Fluid Responsiveness Research Articles

Assessment of Fluid Responsiveness via Central Venous Ultrasound Measurement: A Network Meta-Analysis

Background: Ultrasonographic assessment of the diameters of various veins and their indices are among the most applied diagnostic tools for evaluating fluid responsiveness in clinical practice. Despite their widespread use, there is no definitive answer on which is preferable. Our study aimed to investigate the diagnostic accuracy of different venous diameters and their indices to assess fluid responsiveness. Methods: We conducted a systematic review and network meta-analysis, analyzing prospective studies evaluating the diagnostic accuracy of venous diameters (inferior vena cava [IVC], internal jugular vein [IJV], superior vena cava, and subclavian vena) and their indices for fluid responsiveness. Electronic databases were searched from inception until March 2024; this search was supplemented by snowballing methods. The risk of bias was evaluated with QUADAS-2, and evidence certainty was assessed using the GRADE approach. Nine prospective cohort studies (560 patients) were included. Results: The network meta-analysis revealed that the ΔCaval index exhibited a significant performance advantage over other “venous” test parameters. The caval index significantly outperformed IJV min/max and IVCmax. IJV index and IVCmin significantly outperformed IJVmin/max. The caval index was comparable to the IJV index. The caval index was comparable during mechanical ventilation and spontaneous breathing. Conclusions: In this meta-analysis, the ΔCaval index test showed higher diagnostic accuracy for fluid responsiveness compared with other venous tests. Caval and jugular indices displayed similar accuracy, and caval indices were consistent under mechanical ventilation and spontaneous breathing. Indices generally outperformed absolute values, except for IVCmin, which equaled the caval index in efficacy. This study was registered on the International Platform for Registered Protocols for Systematic Reviews and Meta-Analyses: INPLASY202430104.

Current Concepts in Fluid Resuscitation and Vasopressor Use in Cirrhosis.

Critically ill patients with cirrhosis and liver failure not uncommonly have hypotension due to multifactorial reasons, that include hyperdynamic state with increased cardiac index, low systemic vascular resistance due to portal hypertension, following the use of beta blocker or diuretic therapy, and severe sepsis. These changes are mediated by microvascular alterations in the liver, systemic inflammation, activation of renin angiotensin aldosterone system, and vasodilatation due to endothelial dysfunction. Hemodynamic assessment includes measuring inferior vena cava indices, cardiac output and systemic vascular resistance using point-of-care ultrasound (POCUS), in addition to arterial waveform analysis, or pulmonary artery pressures, and lactate clearance to guide fluid resuscitation. Fluid responsiveness reflects the ability of fluid bolus to increase the cardiac output and is assessed effectively by POCUS, passive leg raise manoeuvre, and dynamic tests such as pulse pressure and stroke volume variation both in spontaneously breathing and mechanically ventilated patients. Albumin has pleotropic benefits through anti-inflammatory properties besides its standard action on oncotic pressure and volume expansion in patients with cirrhosis but has potential for precipitating pulmonary edema. In conclusion, fluid therapy in critically ill patients with liver disease is a complex and dynamic process that requires individualised management protocols to optimise patient outcomes.

The Left Ventricular Outflow Tract Velocity Time Integral as a Predictor of Fluid Responsiveness in Patients With Sepsis-Related Acute Circulatory Failure

The Left Ventricular Outflow Tract Velocity Time Integral as a Predictor of Fluid Responsiveness in Patients With Sepsis-Related Acute Circulatory Failure

The Effect of Peri-Implant Therapy on the Expression of Th17-Related Cytokines in Patients with Peri-Implant Mucositis and Peri-Implantitis: A Prospective Longitudinal Study

