Conservative Fluid Research Articles

Less Is More: Improved Outcomes in Surgical Patients with Conservative Fluid Administration and Central Venous Catheter Monitoring

The ARDS Clinical Trials Network Fluid and Catheter Treatment Trial (FACTT) addressed fluid management and central monitoring of patients with acute respiratory distress syndrome/acute lung injury (ARDS/ALI). Because surgical patients may have been fundamentally different from the overall FACTT cohort, we set out to separately analyze the surgery patients in the trial. We performed a posthoc, surgical subgroup analysis of 1,000 patients enrolled in the FACTT. Patients were randomized using a 2x2 factorial design comparing a conservative (CON) versus a liberal (LIB) strategy of fluid management and the use of a pulmonary artery catheter (PAC) or a central venous catheter (CVC). The primary end point was death at 60 days. Secondary end points included the number of ventilator-free days, ICU-free days, and dialysis-free days until hospital discharge up to day 90. We defined surgical patients as those admitted to a surgical ICU, burn ICU, or cardiac surgical ICU; trauma patients; or those with an APACHE III surgical admission type. There were 244 surgical patients. Risk of death within 60 days of randomization did not vary with catheter or fluid management, and a corresponding lack of effect was evident with regard to dialysis-free days. Ventilator-free days were increased in the fluid-conservative group (LIB, 13+/-1 days; CON, 15+/-1 days; p=0.04) at 28 days. CVC patients had more ventilator-free days at 28 and 90 days (28 days: CVC, 16+/-1 days; PAC, 13+/-1 days; p=0.03; 90 days: CVC, 64+/-3 days; PAC, 57+/-4 days; p=0.03). CVC patients had more ICU-free days at 90 days (90 days: CVC, 63+/-3 days; PAC, 55+/-3 days; p=0.04). The risk of death did not vary with fluid management or catheter. A conservative fluid-administration strategy and central venous catheter monitoring resulted in more ventilator-free and ICU-free days in surgical patients with acute lung injury, and conservative fluid administration did not result in more renal failure.

Detecting volume responsiveness and unresponsiveness in intensive care unit patients: two different problems, only one solution

Policies of fluid administration/restriction in critically ill patients have evolved over recent years. Abundant fluid resuscitation is encouraged during the early stage of severe sepsis. But a conservative fluid strategy is recommended in later stages, in particular when lungs are injured. Both strategies are risky if uncontrolled. Tests detecting volume unresponsiveness at any moment of fluid resuscitation or detecting volume unresponsiveness at any moment of fluid restriction would help to better assess the benefit/risk ratio of continuing such strategies. Measuring the short-term hemodynamic changes during passive leg raising can be reliably used for that purpose in both situations, even when patients are breathing spontaneously.

Intensive care management of life‐threatening avian influenza A (H5N1)

A large proportion of patients with avian influenza A (H5N1) develop life-threatening manifestations, often including ARDS, acute renal failure and multiple organ failure that requires aggressive intensive care management. The pace of development of respiratory failure is often rapid and can occur in previously healthy hosts, mandating close observation and timely intervention of infected individuals. Use of standard, contact, droplet and airborne isolation precautions is recommended to protect healthcare workers. Key components of ARDS management encompass appropriate mechanical ventilation including limiting tidal volume to </=6 mL/kg of predicted body weight, maintaining transpulmonary pressures </=30 cm H(2)O, and utilizing positive end-expiratory pressure to limit alveolar deflation and to improve oxygenation. Additional strategies include conservative fluid management and using nutrition supplemented with antioxidants. Use of corticosteroids is controversial for both early and late ARDS and although often used for avian influenza, beneficial effects on outcomes have not been demonstrated for corticosteroids. Prone positioning can improve oxygenation temporarily and might be useful as rescue therapy for severe hypoxemia. Administration of inhaled nitric oxide and high frequency oscillatory ventilation can improve oxygenation but have not been demonstrated to improve survival in ARDS-their role in avian influenza is uncertain and availability limited. Management of multiple organ failure may include vasopressor support for septic shock and renal replacement therapy for acute renal failure.

