Choice Of Fluid Research Articles

Boiling Heat Transfer of Low GWP Refrigerants: A Review

The boiling heat transfer of low GWP (global warming potential) refrigerants, which are more environmentally benign, is studied in this work. Low GWP applications allow for greater freedom in the choice of suitable working fluids based on application and necessity. Human comfort demands increase as a result of the rapid pace of climate change in order to adapt to its negative effects. HVAC&R (Heating, Ventilation, Air Conditioning, and Refrigeration) is crucial for preserving the level of climate comfort in a closed space and its surrounds by using eco-friendly refrigerants. The purpose of this review is to provide a summary of significant studies on the application of low GWP refrigerants in boiling heat transfer, as well as a background on refrigerants and their many subtypes. Along with explaining the impacts of vpour quality, heat flux, and mass flux on pressure drop, this also discusses the implications of heat flux, mass flow, saturation temperature, and the heat transfer mechanism on the heat transfer coefficient.

Optimization of a recompression supercritical nitrous oxide and helium Brayton cycle for space nuclear system

Long life, high energy density, high efficiency, and compact power system is necessary for space exploration to achieve a future goal. Recompression supercritical Brayton cycle has excellent potential for application of space nuclear power generation systems. However, it faces the choice of cycle working fluid which limits the cycle thermal efficiency and quality. In order to improve the thermal efficiency of the nuclear power system, a new composition of the working fluid, nitrous oxide and helium (N2O–He) mixture is used in the system. Comprehensive studies and optimization are performed for the significant parameters, including the split ratio, pressure ratio, minimum operating temperature, maximum operating temperature, and minimum operating pressure. Optimum values have been obtained at which the maximum thermal efficiency and minimum Brayton rotating unit (BRU) mass of the cycle occur. Results show that the thermal efficiency improves with an increase in the split ratio, main compressor pressure ratio, and maximum operating temperature, and decreasing minimum operating temperature and minimum operating pressure. The proposed novel working fluid cycle has superior performance compared with N2O (deviation of 5.1%) and CO2 (deviation of 6.5%). The optimized thermal efficiency and BRU mass are calculated as 42.67% and 3584.80 kg at optimum conditions.

Combined cooling and power cycle for engine waste heat recovery using CO2-based mixtures

CO2-based mixture is a potential working fluid choice of combined cooling and power cycle (CCP) due to its superior thermodynamic performances and the removal of the limit of CO2 critical temperature. This study proposes a CCP system using CO2-based mixtures, loaded on a refrigerated truck, to realize multi-mode transformations for diverse cooling and power demands. The components of mixtures are strictly screened and key parameter analyses and optimization in terms of energy, exergy, adjustability, and economic performance are conducted to find the general laws and the best composition of the mixtures. The results show CO2-based mixtures have better energy-saving potential, adaptability, adjustability, and compactness than CO2. By comparison, CO2/R32 is recommended for superior output capacity, lower operation parameters, remarkable adjustability, and cheaper investment cost. CCP using CO2/R32 can maximally achieve 6.9% power enhancement or 5.9 times cooling enhancement relative to the refrigerated truck using a stand-alone refrigerator, and 19% power increase or 80% cooling increase relative to the CO2 system. It can realize smooth and steady mode transformation to achieve complex and diverse allocation of refrigeration and power in actual operation.

Retraction Note to: Fluid choice for resuscitation of the trauma patient: a review of the physiological, pharmacological, and clinical evidence.

Volume replacement regimens are discussed very emotionally. Interpretation of the literature is difficult due to variations in study design, patient population, target for volume replacement, endpoints, and type of fluids. Meta-analyses may not be very helpful because all kinds of patients and very old studies are included. The principles and options for volume replacement were reviewed exclusively in trauma patients and studies from the literature focusing on this problem were analyzed. Using a MEDLINE search, volume replacement therapy in adult trauma patients published in the English language from 1985 to the end of 2002 were identified and analyzed. Studies on prehospital volume replacement, volume replacement in the emergency area or in the operating room, and volume therapy in trauma intensive care unit patients were included. The age-old crystalloid/colloid controvery has still not been resolved but has been enlarged to a colloid/colloid debate. It is now widely accepted that human albumin could easily be replaced by synthetic colloids for volume replacement in trauma patients. No superiority of a specific volume replacement strategy with regard to outcome was found. However, in several studies outcome was not the major endpoint. Although showing some promising results, the importance of hypertonic solutions for volume replacement in the trauma patient is not yet defined. The choice of fluid therapy in trauma patients engenders the most controversy and an examination of the body of literature on this subject results in confusion. It is imperative to continue the search for substances that are effective in avoiding the development of post-trauma multi-organ dysfunction syndrome without detrimental side-effects.

