Albumin extravasation and tissue washout of hyaluronan after plasma volume expansion with crystalloid or hypooncotic colloid solutions

Trends in pre-hospital volume resuscitation of blunt trauma patients: a 15-year analysis of the British (TARN) and German (TraumaRegister DGU®) National Registries

INTRODUCTION

Fluid resuscitation has long been a cornerstone of pre-hospital trauma care, yet its optimal approach remains undetermined. Although a liberal approach to fluid resuscitation has been linked with increased complications, the potential survival benefits of a restrictive approach in blunt trauma patients have not been definitively established. Consequently, equipoise persists regarding the optimal fluid resuscitation strategy in this population.

METHODS

We analysed data from the two largest European trauma registries, the UK Trauma Audit and Research Network (TARN) and the German TraumaRegister DGU® (TR-DGU), between 2004 and 2018. All adult blunt trauma patients with an Injury Severity Score > 15 were included. We examined annual trends in pre-hospital fluid resuscitation, admission coagulation function, and mortality rates.

RESULTS

Over the 15-year study period, data from 68,510 patients in the TARN cohort and 82,551 patients in the TR-DGU cohort were analysed. In the TARN cohort, 3.4% patients received pre-hospital crystalloid fluids, with a median volume of 25 ml (20-36 ml) administered. Conversely, in the TR-DGU cohort, 91.1% patients received pre-hospital crystalloid fluids, with a median volume of 756 ml (750-912 ml) administered. Notably, both cohorts demonstrated a consistent year-on-year decrease in the volume of pre-hospital fluid administered, accompanied by improvements in admission coagulation function and reduced mortality rates.

CONCLUSION

Considerable variability exists in pre-hospital fluid resuscitation strategies for blunt trauma patients. Our data suggest a trend towards reduced pre-hospital fluid administration over time. This trend appears to be associated with improved coagulation function and decreased mortality rates. However, we acknowledge that these outcomes are influenced by multiple factors, including other improvements in pre-hospital care over time. Future research should aim to identify which trauma populations may benefit, be harmed, or remain unaffected by different pre-hospital fluid resuscitation strategies.

Hypovolemia with peripheral edema: What is wrong?

Fluid normally exchanges freely between the plasma and interstitial space and is returned primarily via the lymphatic system. This balance can be disturbed by diseases and medications. In inflammatory disease states, such as sepsis, the return flow of fluid from the interstitial space to the plasma seems to be very slow, which promotes the well-known triad of hypovolemia, hypoalbuminemia, and peripheral edema. Similarly, general anesthesia, for example, even without mechanical ventilation, increases accumulation of infused crystalloid fluid in a slowly equilibrating fraction of the extravascular compartment. Herein, we have combined data from fluid kinetic trials with previously unconnected mechanisms of inflammation, interstitial fluid physiology and lymphatic pathology to synthesize a novel explanation for common and clinically relevant examples of circulatory dysregulation. Experimental studies suggest that two key mechanisms contribute to the combination of hypovolemia, hypoalbuminemia and edema; (1) acute lowering of the interstitial pressure by inflammatory mediators such as TNFα, IL-1β, and IL-6 and, (2) nitric oxide-induced inhibition of intrinsic lymphatic pumping.

Hypoalbuminemia within One Hour After Surgery as a Predictor of Post-Operative Urosepsis in Patients Undergoing Flexible Ureteroscopy Lithotripsy: A Retrospective Study

Abstract Background: To investigate retrospectively whether changes in serum albumin levels within one hour of flexible ureteroscopy (fURS) lithotripsy can be used as a predictor of post-operative urosepsis. Patients and Methods: Eligible patients with unilateral upper urinary calculi who underwent fRUS lithotripsy performed by a single surgeon at our center were included in the analysis. The patients were divided into sepsis and non-sepsis groups. The change ratio of albumin and white blood cell (WBC) count was calculated by post-operative/pre-operative index*100%. Univariable and multivariable logistic regression analyses were used to assess whether there was a correlation between risk factors and post-operative urosepsis. The receiver operating characteristic (ROC) curve was used to analyze factors that showed significant differences in multivariable logistic regression analysis. Results: A total of 314 patients were included in the analysis, 20 of whom had post-operative urosepsis and five developed septic shock; no deaths occurred. Multivariable logistic regression analysis showed that urine culture results, WBC counts within one hour after surgery, post-operative albumin levels, and the degree of albumin changes after surgery were independent predictors of post-operative urosepsis. Receiver operating characteristic curve analysis showed that noteworthy hypoalbuminemia after surgery and positive pre-operative urine culture could help screen high-risk patients for post-operative urosepsis effectively. Conclusions: Hypoalbuminemia shortly after operation can be utilized as a predictor for early diagnosis of post-operative urosepsis in patients undergoing fURS lithotripsy.

Effects of rapid fluid infusion on hemoglobin concentration: a systematic review and meta-analysis

Background

Rapid fluid administration may decrease hemoglobin concentration (Hb) by a diluting effect, which could limit the increase in oxygen delivery (DO₂) expected with a positive response to fluid challenge in critically ill patients. Our aim was to quantify the decrease in Hb after rapid fluid administration.

Methods

Our protocol was registered in PROSPERO (CRD42020165146). We searched PubMed, the Cochrane Database, and Embase from inception until February 15, 2022. We selected studies that reported Hb before and after rapid fluid administration (bolus fluid given over less than 120 min) with crystalloids and/or colloids in adults. Exclusion criteria were studies that included bleeding patients, or used transfusions or extracorporeal circulation procedures. Studies were divided according to whether they involved non-acutely ill or acutely ill (surgical/trauma, sepsis, circulatory shock or severe hypovolemia, and mixed conditions) subjects. The mean Hb difference and, where reported, the DO₂ difference before and after fluid administration were extracted. Meta-analyses were conducted to assess differences in Hb before and after rapid fluid administration in all subjects and across subgroups. Random-effect models, meta-regressions and subgroup analyses were performed for meta-analyses. Risk of bias was assessed using the Cochrane Risk of Bias Assessment Tool. Inconsistency among trial results was assessed using the I² statistic.

Results

Sixty-five studies met our inclusion criteria (40 in non-acutely ill and 25 in acutely ill subjects), with a total of 2794 participants. Risk of bias was assessed as “low” for randomized controlled trials (RCTs) and ‘low to moderate’ for non-RCTs. Across 63 studies suitable for meta-analysis, the Hb decreased significantly by a mean of 1.33 g/dL [95% CI − 1.45 to − 1.12; p < 0.001; I² = 96.88] after fluid administration: in non-acutely ill subjects, the mean decrease was 1.56 g/dL [95% CI − 1.69 to − 1.42; p < 0.001; I² = 96.71] and in acutely ill patients 0.84 g/dL [95% CI − 1.03 to − 0.64; p = 0.033; I² = 92.91]. The decrease in Hb was less marked in patients with sepsis than in other acutely ill patients. The DO₂ decreased significantly in fluid non-responders with a significant decrease in Hb.

Conclusions

Hb decreased consistently after rapid fluid administration with moderate certainty of evidence. This effect may limit the positive effects of fluid challenges on DO₂ and thus on tissue oxygenation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13054-022-04191-x.

