Fluid Loading Research Articles

Implementation of a PI Controller in a Helical Falling Film Evaporator Model

This work presents the implementation of a PI controller for a falling film evaporator model, which is part of an Absorption Heat Transformer (AHT). The evaporator control aids the process to maintain adequate performance which benefits the heat produced in the absorber to obtain high performance in the AHT. In this research, the evaporated mass flow rate was controlled by manipulating the mass flow rate flowing inside of the tubes to reach a certain heat transfer rate to evaporate a load of fluid flowing outside of the tubes as a falling film. The control is performed with a PI controller and a proportional controller with an adjusted bias. Additionally, disturbances are applied in the input temperature to simulate the temperature coming from industrial waste heat. This work can be a reference to control the falling film evaporator when it is coupled in the AHT and in other research such as in control of evaporators in the dairy industry.

Novel parameters for predicting fluid responsiveness during the mini fluid challenge and ability of the cardiac power index: an observational cohort study.

The percentage change in the stroke volume index (SVI) due to the mini fluid challenge (MFC) (MFC-ΔSVI%) is used commonly in daily practice. However, up to 20% of patients remain in the gray zone of this variable. Thus, it was aimed to compare the MFC-ΔSVI% and the percentage change in the cardiac power index (CPI) due to the MFC (MFC-ΔCPI%) with the baseline values of the pulse pressure variation (PPV) and stroke volume variation (SVV) in terms of their abilities to predict fluid responsiveness. The SVI, CPI, SVV, and PPV were recorded before 100 mL of isotonic saline was infused (MFC), after MFC was completed, and after an additional 400 mL of isotonic saline was infused to complete 500 mL of fluid loading (FL). Patients whose SVI increased more than 15% after the FL were defined as fluid responders. Sixty-seven patients completed the study and 35 (52%) of them were responders.The areas under the receiver operating characteristics curves for the MFC-ΔSVI% and MFC-ΔCPI% (0.94; 95% CI: 0.86-0.99 and 0.89; 95% CI: 0.79-0.95, respectively) were significantly higher than those for the SVV and PPV (0.63; 95% CI: 0.50-0.75 and 0.55; 95% CI: 0.42-0.67, respectively) (p < 0.001 for all of the comparisons). The gray zone analysis revealed that the MFC-ΔSVI% values of 12 patients were in the gray zone. Of the 12, the MFC-ΔCPI% values of 7 patients were outside of the gray zone. Fluid responsiveness can be predicted more accurately using the MFC-ΔSVI% and MFC-ΔCPI% than using the SVV and PPV. Additionally, concomitant use of the MFC-ΔSVI% and MFC-ΔCPI% is recommended, as this approach diminishes the number of patients in the gray zone.

Albumin Infusion Reduces Fluid Loading for Postresuscitation Syndrome in a Pig Model of Refractory Cardiac Arrest Resuscitated With Venoarterial Extra Corporeal Membrane Oxygenation.

Hemodynamic instability in postresuscitation syndrome worsens survival and neurological outcomes. Venoarterial extracorporeal membrane oxygenation (VA ECMO) for refractory cardiac arrest might improve outcomes. Hemodynamical support under VA ECMO relies on norepinephrine and crystalloids. The present work aims to assess the effects of albumin (ALB) infusion in a swine model of ischemic refractory cardiac arrest implanted by VA ECMO. Cardiac arrest was performed in 18 pigs and VA ECMO was initiated after 30 minutes cardiopulmonary resuscitation (CPR). Pigs were randomly assigned to standard care (norepinephrine + crystalloids) versus ALB group (ALB + standard care). Hemodynamical assessments were performed over 6 hours. Severe hypoalbuminemia was observed in the control group and could be reversed with ALB infusion. Total crystalloid load was significantly reduced with ALB infusion (1,000 [1,000-2,278] ml vs. 17,000 [10,000-19,000] ml, ALB versus control group, respectively, p < 0.001). There was no significant impact with regard to lactate clearance (29.16% [12.5-39.32] and 10.09% [6.78-29.36] for control versus ALB groups, respectively, p = 0.185), sublingual capillary microvascular parameters, or cerebral near-infrared spectrometer (NIRS) values. Compared to standard care, ALB infusion was highly effective in reducing fluid loading in a porcine model of postresuscitation syndrome after refractory cardiac arrest treated with VA ECMO.