Influenza A/H5N1 infection: Other treatment options and issues

Antiviral therapy and vaccination are important strategies for the control of human influenza/H5N1 disease, but the efficacy of these modalities is limited by timing of administration and shortage of supply. Lung protective ventilation strategy with a low tidal volume and low pressure, in addition to a conservative fluid management approach, is recommended when treating patients with ARDS. Low-dose steroids may be considered in the treatment of refractory septic shock. Non-invasive positive pressure ventilation (NPPV) may play a limited supportive role for early ARDS/acute lung injury, but it is contra-indicated in critically ill patients with multi-organ failure and haemodynamic instability. NPPV and oxygen therapy should be applied in healthcare facilities with good ventilation and respiratory protection as substantial exposure to exhaled air occurs within a 0.5 m and 0.4 m radius of patients receiving NPPV and oxygen via a simple mask, respectively. Intravenous gammaglobulin should be used with caution for treatment of reactive haemo-phagocytosis due to its thrombogenic effects, whereas the role of etoposide needs evaluation with animal models. Passive immunotherapy in the form of convalescent plasma may be useful as rescue therapy. More data are needed to explore the potential role of other drugs with immuno-modulating properties such as statins. Healthcare workers currently must apply strict standards, contact and droplet precautions when dealing with suspected cases, and upgrade to airborne precautions when performing aerosol-generating procedures. Non-pharmacological measures such as early case isolation, household quarantine, school/workplace closure, good community hygiene and restrictions on travel are useful measures in controlling a pandemic.

Advances in critical care for the nephrologist: acute lung injury/ARDS.

Acute lung injury (ALI) and the acute respiratory distress syndrome (ARDS) are a major cause of acute respiratory failure in the critically ill patient. ALI and ARDS are characterized by the acute onset of severe hypoxemia and bilateral pulmonary infiltrates in the absence of clinical evidence for left atrial hypertension. These conditions are differentiated from one another by the ratio of the partial pressure of oxygen in the arterial blood to the inspired fraction of oxygen; ARDS requires a more severe oxygenation defect. ALI and ARDS may occur in association with a number of clinical disorders, including sepsis, pneumonia, aspiration, trauma including inhalational injury, and blood transfusions. The mortality rate remains high, in the range of 25% to 40%. The pathophysiology of ALI/ARDS involves resident lung cells, including endothelial and epithelial cells, as well as neutrophils, monocytes/macrophages, and platelets. When ALI/ARDS is complicated by acute kidney injury, mortality increases substantially. Several supportive and pharmacologic therapies have been tested in clinical trials. Of these, a low tidal volume, lung protective ventilation strategy is the only strategy that has been demonstrated in a large, multicenter randomized clinical trial to reduce mortality for patients with ALI/ARDS. Based on a recent randomized trial, a conservative fluid management strategy reduces the duration of mechanical ventilation without increasing the incidence of renal failure. Pharmacologic strategies and other ventilator management strategies have not been successful to date; however, several randomized, placebo controlled treatment trials are ongoing.

Recent developments in the management of acute respiratory distress syndrome in adults

Recent developments in the management of acute respiratory distress syndrome (ARDS) in adults are reviewed. Corticosteroids have been extensively studied in ARDS; however, they have not demonstrated clear benefit in patients with ARDS. Some trials have found increased complications and mortality related to corticosteroid use. The use of conservative fluid management has been associated with significant reductions in morbidity, highlighting the need to avoid fluid over-administration in patients with ARDS. A number of ventilatory strategies have also been studied. Studies have found that higher positive end-expiratory pressure settings do not appear to be harmful in patients with ARDS. In an effort to prevent alveolar overdistention, low tidal volume and plateau pressure ventilation is increasingly being used in patients with acute lung injury (ALI). Given the increasing evidence supporting the use of lower tidal volume ventilation, this strategy has become the new standard of care in patients with suspected ALI and ARDS. No clear benefit has been shown in the treatment of ARDS with nitric oxide and surfactant. Prostaglandins and acetylcysteine are not considered useful in the treatment of ARDS, while no conclusions can be drawn regarding the benefits of albuterol on mortality in patients with ARDS. The use of prone positioning should be discouraged in the treatment of ARDS based on its associated risks. Early administration of moderate-dosage corticosteroids likely helps decrease the time of ventilator dependence and duration of intensive care unit stay. Conservative fluid management and low tidal volume ventilation are becoming increasingly widespread in the management of patients with ARDS. Nitric oxide, surfactant, prostaglandins, albuterol, acetylcysteine, and prone positioning have not been shown to be beneficial in the treatment of ARDS.

