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INTRODUCTION - Recent clinical data suggest intraoperative preservation of human saphenous vein (HSV) in normal saline is associated with vein graft failure. We evaluated the influence of several preservation media on acute physiologic function and cellular viability of HSV conduit.
METHODS - Unprepared (UP) HSV obtained from coronary artery bypass graft patients was characterized on a muscle bath after 2-hour storage in 6 solutions: Plasma-Lyte A, 0.9% NaCl (normal saline), University of Wisconsin solution, Celsior solution, autologous whole blood, or glutathione-ascorbic acid L-arginine (GALA) solution. Vascular smooth muscle contractility was assessed after exposure to depolarizing KCl and phenylephrine. The relaxation of phenylephrine-precontracted HSV to sodium nitroprusside and carbachol (endothelial-independent and -dependent relaxation, respectively) was also assessed. Cellular viability was determined via the methyl thiazolyl tetrazolium (MTT) assay. Rat aortae were used to assess the effect of pH during graft preservation on endothelial-dependent relaxation.
RESULTS - Preservation of HSV in normal saline and autologous whole blood impaired contractile responses to KCl relative to UP tissues, whereas preservation in University of Wisconsin solution and Celsior solution enhanced contractile responses (P < .05). Relative to UP tissues, responses to phenylephrine were decreased with preservation in normal saline, whereas preservation in University of Wisconsin solution, Celsior solution, and GALA all potentiated these responses (P < .05). Only preservation in normal saline impaired endothelial-independent relaxation (P = .005). Preservation in Plasma-Lyte A (P = .02), normal saline (P = .002), and University of Wisconsin solution (P = .02) impaired endothelial-dependent relaxation. Normal saline preservation decreased MTT viability index relative to UP tissues (0.02 ± 0.002 mg(-1)0.5 mL(-1) vs 0.033 ± 0.005 mg(-1)0.5 mL(-1); P = .03). Endothelial function was impaired by acidic pH in rat aorta.
CONCLUSION - Preservation of HSV in normal saline causes graft injury leading to impaired physiologic function and decreased viability of the HSV. This harm is mitigated by the use of buffered salt solutions as preservation media.
Copyright © 2015 Elsevier Inc. All rights reserved.
BACKGROUND - The objective of this systematic review and meta-analysis was to assess the relationship between the chloride content of intravenous resuscitation fluids and patient outcomes in the perioperative or intensive care setting.
METHODS - Systematic searches were performed of PubMed/MEDLINE, Embase and Cochrane Library (CENTRAL) databases in accordance with PRISMA guidelines. Randomized clinical trials, controlled clinical trials and observational studies were included if they compared outcomes in acutely ill or surgical patients receiving either high-chloride (ion concentration greater than 111 mmol/l up to and including 154 mmol/l) or lower-chloride (concentration 111 mmol/l or less) crystalloids for resuscitation. Endpoints examined were mortality, measures of kidney function, serum chloride, hyperchloraemia/metabolic acidosis, blood transfusion volume, mechanical ventilation time, and length of hospital and intensive care unit stay. Risk ratios (RRs), mean differences (MDs) or standardized mean differences (SMDs) and confidence intervals were calculated using fixed-effect modelling.
RESULTS - The search identified 21 studies involving 6253 patients. High-chloride fluids did not affect mortality but were associated with a significantly higher risk of acute kidney injury (RR 1.64, 95 per cent c.i. 1.27 to 2.13; P < 0.001) and hyperchloraemia/metabolic acidosis (RR 2.87, 1.95 to 4.21; P < 0.001). High-chloride fluids were also associated with greater serum chloride (MD 3.70 (95 per cent c.i. 3.36 to 4.04) mmol/l; P < 0.001), blood transfusion volume (SMD 0.35, 0.07 to 0.63; P = 0.014) and mechanical ventilation time (SMD 0.15, 0.08 to 0.23; P < 0.001). Sensitivity analyses excluding heavily weighted studies resulted in non-statistically significant effects for acute kidney injury and mechanical ventilation time.
CONCLUSION - A weak but significant association between higher chloride content fluids and unfavourable outcomes was found, but mortality was unaffected by chloride content.