Onset and performance of a two layer oscillating heat pipe in a heat spreader

Experiments were performed to characterize a two-layer oscillating heat pipe in a heat spreading plate heated locally on one side and cooled throughout the other side. The 23-turn oscillating heat pipe with 2 mm hydraulic diameter square channels and interconnected between the layers was charged with a 70 percent fluid loading of degassed DI water. The effect of heating location, operating temperature and orientation were examined. The results showed that the thermal conductance (W/K) of the plate could be increased by more than 100 percent for a heater position near the edge of the plate but less for a central position where conduction through the plate was more effective. The change in the thermal conductance of the oscillating heat pipe path with the effective heat transfer through this path appeared independent of heater position but decreased modestly with operating temperature and for a horizontal plate orientation. The operation of the oscillating heat pipe was correlated using the heated wall superheat and the change in saturation pressure with temperature. The results suggest these were inversely correlated but the boundary delineating the onset of operation depended on orientation. Evidence of hysteresis effects and suppression of oscillation were observed.

OCOSO2: study protocol for a single-blinded, multicentre, randomised controlled trial assessing a central venous oxygen saturation-based goal-directed therapy to reduce postoperative complications in high-risk patients after elective major surgery

BackgroundFluid loading-based goal-directed therapy is a cornerstone of anaesthesia management in major surgery. Its widespread application has contributed to a significant improvement in perioperative morbidity and mortality. In theory, only hypovolemic patients should receive fluid therapy. However, to achieve such a diagnosis, a surrogate marker of cardiac output adequacy must be used. Current methods of fluid loading-based goal-directed therapy do not assess cardiac output adequacy. Nowadays, new devices make it possible to continuously monitor central venous oxygen saturation (ScvO2) and therefore, to assess the adequacy of perioperative cardiac output during surgery. In major surgery, ScvO2-based goal-directed therapy can be used to enhance fluid therapy and improve patient outcomes.MethodsWe designed a prospective, randomised, single-blinded, multicentre controlled superiority study with a 1:1 allocation ratio. Patients to be included will be high-risk major surgery patients (> 50 years old, ASA score > 2, major intra-abdominal or intra-thoracic surgery > 90 min). Patients in the control group will undergo standard fluid loading-based goal-directed therapy, as recommended by the guidelines. Patients in the intervention group will have ScvO2-based goal-directed therapy and receive fluid loading only if fluid responsiveness and cardiac output inadequacy are present. The primary outcome will be the Comprehensive Complication Index on day five postoperatively.DiscussionThis study is the first to address the issue of cardiac output adequacy in goal-directed therapy. Our hypothesis is that cardiac output optimisation during major surgery achieved by continuous monitoring of the ScvO2 to guide fluid therapy will result in a reduction of postoperative complications as compared with current goal-directed fluid therapy practices.Trial registrationClinicalTrials.gov. NCT03828565. Registered on February 4, 2019.

Comparison of intermittent boluses of noradrenaline vs. phenylephrine for spinal anesthesia induced hypotension during cesarean delivery

