Synthetic Colloids Research Articles

Which intravenous fluid for the surgical patient?

This review appraises recent evidence and provides clinical guidance on optimal perioperative fluid therapy. Choice of perioperative intravenous fluid continues to be the source of much debate. Not all crystalloids are equivalent, and there is growing evidence that balanced solutions are superior to 0.9% saline in many situations. Recent evidence from the critical care population has highlighted risks associated with synthetic colloids; this and the absence of demonstrable benefit in the surgical population make it difficult to recommend their use in the perioperative period. Giving the correct amount of fluid may be as important as the choice of the fluid used. There is increasing evidence that excessive positive fluid balance is harmful to patients but there have been no randomized trials comparing maintenance fluid strategy. A knowledge of the physiology and accurate estimation of fluid balance is important for water and electrolyte homeostasis until the patient is able to resume adequate enteral nutrition. Balanced crystalloids are the fluid of choice for perioperative resuscitation and optimization in patients not requiring blood products. Avoidance of a grossly positive sodium and water balance during the maintenance phase is likely to be important, but has not been assessed in randomized trials.

Albumin in critically ill patients: the ideal colloid?

The use of albumin-containing solutions in critically ill patients has been recently revisited, following evidence on harmful effects of synthetic colloids, and novel randomized controlled trials (RCTs) in sepsis. Here, we review the most recent findings on albumin administration in acutely ill and septic patients. The revision of Starling's theory on microvascular fluid dynamics has highlighted the role of albumin in preserving intravascular compartment volume. In cirrhosis, albumin may be important in maintaining immune system reactivity and cardiac contractility. Preliminary analyses indicate albumin as beneficial in patients with burn, while being associated with increased risk of acute kidney injury after cardiac surgery. The first RCT (ALBIOS trial) testing the efficacy of albumin replacement in severe sepsis did not show a survival benefit associated with albumin, although observing at post-hoc analysis a benefit in septic shock. All the eight meta-analyses performed on albumin in sepsis reveal an absence of harm, and likely a benefit lower than expected, whereas suggesting an advantage, to be verified, in septic shock. Further studies are needed to clarify physiology and clinical impact of albumin in critically ill patients, considering specific phenotypes and secondary outcomes other than survival, yet clinically relevant.

Injectable hemostatic adjuncts in trauma: Fibrinogen and the FIinTIC study.

F adequate hemostasis, sufficient amounts of thrombin and coagulable substrate are fundamental prerequisites. In addition to platelets, on whose surfaces most of the thrombin is generated, fibrinogen can be considered as the substrate of the coagulation process. If sufficient thrombin is formed, it converts fibrinogen into stable fibrin, which determines the firmness of the developing clot in the presence of activated coagulation factor XIII (Fig. 1). Under physiologic conditions, fibrinogen availability is regulated through dynamic changes in synthesis and breakdown to preserve coagulation function. As a consequence of blood loss, consumption of coagulation factors, dilutional coagulopathy, hypothermia and acidosis, as well as profibrinolytic activation, fibrinogen may reach critical levels earlier than any other procoagulant factor and also platelets even before packed red blood cell concentrate administration becomes necessary. Floccard et al. have described even significant drops in fibrinogen levels to occur already during the ultra early prehospital phase of care when comparing blood samples obtained from bleeding trauma patients at the scene and at the time point of arrival to the trauma bay (fibrinogen median, 2.6 g/L; interquartile range [IQR], 2.3Y3.1; 95% confidence interval [CI], 2.4Y2.9 vs. 2.1 g/L; IQR, 1.4Y2.5; 95% CI, 1.7Y2.3) (changes, j0.6 g/L; IQR, j1.1 to j0.3; 95%CI,j0.9 toj0.3;pG 0.001). In this study, fibrinogen levels decreased substantially as a function of injury severity reflected by Injury Severity Scores (ISSs). Recently, Kimura et al. have reported similar results when searching retrospectively for predictors of hypofibrinogenemia in 290 blunt traumapatients upon admission to aLevel 1 trauma center during a 3-year period. Their multivariate regression analysis identified patient’s age (odds ratio [OR], 0.97; p G 0.001), Triage Revised Trauma Score (T-RTS including Glasgow Coma Scale [GCS] score, respiratory rate, and systolic blood pressure; OR, 0.81; p = 0.003), and prehospital volume therapy (OR, 2.54; p = 0.01) as independent predictors for early hypofibrinogenemia. In contrast todisseminated intravascular coagulopathy, there is no generalized intravascular microcoagulation with increased consumption in trauma-induced coagulopathy. Instead, there is hemorrhage-related loss of coagulation factors and platelets with subsequent dilution of procoagulant factors due to (uncritical) volume resuscitation with direct effect on fibrinogen polymerization. Dilution of fibrinogen by crystalloid fluids and additional reduced fibrin interlinkage by synthetic colloids has been discussed. Recently, experimental data confirmed significant fibrinogen breakdown by acidosis following hypoperfusion with no effect on fibrinogen synthesis, while hypothermia decreased fibrinogen synthesis with no effect on fibrinogen degradation. Furthermore, synthesis and degradation seem to be regulated through different mechanisms, and a potential deficit in fibrinogen availability during hypothermia has been suggested.