Long-term resource use, quality of life, and cost-effectiveness of liberal and conservative fluid strategies in acute lung injury

Long-term resource use, quality of life, and cost-effectiveness of liberal and conservative fluid strategies in acute lung injury

Nonventilatory Treatments for Acute Lung Injury and ARDS

Over the past decade, advances in the ventilatory management of acute lung injury (ALI) and ARDS have improved outcomes; however, until recently the search for other therapies has been less fruitful. Recently, the Acute Respiratory Distress Syndrome Network Fluid and Catheter Treatment Trial reported that a conservative fluid management strategy, compared with a fluid liberal strategy, increased the mean (± SE) number of ventilator-free days in patients with ALI (14.6 ± 0.5 vs 12.1 ± 0.5 days, respectively; p < 0.001). In addition to this beneficial effect on outcomes, the study found that the conservative fluid strategy did not increase the incidence of renal failure or the development of shock. Other studies have demonstrated that albumin and furosemide therapy may be beneficial in hypoproteinemic patients with lung injury, though data on outcomes is still lacking. Although several pharmacologic therapies, such as corticosteroids, surfactant, and nitric oxide, have been demonstrated to be ineffective in improving outcomes, several promising new treatments are being investigated in ongoing or upcoming clinical trials. This article reviews these developments and other recent research on the optimal nonventilatory management of patients with ALI.

Acute hyperglycemic emergencies in children with type 2 diabetes

Acute hyperglycemic emergencies in children with type 2 diabetes

A conservative fluid management strategy did not affect risk for death but shortened duration of ventilation in acute lung injury

Source Citation Wiedemann HP, Wheeler AP, Bernard GR, et al. Comparison of two fluid-management strategies in acute lung injury. N Engl J Med. 2006;354:2564-75. 16714767

Comparison of two fluid-management strategies in acute lung injury

Conclusion: A conservative strategy of fluid management in patients with acute lung injury shortens duration of mechanical ventilation without increasing nonpulmonary organ failure. Summary: There is debate about optimal fluid management of patients with acute lung injury. Limiting fluids or inducing diuresis may improve lung function but at the expense of impaired perfusion of other organs. In this randomized study, a conservative or liberal strategy of fluid management in patients with acute lung injuries was used. The protocol was applied for 7 days in 1000 patients with acute lung injury. The primary end point was death at 60 days. Ventilator-free days and organ-failure-free days and measures of lung physiology were secondary end points. There was no difference between the two groups in the primary end point at 60 days. In the conservative strategy group, 25.5% of the patients died, and 28.4% of the patients died in the liberal strategy group (P < .30; 95% confidence interval for a difference, −2.6% to 8.4%). The cumulative fluid balance in the first 7 days in the conservative strategy group was −136 ± 491 mL. The cumulative fluid balance in the first 7 days in the liberal strategy group was +6992 ± 502 mL (P < .001). The conservative strategy group had an improved oxygenation index, lung injury score, and an increased number of ventilator-free days (14.6 ± 0.5 vs 12.1 ± 0.5, P < .001) vs the liberal strategy group. The conservative strategy group also had more days not spent in the intensive care unit (13.4 ± 0.4 vs 11.2 ± 0.4, P < .001) during the first 28 days. There was no difference between the conservative and liberal strategy groups with respect to prevalence of shock during the course of the study or the use of dialysis during the first 60 days (10% vs 14%, P < .06). Comment: A conservative fluid management strategy did not decrease death at 60 days vs a liberal fluid management strategy in patients with acute respiratory distress syndrome. However, intensive care unit days were reduced and lung function was improved with the conservative fluid management posture. The results are consistent with other recent reports suggesting improved overall patient outcome with conservative fluid management in acute respiratory distress syndrome. The days of essentially drowning patients with acute lung injury to preserve distal organ perfusion should be over.

A ghost fluid, moving finite volume plus continuous remap method for compressible Euler flow

AbstractA numerical solution method for accurately capturing material interfaces in unsteady compressible Euler flows is presented. The method consists of a finite volume scheme on a moving computational mesh and employs the HLLC approximate Riemann solver to evaluate intercell numerical fluxes. The mesh is moved in a Lagrangian fashion with the material, and to avoid grid distortion, remapping is performed at the end of each time interval, with the distorted grid being rezoned back to the initial mesh. The focus of the work is multimaterial flows consisting of two immiscible materials separated by an interface. The innovative aspect of the work is the application of a conservative ghost fluid method, together with a volume of fluid technique, within the moving mesh plus continuous remap framework. In addition a preliminary discussion, concerning the extension of the solution method to two spatial dimensions, includes a new area preserving volume fraction version of the interface reconstruction algorithm reported by Bonnell et al. (Material Interface Reconstruction. Lawrence Livermore National Laboratory Report). Copyright © 2005 John Wiley &amp; Sons, Ltd.