Background and Objective: Maternal hypotension is a common consequence of spinal anesthesia for cesarean delivery (CD). A vasopressor is recommended in addition to adequate fluid loading to raise mean arterial pressure in pregnant women. Phenylephrine, a pure α–adrenergic receptor agonist, is the first-line agent to manage it. However, phenylephrine is associated with dose-dependent reflex bradycardia and decreased cardiac output. Noradrenaline is suggested as an alternative due to its mild beta-adrenergic effect, which results in a greater heart rate and cardiac output than phenylephrine. We compared the effectiveness and adverse effects of intermittent boluses of noradrenaline with phenylephrine to treat spinal-induced hypotension during CD.&#x0D; Methodology: A randomized controlled trial was conducted at Bach Mai Hospital, Vietnam, from May 2020 to August 2020. There were 120 pregnant women undergoing elective CD under spinal anesthesia enrolled in the study and divided randomly into two groups: the Group N and the Group P. Group N patients were given noradrenaline 6 µg as an intravenous bolus, and Group P patients were given phenylephrine 100 µg to treat spinal-induced hypotension. The primary outcome was the number of bolus doses of vasopressors needed to treat maternal hypotension. Secondary outcomes were bradycardia, hypertension, nausea, vomiting, umbilical arterial blood gases, and APGAR scores.&#x0D; Results: The number of boluses of vasopressors needed to treat hypotension and maternal hemodynamic changes was equivalent in both groups. The incidence of bradycardia, nausea, and vomiting in the two groups was not significantly different. No pregnant woman suffered from unintended hypertension. APGAR scores were 7 and above at one min and 10 and above at five min for all cases. There were no differences in umbilical arterial pH values between the two groups (7.33 vs. 7.34; P &gt; 0.05).&#x0D; Conclusion: Noradrenaline 6 µg and phenylephrine 100 µg boluses were equally effective in treating spinal-induced hypotension in parturients undergoing cesarean delivery with similar neonatal and maternal outcomes.&#x0D; Abbreviations: CD - Cesarean Delivery; HR - Heart Rate; CO - Cardiac Output; SVR - Systemic Vascular Resistance; SBP - Systolic Blood Pressure; ED 90 - 90 Percent Effective Dose&#x0D; Key words: Anesthesia, Spinal; Hypotension; Cesarean Delivery&#x0D; Citation: Nguyen TT, Nguyen HC, Nguyen ATH, Doan TH, Ngo QS. Comparison of intermittent boluses of noradrenaline vs. phenylephrine for spinal anesthesia induced hypotension during cesarean delivery. Anaesth. pain intensive care 2023;27(5):562−566.&#x0D; DOI: 10.35975/apic.v27i5.2312&#x0D; Received: August 22, 2023; Reviewed: August 23, 2023; Accepted: August 31, 2023

An analytical study on nonlinear viscoelastic lubrication in journal bearings

This paper presents a novel analytical solution for journal-bearing viscoelastic lubrication using the perturbation method. The nonlinear Giesekus model was used for the constitutive equations to study the effects of fluid elasticity, shear-thinning viscometric functions, and strain-hardening elongational viscosity of viscoelastic lubrication. The investigation focuses on the impact of characteristic parameters such as mobility factor, eccentricity ratio, and Weissenberg number on the fluid film pressure distribution, load capacity, and shear stress. Although distinguishing between the normal stress differences and extensional viscosity in mixed viscoelastic flows is complicated, we investigated the role and contribution of these two factors. By increasing the elasticity of the fluid, the portion of both mentioned parameters increases consequently. Furthermore, analyses and comparisons show the contributions of the first normal stress and elongational viscosity to the load capacity of the bearing through the stress ratio and flow type parameter for the first time. The research findings indicate that fluid elasticity enhances the load capacity of the bearing compared to a Newtonian lubricant with the same effective viscosity. Moreover, the bearing load capacity is divided into two regions. In the linear region, the mobility factor and Weissenberg numbers have minimal effects leading to a linear increase in the load distribution, and in the exponential region, the load capacity changes are considerable. This research provides valuable insights into the behavior of viscoelastic lubrication in journal-bearing systems.