Is limited prehospital resuscitation with plasma more beneficial than using a synthetic colloid? An experimental study in rabbits with parenchymal bleeding.

Reports of survival benefits of early transfusion of plasma with red blood cells (1:1 ratio) in trauma patients suggest that plasma may be a better fluid to replace Hextend for battlefield resuscitation. We studied possible advantages of prehospital resuscitation with plasma compared with Hextend or albumin in a model of uncontrolled hemorrhage. Male New Zealand white rabbits (3.3 ± 0.1 kg) were anesthetized, instrumented, and subjected to a splenic injury with uncontrolled bleeding. Ten minutes after injury (mean arterial pressure [MAP] < 40 mm Hg), the rabbits received small and equal volumes (15 mL/kg) of rabbit plasma (n = 10), Hextend (n = 10), or 5% human albumin (n = 9) or no fluid. Fluids were administered in two bolus injections (20 minutes apart) and targeted to a MAP of 65 mm Hg. Animals were monitored for 2.5 hours or until death, and their blood losses were measured. Arterial blood samples were collected at different times and analyzed for ABG, CBC, and coagulation tests. There were no differences in baseline measures among groups. Splenic injury caused similar hemorrhages (9.1 ± 0.4 mL/kg at 10 minutes) and decreased MAP in all subjects. Subsequent resuscitation initiated additional bleeding. At 60 minutes after injury (20 minutes after resuscitation), longer activated partial thromboplastin time and lower fibrinogen concentrations were apparent compared with baseline values with differences among groups. Thrombelastography analysis indicated faster and stronger clot formation with plasma and albumin resuscitation than with Hextend use. Shock indices were increased in all groups, but smaller changes were measured in the albumin group. Total blood loss did not differ among resuscitated rabbits but was higher (p < 0.05) than among nonresuscitated animals. Survival rates were 11% (untreated), 40% (Hextend and plasma), and 89% (albumin, p < 0.05). Resuscitation with plasma or albumin better preserved coagulation function than did Hextend. However, despite these improvements, plasma resuscitation did not reduce blood loss or improve survival, while albumin administration seemed beneficial.

The effect of synthetic colloids on hemodynamic during spinal anesthesia for cesarean section

The article presents results of retrospective analysis of the postinfusion programs that were conducted and their effectiveness in preventing the occurrence and correction of hypotension during spinal anesthesia for cesarean section.