Background/Objectives: Cytokines related to the Th17 response have been associated with peri-implant diseases; however, the effect of peri-implant therapy on their modulation remains underexplored. To evaluate the effect of peri-implant therapy on the expression of cytokines related to the Th17 response in the peri-implant crevicular fluid (PICF) (GM-CSF, IFN-γ, IL-1β, IL-4, IL-6, IL-10, IL-12 (p70), IL-17A, IL-21, IL-23, and TNF-α) of partially edentulous patients with peri-implant disease (PID). Methods: Thirty-seven systemically healthy individuals presenting with peri-implant mucositis (PIM) (n = 20) or peri-implantitis (PI) (n = 17) were treated and evaluated at baseline (T0) and three months after therapy (T1). Clinical parameters (probing depth (PD), clinical attachment level (CAL), plaque index, and bleeding on probing index (BoP), were evaluated. The PIM group underwent non-surgical therapy, while the PI group received a surgical approach. PICF was collected with absorbent paper strips and analyzed with a multiplex assay. Results: Eighty-eight implants were treated in 37 patients (56 in the PIM group and 32 in the PI group). After therapy, significant reductions in PD, CAL, plaque index, and BoP were observed in the PIM group (p < 0.05). In the PI group, significant reductions in PD, CAL, and BoP were noted (p < 0.05). The PIM group showed a significant reduction of IL-17A and TNF-α after therapy, while the PI group showed a significant reduction of IL-1β, IL-6, and TNF-α (p < 0.05). Conclusions: The peri-implant therapy for patients with PID reduced the expression of cytokines related to the Th17 response in PICF.

Hydrodynamic modes in nano-channels

This paper investigates the local hydrodynamics of a dense fluid confined in nanoscale slit-pores with different heights. Using non-equilibrium molecular dynamics simulations of the fluid system, we induce a steady-state sinusoidal velocity profile across the channel having a characteristic wavelength, thus, probing the fluid response to a specific Fourier mode. As expected, for sufficiently large channel heights and wavelengths there is an excellent agreement between the hydrodynamic predictions and simulation data. As the wavelength decreases to around 5 molecular diameters, the classical hydrodynamics fails to predict the steady-state velocity profile; we attribute this to the non-local nature of the fluid response and the presence of density gradients in the wall–fluid interfacial region. Using generalized hydrodynamics and the Fourier spectrum of the density profile, we derive the strain rate amplitude and shear pressure corrections due to these two effects. The local relaxation from the steady-state to the zero flow situation is tracked for different channel heights and wavelengths. The relaxation is in general visco-elastic in the wall–fluid region, and we argue that this phenomenon is the mechanism behind the “enhanced viscosity” used in the literature. We also report a surprising dynamics for the fluid located between the wall–fluid region and bulk region, which cannot be explained by classical hydrodynamics; here, an initial exponential relaxation abruptly transitions into a linear relaxation. The work highlights the many different physical mechanisms present in nano-confined fluids, and that the fluid response is in general position and wavelength dependent.

Demystifying Volume Status: An Ultrasound-Guided Physiologic Framework.

Accurate assessment of a patient's volume status is crucial in many conditions, informing decisions on fluid prescribing, vasoactive agents, and decongestive therapies. Determining a patient's volume status is challenging, due to limitations in examination and investigations and the complexities of fluid homeostasis in disease states. Point-of-care ultrasound (POCUS) is useful in assessing hemodynamic parameters related to volume status, fluid responsiveness, and fluid tolerance. It requires understanding several physiologic concepts to accurately interpret and integrate POCUS findings into volume-related clinical decision-making. The following concepts serve as a scaffold for a comprehensive volume status assessment: central venous pressure, right heart function, left heart assessment, extravascular volume, and venous congestion. POCUS allows us access to these hemodynamic and structural data points as an extension and refinement of the physical exam. Often, multiple POCUS applications are employed, and findings must be integrated with the rest of the clinical evaluation. We illustrate this using three common scenarios: hypotension, hypoxia, and acute kidney injury. Clinicians must be aware of the strengths and weaknesses of findings in different physiologic states, and potential pitfalls of image acquisition and interpretation. Further studies are necessary to determine the benefits and clinical outcomes of a POCUS-directed volume status assessment. Volume status assessment is ubiquitous, yet challenging to perform. This review summarizes foundational physiologic concepts relevant to volume status evaluation, and highlights how multiorgan POCUS informs on hemodynamic parameters that can be combined with the conventional clinical assessment to make fluid-related decisions.

Analysis and optimization of microfluidic systems for real-time detection of nutrients in soil based on computational fluid dynamics and response surface methodology

Analysis and optimization of microfluidic systems for real-time detection of nutrients in soil based on computational fluid dynamics and response surface methodology

Echocardiography in the Ventilated Patient: What the Clinician Has to Know.