EP.TU.364Intravenous fluid prescribing – common pitfalls and suggestions for improvement

Abstract Aim Intravenous fluids are no doubt most prescribed treatments in surgical practice. It is also an area where junior doctors’ performance is commonly found deficient. There appeared to be a gap in general knowledge of fluid and electrolyte management. Our audit aims to assess the competency of surgical juniors in fluid prescribing as compared to recommendations set out by GIFTASUP 2011. FY1s have also been asked to complete a survey on fluid and electrolyte management. Method We included all adult surgical inpatients (28) admitted over one week to our DGH who were started on IV fluids for maintenance only. We retrospectively audited their prescription charts and medical notes. FY1's in the department have been also asked to fill out a short survey testing their knowledge on fluid and electrolyte requirements. Following this, we held a tutorial on fluid management of surgical inpatients for FY1's. We also made fluid management algorithm available in SAU for reference. Results Data was tabulated and outcomes compared with CG174 guidance. Cycle 1 showed poor compliance with only about 50% patients being prescribed appropriate intravenous fluid volumes. FY1’s completing the survey scored 54% on average. Often previous fluid prescription was copied. Cycle 2 showed some improvement in appropriate volumes and choice of maintenance fluids prescribed, and better survey score of 64%. There was also improvement on the understanding of daily fluid and electrolyte requirement from the FY1 cohort. Conclusions We suggest implementing varied educational approach to improve on fluid prescribing and patient outcomes in hospital.

DOES EARLY VASOPRESSOR USE IN SEPSIS RESULT IN BETTER OUTCOMES? A SYSTEMATIC REVIEW AND META-ANALYSIS

TOPIC: Critical Care TYPE: Original Investigations PURPOSE: Advancements in the management of septic shock have been significant over the past decade, however mortality rates still remain high. The latest sepsis guidelines recommend aggressive fluid therapy followed by vasopressor use in persistently hypotensive patients. The exact timing of vasopressor initiation remains unknown. Recent data suggests that there may be more benefit in starting vasoactive agents earlier or simultaneously along with the fluid of choice. Therefore, we conducted a meta-analysis to evaluate the effect of early versus late vasopressor use on clinical outcomes in septic shock patients. METHODS: PubMed, Cochrane, and Embase databases were searched systematically for studies that compared early versus late vasopressor initiation in septic shock patients and reported our pre-defined primary outcome of short-term mortality. Other inclusion criteria included administration of vasopressors within a 6-hour (h) window, minimum 2 group comparison, > 50 patients, and suffering from septic shock. Study selection, data extraction, and evaluation were performed by two investigators independently. Secondary outcomes that were collected included ICU length of stay, hospital length of stay, the volume of intravenous fluids within the first 6 hours, and time to achieved target mean arterial pressure (≥ 65 mmHg). RESULTS: Of the 601 articles identified, 48 underwent full-text screening and 7 articles with a total of 1,867 patients were included in the meta-analysis. Early vasopressor initiation resulted in decreased short term mortality compared to late vasopressor administration (odds ratio [OR] = 0.54; 95% CI,0.4 to 0.713; P < 0.001; I2 = 30.28%). Secondary outcomes showed time (in hours) to achieve target MAP of 65mmHg was shorter in the early vasopressor group (mean difference: − 1.15; 95% CI, − 1.37 to -0.92; P = <0.001; I2 = 44.58%). There was no difference in ICU length of stay (mean difference = − 0.42; 95% CI, − 0.18 to 1.01; I2 = 86.52%), hospital length of stay (mean difference = − 1.29; 95% CI, − 0.54 to 3.12; I2 = 91.94%), or net fluids in first 6 hours (mean difference = − 295.08; 95% CI, − 717.74 to 127.58; I2 = 97.77%) between the two groups, respectively. CONCLUSIONS: The use of early vasopressors in septic shock patients decreased short-term mortality and time to target MAP of ≥ 65 mmHg. However, no statistically significant difference was shown for hospital length of stay, ICU length of stay, or total net fluids required within the first 6 hours. Further randomized controlled trials are warranted to better address the study question. CLINICAL IMPLICATIONS: Early vasopressor initiation in septic shock patients appears to benefit mortality outcomes. This approach to septic shock management may potentially limit the complications of aggressive fluid resuscitation. These results will encourage clinicians to not delay vasoactive agents use in favor of extensive fluid resuscitation and consequently minimize delays in hypotension correction. DISCLOSURES: No relevant relationships by Tewodros Eguale, source=Web Response No relevant relationships by Mohammad Ghanbar, source=Web Response No relevant relationships by Ethar Makhseed, source=Web Response

Application of bench studies at the bedside to improve outcomes in the management of severe diabetic ketoacidosis in children-a narrative review.