© 2014 The Authors. BJS published by John Wiley & Sons Ltd on behalf of BJS Society Ltd.
OBJECTIVE - Isotonic saline is the most commonly used crystalloid in the ICU, but recent evidence suggests that balanced fluids like Lactated Ringer's solution may be preferable. We examined the association between choice of crystalloids and in-hospital mortality during the resuscitation of critically ill adults with sepsis.
DESIGN - A retrospective cohort study of patients admitted with sepsis, not undergoing any surgical procedures, and treated in an ICU by hospital day 2. We used propensity score matching to control for confounding and compared the following outcomes after resuscitation with balanced versus with no-balanced fluids: in-hospital mortality, acute renal failure with and without dialysis, and hospital and ICU lengths of stay. We also estimated the dose-response relationship between receipt of increasing proportions of balanced fluids and in-hospital mortality.
SETTING - Three hundred sixty U.S. hospitals that were members of the Premier Healthcare alliance between November 2005 and December 2010.
PATIENTS - A total of 53,448 patients with sepsis, treated with vasopressors and crystalloids in an ICU by hospital day 2 including 3,396 (6.4%) that received balanced fluids.
INTERVENTIONS - None.
MEASUREMENTS AND MAIN RESULTS - Patients treated with balanced fluids were younger and less likely to have heart or chronic renal failure, but they were more likely to receive mechanical ventilation, invasive monitoring, colloids, steroids, and larger crystalloid volumes (median 7 vs 5 L). Among 6,730 patients in a propensity-matched cohort, receipt of balanced fluids was associated with lower in-hospital mortality (19.6% vs 22.8%; relative risk, 0.86; 95% CI, 0.78, 0.94). Mortality was progressively lower among patients receiving larger proportions of balanced fluids. There were no significant differences in the prevalence of acute renal failure (with and without dialysis) or in-hospital and ICU lengths of stay.
CONCLUSIONS - Among critically ill adults with sepsis, resuscitation with balanced fluids was associated with a lower risk of in-hospital mortality. If confirmed in randomized trials, this finding could have significant public health implications, as crystalloid resuscitation is nearly universal in sepsis.
Endogenous chemical exchange saturation transfer (CEST) effects are always diluted by competing effects, such as direct water proton saturation (spillover) and semi-solid macromolecular magnetization transfer (MT). This leads to unwanted T2 and MT signal contributions that lessen the CEST signal specificity to the underlying biochemical exchange processes. A spillover correction is of special interest for clinical static field strengths and protons resonating near the water peak. This is the case for all endogenous CEST agents, such as amide proton transfer, -OH-CEST of glycosaminoglycans, glucose or myo-inositol, and amine exchange of creatine or glutamate. All CEST effects also appear to be scaled by the T1 relaxation time of water, as they are mediated by the water pool. This forms the motivation for simple metrics that correct the CEST signal. Based on eigenspace theory, we propose a novel magnetization transfer ratio (MTRRex ), employing the inverse Z-spectrum, which eliminates spillover and semi-solid MT effects. This metric can be simply related to Rex , the exchange-dependent relaxation rate in the rotating frame, and ka , the inherent exchange rate. Furthermore, it can be scaled by the duty cycle, allowing for simple translation to clinical protocols. For verification, the amine proton exchange of creatine in solutions with different agar concentrations was studied experimentally at a clinical field strength of 3 T, where spillover effects are large. We demonstrate that spillover can be properly corrected and that quantitative evaluation of pH and creatine concentration is possible. This proves that MTRRex is a quantitative and biophysically specific CEST-MRI metric. Applied to acute stroke induced in rat brain, the corrected CEST signal shows significantly higher contrast between the stroke area and normal tissue, as well as less B1 dependence, than conventional approaches.
Copyright © 2014 John Wiley & Sons, Ltd.
OBJECTIVE - Sustained low efficiency dialysis (SLED) involves the use of standard dialysis machines for prolonged intermittent renal replacement therapy in critically ill patients. In this study we aimed to quantify dialysate amino acid (AA) and albumin losses in 5 patients who underwent successful SLED treatment.
DESIGN - This was a prospective observational study.
SETTING - The study was performed in a general intensive care unit.