COVARIANT ANALYSIS OF NEWTONIAN MULTI-FLUID MODELS FOR NEUTRON STARS I: MILNE–CARTAN STRUCTURE AND VARIATIONAL FORMULATION

This is the first of a series of articles showing how 4 dimensionally covariant analytical procedures developed in the context of General Relativity can be usefully adapted for application in a purely Newtonian framework where they provide physical insights (e.g. concerning helicity currents) that are not so easy to obtain by the traditional approach based on a 3+1 spacetime decomposition. After an introductory presentation of the relevant Milne spacetime structure and the associated Cartan connection, the essential principles are illustrated by application to the variational formulation of simple barotropic perfect fluid models. This variational treatment is then extended to conservative multiconstituent self-gravitating fluid models of the more general kind that is needed for treating the effects of superfluidity in neutron stars.

Folding characterization in conservative chaotic fluid flows

We study transport of passive scalar fields in a bidimensional incompressible chaotic fluid flow. For a spatially smooth velocity field with impulsive perturbations, the model is described by a randomized standard mapping. We numerically investigate passive scalar field transport for given initial concentration distributions and their dependence on the nonlinearity and noise amplitude. We show that space and time concentration histograms are determined by the underlying mechanism of stretching and folding. Moreover, to characterize this process we introduce a parameter, the average derivative of a tracer line length, which shows interesting scale properties.

Supplemental perioperative fluid administration increases tissue oxygen pressure

Background. Wound infections are common and serious surgical complications. Wound perfusion delivers oxygen, inflammatory cells, growth factors, and cytokines to injured tissues. Hypoperfused regions experience low oxygen tensions that do not support adequate oxidative killing or wound healing. Clinicians may fail to recognize clinically important hypovolemia because hemodynamic stability and urine output are maintained after peripheral perfusion is compromised. We tested the hypothesis that supplemental fluid administration during and after elective colon resection increases tissue perfusion and tissue oxygen pressure. Methods. Fifty-six patients undergoing colon resection were randomly assigned to conservative (8 mL·kg−1·h−1, n = 26) or aggressive (16 to 18 mL·kg−1·h−1, n = 30) fluid management. Anesthetic technique was standardized. We used 60% nitrous oxide in 40% oxygen. During surgery and postanesthetic recovery, subcutaneous oxygen tension (PsqO2) was measured by using a polarographic sensor implanted subcutaneously into 1 upper arm. Capillary blood flow was evaluated postoperatively with a thermal diffusion system. Data were analyzed with 2-tailed t tests; P value less than.05 was considered statistically significant. Results. Hemodynamic and renal responses were similar in the groups. Intraoperative tissue oxygen tension was significantly greater in patients given supplemental fluid: 81 ± 26 vs 67 ± 18 mm Hg, P =.03. Postoperative PsqO2 (77 ± 26 vs 59 ± 15 mm Hg, P =.009) and capillary blood flow (69 ± 12 vs 53 ± 12, P <.001) were also greater in the supplemental fluid patients. Conclusions. Supplemental perioperative fluid administration significantly increases tissue perfusion and tissue oxygen partial pressure. Optimizing tissue perfusion will require providing more fluid than indicated by normal clinical criteria or use of invasive monitoring to guide treatment. The actual effect of supplemental fluid administration on incidence of wound infection requires further investigation. (Surgery 2003;133:49-55.)

The role of hypertonic saline dextran in trauma resuscitation

Modern trauma management has recognized the importance of using conservative fluid resuscitation regimes in order to prevent complications from fluid overload arising. Hypertonic/hyperoncotic fluids appear to provide an ideal means of facilitating this, requiring only small volumes to rapidly elevate blood pressure. Hypertonic saline dextran (HSD) was introduced in 1985 but its take up has been slow, a large part of this has been due to the lack of human trials and concerns about complications.The current evidence has been reviewed and it is clear that HSD is an efficient means of correcting hypotension, doing so mainly by the mobilizing endogenous water. It is becoming apparent that early administration has the potential to modulate the inflammatory cascade in patients at risk of developing adult respiratory distress syndrome (ARDS) and multiorgan failure. This is reflected in the handful of human trials that show a trend towards increased survival (particularly for head injuries) and a possible reduction in ARDS. The side effect profile appears to be good, even in the presence of dehydration or penetrating trauma.Published human trials have methodological problems and lack of power of study this has led to a reliance on animal studies. Clearly there is great potential, but before large-scale prehospital usage can be justified further well-conducted randomized human trials are needed.

