current knowledge of the potential correlations between different acid–base status parameters and cerebral tissue oxygenation measured via NIRS in neonates. Methods: A systematic search of PubMed and Ovid Embase was performed, focusing on cerebral oxygenation, neonates, and acid–base status. Risk of bias was assessed using the ‘‘Risk of Bias for Non-randomized Studies of Exposures’’ (ROBINS-E) instrument. Results: Fifty studies that measured parameters of the acid–base status and cerebral tissue oxygenation in the neonatal period were identified. Seven studies demonstrated a correlation between pH and cerebral tissue oxygenation, while eleven studies found no such correlation. Five studies demonstrated a correlation between the BE/BD and cerebral tissue oxygenation, while six studies found no such correlation. Three studies demonstrated a correlation between HCO₃ and cerebral tissue oxygenation, while five studies found no such correlation. Discussion: Associations between acid–base status parameters and cerebral tissue oxygenation remain controversial. However, studies with the lowest risk of bias mainly demonstrated no significant correlation between any of the acid–base status parameters and cerebral tissue oxygenation. Full article

In the current study, we focus on analyzing the relationship between changes in micro- and macrocirculation and different stages of metabolic memory. We hypothesized that early poor glycemic control induces lasting endothelial changes detectable in pediatric type 1 diabetes (T1D) microcirculation. We assessed microcirculation structure and function using capillaroscopy, transcutaneous oxygen pressure (TcPO₂), and optical coherence tomography (OCT). We evaluated macrovascular circulation using pulsatility index (PI), ankle-brachial index (ABI) and pulse pressure (PP). We also examined the relationship between circulation parameters, the age at onset, and diabetes duration. The study included 67 patients with uncomplicated type 1. We divided all patients into four groups based on their HbA_1c levels at T1D onset and their average HbA_1c after one and two years. We assessed the concentrations of TNF-α, IL-35, IL-4, IL-10, IL-18, IL-12, serum angiogenin, VEGF, sVCAM-1, ICAM-1, sP-Selectin, AGEs, and sRAGE. We compared subgroups with different levels of metabolic memory but comparable T1D duration and age at diagnosis. Micro- and macrovascular parameters were similar between the groups. Our comparison of subgroups with identical metabolic memory but different durations and ages at diagnosis revealed clear differences. The subgroup with a shorter T1D duration showed higher capillary density and a smaller inter-capillary distance compared to those with a longer diabetes duration. This subgroup with shorter duration had significantly lower AGE levels and a reduced TNF-α/IL-35 ratio, along with higher levels of IL-35, IL-4, and IL-12, compared to the longer-duration group. Our findings indicate that in youths with uncomplicated T1D, disease duration—not metabolic memory—plays a dominant role in early microvascular alterations. Full article

Arterial stiffness indicates early atherosclerotic changes prevalent in children and adolescents with type 1 diabetes (T1D), even in those with a well–controlled disease and without additional cardiovascular risk factors. This study aimed to determine whether low–density lipoprotein (LDL) cholesterol and cytokine levels can indicate vascular stiffness in pediatric patients without conventional microangiopathic complications who are not undergoing lipid–lowering therapy. The total study group consisted of 59 pediatric patients divided into two subgroups based on their LDL cholesterol levels and matched for age, age at onset, and duration of diabetes. The investigation involved the precise measurement of several biomarkers including tumor necrosis factor (TNF–α), interleukin 35 (IL-35), interleukin 4 (IL-4), interleukin 10 (IL-10), interleukin 12 (IL-12), interleukin 18 (IL-18), vascular endothelial growth factor (VEGF), Soluble Vascular Cell Adhesion Molecule–1 (sVCAM–1), Intercellular Adhesion Molecule–1 (ICAM-1), Soluble Platelet Selectin (sP–Selectin), Advanced Glycation End Products (AGEs), and Receptors for Advanced Glycation End Products (sRAGE). Arterial stiffness was assessed by calculating pulsatility indices in the common carotid artery and the peripheral arteries in the upper and lower limbs. The comparative analysis indicated that, in the subgroup with LDL cholesterol levels below 100 mg/dL, in comparison to the subgroup with LDL above 100 mg/dL, there was a significant increase in pulsatility indices in elastic and large muscle arteries and notably higher levels of IL-35, IL-10, sVCAM–1, and ICAM-1. This study is the first to recommend the pulsatility index of elastic and large muscular arteries as an effective diagnostic tool for evaluating early atherosclerotic lesions in children and adolescents diagnosed with type 1 diabetes. Elevated LDL cholesterol levels may contribute to vascular stiffness through mechanisms related to a weakened inflammatory response, highlighting the complex interaction between lipid levels, inflammation, and vascular health in patients with type 1 diabetes. Full article