SUBJECTS - The study was performed in critically ill patients with acute kidney injury undergoing SLED using low-flux hemodialyzers.
INTERVENTION - We performed total dialysate collection and measured dialysate AA profiles by reverse phase high-pressure liquid chromatography using an automated AA analyser.
MAIN OUTCOME MEASURE - Individual and total amino acid losses.
RESULTS - Albumin was undetectable in dialysate. The median (mean ± SD) total amino acid loss was 15.7 (23.4 ± 19.2) g/treatment, or 122.1 (180.6 ± 148.5) mmol/treatment. Two patients were receiving intravenous nutrition. One patient had severe hepatic failure with encephalopathy, and had high dialysate AA levels with a total loss of 57 g/treatment.
CONCLUSIONS - During SLED with low-flux hemodialyzers, albumin losses are negligible but AA losses to dialysate are comparable to those during continuous renal replacement therapy. Patients' nutritional protein prescriptions should be augmented to account for this.
PURPOSE OF REVIEW - Septic shock is one of the most common and life-threatening conditions afflicting critically ill patients. Intravenous volume resuscitation is considered an initial and very important step in management. The most suitable fluid for volume expansion during septic shock remains unclear. In this review, we focus on the benefits and adverse effects of the most commonly used intravenous fluids in critically ill septic patients.
RECENT FINDINGS - The debate about the benefits of colloids over crystalloids has been ongoing for the last few decades. With recent literature showing apparent harm from the use of hydroxyethyl starches (HESs), and given the growing concerns of adverse renal and acid-base abnormalities associated with 0.9% saline compared with balanced crystalloid solutions, it may be time to change the nature of the 'fluid debate'.
SUMMARY - Crystalloids should still be considered as the first-choice drug for volume resuscitation in patients with septic shock. Colloids such as albumin can be considered in some clinical settings. HES should be avoided. Balanced crystalloids might have an important role to play in the management of septic shock.
PURPOSE OF REVIEW - This review examines recent advances in understanding of how clinical outcomes for hemodialysis patients may be improved by achieving longer or more frequent treatment times, lower ultrafiltration rates (UFRs), improving nutritional status, and individualizing dialysate composition. This review also discusses the controversy related to timing of dialysis initiation.
RECENT FINDINGS - Many observational studies and several randomized controlled trials indicate longer dialysis treatment times, particularly nocturnal dialysis, and/or more frequent dialysis improve morbidity and mortality. Recent evidence also suggests that lower UFR and more consistent achievement of 'dry weight' may help minimize the damage from myocardial stunning and chronic volume overload that occurs in the majority of patients who receive conventional hemodialysis during the day with a standard schedule of 3-5 h, 3 times a week. Other aspects of the dialysis procedure such as appropriate estimated glomerular filtration rate for dialysis initiation and individualizing dialysate composition may also minimize cardiovascular risk. Finally, several studies have highlighted the benefits of oral nutritional supplementation (ONS) during dialysis.
SUMMARY - Greater treatment times per week with slower UFR, consistent attainment of 'dry weight', individualized dialysate prescriptions, and administration of ONS to malnourished patients are likely to reduce hospitalizations and improve survival in this high-risk population of end-stage renal disease patients.
Two different techniques - replica-exchange Wang-Landau (REWL) and statistical temperature molecular dynamics (STMD) - were applied to systematically study the phase transition behavior of self-assembling lipids as a function of temperature using an off-lattice lipid model. Both methods allow the direct calculation of the density of states with improved efficiency compared to the original Wang-Landau method. A 3-segment model of amphiphilic lipids solvated in water has been studied with varied particle interaction energies (ε) and lipid concentrations. The phase behavior of the lipid molecules with respect to bilayer formation has been characterized through the calculation of the heat capacity as a function of temperature, in addition to various order parameters and general visual inspection. The simulations conducted by both methods can go to very low temperatures with the whole system exhibiting well-ordered structures. With optimized parameters, several bilayer phases are observed within the temperature range studied, including gel phase bilayers with frozen water, mixed water (i.e., frozen and liquid water), and liquid water, and a more fluid bilayer with liquid water. The results obtained from both methods, STMD and REWL, are consistently in excellent agreement with each other, thereby validating both the methods and the results.