Biomarkers of Glycocalyx Injury and Endothelial Activation are Associated with Clinical Outcomes in Patients with Sepsis: A Systematic Review and Meta-Analysis

OBJECTIVE

Sepsis is one of the main causes of morbidity and mortality worldwide. Microcirculatory impairment, especially damage to the endothelium and glycocalyx, is often not assessed. The objective of this systematic review and meta-analysis was to summarize the available evidence of the risk of unsatisfactory outcomes in patients with sepsis and elevated glycocalyx injury and endothelial activation biomarkers.

DESIGN

A systematic search was carried out on PubMed/MEDLINE, Embase, Cochrane and Google Scholar up to December 31, 2021, including studies in adults and children with sepsis which measured glycocalyx injury and endothelial activation biomarkers within 48 hours of hospital admission. The primary outcome was the risk of mortality from all causes and the secondary outcomes were the risk of developing respiratory failure (RF) and multiple organ dysfunction syndrome (MODS) in patients with elevations of these biomarkers.

MEASUREMENTS AND MAIN RESULTS

A total of 17 studies (3,529 patients) were included: 11 evaluated syndecan-1 (n=2,397) and 6 endocan (n=1,132). Syndecan-1 was higher in the group of patients who died than in those who survived [255 ng/mL (IQR: 139-305) vs. 83 ng/mL (IQR:40-111); p=0.014]. Patients with elevated syndecan-1 had a greater risk of death (OR 2.32; 95% CI 1.89, 3.10: p<0.001), MODS (OR 3.3; 95% CI 1.51, 7.25: p=0.003;), or RF (OR 7.53; 95% CI 1.86-30.45: p=0.005). Endocan was higher in patients who died [3.1 ng/mL (IQR 2.3, 3.7) vs. 1.62 ng/mL (IQR 1.2, 5.7); OR 9.53; 95% CI 3.34, 27.3; p<0.001], who had MODS (OR 8.33; 95% CI 2.07, 33.58; p=0.003) and who had RF (OR 9.66; 95% CI 2.26, 43.95; p=0.002).

CONCLUSION

Patients with sepsis and abnormal glycocalyx injury and endothelial activation biomarkers have a greater risk of developing respiratory failure, multiple organ failure, and death. Microcirculatory impairment should be routinely evaluated in patients with sepsis, using biomarkers to stratify risk groups.

No association between intravenous fluid volume and endothelial glycocalyx shedding in patients undergoing resuscitation for sepsis in the emergency department

Endothelial glycocalyx (EG) shedding is associated with septic shock and described following intravenous (IV) fluid administration. To investigate the possible impact of IV fluids on the pathobiology of septic shock we investigated associations between biomarkers of EG shedding and endothelial cell activation, and relationships with IV fluid volume. Serum samples were obtained on admission (T0) and at 24 h (T24) in patients undergoing haemodynamic resuscitation for suspected septic shock in the emergency department. Biomarkers of EG shedding—Syndecan-1 (Syn-1), Syndecan-4 (Syn-4), Hyaluronan, endothelial activation—Endothelin-1 (ET-1), Angiopoeitin-2 (Ang-2), Vascular Endothelial Growth Factor Receptor-1(VEGF-1) and leucocyte activation/inflammation—Resistin, Neutrophil Gelatinase Associated Lipocalin (NGAL) and a marker of cardiac stretch—Pro-Atrial Natriuretic Peptide (Pro-ANP) were compared to the total IV fluid volume administered using Tobit regression. Data on 86 patients (52 male) with a mean age of 60 (SD 18) years were included. The mean fluid volume administered to T24 was 4038 ml (SD 2507 ml). No significant association between fluid volume and Pro-ANP or any of the biomarkers were observed. Syn-1 and Syn-4 were significantly correlated with each other (Spearman Rho 0.43, p < 0.001) but not with Hyaluronan. Syn-1 and Syn-4 both correlated with VEGFR-1 (Rho 0.56 and 0.57 respectively, p < 0.001) whereas Hyaluronan correlated with ET-1 (Rho 0.43, p < 0.001) and Ang-2 (Rho 0.43, p < 0.001). There was no correlation between Pro-ANP and any of the EG biomarkers. Distinct patterns of association between biomarkers of EG shedding and endothelial cell activation were observed among patients undergoing resuscitation for sepsis. No relationship between IV fluid volume and Pro-ANP or any of the other biomarkers was observed.

Serum Albumin Kinetics in Major Ovarian, Gastrointestinal, and Cervico Facial Cancer Surgery

Hypoalbuminemia in major cancer surgery can lead to postoperative short and long-term complications. Our study was designed to detect albumin variations in three major cancer surgeries: ovarian debulking (DBK), major abdominal gastrointestinal surgery (ABD), and major cervico-facial, or ear, nose and throat cancer surgery (ENT). Single-center prospective study inclusion criteria were non-emergency procedures scheduled to last at least five hours. We performed hourly perioperative monitoring of the patients’ albuminemia and hemoglobinemia. Electronic charts were followed for at least five years for survival analysis. Sixty-three patients were analyzed: 30 in the DBK group, 13 in the ABD group, and 20 in the ENT group. There was a significant difference in albumin decrease between the ENT group and the two others (−19% at six hours in the ENT group versus -49% in the debulking group and −31% in the ABD group (p < 0.05). There was no significant difference between the DBK and ABD groups. The decrease in hemoglobin was not significantly different between the groups, and no significant difference was observed in long-term survival. DBK and ABD surgery yielded significant hypoalbuminemia. Therefore, the extent of decrease in serum albumin is probably not the only etiology of the specific postoperative complications of these major surgeries. No significant difference was noticed in five-year mortality, and no correlation was found in relation to the degree of intraoperative albumin kinetics.

Measuring the Concentration of Serum Syndecan-1 to Assess Vascular Endothelial Glycocalyx Injury During Hemodialysis

Glycocalyx is present on the surface of healthy endothelium, and the concentration of serum syndecan-1 can serve as an injury marker. This study aimed to assess endothelial injury using serum syndecan-1 as a marker of endothelial glycocalyx injury in patients who underwent hemodialysis. In this single-center, retrospective, observational study, 145 patients who underwent hemodialysis at the Gifu University Hospital between March 2017 and December 2019 were enrolled. The median dialysis period and time were 63 months and 3.7 h, respectively. The serum syndecan-1 concentration significantly increased from 124.6 ± 107.8 ng/ml before hemodialysis to 229.0 ± 138.1 ng/ml after hemodialysis (P &lt; 0.001). Treatment with anticoagulant nafamostat mesylate inhibited hemodialysis-induced increase in the levels of serum syndecan-1 in comparison to unfractionated heparin. Dialysis time and the change in the syndecan-1 concentration were positively correlated. Conversely, the amount of body fluid removed and the changes in the syndecan-1 concentration were not significantly correlated. The reduction in the amount of body fluid removed and dialysis time inhibited the change in the syndecan-1 levels before and after hemodialysis. In conclusion, quantitative assessment of the endothelial glycocalyx injury during hemodialysis can be performed by measuring the serum syndecan-1 concentration, which may aid in the selection of appropriate anticoagulants, reduction of hemodialysis time, and the amount of body fluid removed.