During the first minutes of life, complex dynamic processes occur, facilitating a normal transition to ex utero life. In healthy term infants, these processes typically occur with minimal intervention required but are often more challenging for the preterm infant. These challenges involve not only the physiological processes encountered but also an organizational process: that of a team of healthcare providers led by a neonatologist, establishing a diagnosis based on clinical and technical information and initiating time-critical and potentially life-altering interventions. In this narrative review, we highlight the challenges of both processes. We explore the role and limitations of well-established and newer potential monitoring modalities, in particular respiratory function monitoring and cerebral near-infrared spectroscopy, to optimally inform the team in regards to physiological processes. We also evaluate the important role that human factors play in the process of decision-making. Both are important for optimal performance to enable successful transition and thereby reduce short- and long-term problems. We identify research goals to inform future studies to further optimize technological and human aspects in the first minutes of life. Full article

Background/Objectives: The perioperative interplay between blood pressure, vasopressors, and macrocirculation is well established. However, in the context of free flap surgery, the potential impact of these factors on microvascular flow remains elusive. The aim was to evaluate the impact of norepinephrine administration on the microcirculation of free flaps. Methods: Postoperative systolic blood pressure (sBP), norepinephrine infusion rates (NIRs), and free flap microcirculation were monitored prospectively and analyzed retrospectively in patients receiving free flap surgery who required postoperative intermediate (IMC) or intensive care (ICU). Blood flow, hemoglobin oxygenation (SO₂), and relative hemoglobin levels (rHbs) were measured over a period of 24 hours post-anastomosis by laser-doppler flowmetry and white light spectroscopy using the “Oxygen to See” device (O2C, LEA Medizintechnik, Gießen, Germany). Multivariate analysis was performed to determine the impact of NIR on microvascular flow, adjusting for several confounding factors. Subgroup analysis was conducted by categorizing into three groups based on patients’ postoperative sBP. Results: Flaps were performed in 105 patients with a mean age of 61.46 ± 16.29 years. Postoperatively, an increase in microvascular flow over time was observed across all free flaps, while NIR decreased and sBP maintained stable values. Multivariate analysis revealed that the time post-anastomosis (B = 3.76, p < 0.001), SO₂ (B = 0.55, p < 0.001), rHb (B= −0.79, p < 0.001), female gender (B = 29.25, p = 0.02), and no previous radiation therapy (B = 41.21, p = 0.04) had a significant impact on postoperative microvascular flow in free flaps. NIR, sBP, smoking status, old age, and ASA score showed no significant impact on free flap flow. Further, NIR showed no significant impact on microvascular flow in any of the subgroups investigated. Conclusions: These findings support the safety of using norepinephrine for maintaining stable blood pressure without compromising microvascular flow, offering valuable guidance for postoperative management. Full article

This study aimed to analyze the relationship between cutaneous microcirculation reactivity, retinal circulation, macrocirculation function, and specific adhesion molecules in young patients with uncomplicated type 1 diabetes. Fifty-five patients with type 1 diabetes mellitus (T1DM), aged 8 to 18 years, were divided into subgroups based on skin microcirculation reactivity. The cutaneous microcirculatory vessels were considered reactive if post-test PORH coverage increased compared to pre-test coverage. Optical coherence tomography (OCT) was conducted to detect early retinopathic changes. Macrocirculation was described using pulsatility indices (PIs) determined for common carotid (CCA) and peripheral arteries of the upper and lower limbs. The ankle–brachial index was also assessed. There were no significant differences in retinal circulation and macrocirculation between the studied subgroups. However, there were significant differences between the various subgroups concerning the age at onset of diabetes and the sP-selectin levels but not ICAM-1 and sVCAM-1. The sP-selectin differences remained true after adjusting for age at onset. The sP-selectin level was significantly higher in the subgroup of patients with non-reactive cutaneous microcirculation. The results of our study indicate that sP-selectin may be considered as an immunological marker for cutaneous abnormalities, which serve as an early indicator of endothelial dysfunction in young patients with type 1 diabetes in the absence of classical complication. Full article

A dysregulated immune response is associated with an excessive release of cytokines that can lead to systemic vasoplegia and vasoplegic shock with the development of multiorgan failure that is associated with an increased risk of dying. Under physiological circumstances, the endothelium and the glycocalyx are responsible for maintaining vascular tone, capillary permeability, and hemostasis, and controlling inflammation. In hyperinflammation, the endothelium and glycocalyx become damaged due to the excessive production of certain toxic proteins, along with an overwhelming release of cytokines. It has been shown in both in vitro animal experiments and in humans that extracorporeal hemoadsorption can reduce circulating levels of cytokines and may also remove toxic proteins that directly take part in endothelium and glycocalyx damage. The current review aims to summarize current knowledge, put recent findings into context, and introduce the hypothesis of “endothelial protection with hemoadsorption” in critically ill patients. Full article