Heart and lung sharing the same anatomical space are influenced by each other. Spontaneous breathing induces dynamic changes in intrathoracic pressure, impacting cardiac function, particularly the right ventricle. In intensive care units (ICU), mechanical ventilation (MV) and therefore positive end-expiratory pressure (PEEP) are often applied, and this inevitably influences cardiac function. In ventilated patients, the use of positive pressures leads to an increase in intrathoracic pressure and, consequently, to a reduction in the right ventricular preload and thus cardiac output. The clinician working in the intensive care unit must be able to assess the effects MV has on the heart in order to set it up appropriately and to manage any complications. The echocardiographic evaluation of the ventilated patient has the main purpose of studying the right ventricle; in fact, they are the ones most affected by PEEP. It is therefore necessary to assess the size, thickness, and systolic function of the right ventricle. In the mechanically ventilated patient, it may be difficult to assess the volemic status and fluid responsiveness, in fact, the study of the inferior vena cava (IVC) is not always reliable in these patients. In patients with MV, it is preferable to assess fluid responsiveness with dynamic methods such as the end-expiration occlusion (EEO) test, passive leg raise (PLR), and fluid challenge (FC). The study of the diaphragm is also essential to identify possible complications, manage weaning, and provide important prognostic information. This review describes the basis for echocardiographic evaluation of the mechanically ventilated patient with the aim of supporting the clinician in managing the consequences of MV for heart-lung interaction.

Integrating AI into global fluid healthcare workforces: student perspectives and future trends

PurposeThis study investigates healthcare administration students’ perspectives on integrating artificial intelligence (AI) in fluid healthcare work environments, focusing on its potential impact on future healthcare practices.Design/methodology/approachThe research utilizes a mixed-methods strategy, combining quantitative surveys and qualitative interviews to collect data from healthcare administration students at a mid-sized urban university. This comprehensive approach allows for an in-depth analysis of students’ understanding of, attitudes toward and expectations of AI in healthcare settings.FindingsResults reveal that students have a nuanced understanding of AI’s capabilities to enhance healthcare operations and patient care, showcasing readiness to adopt these technologies. Nonetheless, there are significant concerns about job security and the depersonalization of care with the integration of AI. The study highlights the critical need for healthcare curricula to evolve to incorporate AI training that equips future professionals to use these technologies in increasingly flexible work settings.Originality/valueThis research offers new perspectives on how future healthcare professionals view AI integration within evolving work arrangements. It emphasized the need for educational institutions to update and adapt educational frameworks to prepare a workforce that can effectively navigate the challenges and opportunities presented by AI in the healthcare sector. This is particularly relevant in fluid work dynamics, where adaptability and responsiveness are key.

Management of adult sepsis in resource-limited settings: global expert consensus statements using a Delphi method.

To generate consensus and provide expert clinical practice statements for the management of adult sepsis in resource-limited settings. An international multidisciplinary Steering Committee with expertisein sepsis management and including a Delphi methodologist was convened by the Asia Pacific Sepsis Alliance (APSA). The committee selected an international panel of clinicians and researchers with expertise in sepsis management. A Delphi process based on an iterative approach was used to obtain the final consensus statements. A stable consensus was achieved for 30 (94%) of the statements by 41 experts after four survey rounds. These include consensus on managing patients with sepsis outside a designated critical care area, triggers for escalating clinical management and criteria for safe transfer to another facility. The experts agreed on the following: in the absence of serum lactate, clinical parameters such as altered mental status, capillary refill time and urine output may be used to guide resuscitation; special considerations regarding the volume of fluid used for resuscitation, especially in tropical infections, including the use of simple tests to assess fluid responsiveness when facilities for advanced hemodynamic monitoring are limited; use of Ringer's lactate or Hartmann's solution as balanced salt solutions; epinephrine when norepinephrine or vasopressin are unavailable; and the administration of vasopressors via a peripheral vein if central venous access is unavailable or not feasible. Similarly, where facilities for investigation are unavailable, there was consensus for empirical antimicrobial administration without delay when sepsis was strongly suspected, as was the empirical use of antiparasitic agents in patients with suspicion of parasitic infections. Using a Delphi method, international experts reached consensus to generate expert clinical practice statements providing guidance to clinicians worldwide on the management of sepsis in resource-limited settings. These statements complement existing guidelines where evidence is lacking and add relevant aspects of sepsis management that are not addressed by current international guidelines. Future studies are needed to assess the effects of these practice statements and address remaining uncertainties.