Serum syndecan-1 concentration in hospitalized patients with heart failure may predict readmission-free survival

Syndecan-1 is found in the endothelial glycocalyx and is released into the bloodstream during stressed conditions, including severe diseases such as acute kidney injury, chronic kidney disease, and cardiovascular disease. This study investigated the prognostic value of serum syndecan-1 concentration in patients with heart failure upon admission. Serum syndecan-1 concentration was analyzed in 152 patients who were hospitalized for worsening heart failure from September 2017 to June 2018. The primary outcome of the study was readmission-free survival, defined as the time from the first admission to readmission for worsened heart failure or death from any cause, which was assessed at 30 months after discharge from the hospital. The secondary outcome of the study was survival time. Blood samples and echocardiogram data were analyzed. Univariate and multivariable time-dependent Cox regression analyses adjusted for age, creatinine levels, and use of antibiotics were conducted. The serum syndecan-1 concentration was significantly associated with readmission-free survival. Subsequently, the syndecan-1 concentration may have gradually decreased with treatment. The administration of human atrial natriuretic peptide and antibiotics may have modified the relationship between readmission-free survival and serum syndecan-1 concentration (p = 0.01 and 0.008, respectively). Serum syndecan-1 concentrations, which may indicate injury to the endothelial glycocalyx, predict readmission-free survival in patients with heart failure.

Effect of cryoprecipitate transfusion therapy in patients with postpartum hemorrhage: a retrospective cohort study

To evaluate the effect of cryoprecipitate (CRYO) transfusion in women referred for postpartum hemorrhage (PPH). This retrospective cohort study included patients with primary PPH referred to Gifu University Hospital between April 2013 and March 2020. We analyzed the effect of CRYO transfusion on fluid balance 24 h after the initial examination using a multivariable linear regression model adjusted for several confounding variables. To evaluate whether outcomes were modified by active bleeding, an interaction term of CRYO*active bleeding was incorporated into the multivariable model. We identified 157 women: 38 in the CRYO group (cases) and 119 in the control group. Fluid balance in the aforementioned period tended to decrease in the CRYO group compared with that in the control group (coefficient - 398.91; 95% CI - 1298.08 to + 500.26; p = 0.382). Active bleeding on contrast-enhanced computed tomography affected the relationship between CRYO transfusion and fluid balance (p = 0.016). Other outcomes, except for the overall transfusion requirement, were not significantly different; however, the interaction effect of active bleeding was significant (p = 0.016). CRYO transfusion may decrease the fluid balance in the first 24 h in PPH patients, especially in those without active bleeding.

Effect of Different-Volume Fluid Resuscitation on Organ Functions in Severe Acute Pancreatitis and Therapeutic Effect of Poria cocos

OBJECTIVE

To explore the effect of different-volume fluid resuscitation (FR) on organ functions in severe acute pancreatitis (SAP) and to elucidate the therapeutic effect and mechanism of Poria cocos on organ injuries caused by high-volume FR.

METHODS

1. Clinical study: retrospective analysis of thirty-one patients about the effect of titrated fluid resuscitation protocol (TFR) on the occurrence of acute kidney injury (AKI) secondary to SAP. 2. Experimental study: rats (N = 30) were randomly divided into five groups: sham, model, low-volume FR (1.5 ml/kg/h), high-volume FR (10 ml/kg/h), and Poria cocos combined with high-volume FR (10 ml/kg/h + intraintestinal administration Poria cocos 5 g/kg); serum or plasma indicators and histopathologic scores were compared to explore the effect and mechanism of different fluid volumes and Poria cocos on organ function in SAP.

RESULTS

The occurrence of AKI, fluid volume, and fluid velocity in TFR group was lower than that in the control group. Logistic regression analysis showed that increased Marshall scores and fluid velocity were risk factors for predicting occurrence of AKI in SAP. Low-volume FR decreased the levels of blood urea nitrogen (BUN), serum creatinine (Cr), matrix metalloproteinase (MMP), and pathologic scores of the pancreas and kidney. High-volume FR increased ascites, MMPs, and kidney pathologic scores. Poria cocos decreased the levels of BUN, Cr, MMPs, and pathologic scores of the pancreas and kidney and increased the arterial oxygen saturation.

CONCLUSION

TFR-associated lower fluid volume and velocity reduced the occurrence of AKI secondary to SAP. High volume might aggravate AKI via increased MMP release leading to endothelial glycocalyx damage and vascular endothelial dysfunction. Poria cocos reduced MMP release, relieved glycocalyx damage, and alleviated the pancreas and kidney injury aggravated by high fluid volume in SAP. Therefore, endothelial glycocalyx protection might be a new strategy in the treatment of SAP.

Evaluation of the effects of hydroxyethyl starch (130/0.4) administration as a constant rate infusion on plasma colloid osmotic pressure in hypoabluminemic dogs

OBJECTIVE

To evaluate the effects of 2 constant rate infusions of hydroxyethyl starch (HES) 130/0.4 on plasma colloid osmotic pressure (COP) in hypoalbuminemic dogs.

DESIGN

Prospective, randomized clinical trial.

ANIMALS

A total of 24 client-owned dogs.

INTERVENTIONS

Hypoalbuminemic euvolemic dogs (albumin < 20 g/L [<2 g/dL]) with normal perfusion parameters requiring IV fluid therapy were enrolled. In addition to crystalloid, HES 130/0.4 was administered as a constant rate infusion over 24 hours at 1 mL/kg/h (group 1, n = 15) or at 2 mL/kg/h (group 2, n = 9), in order to support plasma COP. Before infusion, a blood sample was collected to perform CBC, serum electrophoresis, and serologic tests for some infective diseases. Plasma COP, albumin concentration, PCV, and total plasma protein concentration were evaluated serially at baseline (T0) and then at 6, 12, and 24 hours after the start of infusion, and a multilevel model was performed for these parameters to detect statistically significant differences between the 2 groups.

MEASUREMENT AND MAIN RESULTS

Twenty-four dogs were included. No statistically significant differences in COP were found between the 2 groups; however, a high level of variability has been identified within the single individual. Among the other laboratory analyses, PCV was significantly decreased in group 1 at T12 and T24 compared with T0 (P < 0.001) and total plasma protein concentration was significantly increased in group 2 at T12 and T24 compared with T0 (P < 0.008).

CONCLUSION

No significant effect on plasma COP was found following infusion with HES 130/0.4 at doses of 1 mL/kg/h and 2 mL/kg/h for 24 hours to hypoalbuminemic dogs. The administered concomitant dose of crystalloids, underlying disease, and small sample size were all potential confounding factors.

Fluid Overload and Acute Kidney Injury

Commonest intervention in hospitalized patient is fluid therapy, and practically every critically ill patient receives fluid resuscitation. Commonest indication for fluid administration is to achieve hemodynamic stability and prevent or manage acute kidney injury (AKI). However, fluid administration is a two-edged sword, i.e., inadequate fluids give rise to hypoperfusion and organ injury and overzealous fluid therapy can give rise to fluid overload and related consequences. Though fluids are commonly given to prevent development of AKI, hypervolemia itself has the potential to cause AKI.