Background: Systemic sclerosis (SSc) represents a multidimensional disease affecting various organs and systems, with the common denominator being the vascular pathology encountered in the micro- and macrocirculation of SSc patients. Recently, much progress has been made toward understanding the molecular basis of endothelial injury and subsequent fibroblast activation, thus paving the way for specific therapy that can target and counteract these processes. Aim: In this review, we examined the latest preclinical and clinical data on therapeutic options to address vascular abnormalities in SSc. Results: We discuss the efficacy of current treatments, including pharmacological agents and emerging therapies, in mitigating vascular damage and improving patient outcomes based on preclinical models and clinical trials that offer evidence of their safety and effectiveness. Conclusions: Although promising therapeutic strategies emerge, optimizing the management of vascular abnormalities in SSc requires further research. Full article

Background: It is established that diabetes mellitus (DM) is characterized by increased cardiovascular risk associated with subclinical atherosclerosis as well as microvascular alterations. Laser speckle contrast analysis (LASCA) is an innovative, non-invasive method for assessing skin microvascular function. Objectives: We sought to assess skin microvascular function in patients with type 2 DM and matched controls. Methods: Consecutive patients with DM and individuals matched for age, sex and BMI were included in the study. Skin microvascular perfusion was assessed, using LASCA, during baseline, a 5 min occlusion period and a 5 min reperfusion period. Carotid intima-media thickness (cIMT) was measured as a surrogate marker of macrocirculation. Results: In total, 18 patients with DM and 22 in the control group were enrolled. No statistically significant differences were observed in baseline flux, peak flux and percentage decrease during arterial occlusion. During reperfusion, individuals with DM exhibited a smaller peak magnitude compared to controls (147.0 ± 64.7% vs. 189.4 ± 46.0%, respectively; p < 0.05). Moreover, cIMT was higher in patients with DM compared to controls (0.68 ± 0.09 mm vs. 0.60 ± 0.08 mm, respectively, p < 0.01) and was negatively correlated with skin microvascular reactivity in the univariate analysis. In the multivariate analysis, glucose and office systolic blood pressure levels remained significant predictors of microvascular reactivity. Conclusions: Our study shows that patients with type 2 DM exhibit impaired skin microvascular function compared to controls. Furthermore, glucose levels and blood pressure play a key role in microvascular dysfunction. However, additional studies are needed to address the clinical significance of early microvascular changes in DM. Full article

Managing chronic limb-threatening ischemia (CLTI) is challenging due to difficulties in assessing tissue oxygen saturation in ulcers. Near-infrared spectroscopy (NIRS) is a non-invasive method for measuring tissue oxygen saturation (StO₂). This study evaluated the effects of endovascular treatment (EVT) on StO₂ and wound healing in CLTI patients, comparing NIRS to standard ankle–brachial index (ABI) measurements. Using the Duesseldorf PTA Registry, 43 CLTI patients were analyzed: 27 underwent EVT, and 16 received conservative treatment. ABI assessed macrocirculation, while NIRS measured wound, wound area, and mean foot StO₂ at baseline, post-EVT, and four-month follow-up. Wound severity was classified by wound area and wound, ischemia, and foot infection (WIfI) score. Wound StO₂ increased significantly (median (interquartile range (IQR)), 38 (49.3) to 60 (34.5)%, p = 0.004), as did wound area StO₂ (median (IQR), 70.9 (21.6) to 72.8 (18.3)%, p < 0.001), with no significant changes in the control group by four-month follow-up. Wound area decreased significantly after EVT (mean ± SD, 343.1 ± 267.8 to 178.1 ± 268.5 mm², p = 0.01) but not in the control group. Changes in wound StO₂, wound area StO₂, and WIfI score correlated with wound area reduction, unlike ABI. This small exploratory study shows that NIRS-measured StO₂ improvements after EVT correlate with reduced wound area and WIfI scores, highlighting NIRS as a potential enhancement for CLTI wound management in addition to ABI. Full article