ObjectiveIn this review, we address a few key issues and the challenges faced in the management of severe diabetic ketoacidosis (DKA) in children, highlighting the existing standard of care, supported by evidence and bench studies.BackgroundThe classic triad of DKA namely hyperglycemia, metabolic acidosis and ketonemia warrants immediate attention with fluids and insulin. Correction of dehydration in DKA is of utmost priority and the calculation of fluid volume and choice of fluid have remained a matter of debate. Insulin therapy, to halt the ketone production, in DKA has undergone wide variations in dose and preparation since its discovery. Although the mortality due to severe DKA has remarkably decreased, complications like cerebral edema and acute kidney injury (AKI) continue to haunt the intensivists and endocrinologists on a few occasions.MethodsWe have selected a few important questions in the management of severe DKA in children, addressing the challenges, reviewing the studies, guidelines and bedside practices with evidence in this narrative review.ConclusionsThe focus of management should be to understand and normalise the deranged physiology rather than trying to get normal laboratory reports. This needs careful understanding of the pathogenesis and deriving conclusion from bench studies. With newer studies and evidence, guidelines are revised every few years. There is a trend towards more conservative therapy, with continuous and advanced monitoring. Switching to subcutaneous insulin and oral hydration is done as early as possible with clinical monitoring and resolution of DKA. Management of severe DKA in children can vary from simple fluid titration and insulin infusion in mild cases to a scenario with multiorgan dysfunction requiring intensive monitoring and advanced organ support. Individualisation of therapy to suit the needs with the available evidence and expertise is extremely essential.

Выбор инфузионно-трансфузионной среды для защиты эндотелиального гликокаликса

До недавнего времени теоретические преимущества одного типа жидкости для ресусцитации перед другим основывались на устаревшем в настоящее время понимании проницаемости сосудов. Коллоидные жидкости считались превосходящими кристаллоиды из-за их теоретически более высокого удержания во внутрисосудистом пространстве, но данные клинических исследований не подтвердили это и неубедительно продемонстрировали преимущества в отношении смертности пациентов или эффективности одного типа раствора перед другим. Эти наблюдения становятся понятными благодаря пересмотренному уравнению Старлинга, которое объясняет сходные свойства объемного расширения и образования отека из межклеточной жидкости у кристаллоидных и коллоидных растворов, когда повреждается эндотелиальный гликокаликс, а гидростатическое давление у критических пациентов падает. Принимаются во внимание также другие соображения, такие как эффекты накопления коллоидов в интерстициальном пространстве. Будущие исследования в области жидкостной реанимации получат пользу от обновленного понимания детерминант проницаемости сосудов, и, возможно, наиболее многообещающим является определение эндотелиального гликокаликса в качестве возможной терапевтической мишени. Инфузионно-трансфузионные среды различаются по своей способности защищать и восстанавливать эндотелиальный гликокаликс. Хотя свежезамороженная плазма была определена как наиболее эффективная субстанция, необходимы дальнейшие исследования для установления механизмов и определения того, улучшает ли репарация гликокаликса клинические результаты. Стратегия реанимации, которая защищает и восстанавливает эндотелиальный гликокаликс, может оказаться наиболее эффективной.