Heterogeneous Cluster Energetics and Nonlinear Thermodynamic Response in Supercritical Fluids

Heterogeneous Cluster Energetics and Nonlinear Thermodynamic Response in Supercritical Fluids

Validity of Pleth Variability Index to Predict Fluid Responsiveness in Patients Undergoing Cervical Spine Surgery in the Modified Prone Position

Background and Objective: The modified prone position, which is an alteration of the standard prone position, reduces cardiac preload. Dynamic variables including stroke volume variation (SVV), pulse pressure variation (PPV), and pleth variability index (PVI) are reliable predictors for fluid responsiveness during surgery. To the best of our knowledge, no studies assessing dynamic variables for fluid responsiveness have been conducted in the modified prone position. This study aimed to evaluate the ability of PVI to predict fluid responsiveness in the modified prone position during cervical spine surgery. Materials and Methods: PVI, SVV, and PPV were recorded at the following times: before and after a 4 mL/kg crystalloid load in the supine position (T1, T2); after placement in the modified prone position (T3); and before and after a 4 mL/kg crystalloid administration in the modified prone position (T4, T5). Fluid responsiveness was defined as stroke volume (SV) ≥ 15%, assessed by the FloTrac/Vigileo™ (Edwards Lifesciences Corp, Irvine, CA, USA). Receiver operating characteristic (ROC) curves were analyzed to identify changes in each dynamic variable that could predict fluid responsiveness in the modified prone position. Results: Data from a total of 43 subjects were analyzed. In the supine position, 21 subjects were responders. After subjects were placed in the modified prone position, SV significantly decreased, while PVI, SVV, and PPV significantly increased (p < 0.001 for all). In the modified prone position, 13 subjects were responders, and the areas under the ROC curves for ΔPVI, ΔSVV, and ΔPPV after fluid loading were 0.524 (95% confidence interval [CI] 0.329–0.730, p = 0.476), 0.749 (95% CI 0.566–0.931, p = 0.004), and 0.790 (95% CI 0.641–0.938, p < 0.001), respectively. Conclusions: Crystalloid pre-loading could not mitigate the decrease in SV caused by the modified prone position. Changes in PVI were less reliable in predicting fluid responsiveness in the modified prone position.

Assessment of change in end-tidal CO2 after fluid challenge as a marker of fluid responsiveness as measured by the aortic velocity time integral in healthy anesthetized mechanically ventilated dogs.

To evaluate if variation in the end-tidal CO2 partial pressure (∆Petco2) after a fluid challenge could predict fluid responsiveness with a sensitivity of 75% and a specificity of 70% in healthy anesthetized and mechanically ventilated dogs. Diagnostic accuracy study. University hospital. Twenty-seven dogs admitted for neutering. To obtain a balanced sample between fluid responder and nonresponder dogs, a 10-mL/kg lactated Ringer's solution was administered over 15minutes to half of the population before the baseline measurements. All animals then received a fluid challenge of 10mL/kg lactated Ringer's solution in 5minutes. The velocity-time integral of aortic blood flow (VTIAo) was evaluated with Doppler echocardiography before and after a fluid challenge to classify the included dogs as fluid responders or nonresponders. Fluid responsiveness was defined as an increase of ≥15% of the VTIAo after the fluid challenge. Petco2 was evaluated at 1, 5, and 10(T1,T5,T10)minutes after fluid expansion. Area under the receiver operating characteristic curve (AUROC) analysis was used to assess the ability of ∆Petco2 to predict fluid responsiveness at different time points. A total of 13 dogs were fluid responders, and 14 were nonresponders. The best predictive capacity for ∆Petco2 was observed at T10. The AUROC with its 95% confidence interval (CI) for ∆Petco2 at T10 was 0.75 (0.56-0.93), with a sensitivity of 84.62% (95% CI, 54.60-98.10), a specificity of 64.29% (95% CI, 35.10-87.20), a positive predictive value of 68.80% (95% CI, 41.30-89.00), and a negative predictive value of 81.80% (95% CI, 48.20-97.70). The optimal cutoff was 1mmHg. The current study showed that, although minimal, ∆Petco2 predicted fluid responsiveness in the dogs studied.