SAT306 Comparison Of Sodium Nitroprusside And Urapidil In Laparoscopic Adrenalectomy For Pheochromocytoma

Abstract Disclosure: M.G. Rusalenko: None. E. Pispanen: None. M. Wisham: None. I. Savasteeva: None. S. Marchenko: None. D. Borovik: None. D.O. Rusalenko: None. The aim: of the study was to compare the efficacy of Sodium Nitroprusside and Urapidil in management of blood pressure in laparoscopic adrenalectomy for pheochromocytoma. Material and methods : This study includes of 58 cases of pheochromocytoma operated in the Republican Scientific and Practical Center for Radiation Medicine. The mean age of patients was 57.0 years (31 men and 27 women). For preliminary preparations, oral α1-blocker Doxazosin was used. In-operative blood pressure (BP) was recorded via intra-radial artery BP monitoring and via intra-venous BP monitoring from the external jugular vein. Fluid loading was done with colloids and crystalloids. Epidural anesthesia was given with a combination of Ropivacaine 10mg/ml-10ml and Spinal Morphine 1mg/ml-1-2ml was given between T4 - T5 for relaxation of the abdominal cavity. For anesthesia Sevoflurane was used with non-depolarizing short and medium-acting muscle relaxants (rocuronium, atracurium). In the study we included 12 patients who underwent surgery under BP control with Uradipil and 46 patients with Nitroprusside. Results: Long-term administered Doxazosin (more than 14 days) demonstrated lower BP values ​​in the starting phase of the operations (SBP 125.0[110.0; 130.0]; DBP [75.0(60.0; 80.0]) § (SBP 140.0[130.0; 150.0]; DBP [90.0(80.0; 90.0]); p&amp;lt;0.05. Statistically significant differences in BP variability from baseline to maximum values, as well as minimum values were obtained. In both groups (Nitroprusside and Urapidil), using the Wilcoxon criteria, we did not obtain significant differences in the increase in the initial blood pressure in maximum values. In contrast, in the Nitroprusside group, a statistically significant decrease in baseline blood pressure to the minimum values (SBP 90.0[75.0; 100.0]; DBP [50.0(50.0; 55.0]); p&amp;lt;0.004) was obtained, as in the Urapidil group: (SBP 130.0[ 110.0; 140.0]; DBP [80.0(60.0; 90.0]), to minimal values (SBP 95.0[90.0; 110.0]; DBP [60.0(50.0; 60.0]); p&amp;lt;0.008. Comparison of all blood pressure indicators when using Nitroprusside or Urapidil using the Mann-Whitney U test did not show statistically significant differences. However, there was a minor significance in minimum SBP values ​​(N 90.0[75.0; 100.0] § [U 95.0(90.0; 110.0]); z=-1.44; p=0.15) and DBP (N 50.0[50.0; 55.0] § [U 60.0(50.0; 60.0]); z=-1.81; p=0.07. Initial, maximum and final BP values ​​were equivalent in two groups. Conclusion: This data shows that to stabilize patient blood pressure in adrenalectomy for pheochromocytoma, preparation with α1-blockers is significant. The use of Sodium Nitroprusside and Urapidil is equally effective for managing BP during adrenalectomy, however, Urapidil shows to have advantages due to its lower side effects compared to Nitroprusside. Presentation: Saturday, June 17, 2023

Nonlocal Theory for Submerged Cantilever Beams Undergoing Torsional Vibrations

Abstract We propose a new theory for fluid–structure interactions of cantilever microbeams undergoing small amplitude vibrations in viscous fluids. The method is based on the concept of nonlocal modal hydrodynamic functions that accurately capture three-dimensional (3D) fluid loading on the structure. For short beams for which 3D effects become prominent, existing local theories based on two-dimensional (2D) fluid approximations are inadequate to predict the dynamic response. We discuss and compare model predictions in terms of frequency response functions, modal shapes, quality factors, and added mass ratios with the predictions of the local theory, and we validate our new model with experimental results.