S3209 Choice of Initial Resuscitation Fluid in Patients Admitted for Acute Pancreatitis

Introduction: Fluid resuscitation is a cornerstone in the management of acute pancreatitis (AP). Buffered crystalloids, Lactated Ringer's (LR), theoretically reduce the risk of metabolic acidosis in large volume resuscitation compared to normal saline (NS) in AP. However, studies comparing the two have been small and yield conflicting results with society guideline recommendations acknowledging the limited evidence. This study examines the hypothesis that patients with AP, initial resuscitation with LR is associated with improved outcomes compared to NS. Methods: We conducted a retrospective cohort study to compare fluid resuscitation among AP in patients admitted to the Omaha Veterans Affairs hospital from 2011 through 2017. Patients were stratified by initial fluid received (LR vs NS). Co-primary outcomes were overall length of stay (LOS), intensive care unit (ICU) LOS, and 30-day rate of major complication (MC defined as a composite of mortality, intubation, pancreatic necrosis, enteral or parenteral nutrition, surgical or endoscopic intervention, or readmission). For each outcome, we used generalized estimating equations (GEE) to model the outcome with Poisson links for overall and ICU length of stays and a binomial link for each MC. Exchangeable correlation structures were used for all models. Measures with skewness values > 2 were log-transformed to shift their distributions closer to normal distributions. For each outcome, we analyzed simple models using one predictor at a time. Age and all other predictors with P-values of < 0.2 in the simple models were entered into multivariable models. A P-value of < 0.05 was considered significant. Results: A total of 512 admissions met inclusion criteria. Mean age was 57, 78% were white, and 92% were male. Forty-seven (9%) admissions received LR as initial fluid, and 59 (12%) admissions were to ICU. Complete baseline characteristics are shown in Table. In unadjusted analysis, all primary outcomes favored the LR group. After adjustment for covariates, none of these remained significant (see Figure 1 and Table 1). Conclusion: Initial resuscitation with LR was not significantly associated with improved outcomes after adjusting for covariates when comparing to NS in patients hospitalized for AP. The limited number of cases treated with LR may reflect a selection bias of providers favoring NS based upon practice habits. Future multicenter cohort or RCTs would help account for this potential bias.Figure 1.: Adjusted outcomes by initial resuscitation fluid received a) P-values after adjustment for multiple covariates. b) Major complication is defined as a composite of mortality, intubation, pancreatic necrosis, enteral or parenteral nutrition, surgical or endoscopic intervention, or readmission. Abbreviations: LOS, length of stay; ICU, intensive care unit; LR, Lactated Ringer's; NS, normal saline.Table 1.: Baseline Characteristics and Outcomes a) Major complication is defined as a composite of mortality, intubation, pancreatic necrosis, enteral or parenteral nutrition, surgical or endoscopic intervention, or readmission. Abbreviations: SD, standard deviation; n, number; ICU, intensive care unit; LR, Lactated Ringer’s; LOS, length of stay; d, days; Coeff, coefficient; OR, odds ratio; CI, confidence interval; NS, normal saline; Unadj, unadjusted; Adj, adjusted.

Case report: Management of septic knee arthritis with Pseudomonas aeruginosa by arthroscopic debridement and lavage with diluted povidone iodine.

IntroductionSeptic knee arthritis after elective arthroscopic procedures is a rare surgical emergency, with Pseudomonas aeruginosa even more rarely causing the infection. The treatment by arthroscopic debridement and lavage with diluted Povidone-Iodine has potential benefits that may be useful in improving the prognosis for patients. This case report discusses the potential benefits of using antiseptics like Povidone-Iodine in the washout of the affected joint.Presentation of caseWe present a patient with post arthroscopic septic knee arthritis caused by P. aeruginosa treated successfully by arthroscopic synovectomy and washout with normal saline and diluted povidone‑iodine, and prolonged antimicrobial therapy.DiscussionPreceding reports of P. aeruginosa suggest intraoperative factors, postoperative factors, and host factors that may lead to this uncommon infection. There is controversy over the optimal management regarding arthroscopic versus open debridement, and the choice of the irrigating fluid.ConclusionThe use of antiseptics like Povidone-Iodine in the washout procedure may lead to improved outcomes if used for a short controlled period of time and followed by copious irrigation with saline. Further studies must be done to determine the efficacy and risk-to-benefit ratio of this method.

Fluid management in patients undergoing neurosurgery

Fluid management is an important component of perioperative care for patients undergoing neurosurgery. The primary goal of fluid management in neurosurgery is the maintenance of normovolemia and prevention of serum osmolarity reduction. To maintain normovolemia, it is important to administer fluids in appropriate amounts following appropriate methods, and to prevent a decrease in serum osmolarity, the choice of fluid is essential. There is considerable debate about the choice and optimal amounts of fluids administered in the perioperative period. However, there is little high-quality clinical research on fluid therapy for patients undergoing neurosurgery. This review will discuss the choice and optimal amounts of fluids in neurosurgical patients based on the literature, recent issues, and perioperative fluid management practices.