Endothelial glycocalyx in acute care surgery - what anaesthesiologists need to know for clinical practice

The endothelial glycocalyx (EG) is the thin sugar-based lining on the apical surface of endothelial cells. It has been linked to the physiological functioning of the microcirculation and has been found to be damaged in critical illness and after acute care surgery. This review aims to describe the role of EG in severely injured patients undergoing surgery, discuss specific situations (e.G. major trauma, hemorrhagic shock, trauma induced coagulopathy) as well as specific interventions commonly applied in these patients (e.g. fluid therapy, transfusion) and specific drugs related to perioperative medicine with regard to their impact on EG.EG in acute care surgery is exposed to damage due to tissue trauma, inflammation, oxidative stress and inadequate fluid therapy. Even though some interventions (transfusion of plasma, human serum albumin, hydrocortisone, sevoflurane) are described as potentially EG protective there is still no specific treatment for EG protection and recovery in clinical medicine.The most important principle to be adopted in routine clinical practice at present is to acknowledge the fragile structure of the EG and avoid further damage which is potentially related to worsened clinical outcome.

Hydroxyethyl starches in equine medicine

OBJECTIVE

To review and discuss the use of hydroxyethyl starches (HES) in equine veterinary medicine, and to provide recommendations for its use.

DATA SOURCES

Veterinary and human peer-reviewed medical literature including scientific reviews, meta-analyses, and original research articles.

HUMAN DATA SYNTHESIS

Increasing evidences on adverse effects after HES use and decreasing support for beneficial effects with regards to volume expansion and colloid osmotic pressure (COP) support in critically ill subjects have led to a recent guideline to limit the use of HES in critically ill people.

EQUINE VETERINARY DATA SYNTHESIS

The rationale for HES use in horses is mainly extrapolated from human medicine, and very limited studies in horses are available. There is limited evidence suggesting a superiority of volume expansion effects of HES over crystalloids. The potential for HES to increase and maintain COP is well supported, but there is no evidence that maintaining or increasing plasma COP influences outcome, tissue edema formation, or rates of complications that potentially relate to edema formation. HES induce dose-dependent changes in coagulopathic parameters, but there is no evidence that HES causes clinical coagulopathies. Insufficient data are available on other adverse effects such as acute kidney injury, or mortality in horses. The use of HES should be restricted in septic patients, but may still have some use in cases of hemorrhagic shock resuscitation, hypoalbuminemia, or perioperative fluid replacement.

CONCLUSION

The evidence supporting the use of HES in horses is weak due to lack of species-specific investigations. Acknowledging species differences, the use of HES should be judicious, yet with some recognition of its benefits in particular cases. More research is necessary to improve knowledge on use of HES in horses and to establish better future recommendations.

Endothelial glycocalyx: Role in body fluid homeostasis and fluid management

Endothelial glycocalyx layer (EGL) coating the luminal surface of vascular endothelium plays an essential role in maintaining the normal fluid homeostasis of the body. This highly fragile layer can be damaged by a number of pathophysiological conditions and interventions. Disease state management should be directed to maintain EGL integrity to improve patient's outcome. When intravenous (IV) fluids are used, appropriate type, rate and amount of fluid should be determined by the pathophysiology of the condition and measures to maintain the integrity of the EGL. This review depicts the structure and function of the EGL, its alteration in common pathological states and the rationale of IV fluid management to preserve EGL in such conditions.

Role of albumin, starches and gelatins versus crystalloids in volume resuscitation of critically ill patients

PURPOSE OF REVIEW

The review focuses on fluid resuscitation of critically ill patients with either colloid or crystalloid solutions.

RECENT FINDINGS

In healthy patients, the volume expanding effect of colloids is greater than that of crystalloids. However, in critically ill patients, a similar amount of crystalloids and colloids is required for fluid resuscitation, suggesting a lower efficiency of colloids when capillary permeability is increased, and endothelial glycocalyx disrupted. Recent studies on synthetic colloids in surgical patients confirmed the increased risk of renal failure reported in large clinical trials performed in critically ill patients. Experimental studies suggest that albumin maintains plasma volume expansion efficiency even when the capillary permeability is impaired, and that extravasation of albumin to the interstitium is lower than that of hydroxyethyl starch.

SUMMARY

Fluid administration should be tailored to patient characteristics. Synthetic colloids should be avoided when possible, especially in patients at risk for kidney injury. In critically ill patients with suspected increased permeability, colloids may not be superior to crystalloids in expanding plasma volume. Albumin appears to be less harmful than synthetic colloids, although its beneficial effects need to be further investigated. The endothelial glycocalyx layer is the key structure finely regulating intravascular fluid distribution.

Personalised fluid resuscitation in the ICU: still a fluid concept?

The administration of intravenous fluid to critically ill patients is one of the most common, but also one of the most fiercely debated, interventions in intensive care medicine. Even though many thousands of patients have been enrolled in large trials of alternative fluid strategies, consensus remains elusive and practice is widely variable. Critically ill patients are significantly heterogeneous, making a one size fits all approach unlikely to be successful.New data from basic, animal, and clinical research suggest that fluid resuscitation could be associated with significant harm. There are several important limitations and concerns regarding fluid bolus therapy as it is currently being used in clinical practice. These include, but are not limited to: the lack of an agreed definition; limited and short-lived physiological effects; no evidence of an effect on relevant patient outcomes; and the potential to contribute to fluid overload, specifically when fluid responsiveness is not assessed and when targets and safety limits are not used.Fluid administration in critically ill patients requires clinicians to integrate abnormal physiological parameters into a clinical decision-making model that also incorporates the likely diagnosis and the likely risk or benefit in the specific patient's context. Personalised fluid resuscitation requires careful attention to the mnemonic CIT TAIT: context, indication, targets, timing, amount of fluid, infusion strategy, and type of fluid.The research agenda should focus on experimental and clinical studies to: improve our understanding of the physiological effects of fluid infusion, e.g. on the glycocalyx; evaluate new types of fluids; evaluate novel fluid minimisation protocols; study the effects of a no-fluid strategy for selected patients and scenarios; and compare fluid therapy with other interventions. The adaptive platform trial design may provide us with the tools to evaluate these types of interventions in the intrinsically heterogeneous intensive care unit population, accounting for the explicit assumption that treatment effects may be heterogeneous.

Three-dimensional ultrastructure of capillary endothelial glycocalyx under normal and experimental endotoxemic conditions

BACKGROUND

Sugar-protein glycocalyx coats healthy endothelium, but its ultrastructure is not well described. Our aim was to determine the three-dimensional ultrastructure of capillary endothelial glycocalyx in the heart, kidney, and liver, where capillaries are, respectively, continuous, fenestrated, and sinusoidal.

METHODS

Tissue samples were processed with lanthanum-containing alkaline fixative, which preserves the structure of glycocalyx.