Fluid loading during the hemodynamic evaluation of pulmonary hypertension: a cross-sectional study

Fluid loading during the hemodynamic evaluation of pulmonary hypertension: a cross-sectional study

Acoustic radiation from a baffled finite shell in an underwater waveguide

Analytical modelling of vibroacoustic systems can help us to understand the physical phenomena involved in more complex problems, and it provides a benchmark solution and reference upon which more complex systems can be built. In the present work, the system of interest consists of a finite elastic cylindrical shell inserted in infinitely rigid cylindrical baffles and immersed in an underwater acoustic waveguide. The latter consists of a finite fluid layer bounded by an upper free surface and a lower rigid floor. In such a fluid domain, the acoustic waves radiated from the excited shell will exhibit reflections off the boundaries. This phenomenon is modelled by the image-source theory and embedded in the fluid loading term, which intervenes in the shell equations. Investigations into the influence on the finiteness of the elastic shell, types of supports (i.e., simply supported, clamped, free, and combinations of these), and depth of the waveguide on the shell’s acoustic radiation are presented.

Post-spinal hypotension management for cesarean section in low resource settings: efficiency and safety of two very low-dose boluses of norepinephrine, a randomized double-blinded controlled trial

Spinal anesthesia is the gold standard anesthetic technique for cesarean section. However, its major complication is hypotension. Norepinephrine has recently been described as an efficient and safe alternative to Phenylephrine. The aim of this study was to determine the effective target bolus of Norepinephrine to prevent and treat post-spinal anesthesia hypotension. We conducted a prospective controlled randomized study including 126 parturients scheduled for cesarean delivery under spinal anesthesia. We compared two groups that received a prophylactic bolus of either 1μg/kg or 0.5μg/kg of Norepinephrine without fluid loading. The rescue intravenous bolus of Norepinephrine was half the dose of the prophylactic bolus. The main outcomes were the percentage of decrease in systolic and mean blood pressure. The secondary outcomes included the timing of the first hypotension, duration of hypotension, number of rescue boluses, total Norepinephrine consumption, incidence of hypotension and maternal adverse effects and fetal outcomes. Our primary outcome has shown similarities between groups; delta systolic blood pressure before delivery was 19.4% in group 1µg/kg versus 20.5% in group 0.5µg/kg. Both groups were similar for all secondary outcomes, except that the higher dose of Norepinephrine resulted in more hypertension. Fetal outcomes were similar in both groups. Bolus of 0.5μg/kg followed by rescue doses of 0.25μg/kg of Norepinephrine was efficient in preventing and treating spinal anesthesia-induced hypotension. These doses may be recommended for routine use in healthy parturients.

Variables influencing the prediction of fluid responsiveness: a systematic review and meta-analysis

IntroductionPrediction of fluid responsiveness in acutely ill patients might be influenced by a number of clinical and technical factors. We aim to identify variables potentially modifying the operative performance of fluid responsiveness predictors commonly used in clinical practice.MethodsA sensitive strategy was conducted in the Medline and Embase databases to search for prospective studies assessing the operative performance of pulse pressure variation, stroke volume variation, passive leg raising (PLR), end-expiratory occlusion test (EEOT), mini-fluid challenge, and tidal volume challenge to predict fluid responsiveness in critically ill and acutely ill surgical patients published between January 1999 and February 2023. Adjusted diagnostic odds ratios (DORs) were calculated by subgroup analyses (inverse variance method) and meta-regression (test of moderators). Variables potentially modifying the operative performance of such predictor tests were classified as technical and clinical.ResultsA total of 149 studies were included in the analysis. The volume used during fluid loading, the method used to assess variations in macrovascular flow (cardiac output, stroke volume, aortic blood flow, volume‒time integral, etc.) in response to PLR/EEOT, and the apneic time selected during the EEOT were identified as technical variables modifying the operative performance of such fluid responsiveness predictor tests (p < 0.05 for all adjusted vs. unadjusted DORs). In addition, the operative performance of fluid responsiveness predictors was also influenced by clinical variables such as the positive end-expiratory pressure (in the case of EEOT) and the dose of norepinephrine used during the fluid responsiveness assessment for PLR and EEOT (for all adjusted vs. unadjusted DORs).ConclusionPrediction of fluid responsiveness in critically and acutely ill patients is strongly influenced by a number of technical and clinical aspects. Such factors should be considered for individual intervention decisions.