Mass conservative fluid flow visualization for CFD velocity fields

Mass conservation is a key issue for accurate streamline and stream surface visualization of flow fields. This paper complements an existing method (Feng et al., 1997) for CFD velocity fields defined at discrete locations in space that uses dual stream functions to generate streamlines and stream surfaces. Conditions for using the method have been examined and its limitations defined. A complete set of dual stream functions for all possible cases of the linear fields on which the method relies are presented. The results in this paper are important for developing new methods for mass conservative streamline visualization from CFD data and using the existing method.

Temperature-driven fluid flow in porous media using a mixed finite element method and a finite volume method

We present a numerical scheme for the computation of conservative fluid velocity, pressure and temperature fields in a porous medium. For the velocity and pressure we use the primal–dual mixed finite element method of Trujillo and Thomas while for the temperature we use a cell-centered finite volume method. The motivation for this choice of discretization is to compute accurate conservative quantities. Since the variant of the mixed finite element method we use is not commonly used, the numerical schemes are presented in detail. We sketch the computational details and present numerical experiments that justify the accuracy predicted by the theory.

Maternal metabolic abnormalities in twin–to–twin transfusion syndrome at mid–pregnancy

We report abnormal maternal laboratory parameters in twin-to-twin transfusion syndrome (TTTS) at mid-pregnancy. A retrospective chart review was undertaken of 109 patients with TTTS evaluated for placental laser surgery. Complete blood count (CBC), blood type and Rh factor, urine analysis and serum chemistry panel were obtained preoperatively, with the CBC and serum albumin repeated on the first postoperative day. The mean gestational age was 21.2+/-1.7 weeks. Initial abnormal values included hematocrit (32.1+/-3.0%), hemoglobin (11.0+/-1.03 g/dl), serum magnesium (1.71+/-0.17 mg/dl), total protein (6.08+/-0.55 g/dl) and albumin (3.06+/-0.34 g/dl). Despite minimal blood loss and conservative fluid replacement mean hematocrit, hemoglobin, and albumin were 27.3+/-2.74%, 9.3+/-0.94 g/dl and 2.56+/-0.23 g/dl, respectively on postoperative day one. Weight gain (8.0+/-5.5 lb.) and low urinary output were characteristic peri-operative events. Maternal hypoproteinemia and anemia occur in TTTS at mid-pregnancy. This may contribute independently to amniotic fluid production rates in the fetuses, and explain in part the maternal sensitivity to intravenous fluids in multiple pregnancy.

Maternal metabolic abnormalities in twin–to–twin transfusion syndrome at mid-pregnancy

We report abnormal maternal laboratory parameters in twin-to-twin transfusion syndrome (TTTS) at mid-pregnancy. A retrospective chart review was undertaken of 109 patients with TTTS evaluated for placental laser surgery. Complete blood count (CBC), blood type and Rh factor, urine analysis and serum chemistry panel were obtained preoperatively, with the CBC and serum albumin repeated on the first postoperative day. The mean gestational age was 21.2+/-1.7 weeks. Initial abnormal values included hematocrit (32.1+/-3.0%), hemoglobin (11.0+/-1.03 g/dl), serum magnesium (1.71+/-0.17 mg/dl), total protein (6.08+/-0.55 g/dl) and albumin (3.06+/-0.34 g/dl). Despite minimal blood loss and conservative fluid replacement mean hematocrit, hemoglobin, and albumin were 27.3+/-2.74%, 9.3+/-0.94 g/dl and 2.56+/-0.23 g/dl, respectively on postoperative day one. Weight gain (8.0+/-5.5 lb.) and low urinary output were characteristic peri-operative events. Maternal hypoproteinemia and anemia occur in TTTS at mid-pregnancy. This may contribute independently to amniotic fluid production rates in the fetuses, and explain in part the maternal sensitivity to intravenous fluids in multiple pregnancy.