RESULTS

Scanning and transmission electron microscopy revealed that the endothelial glycocalyx layer in continuous and fenestrated capillaries was substantially thicker than in sinusoids. In the heart, the endothelial glycocalyx presented as moss- or broccoli-like and covered the entire luminal endothelial cell surface. In the kidney, the glycocalyx appeared to nearly occlude the endothelial pores of the fenestrated capillaries and was also present on the surface of the renal podocytes. In sinusoids of the liver, glycocalyx covered not only the luminal side but also the opposite side, facing the space of Disse. In a mouse lipopolysaccharide-induced experimental endotoxemia model, the capillary endothelial glycocalyx was severely disrupted; that is, it appeared to be peeling off the cells and clumping. Serum concentrations of syndecan-1, a marker of glycocalyx damage, were significantly increased 24 h after administration of lipopolysaccharide.

CONCLUSIONS

In the present study, we visualized the three-dimensional ultrastructure of endothelial glycocalyx in healthy continuous, fenestrated, and sinusoidal capillaries, and we also showed their disruption under experimental endotoxemic conditions. The latter may provide a morphological basis for the microvascular endothelial dysfunction associated with septic injury to organs.

Targeting the endothelial glycocalyx in acute critical illness as a challenge for clinical and laboratory medicine

The purpose of this manuscript is to review the role of endothelial glycocalyx (EG) in the field of critical and perioperative medicine and to discuss possible future directions for investigations in this area. Under physiological conditions, EG has several well-defined functions aimed to prevent the disruption of vessel wall integrity. Under pathological conditions, the EG represent one of the earliest sites of injury during inflammation. EG structure and function distortion contribute to organ dysfunction related to sepsis, trauma, or global ischemia of any origin. Discovering new therapeutic approaches (either pharmacological or non-pharmacological) aimed to protect the EG against injury represents a promising direction in clinical medicine. Further, the currently-used common interventions in the acutely ill - fluids, blood products, nutritional support, organ-supporting techniques (e.g. continuous renal replacement therapy, extracorporeal circulation), temperature modulation and many others - should be re-evaluated during acute illness in terms of their EG "friendliness". To assess new therapies that protect the EG, or to evaluate the effect of currently-used interventions on EG integrity, a relevant marker or method to determine EG damage is needed. Such marker or method should be available to clinicians within hours, preferably in the form of a point-of-care test at the bedside. Collaborative research between clinical disciplines and laboratory medicine is warranted, and targeting the EG represents major challenges for both.

Intravenous Fluid Challenge Decreases Intracellular Volume: A Bioimpedance Spectroscopy-Based Crossover Study in Healthy Volunteers

The effects of intravenous fluid therapy on fluid compartments and hemodynamics of the human body remain enigmatic. We therefore tested the efficacy of bioimpedance spectroscopy in a crossover study, where 15 males received 0.5 ml/kg/min ELO-MEL-isoton (osmolarity = 302 mosmol/l) during 60 minutes, or nothing at all. In group “Fluid”, fluid load increased from −0.2 ± 1.0 l extracellular volume at baseline to its maximum of 1.0 ± 0.9 l in minute 70, and remained continuously elevated throughout minute 300. In group “Zero”, fluid load decreased from 0.5 ± 1.1 l at baseline to its minimum of −1.1 ± 1.1 l in minute 300. In group “Fluid”, intracellular volume decreased from 26.8 ± 3.9 l at baseline to its minimum of 26.0 ± 3.9 l in minute 70, and remained continuously decreased throughout minute 300. In group “Zero”, intracellular volume increased from 26.5 ± 3.8 l at baseline to its maximum of 27.1 ± 3.9 l in minute 120, and decreased thereafter. In group “Fluid” compared to “Zero”, systolic blood pressure was significantly higher, from minute 50–90. In conclusion, intravenous fluid therapy caused a clinically meaningful, sustained increase in fluid load, and a decrease in intracellular volume. These data raise interest in studying fluid administration by the gastrointestinal route, perhaps even when managing critical illness.

Intravenous Fluids and Acute Kidney Injury

Over 50% of the human body is comprised of fluids that are distributed in defined compartments. Although compartmentalized, these fluids are dynamically connected. Fluids, electrolytes, and acid-base balance in each compartment are tightly regulated, mostly in an energy-dependent manner to achieve their designed functions. For over a century, our understanding of the microvascular fluid homeostasis has evolved from hypothesized Ernest Starling principle to evidence-based and the revised Starling principle, incorporating the functional endothelial surface layer. The kidney is a highly vascular and encapsulated organ that is exquisitely sensitive to inadequate (insufficient or excess) blood flow. The kidney is particularly sensitive to venous congestion, and studies show that reduced venous return triggers a greater degree of kidney damage than that from lacking arterial flow. Thus, fluid overload can induce severe and sustained kidney injury. In the setting of established acute kidney injury, fluid management can be challenging. Impaired capacity of urine output and urine concentration and dilution should be taken into consideration when designing fluid therapy. Video Journal Club 'Cappuccino with Claudio Ronco' at http://www.karger.com/?doi=452702.

Monitoring perioperative serum albumin can identify anastomotic leakage in colorectal cancer patients with curative intent

BACKGROUND

Preoperative hypoalbuminemia is a well-known risk factor for anastomotic leakage after colorectal surgery, but the association between perioperative albumin level and anastomotic leakage has not been fully investigated in curative colorectal cancer (CRC) patients.

METHODS

In total, 200 CRC patients (Stage I-III) undergoing curative laparoscopic surgery between January 2004 and December 2013 were enrolled in this study. We collected data on surgical factors, perioperative levels of serum albumin and inflammatory markers, and perioperative factors affecting hypoalbuminemia from 196 CRC patients to assess the relation to anastomotic leakage.

RESULTS

Anastomotic leakage occurred in 11 cases (5.6%) and the frequency was higher in rectal cancer patients (p = 0.0044). There was no significant difference of preoperative serum albumin level between the anastomotic leakage group (AL) and the nonanastomotic leakage group (NAL). Postoperative serum albumin levels in AL were significantly lower than in NAL [postoperative day (POD) 0, p = 0.0004; POD1, p = 0.0001; POD3, p = 0.0004; and POD7, p = 0.0021]. On multivariate analysis, lower average level of serum albumin on POD1 and POD3 {odds ratio (OR) [95% confidence interval (CI)] = 7.53 (1.60-55.80), p = 0.0095}, higher average level of serum white blood cells on POD1 and POD3 [OR (95% CI) = 7.24 (1.40-59.25), p = 0.0165], and surgery for rectal cancer [OR (95% CI) = 15.18 (3.26-93.99), p = 0.0004] were independent risk factors for anastomotic leakage.

CONCLUSION

Lower early postoperative serum albumin levels are a potentially valuable indicator of anastomotic leakage in CRC patients undergoing curative surgery.