Method for evaluating volume responsiveness during the passive leg raising test

Accurate fluid assessment is essential in critically ill patients, as both fluid insufficiency and fluid excess can result in adverse outcomes. The passive leg raising test (PLR) is a dependable and simple method of evaluating fluid responsiveness. Its accuracy and specificity have been validated over the past decade. Consequently, we have compiled a list of indicators that can be used to predict fluid responsiveness. By selecting more suitable hemodynamic indicators, fluid therapy can be more effectively guided.

Vibroacoustic response of a heavy fluid loaded plate with ABH stiffeners

Abstract Stiffened structures are essential for a wide range of engineering applications including aeronautics, marine and rail systems. Adding stiffeners to a host structure leads to generation of Bloch-Floquet waves, which are induced by the interaction between the flexural waves in the host structure and the flexural/torsional waves in the stiffeners. These waves could generate unwanted noise and vibrations which should be mitigated. Acoustic black holes (ABHs) are widely used as a passive-control approach to mitigate vibrations of elastic structures. This study aims to use ABHs integrated as stiffeners for a fluid-loaded plate. Hence, the host structure is not modified, and its structural integrity is maintained. A heavy fluid-loaded infinite plate with periodic ABH stiffeners under a line force excitation is considered (i.e., a two-dimensional model). To obtain the vibrocoustic response, the system is modelled using the COMSOL Multiphysics®. The effectiveness of the ABH stiffeners in mitigating the vibration and noise from the fluid loaded plate is examined.

Point-of-care ultrasonography in pediatric intensive care units

Bedside ultrasonography, or point-of-care ultrasonography (POCUS), is increasingly becoming widely adopted in pediatric intensive care units (ICU) for procedural interventions and diagnostics. Although vascular access remains one of the primary applications of POCUS in the pediatric ICU, its use for assessing fluid status and responsiveness is growing. POCUS helps identify reversible causes of cardiac arrest, such as pericardial effusion and pneumothorax, although its impact on outcomes is still under investigation. Here, we will review the applications of POCUS in the pediatric ICU, including the general pediatric and cardiac ICUs. We will discuss the up-to-date evidence guiding its use and adoption for critically ill children.

Two-phase fluid resonance frequency and improved elastic water model for pipes conveying fluid with entrapped air

The entrapped air in pipe has a significant impact on the dynamic characteristics of the pipeline system, as it can induce transient high pressures and pressure oscillations similar to water hammer during system opening and closing. In this study, plane wave equations for the liquid and air phases in pipe are formulated with considering various conditions of entrapped air. The approximate solution for the resonance frequency of the two-phase fluid is derived via the separation variables method and the coupling relationship at the air–liquid interface. The resonance frequencies obtained from the approximate solution closely match those from the finite element method, confirming the accuracy and universality of the presented approximate solutions. Furthermore, based on the criterion of consistent first-order resonance frequency, an improved elastic water model and the corresponding analysis process of fluid dynamic response are proposed by correcting the first resonance frequency of the dynamic model of pipes conveying fluid with entrapped air. The predicted results are consistent with experimental data and computational fluid dynamics results, thus validating the proposed model. Compared with existing models, the improved elastic water model proposed in this paper can obtain accurate calculation results under all entrapped air conditions, overcoming the limitation of existing models that are only applicable to a single entrapped air condition. It is found that the air–liquid interface angle influences the fluid resonance frequency and dynamic response significantly. As the angle of the air–liquid interface increases, the pressure peak and oscillation frequency of the pipe fluid response decrease remarkedly.