A novel vortex-induced vibration model for a circular cylinder in the vicinity of a plane wall

A novel vortex-induced vibration (VIV) model is proposed to predict the transverse responses of an elastically mounted circular cylinder in the proximity of the wall. Firstly, flow characteristics and hydrodynamic loads on a near-wall stationary circular cylinder are summarized and analyzed based on the existing experimental results, and then the Strouhal shedding frequency and the empirical correlations of the mean lift coefficient and oscillating lift coefficient are established. Subsequently, by introducing the empirical correlations of fluid loads to the equations of structure vibration, a novel VIV model for the near-wall circular cylinder is proposed to describe more precisely the effect of the plane wall. The accuracy, stability, and adaptability are validated by employing experimental VIV results. Compared to existing models, the novel model has advantages in achieving acceptable accuracy in various scenarios. Finally, using the proposed VIV model, the dynamic features of a near-wall circular cylinder to the reduced velocity and gap ratio are studied in detail, including the time-averaged displacements, lock-in regime, maximum amplitude, and dominant frequency. The results obtained are valuable for understanding the VIV characteristics of the near-wall cylinder, and the semi-empirical VIV model proposed could be applied in engineering prediction in the future.

Pulmonary Hypertension Associated with Left Heart Disease.

Pulmonary hypertension (PH) is a common complication of diseases affecting the left heart, mostly found in patients suffering from heart failure, with or without preserved left ventricular ejection fraction. Initially driven by a passive increase in left atrial pressure (postcapillary PH), several mechanisms may lead in a subset of patient to significant structural changes of the pulmonary vessels or a precapillary component. In addition, the right ventricle may be independently affected, which results in right ventricular to pulmonary artery uncoupling and right ventricular failure, all being associated with a worse outcome. The differential diagnosis of PH associated with left heart disease versus pulmonary arterial hypertension (PAH) is especially challenging in patients with cardiovascular comorbidities and/or heart failure with preserved ejection fraction (HFpEF). A stepwise approach to diagnosis is proposed, starting with a proper clinical multidimensional phenotyping to identify patients in whom hemodynamic confirmation is deemed necessary. Provocative testing (exercise testing, fluid loading, or simple leg raising) is useful in the cath laboratory to identify patients with abnormal response who are more likely to suffer from HFpEF. In contrast with group 1 PH, management of PH associated with left heart disease must focus on the treatment of the underlying condition. Some PAH-approved targets have been unsuccessfully tried in clinical studies in a heterogeneous group of patients, some even leading to an increase in adverse events. There is currently no approved therapy for PH associated with left heart disease.

Comparison of crystalloid and colloid co-load combined with norepinephrine prophylaxis on post-spinal anesthesia hypotension during cesarean delivery: a randomized sequential allocation dose-finding study.