Urine the Right Direction: The Consensus Statement From the Committee on Transplant Anesthesia of the American Society of Anesthesiologists on Fluid Management During Kidney Transplantation.

Urine the Right Direction: The Consensus Statement From the Committee on Transplant Anesthesia of the American Society of Anesthesiologists on Fluid Management During Kidney Transplantation.

0.9% Sodium chloride solution versus Plasma-Lyte 148 versus compound sodium lacTate solution in children admitted to PICU\u2014a randomized controlled trial (SPLYT-P): study protocol for an intravenous fluid therapy trial

BackgroundIntravenous fluid therapy represents the most common intervention critically ill patients are exposed to. Hyperchloremia and metabolic acidosis associated with 0.9% sodium chloride have been observed to lead to worse outcomes, including mortality. Balanced solutions, such as Plasma-Lyte 148 and Compound Sodium Lactate, represent potential alternatives but the evidence on optimal fluid choices in critically ill children remains scarce. This study aims to demonstrate whether balanced solutions, when used as intravenous fluid therapy, are able to reduce the incidence of a rise in serum chloride level compared to 0.9% sodium chloride in critically ill children.MethodsThis is a single-centre, open-label randomized controlled trial with parallel 1:1:1 assignment into three groups: 0.9% sodium chloride, Plasma-Lyte 148, and Compound Sodium Lactate solutions for intravenous fluid therapy. The intervention includes both maintenance and bolus fluid therapy. Children aged < 16 years admitted to intensive care and receiving intravenous fluid therapy during the first 4 h of admission are eligible. The primary outcome measure is a ≥ 5mmol/L increase in serum chloride level within 48 h post-randomization. The enrolment target is 480 patients. The main analyses will be intention-to-treat.DiscussionThis study tests three types of intravenous fluid therapy in order to compare the risk of hyperchloremia associated with normal saline versus balanced solutions. This pragmatic study is thereby assessing the most common intervention in paediatric critical care.This is a single-centre open-label study with no blinding at the level of delivery of the intervention. Certain paediatric intensive care unit (PICU) patient groups such as those admitted with a cardiac condition or following a traumatic brain injury are excluded from this study.Trial registrationThe study has received ethical approval (HREC/19/QCHQ/53177: 06/06/2019). It is registered in the Australian New Zealand Clinical Trials Registry (ACTRN12619001244190) from 9th September 2019. Recruitment commenced on 12th November 2019. The primary results manuscript will be published in a peer-reviewed journal.

Efficacy and safety of early target-controlled plasma volume replacement with a balanced gelatine solution versus a balanced electrolyte solution in patients with severe sepsis/septic shock: study protocol, design, and rationale of a prospective, randomized, controlled, double-blind, multicentric, international clinical trial

BackgroundSepsis is associated with capillary leakage and vasodilatation and leads to hypotension and tissue hypoperfusion. Early plasma volume replacement is required to achieve haemodynamic stability (HDS) and maintain adequate tissue oxygenation. The right choice of fluids to be used for plasma volume replacement (colloid or crystalloid solutions) is still a matter of debate, and large trials investigating the use of colloid solutions containing gelatine are missing. This study aims to investigate the efficacy and safety of plasma volume replacement using either a combined gelatine-crystalloid regime (1:1 ratio) or a pure crystalloid regime.MethodsThis is a prospective, controlled, randomized, double-blind, international, multicentric phase IV study with two parallel groups that is planned to be conducted at European intensive care units (ICUs) in a population of patients with hypovolaemia in severe sepsis/septic shock. A total of 608 eligible patients will be randomly assigned to receive either a gelatine-crystalloid regime (Gelaspan® 4% and Sterofundin® ISO, B. Braun Melsungen AG, in a 1:1 ratio) or a pure crystalloid regime (Sterofundin® ISO) for plasma volume replacement. The primary outcome is defined as the time needed to achieve HDS. Plasma volume replacement will be target-controlled, i.e. fluids will only be administered to volume-responsive patients. Volume responsiveness will be assessed through passive leg raising or fluid challenges. The safety and efficacy of both regimens will be assessed daily for 28 days or until ICU discharge (whichever occurs first) as the secondary outcomes of this study. Follow-up visits/calls will be scheduled on day 28 and day 90.DiscussionThis study aims to generate evidence regarding which regimen—a gelatine-crystalloid regimen or a pure crystalloid regimen—is more effective in achieving HDS in critically ill patients with hypovolaemia. Study participants in both groups will benefit from the increased safety of target-controlled plasma volume replacement, which prevents fluid administration to already haemodynamically stable patients and reduces the risk of harmful fluid overload.Trial registrationThe European clinical trial database EudraCT 2015-000057-20 and the ClinicalTrials.gov Protocol Registration and Results System ClinicalTrials.gov NCT02715466. Registered on 17 March 2016.