Plasma syndecan-1 and heparan sulfate correlate with microvascular glycocalyx degradation in hemorrhaged rats after different resuscitation fluids

The endothelial glycocalyx plays an essential role in many physiological functions and is damaged after hemorrhage. Fluid resuscitation may further change the glycocalyx after an initial hemorrhage-induced degradation. Plasma levels of syndecan-1 and heparan sulfate have been used as indirect markers for glycocalyx degradation, but the extent to which these measures are representative of the events in the microcirculation is unknown. Using hemorrhage and a wide range of resuscitation fluids, we studied quantitatively the relationship between plasma biomarkers and changes in microvascular parameters, including glycocalyx thickness. Rats were bled 40% of total blood volume and resuscitated with seven different fluids (fresh whole blood, blood products, and crystalloids). Intravital microscopy was used to estimate glycocalyx thickness in >270 postcapillary venules from 58 cremaster preparations in 9 animal groups; other microvascular parameters were measured using noninvasive techniques. Systemic physiological parameters and blood chemistry were simultaneously collected. Changes in glycocalyx thickness were negatively correlated with changes in plasma levels of syndecan-1 ( r = −0.937) and heparan sulfate ( r = −0.864). Changes in microvascular permeability were positively correlated with changes in both plasma biomarkers ( r = 0.8, P < 0.05). Syndecan-1 and heparan sulfate were also positively correlated ( r = 0.7, P < 0.05). Except for diameter and permeability, changes in local microcirculatory parameters (red blood cell velocity, blood flow, and wall shear rate) did not correlate with plasma biomarkers or glycocalyx thickness changes. This work provides a quantitative framework supporting plasma syndecan-1 and heparan sulfate as valuable clinical biomarkers of glycocalyx shedding that may be useful in guiding resuscitation strategies following hemorrhage.

A rational approach to fluid therapy in sepsis

Aggressive fluid resuscitation to achieve a central venous pressure (CVP) greater than 8 mm Hg has been promoted as the standard of care, in the management of patients with severe sepsis and septic shock. However recent clinical trials have demonstrated that this approach does not improve the outcome of patients with severe sepsis and septic shock. Pathophysiologically, sepsis is characterized by vasoplegia with loss of arterial tone, venodilation with sequestration of blood in the unstressed blood compartment and changes in ventricular function with reduced compliance and reduced preload responsiveness. These data suggest that sepsis is primarily not a volume-depleted state and recent evidence demonstrates that most septic patients are poorly responsive to fluids. Furthermore, almost all of the administered fluid is sequestered in the tissues, resulting in severe oedema in vital organs and, thereby, increasing the risk of organ dysfunction. These data suggest that a physiologic, haemodynamically guided conservative approach to fluid therapy in patients with sepsis would be prudent and would likely reduce the morbidity and improve the outcome of this disease.

Intravenous solutions in the care of patients with volume depletion and electrolyte abnormalities

Infusion fluids are often given to restore blood pressure (volume resuscitation), but may also be administered to replace ongoing losses, match insensible losses, correct electrolyte or acid-base disorders, or provide glucose. The development of new infusion fluids has provided clinicians with a wide range of products. Although the choice for a certain infusion fluid is often driven more by habit than by careful consideration, we believe it is useful to approach infusion fluids as drugs and consider their pharmacokinetic and pharmacodynamic characteristics. This approach not only explains why infusion fluids may cause electrolyte and acid-base disturbances, but also why they may compromise kidney function or coagulation. In this teaching case, we present a 19-year-old patient in whom severe hypernatremia developed as a result of normal saline solution infusion and explore the pharmacokinetic and pharmacodynamic effects of frequently used infusion fluids. We review clinical evidence to guide the selection of the optimal infusion fluid.

Physiological changes after fluid bolus therapy in sepsis: a systematic review of contemporary data

Fluid bolus therapy (FBT) is a standard of care in the management of the septic, hypotensive, tachycardic and/or oliguric patient. However, contemporary evidence for FBT improving patient-centred outcomes is scant. Moreover, its physiological effects in contemporary ICU environments and populations are poorly understood. Using three electronic databases, we identified all studies describing FBT between January 2010 and December 2013. We found 33 studies describing 41 boluses. No randomised controlled trials compared FBT with alternative interventions, such as vasopressors. The median fluid bolus was 500 ml (range 100 to 1,000 ml) administered over 30 minutes (range 10 to 60 minutes) and the most commonly administered fluid was 0.9% sodium chloride solution. In 19 studies, a predetermined physiological trigger initiated FBT. Although 17 studies describe the temporal course of physiological changes after FBT in 31 patient groups, only three studies describe the physiological changes at 60 minutes, and only one study beyond this point. No studies related the physiological changes after FBT with clinically relevant outcomes. There is a clear need for at least obtaining randomised controlled evidence for the physiological effects of FBT in patients with severe sepsis and septic shock beyond the period immediately after its administration.

‘Just as water retains no shape, so in warfare there are no constant conditions’

Sun Tzu (‘The Art of War’)

Early management of severe sepsis: concepts and controversies

Sepsis is among the most common reasons for admission to ICUs throughout the world, and it is believed to be the third most common cause of death in the United States. The pathogenetic mechanism and physiologic changes associated with sepsis are exceedingly complex, but our understanding is evolving rapidly. The major pathophysiologic changes in patients with septic shock include vasoplegic shock (distributive shock), myocardial depression, altered microvascular flow, and a diffuse endothelial injury. These pathophysiologic changes play a central role in the management of sepsis. The early management of patients with severe sepsis and septic shock centers on the administration of antibiotics, IV fluids, and vasoactive agents, followed by source control. However, the specific approach to the resuscitation of patients with septic shock remains highly controversial. This review provides a practical and physiologic-based approach to the early management of sepsis and explores the controversies surrounding the management of this complex condition.

Iatrogenic salt water drowning and the hazards of a high central venous pressure

Current teaching and guidelines suggest that aggressive fluid resuscitation is the best initial approach to the patient with hemodynamic instability. The source of this wisdom is difficult to discern, however, Early Goal Directed therapy (EGDT) as championed by Rivers et al. and the Surviving Sepsis Campaign Guidelines appears to have established this as the irrefutable truth. However, over the last decade it has become clear that aggressive fluid resuscitation leading to fluid overload is associated with increased morbidity and mortality across a diverse group of patients, including patients with severe sepsis as well as elective surgical and trauma patients and those with pancreatitis. Excessive fluid administration results in increased interstitial fluid in vital organs leading to impaired renal, hepatic and cardiac function. Increased extra-vascular lung water (EVLW) is particularly lethal, leading to iatrogenic salt water drowning. EGDT and the Surviving Sepsis Campaign Guidelines recommend targeting a central venous pressure (CVP) > 8 mmHg. A CVP > 8 mmHg has been demonstrated to decrease microcirculatory flow, as well as renal blood flow and is associated with an increased risk of renal failure and death. Normal saline (0.9% salt solution) as compared to balanced electrolyte solutions is associated with a greater risk of acute kidney injury and death. This paper reviews the adverse effects of large volume resuscitation, a high CVP and the excessive use of normal saline.

Revised Starling equation and the glycocalyx model of transvascular fluid exchange: an improved paradigm for prescribing intravenous fluid therapy

I.V. fluid therapy does not result in the extracellular volume distribution expected from Starling's original model of semi-permeable capillaries subject to hydrostatic and oncotic pressure gradients within the extracellular fluid. Fluid therapy to support the circulation relies on applying a physiological paradigm that better explains clinical and research observations. The revised Starling equation based on recent research considers the contributions of the endothelial glycocalyx layer (EGL), the endothelial basement membrane, and the extracellular matrix. The characteristics of capillaries in various tissues are reviewed and some clinical corollaries considered. The oncotic pressure difference across the EGL opposes, but does not reverse, the filtration rate (the 'no absorption' rule) and is an important feature of the revised paradigm and highlights the limitations of attempting to prevent or treat oedema by transfusing colloids. Filtered fluid returns to the circulation as lymph. The EGL excludes larger molecules and occupies a substantial volume of the intravascular space and therefore requires a new interpretation of dilution studies of blood volume and the speculation that protection or restoration of the EGL might be an important therapeutic goal. An explanation for the phenomenon of context sensitivity of fluid volume kinetics is offered, and the proposal that crystalloid resuscitation from low capillary pressures is rational. Any potential advantage of plasma or plasma substitutes over crystalloids for volume expansion only manifests itself at higher capillary pressures.