Volume assessment comparing femoral vein and inferior vena cava among chest pain patients presenting to the emergency department

BackgroundInferior vena cava (IVC) diameter measurement using ultrasound for volume status assessment has shown satisfactory results and is being adopted in Emergency and critical care settings. IVC diameter can vary depending on the cardiac function, respiratory efforts, intraabdominal pressure, and mechanical ventilation. Due to these factors, IVC measurement cannot be considered a stand-alone technique appropriate for every patient. The femoral vein (FV), a more superficial vein than IVC, can be considered an alternative method for assessing fluid responsiveness in patients presenting to the Emergency department. It is easily accessible and can be used in scenarios where IVC cannot be visualized or reliable.MethodsThis was a single-center diagnostic study where 85 patients who presented to the ED with chest pain were enrolled prospectively. IVC and femoral vein collapsibility indices, stroke volume, and cardiac output are measured using an ultrasound machine. The measurements were repeated after a passive leg-raising test. These values were compared with each other to assess an intra-class correlation between IVC and femoral vein collapsibility indices. We have also evaluated the relationship between the collapsibility indices of both veins and cardiac output.Discussion & limitationsOur findings show an insufficient correlation between IVC and FV collapsibility indices. However, both vein diameters significantly increased after passive leg raising (PLR), indicating a response to fluid challenge. Post-PLR reduced IVC, and FV collapsibility index (CI) suggests intravascular volume expansion after a fluid challenge, also reflected in the hemodynamic parameters. Our study was conducted only in a subset of relatively stable patients. The applicability of the study in different subsets of patients presenting to ED is still questionable.ConclusionWe conclude that femoral vein indices may not be an accurate alternative for volume assessment in the chosen cohort of patients. IVC and FV metrics do not correlate and may not be accurate for volume responsiveness. We may need to explore the utility of FV and its indices in a larger population in multiple settings for a better understanding of its role in volume assessment and responsiveness.Trial registration(EC/NEW/INST/2021/1707). Registered 03 January 2023.

A Single Electrode Organic Neuromorphic Device for Dopamine Sensing in Vivo

AbstractOrganic Electronic platforms for biosensing are being demonstrated at a fast pace, especially in healthcare applications where the use of organic (semi‐)conductive materials leads to devices that efficiently interface living matter. Nevertheless, interesting properties of organic (semi‐)conductors are usually neglected in the development of (bio‐)sensors. Among these, the non‐linear response when operated under dynamic biasing conditions (i.e., with pulsed driving voltages), thus mimicking synaptic plasticity phenomena, offers promising and largely unexplored possibilities for bio‐sensing. The artificial synaptic response's figures of merit reflect the composition of the surrounding environment and, ultimately, the ion concentration and dynamics at the organic (semi‐)conductor/electrolyte interface. Therefore, new sensing strategies that rely on the effect of target analytes on the short‐term plasticity response of Organic Neuromorphic Devices are being demonstrated. This work presents the development of a label‐free Single Electrode Neuromorphic Device (SEND) specifically designed for in vivo real‐time mapping of dopamine concentration. The device response is investigated as a function of the driving frequency, resulting in the determination of the optimal operational configuration for minimally invasive neuromorphic devices. It exhibits stable multi‐parametric response in complex fluids, in brain's mechanical models and in vivo, enabling monitoring of local variations of dopamine concentration in the rat brain.

Geometrical optimization of premixed hydrogen-air combustion in a novel counter-flow preheating micro-combustor

Developing a more efficient and cleaner combustion technologies is a major step in realizing the sustainable Development Goals. By using Computational Fluid Dynamics and Response Surface Methodology, this study, optimizes a novel counter-opposed combustor with platinum-coated, stepped baffles to enhance the combustion efficiency. Key geometrical parameters such as baffle lengths (L1 and L2), gaps (L3) and height (H) are studied. The study found that, the optimization objectives of reducing H2 outlet mass fraction, increasing outlet H2O mass fraction and outlet temperature were usefully achieved. Due to the flow's laminar and high velocity nature, the high temperature flow could not effectively reach the preheat zones of the upstream baffle, however, hydrogen was completed burned. The optimization identified three geometric configurations, with one candidate point (P1 = 5.497 mm, P2 = 0.616 mm, P3 = 1.668 mm, and P4 = 0.182 mm) achieving the best performance in terms of outlet temperature and H2O mass fraction. These insights can be leveraged to guide the design and operation of the system, ensuring that it performs at its best, while minimizing the presence of H2 at the outlet, and achieve a suitable outlet temperature, all of which contribute to the overall efficiency and effectiveness of the process.