No-boundary wave function, Wheeler-DeWitt equation, and path integral analysis of the bouncing quantum cosmology

Bouncing models are alternatives to inflationary cosmology that replace the initial big bang singularity by a ``bouncing'' phase. A deeper understanding of the initial conditions of the universe, in these scenarios, requires knowledge of quantum aspects of bouncing models. In this work, we propose two classes of bouncing models that can be studied with great analytical ease and hence, provide a test bed for investigating more profound problems in quantum cosmology of bouncing universes. Our model's two key ingredients enable us to do straightforward analytical calculations: (i) a convenient parametrization of the minisuperspace of FRLW spacetimes and (ii) two distinct choices of the effective perfect fluids that source the background geometry of the bouncing universe. We study the quantum cosmology of these models using both the Wheeler-de Witt equations and the path integral approach. In particular, we found a bouncing model analogue of the no-boundary wave function and presented a Lorentzian path integral representation for the same. We also discuss the introduction of real scalar perturbations.

Effect of perioperative fluids on serum osmolality and serum sodium in patients undergoing transcranial excision of craniopharyngioma: A prospective randomized controlled trial

Background:Electrolyte imbalance and acute diabetes insipidus (DI) are the most common complications in patients undergoing craniopharyngioma excision. Data are sparse regarding the choice of fluid in these patients. We compared the effects of balanced salt solution and 0.45% saline infused perioperatively on serum osmolality and serum sodium levels in these patients.Methodology:A prospective randomized double-blinded study was conducted in 30 patients undergoing transcranial excision of craniopharyngioma. The patients received either balanced salt solution or 0.45% sodium chloride solution perioperatively till they were allowed orally. Serum and urine osmolality, serum and urine sodium, urine specific gravity, and total dose of desmopressin required to treat DI were measured in the perioperative period.Results:Demographic data were comparable. We observed that there was significantly higher serum osmolality in the intraoperative period at 2nd h (P = 0.04), 3rd h (P = 0.01), at end of the surgery (P = 0.034) and on postoperative day 0 (POD 0) with P = 0.03 in patients receiving balanced salt solution. We also observed that the difference in serum sodium levels were significantly higher in patients receiving balanced salt solution as compared to those receiving 0.45% sodium chloride solution intraoperatively, at 3rd h (P = 0.02) and at the end of surgery (P = 0.04) although the values were comparable in both the groups as measured on POD 0, 1 and 2.Conclusion:0.45% sodium chloride solution has better effect on serum osmolality than balanced salt solution in patients undergoing transcranial resection of craniopharyngioma.

The impact of Drinking in the Dark (DID) procedural manipulations on ethanol intake in High Drinking in the Dark (HDID) mice.

The High Drinking in the Dark mouse lines (HDID-1 and HDID-2) were selectively bred to achieve high blood ethanol concentrations (BECs) in the Drinking in the Dark (DID) task, a widely used model of binge-like intake of 20% ethanol. There are several components that differentiate DID from other animal models of ethanol intake: time of day of testing, length of ethanol access, single-bottle access, and individual housing. Here, we sought to determine how some of these individual factors contribute to the high ethanol intake observed in HDID mice. HDID-1, HDID-2, and non-selected HS/NPT mice were tested in a series of DID experiments where one of the following factors was manipulated: length of ethanol access, fluid choice, number of ethanol bottles, and housing condition. We observed that 1) HDID mice achieve intoxicating BECs in DID, even when they are group-housed; 2) HDID mice continue to show elevated ethanol intake relative to HS/NPT mice during an extended access session, but this is most apparent during the first 4h of access; and 3) offering a water choice during DID prevents elevated intake in the HDID-1 mice, but not necessarily in HDID-2 mice. Together, these results suggest that the lack of choice in the DID paradigm, together with the length of ethanol access, are important factors contributing to elevated ethanol intake in the HDID mice. These results further suggest important differences between the HDID lines in response to procedural manipulations of housing condition and ethanol bottle number in the DID paradigm, highlighting the distinct characteristics that each of these lines possess, despite being selectively bred for the same phenotype.