Is albumin administration beneficial in early stage of postoperative hypoalbuminemia following gastrointestinal surgery?: a prospective randomized controlled trial

BACKGROUND

Surgeons commonly see postoperative hypoalbuminemia, but whether exogenous albumin administration is beneficial for these patients is unclear.

METHODS

A prospective, randomized study design was used, allocating 127 hypoalbuminemic patients into the albumin or saline group after gastrointestinal surgery. We investigated the development of postoperative hypoalbuminemia, nutritional status, postoperative fluid balance, postoperative complications, and postoperative hospital stay.

RESULTS

Plasma albumin concentrations of both groups decreased after operations (P <.01). No significant differences were found between groups (P >.05) in changes in postoperative plasma albumin concentration from baseline levels. Postoperative plasma albumin, total protein, and prealbumin levels were similar in the 2 groups. While 3-day and 5-day recovery ratios were similar, 7-day recovery ratios were lower in the albumin group (P <.05). No significant difference was found in overall fluid administration, urine output, or the incidence of postoperative complications between groups (23.4% for albumin group and 12.7% for control group, P = .116).

CONCLUSIONS

Albumin administration in the early stage of postoperative hypoalbuminemia following gastrointestinal surgery is not beneficial in correcting hypoalbuminemia or in clinical outcomes.

Rapid restoration of microcirculatory blood flow with hyperviscous and hyperoncotic solutions lowers the transfusion trigger in resuscitation from hemorrhagic shock

Resuscitation from hemorrhagic shock relies on fluid retransfusion. However, the optimal properties of the fluid have not been established. The aim of the present study was to test the influence of the concentration of hydroxyethyl starch (HES) solution on plasma viscosity and colloid osmotic pressure (COP), systemic and microcirculatory recovery, and oxygen delivery and consumption after resuscitation, which were assessed in the hamster chamber window preparation by intravital microscopy. Awake hamsters were subjected to 50% hemorrhage and were resuscitated with 25% of the estimated blood volume with 5%, 10%, or 20% HES solution. The increase in concentration led to an increase in COP (from 20 to 70 and 194 mmHg) and viscosity (from 1.7 to 3.8 and 14.4 cP). Cardiac index and microcirculatory and metabolic recovery were improved with HES 10% and 20% when compared with 5% HES. Oxygen delivery and consumption in the dorsal skinfold chamber was more than doubled with HES 10% and 20% when compared with HES 5%. This was attributed to the beneficial effect of restored or increased plasma COP and plasma viscosity as obtained with HES 10% and 20%, leading to improved microcirculatory blood flow values early in the resuscitation period. The increase in COP led to an increase in blood volume as shown by a reduction in hematocrit. Mean arterial pressure was significantly improved in animals receiving 10% and 20% solutions. In conclusion, the present results show that the increase in the concentration of HES, leading to hyperoncotic and hyperviscous solutions, is beneficial for resuscitation from hemorrhagic shock because normalization of COP and viscosity led to a rapid recovery of microcirculatory parameters.

Recombinant Human Serum Albumin Dimer has High Blood Circulation Activity and Low Vascular Permeability in Comparison with Native Human Serum Albumin

PURPOSE

Human serum albumin (HSA) is used clinically as an important plasma expander. Albumin infusion is not recommended for critically ill patients with hypovolemia, burns, or hypoalbuminemia because of the increased leakage of albumin into the extravascular spaces, thereby worsening edema. In the present study, we attempted to overcome this problem by producing a recombinant HSA (rHSA) dimer with decreased vascular permeability and an increased half-life.

METHODS

Two molecules of rHSA were genetically fused to produce a recombinant albumin dimer molecule. The pharmacokinetics and biodistribution of the recombinant proteins were evaluated in normal rats and carrageenin-induced paw edema mouse model.

RESULTS

The conformational properties of this rHSA dimer were similar to those for the native HSA (the HSA monomer), as evidenced by the Western blot and spectroscopic studies. The biological half-life and area under the plasma concentration-time curve of the rHSA dimer were approximately 1.5 times greater than those of the monomer. Dimerization has also caused a significant decrease in the total body clearance and distribution volume at the steady state of the native HSA. rHSA dimer accumulated to a lesser extent in the liver, skin, muscle, and fat, as compared with the native HSA. Up to 96 h, the vascular permeability of the rHSA dimer was less than that of the native HSA in paw edema mouse models. A prolonged plasma half-life of the rHSA dimer was also observed in the edema model rats.

CONCLUSIONS

rHSA dimer has a high retention rate in circulating blood and a lower vascular permeability than that of the native HSA.

Hemofiltration for cytokine-driven illnesses: the mediator delivery hypothesis

Hemofiltration is evolving as an adjunctive therapy for sepsis and other forms of systemic inflammation. Designed as a substitute for lost renal function, it is sometimes employed prior to the onset of renal failure to facilitate the nonspecific clearance of pro-inflammatory mediators. Prevailing theories suggest that hemofiltration attenuates the immune response when a threshold amount of excess cytokine is removed at the semi-permeable membrane. In this article we introduce an alternative hypothesis, in which hemofiltration exerts its effect by reinvigorating lymphatic flow and function. Crystalloid "replacement" solution, as much as 48 to 72 liters daily, is infused to restore intravascular volume lost through production of ultrafiltrate. Partial redistribution into interstitium and lymph mobilizes inflammatory mediators and other proteins, cellular byproducts, excessive ground matrix, fragments of apoptotic cells and free DNA. These substances are then metabolized, scavenged or cleared at multiple sites, including the reticuloendothelial system, liver, kidney, erythrocyte, and hemofilter.

Measuring the Size of the Extracellular Fluid Space Using Bromide, Iohexol, and Sodium Dilution

There is a need to find methods to assess the size of the extracellular fluid (ECF) volume without involving radioactive tracers. For this purpose, we applied 3 methods for measuring the ECF volume in 10 male volunteers (mean age, 34 yr). Steady-state plasma bromide concentration (control) was compared to the results of kinetic analysis of plasma iohexol and to kinetic analysis of the dilution of serum sodium after IV infusion of 1 L of isotonic mannitol. The volume of distribution of these tracers was used to indicate the ECF volume. The results disclosed statistically significant correlations between the results of all 3 methods, although the average sodium dilution showed 0.7 L lower values than iohexol and 1.4 L lower than bromide. All three methods correlated significantly with body weight. The percentage of the body weight indicated by the methods was 18.3% (3.1%) for sodium, 19.6% (1.0%) for iohexol, and 20.5% (1.1%) for bromide. We conclude that sodium dilution may be performed at bedside but iohexol and bromide showed less intersubject variability. Iohexol simultaneously measures the glomerular filtration rate and should be a viable clinical option if the hospital performs routine assessments of kidney function using this tracer.