Fluid loading is an essential component of treatment for reducing the incidence of post-spinal anesthesia hypotension and is necessary to maintain intravascular volume, perfuse tissues, and control spinal anesthesia hypotension after sympathetic blockade. We performed a randomized sequential allocation dose-finding study to compare the effects of 10 mL/kg crystalloid and 6% hydroxyethyl starch (130/0.4) co-load on the ED90 of prophylactic norepinephrine infusion for preventing post-spinal anesthesia hypotension during cesarean delivery. Eighty patients were randomly allocated to receive either a 10 mL/kg crystalloid (Crystalloid Group, n = 40) or 6% hydroxyethyl starch (130/0.4) (Colloid Group, n = 40) co-load combined with prophylactic norepinephrine infusion during spinal anesthesia for cesarean delivery. The first patient received an initial prophylactic norepinephrine infusion rate of 0.025 μg/kg/min. Subsequent patients received a 0.005 μg/kg/min gradient dose of prophylactic norepinephrine. This dose was administered as a gradient based on its effectiveness for preventing post-spinal anesthesia hypotension (defined as SBP < 80% of baseline value) and determined by the up-and-down sequential allocation methodology. The primary study outcome was the ED90 of prophylactic norepinephrine infusion. Secondary outcomes included the incidence of post-spinal anesthesia hypotension, bradycardia, hypertension, Apgar scores, and umbilical artery blood gas values were also measured. The ED90 values of prophylactic norepinephrine infusion for preventing post-spinal anesthesia hypotension during cesarean delivery were 0.063 μg (95% CI: 0.050 to 0.064) and 0.062 μg (95% CI: 0.045 to 0.064) using isotonic regression analysis, and 0.068 μg (95% CI: 0.056 to 0.353) and 0.060 μg (95% CI: 0.050 to 3.590) using probit regression analysis in the Crystalloid Group and Colloid Group, respectively. The secondary outcomes were comparable between the two groups. The administration of a 10 mL/kg 6% hydroxyethyl starch (130/0.4) does not provide additional benefits compared to crystalloid co-load in reducing the ED90 of prophylactic norepinephrine infusion for preventing post-spinal anesthesia hypotension during cesarean delivery.

Therapeutic Potential of Biochanin A in Herpes Simplex Keratitis.

Herpes simplex keratitis (HSK) is a blinding eye disease that is initiated by the herpes simplex virus type 1 (HSV-1). Resistance to acyclovir (ACV) and the side effects of corticosteroid drugs have become concerning issues, so it is crucial to develop new antivirals for treating HSK. In this study, we report that biochanin A (BCA), a naturally occurring flavonoid compound, provides multifaceted protective effects with anti-viral, anti-inflammatory, anti-oxidative stress and anti-apoptotic activities to alleviate HSK. The results show that BCA significantly inhibited HSV-1 replication in vitro and further proved that BCA principally influenced the early stage of virus infection. We reveal that BCA downregulated the expression of pro-inflammatory factors triggered by HSV-1, including TNF-α, RANTES, IL-1β and IL-6. Furthermore, BCA treatment alleviated oxidative stress and apoptotic arising from HSV-1 infection. Lastly, we induced HSK in male C57BL/6 mice and treated them with either BCA or phosphate buffer solution (PBS) eye drops. We observed the ocular surface lesions; determined the virus load in the tear fluid, corneas as well as trigeminal ganglions (TGs); and detected the levels of inflammation and apoptosis in the corneas simultaneously. These results show that BCA inhibits HSV-1 and alleviates the corneal lesion degree. Our study illustrates that BCA is a promising therapeutic approach for application in treating HSK.

UNVEILING THE SIGNIFICANCE OF DYNAMIC ARTERIAL ELASTANCE: AN INSIGHTFUL APPROACH TO ASSESSING ARTERIAL LOAD IN AN ENDOTOXIN SHOCK MODEL.

Background: The aim of this study was to investigate the relationship between dynamic arterial elastance (EaDyn) and the pulsatile and steady components of arterial load in an endotoxin shock model using a two-element Windkessel model and to describe the behavior of EaDyn in this model. Methods : Ten female Yorkshire pigs were administered lipopolysaccharide intravenously to induce endotoxin shock, while three female pigs served as the control group. Measurements of EaDyn (ratio between pulse pressure variation and stroke volume variation), effective arterial elastance, arterial compliance (Cart), and systemic vascular resistance were taken every 30 min in the endotoxin group until shock was induced. In the control group, these variables were measured every 30 min for 3 h. Subsequently, a fluid load was administered to both groups, and measurements were repeated every 30 min. After 1 hour of shock induction, the endotoxin group was divided into two subgroups: one receiving norepinephrine (END-NE) and the other not receiving it (END-F). Results: EaDyn showed an association with Cart, while pulse pressure variation was connected to both pulsatile and steady components, and stroke volume variation was solely associated with steady components. In addition, EaDyn exhibited higher values in the END groups than in the control group when shock was achieved. Furthermore, after the administration of norepinephrine, EaDyn displayed higher values in END-F than in END-NE. Conclusions: The EaDyn variable helps identify changes in the pulsatile component of arterial load, providing valuable guidance for management strategies aimed at improving cardiac performance.