Endothelial cells (ECs) are vital structural units of the cardiovascular system possessing two principal distinctive properties: heterogeneity and plasticity. Endothelial heterogeneity is defined by differences in tissue-specific endothelial phenotypes and their high predisposition to modification along the length of the vascular bed. This aspect of heterogeneity is closely associated with plasticity, the ability of ECs to adapt to environmental cues through the mobilization of genetic, molecular, and structural alterations. The specific endothelial cytoarchitectonics facilitate a quick structural cell reorganization and, furthermore, easy adaptation to the extrinsic and intrinsic environmental stimuli, known as the epigenetic landscape. ECs, as universally distributed and ubiquitous cells of the human body, play a role that extends far beyond their structural function in the cardiovascular system. They play a crucial role in terms of barrier function, cell-to-cell communication, and a myriad of physiological and pathologic processes. These include development, ontogenesis, disease initiation, and progression, as well as growth, regeneration, and repair. Despite substantial progress in the understanding of endothelial cell biology, the role of ECs in healthy conditions and pathologies remains a fascinating area of exploration. This review aims to summarize knowledge and concepts in endothelial biology. It focuses on the development and functional characteristics of endothelial cells in health and pathological conditions, with a particular emphasis on endothelial phenotypic and functional heterogeneity. Full article

Critical illness is often accompanied by a hemodynamic imbalance between macrocirculation and microcirculation, as well as mitochondrial dysfunction. Microcirculatory disorders lead to abnormalities in the supply of oxygen to tissue cells, while mitochondrial dysfunction leads to abnormal energy metabolism and impaired tissue oxygen utilization, making these conditions important pathogenic factors of critical illness. At the same time, there is a close relationship between the microcirculation and mitochondria. We introduce here the concept of a “critical unit”, with two core components: microcirculation, which mainly comprises the microvascular network and endothelial cells, especially the endothelial glycocalyx; and mitochondria, which are mainly involved in energy metabolism but perform other non-negligible functions. This review also introduces several techniques and devices that can be utilized for the real-time synchronous monitoring of the microcirculation and mitochondria, and thus critical unit monitoring. Finally, we put forward the concepts and strategies of critical unit-guided treatment. Full article

Objective: The aim of this qualitative systematic review was to identify publications on blood pressure monitoring in combination with cerebral tissue oxygenation monitoring during the first week after birth focusing on cerebral autoregulation. Methods: A systematic search was performed on PubMed. The following search terms were used: infants/newborn/neonates, blood pressure/systolic/diastolic/mean/MAP/SAP/DAP, near-infrared spectroscopy, oxygenation/saturation/oxygen, and brain/cerebral. Additional studies were identified by a manual search of references in the retrieved studies and reviews. Only human studies were included. Results: Thirty-one studies focused on preterm neonates, while five included preterm and term neonates. In stable term neonates, intact cerebral autoregulation was shown by combining cerebral tissue oxygenation and blood pressure during immediate transition, while impaired autoregulation was observed in preterm neonates with respiratory support. Within the first 24 h, stable preterm neonates had reduced cerebral tissue oxygenation with intact cerebral autoregulation, while sick neonates showed a higher prevalence of impaired autoregulation. Further cardio-circulatory treatment had a limited effect on cerebral autoregulation. Impaired autoregulation, with dependency on blood pressure and cerebral tissue oxygenation, increased the risk of intraventricular hemorrhage and abnormal neurodevelopmental outcomes. Conclusions: Integrating blood pressure monitoring with cerebral tissue oxygenation measurements has the potential to improve treatment decisions and optimizes neurodevelopmental outcomes in high-risk neonates. Full article

(1) Background: Oncological demolitive–reconstructive surgeries in the head and neck region cause significant stress on patients’ biohumoural, cardiac, and vascular systems, leading to disturbances in macrocirculatory and microcirculatory parameters. Traditional monitoring addresses the symptoms, but not the underlying cause. Microcirculatory assessments complement macrocirculatory monitoring, and bladder-catheter-based technology offers a better representation of central microcirculation. Flap reconstruction surgeries involve demolitive and reconstructive phases, requiring optimal tissue perfusion. The literature lacks a consensus on macro–microcirculation coupling, and there is no agreement on the use of vasopressors during head and neck surgeries. Evidence-based guidelines are lacking, resulting in variations in vasopressor administration. (2) Methods: This is a 12-month observational, prospective study conducted in a single center. It aims to evaluate the impact of macro–microcirculation coupling on clinical complications in head and neck surgery. All consecutive patients undergoing oncologic surgery requiring flap reconstruction and meeting the inclusion criteria will be enrolled. The study will utilize standard hemodynamic monitoring and bladder catheterization for measuring urine output and temperature. (3) Conclusions: The study aims to evaluate the coupling of macro- and microcirculation in head and neck surgeries, assess hemodynamic parameters and microcirculatory changes, and investigate their association with postoperative complications. The results can enhance patient care and surgical outcomes. Full article