Cold-induced fluid extravasation during cardiopulmonary bypass in piglets can be counteracted by use of iso-oncotic prime

OBJECTIVE

Hypothermic cardiopulmonary bypass is associated with increased fluid extravasation. This study aimed to compare whether iso-oncotic priming solutions, in contrast to crystalloids, could reduce the cold-induced fluid extravasation during cardiopulmonary bypass in piglets.

METHODS

Three groups were studied: the control group (CT group; n = 10), the albumin group (Alb group; n = 7), and the hydroxyethyl starch group (HES group; n = 7). Prime (1000 mL) and supplemental fluid were acetated Ringer solution, 4% albumin, and 6% hydroxyethyl starch, respectively. After 1 hour of normothermic cardiopulmonary bypass, hypothermic cardiopulmonary bypass (cooling to 28 degrees C within 15 minutes) was initiated and continued to 90 minutes. Fluid needs, plasma volume, changes in colloid osmotic pressure in plasma and interstitial fluid, hematocrit levels, and tissue water content were recorded, and protein masses and fluid extravasation rates were calculated.

RESULTS

Colloid osmotic pressure in plasma decreased immediately after the start of cardiopulmonary bypass in the CT group but remained stable in the Alb and HES groups. Colloid osmotic pressure in interstitial fluid tended to decrease in the CT group and remained unchanged in the Alb group, whereas a slight increase was observed in the HES group. Immediately after the start of cooling, fluid extravasation rates increased from 0.15 +/- 0.10 to 0.64 +/- 0.12 mL . kg -1 . min -1 in the CT group, whereas no such increase was observed in the Alb and HES groups. The changes in fluid extravasation rates were reflected by corresponding changes in tissue water content.

CONCLUSION

The use of albumin or hydroxyethyl starch as prime to preserve the colloid osmotic pressure during cardiopulmonary bypass causes a reduction in the cold-induced fluid extravasation compared with that seen with crystalloids. Albumin seems more effective than hydroxyethyl starch to limit cold-induced fluid shifts during cardiopulmonary bypass.

Modeling a hydropic recipient twin in twin-twin transfusion syndrome

We developed a mathematical model of twin-twin transfusion syndrome (TTTS) that includes a hydropic recipient twin, adding interstitial and intracellular fluid compartments, fetal congestive cardiac failure, and the dynamics of renin-angiotensin system (RAS) mediators to our previous TTTS model. Ten differential equations for each twin, coupled by the net fetofetal transfusion of blood and blood components, i.e., colloids, osmoles, and RAS mediators, describe the development of fetal arterial and venous blood volumes, blood osmolality and colloid osmotic pressure (COP), interstitial fluid volume and COP, intracellular fluid volume, amniotic fluid volume and osmolality, and RAS mediator concentration. We included varying placental anastomoses, placental sharing, and amnionicity. The 20 differential equations were solved numerically from 0 to 40 wk with a 0.6-s time step. Consistent with clinical experience, model predictions are as follows. Unidirectional arteriovenous anastomoses and arteriovenous anastomoses inadequately compensated by oppositely directed anastomoses cause severe TTTS that includes a hydropic recipient. Adequately compensated arteriovenous anastomoses simulated TTTS without hydrops. The probability that oppositely directed anastomoses prevent onset of a hydropic recipient after TTTS onset, i.e., the largest interval between onset of TTTS and onset of hydrops in the recipient, was best for a venovenous anastomosis, closely followed by an arterioarterial and finally an oppositely directed arteriovenous anastomosis. Hydropic recipients have decreased amniotic fluid volume. Unequal placental sharing and amnionicity modify hydrops onset. In conclusion, our model simulates a sequence of events that results in a hydropic recipient twin in severe TTTS. The model may allow an assessment of the efficacy of current therapeutic interventions for TTTS cases that include a hydropic recipient twin.

[Exact measurement of the volume effect of 6% hydoxyethyl starch 130/0.4 (Voluven) during acute preoperative normovolemic hemodilution]

BACKGROUND

What is the effect of preoperative acute normovolemic hemodilution (ANH) with 6% hydroxyethyl starch (HES) 130/0.4 (Voluven) on blood volume?

METHODS

In 10 patients undergoing radical hysterectomy, ANH was performed to a hematocrit of 21% using 6% HES 130/0.4 (Voluven) whereby a replacement of blood with 115% of colloid was planned. Plasma volume (indocyanine green dilution technique) and hematocrit were determined before, 30 and 60 min after ANH. Red cell volume (labelling erythrocytes with fluorescein) was determined before and 30 min after ANH.

RESULTS

After removal of 1,431+/-388 ml of blood and simultaneous replacement with 1,686+/-437 ml of colloid, blood volumes were 218+/-174 ml higher than before (at 105+/-4%). The volume effect was 98+/-12%, 30 min after ANH. Even 60 min after ANH, mean blood volumes were with 4,228+/-986 ml slightly higher than before ANH (102+/-5%). The hematocrit decreased disproportionally in relation to the residual intravascular volume. Consequently, estimating the volume effect from the changes in hematocrit led to an overestimation (about +30%).

CONCLUSION

Double label measurements of blood volume demonstrated that the volume effect of 6% HES 130/0.4 (Voluven) is about 100% in the course of ANH. The reason for the disproportionally large decrease in hematocrits could be the mobilization of a fraction of the plasma volume which was retained within the endothelial glycocalyx.

Continuous veno-venous hemofiltration may improve survival from acute respiratory distress syndrome after bone marrow transplantation or chemotherapy

PURPOSE

Acute respiratory distress syndrome (ARDS) may result from immunologic activity triggered by irradiation and/or chemotherapy. Hemofiltration removes plasma water and soluble components below 25 kilodaltons. The authors hypothesized that early hemofiltration might attenuate the inflammatory component of ARDS, resulting in increased survival in immunocompromised children and young adults.

METHODS

Ten children (6 bone marrow transplantation, 3 chemotherapy, 1 lymphoma/hemophagocytosis) with ARDS (Pao2/Fio2 94 +/- 37 torr) received early continuous veno-venous hemodiafiltration as adjunctive therapy for respiratory failure, regardless of renal function. Six children had normal urine output and initial serum creatinine (range 0.1-1.2 mg/dL); four had renal insufficiency (initial creatinine 1.7-2.4 mg/dL). Hemofiltration was instituted coincident with intubation. Respiratory failure was precipitated by Enterobacter sepsis in two patients and by Aspergillus in one.

RESULTS

Hemodiafiltration was performed for 13 +/- 9 days. A high rate of clearance was achieved (52 +/- 17 mL/min/1.73 m2). Duration of mechanical ventilation was 14 +/- 9 days. Nine of the 10 children were successfully extubated; 8 survived.

CONCLUSIONS

Early hemofiltration may improve survival from ARDS following bone marrow transplantation or chemotherapy. Possible mechanisms include strict fluid balance, immunomodulation through filtration of inflammatory constituents, and immunomodulation through intensive extracellular water exchange that delivers biochemicals to organs of metabolism as well as the hemofilter.