Application of volumetric expanders in small vapour power plants used in distributed energy generation – Selected design and thermodynamic issues

Abstract Air pollution with dust is particularly noticeable in winter. This problem is visible especially in those living areas in which furnaces fed by low-quality fuels are used for heating houses and flats. One of the possible ways of limiting the number of used furnaces may be heating and powering of the housing estates and villages by specially designed combined heat and power (CHP) steam (or vapor) power plants. To be competitive to other heating technologies these systems should be cheap, reliable and easy to operate. Therefore, their design should be as simple as possible. Steam or organic Rankine cycle (ORC) energy conversion systems utilizing simple volumetric expanders, which can be applied for distributed power generation are meeting these conditions. The article presents literature review as well as selected thermodynamic and design issues concerning these systems. Literature review gave an outlook on the modeling, experiments, operating conditions and possible configurations of steam and ORC CHP systems. Then, model of the CHP system was implemented in computer software. Thanks to the positive technical features and ability to operate with wet gas the screw machine was selected as the system’s expander. Selected experimental data obtained from the literature review were used for system modeling. Especially the operating conditions of the selected expander (i.e., maximum mechanical power, maximum inlet pressure, expansion ratio and internal efficiency) were assumed based on the experimental results, technical data and information reported in different papers. Expander’s operating conditions and technical data (in particular the value of maximum working fluid pressure allowable at the inlet to the expander) were the basis for pre-selection of working fluids which are possible to apply in the modelled system and selection of the heat source thermal parameters. Modeling was proceeded for different conditions and the results show that depending on the operating conditions and applied working fluid electric power output of the CHP system ranges between 1570 and 2511 kWe (for heat source temperature of 200 °C) and between 1583 and 2631 kWe (for heat source temperature of 150 °C). However, not only maximum power output should be considered as the selection criteria of the system design and working fluid choice. The other important criteria are related to maximization of the obtained electric power, minimization of the vapor pressure at the outlet of the vapor generator and at the inlet to the expander, minimization of the working fluid flow, minimization of fuel consumption and maximization of the temperature of the working fluid at the outlet of the expander. The modeling results show that from all cases studied the ORC CHP power plant utilizing screw expander, using MD2M as working fluid and featuring the electric power of 1570 kWe fed by rapeseed oil is the best possible solution if technical assessment criteria are taken into consideration. Such a system can cover the heating demands of ca. 9615 flats.

Influence of hydraulic versus pneumatic working fluids on quasi-static force response of fluidic artificial muscles

There is currently an increased interest in extending the application of McKibben actuators beyond gaseous environments and working fluids. Extensive efforts have already established force response models for pneumatically driven McKibben actuators that are independent of working fluid material properties, however, the model’s independence to working fluid choice has yet to be validated with empirical evidence. This paper experimentally investigates the effect of working fluid type on the quasi-static pressure dependent force-contraction response of McKibben actuators. Using either air or water as the working fluid, characteristic isobaric force-contraction response curves are compared for both large and small-scale McKibben actuators. To ensure truly isobaric force-contraction characterizations, hydraulic and pneumatic pressure systems were developed to provide precise and accurate control of pressure. Experimental testing proved using air or water as the working fluid resulted in nearly identical isobaric force-contraction response curves, demonstrating that McKibben actuator’s quasi-static force response is independent of working fluid choice. This study establishes that the applicability of existing force response models for pneumatic McKibben actuators can be extended to any practical liquids or gases.

Fluid management: An update for perioperative practitioners

An interprofessional team approach is required to achieve optimum fluid balance for patients during the perioperative period. Incorrect management of fluid assessment and monitoring is associated with adverse outcomes. The scientific understanding of perioperative fluid balance has improved over recent years leading to changes in clinical practice with regard to volume and choice of intravenous fluid. It is important that perioperative practitioners have an understanding of intravenous fluid, fluid compartmentalisation, fluid mechanics and intravascular fluid control mechanisms. Optimum fluid status not only shortens hospital stay but also reduces the incidence of postoperative nausea and vomiting and complication profiles. This article aims to provide perioperative practitioners with a comprehensive overview of fluid management. It will cover important issues surrounding physiological control of fluid balance, choice of intravenous fluid therapy, methods to monitor intravascular volume and factors which influence delivery.