Effect of tidal volume change on pressure-based prediction of fluid responsiveness in children.

It is known that pulse pressure variation and systolic pressure variation cannot predict fluid responsiveness in children. In adults, the ability of these dynamic parameters to predict fluid responsiveness is improved by increasing tidal volume. We planned to investigate whether pulse pressure variation or systolic pressure variation can predict fluid responsiveness in children when augmented by increasing tidal volume by conducting a prospective study. We enrolled children younger than 7 years who underwent cardiac surgery for atrial septal defect or ventricular septal defect. After sternum closure, pulse pressure variation and systolic pressure variation were continuously recorded while changing the tidal volume to 6, 10, and 14 mL/kg. Fluid loading was done with 10 mL/kg of crystalloids for 10 min, and stroke volume index was measured via transesophageal echocardiography. Children whose stroke volume index increased by more than 15% after the fluid loading were defined as responders to fluid therapy. We set primary outcome as the predictability of pulse pressure variation and systolic pressure variation for fluid responsiveness and measured the area under the curve of receiver operating characteristics curve. Twenty-six children were included, of which 15 were responders. At the tidal volume of 14 mL/kg, the area under the curves of receiver operating characteristics curves of pulse pressure variation and systolic pressure variation were 0.576 (p = .517) and 0.548 (p = .678), respectively. The differences in dynamic parameters between responders and nonresponders were not significant. Failure of pulse pressure variation or systolic pressure variation at augmented tidal volume in children may be due to difference in their arterial compliance from those of adults. Large compliance of thoracic wall may be another reason. Augmented pulse pressure variation or systolic pressure variation due to increased tidal volume cannot predict fluid responsiveness in children after simple cardiac surgery.

The Effect of Fluid Pre-loading on Vital Signs and Hemodynamic Parameters in a Porcine Model of Lipopolysaccharide-Induced Endotoxemia.

Background Animal models of distributive hypotension and resuscitation allow the assessment of hemodynamic monitoring modalities and resuscitation strategies. The fluid-first paradigm for resuscitation is currently being challenged with clinical trials. In this investigation, venous return and perfusion are assessed, and full hemodynamics are characterized, in a porcine model of endotoxemic hypotension with and without fluid pre-loading. Methods Two groups of six pigs had the induction of standardized endotoxemic hypotension("critical hypotension"). Group 1 underwent four 10 cc/kg crystalloid boluses, and Group 2 was not fluid pre-resuscitated. Both groups underwent progressive norepinephrine (NE) up-titration to 0.25 mcg/kg/minute over 30 minutes. Vital signs, central parameters, and laboratory values were obtained at baseline, "critical hypotension,"after each bolus and during NE administration. Results Endotoxemia decreased the systemic vascular resistance (SVR) in Group 1 (1031±106 dyn/s/cm-5 versus738±258 dyn/s/cm-5; P=0.03) and Group 2 (1121±196 dyn/s/cm-5 versus759±342 dyn/s/cm-5; P=0.003). In Group 1, the four fluid boluses decreased heart rate (HR), pulmonary capillary wedge pressure (PCWP), and central venous pressure (CVP) (P<0.05). No changes were observed in blood pressure, cardiac output (CO), or lactate. NE up-titration increased HR in Group 1and decreased CVP in both groups. Higher final CVP (11 {3} versus4 {4} mmHg; P=0.01) and PCWP (5 {1} versus2 {2} mmHg; P=0.005) values were observed in Group 1 relative to Group 2, reflecting increased venous return. Conclusions Porcine endotoxemic hypotension and resuscitation were robustly characterized. In this model, fluid loading improved venous return with NE, though perfusion (CO) was preserved by increased NE-induced chronotropy.