Motility-Induced Phase Separation

Self-propelled particles include both self-phoretic synthetic colloids and various microorganisms. By continually consuming energy, they bypass the laws of equilibrium thermodynamics. These laws enforce the Boltzmann distribution in thermal equilibrium: The steady state is then independent of kinetic parameters. In contrast, self-propelled particles tend to accumulate where they move more slowly. They may also slow down at high density for either biochemical or steric reasons. This creates positive feedback, which can lead to motility-induced phase separation (MIPS) between dense and dilute fluid phases. At leading order in gradients, a mapping relates variable-speed, self-propelled particles to passive particles with attractions. This deep link to equilibrium phase separation is confirmed by simulations but generally breaks down at higher order in gradients: New effects, with no equilibrium counterpart, then emerge. We give a selective overview of the fast-developing field of MIPS, focusing on theory and simulation but including a brief speculative survey of its experimental implications.

Effects of synthetic colloid and crystalloid solutions on hemorheology in vitro and in hemorrhagic shock.

BackgroundPlasma expanders are commonly used in the management of critically ill patients, which may exhibit altered hemorheology. We evaluated the effects of various synthetic colloids and Lactated Ringer’s (LR) solution on hemorheological parameters in vitro and in a rodent hemorrhagic shock model.MethodsFor the in vitro experiments, rat blood was incubated with hydroxyethyl starch (HES) 130/0.4, HES 200/0.5, succinylated gelatine (GEL), or LR at various ratios. The control consisted of blood without dilution. The hemorheological parameters were measured after a 15-min incubation. For the in vivo study, rats were subjected to a severe volume-controlled hemorrhage and were resuscitated using a colloid solution (HES 130/0.4, HES 200/0.5, or GEL) or LR. The hemorheological parameters were measured 2 h after resuscitation.ResultsThe GEL significantly elevated the plasma viscosity compared to the other groups. In the in vitro study, GEL and LR accelerated the erythrocyte aggregation. There was no significant difference between HES 130/0.4, HES 200/0.5, and control groups regarding the aggregation amplitude and index. In the in vivo study, the aggregation amplitude increased significantly in the GEL group compared to the HES 130/0.4, HES 200/0.5, LR, and sham groups. There was no significant difference between the groups with respect to the elongation index in vivo.ConclusionsHydroxyethyl starch did not change the erythrocyte aggregation compared to the control. GEL significantly accelerates the erythrocyte aggregation and elevates the plasma viscosity compared to hydroxyethyl starch. The in vitro hemorheological measurements most likely provide hints for the in vivo study.

Viscoelastic haemostatic assays and fibrinogen concentration tests during haemodilution

BackgroundThe efficacy of concentrates of fibrinogen and factor XIII in hypothermia and haemodilution has not yet been completely investigated. Clauss fibrinogen measurement may overestimate fibrinogen concentrations during in vitro haemodilution with hydroxyethyl starch (HES).MethodsCoagulation was assessed with viscoelastic haemostatic assays [rotational thromboelastometry (ROTEM) or free oscillation rheometry (FOR)] in vitro. Fibrinogen measurement methods were compared in observational studies.ResultsHaemodilution with human albumin (HA) decreased the clot strength of ROTEM assay with tissue factor activation [EXTEM maximal clot formation (MCF)] less than the synthetic colloids HES or dextran (P &lt; 0.001), but equal with crystalloid fluids [normal saline (NA) or Ringer's acetated solution (RA)]. Addition of fibrinogen increased the clot strength of ROTEM assay with tissue factor activation and platelet inhibitor cytochalasin D, i.e. fibrinogen‐dependent clot strength (FIBTEM MCF) more after haemodilution with HA than synthetic colloids (P &lt; 0.001), but less than or equal with crystalloids. In haemodilution with HA, fibrinogen increased coagulation as measured with ROTEM dose dependently (P &lt; 0.001). Factor XIII (FXIII) had no effect alone, but an additional effect to that of fibrinogen on clot strength, FIBTEM MCF (P &lt; 0.02). Hypothermia at 33°C and haemodilution with HES, but not RA, interacted to decrease fibrinogen‐dependent clot strength measured with FOR (Fibscreen2 G′max, P &lt; 0.001), and clot velocity measured with FOR (Fibscreen1 coagulation time 2, P = 0.035) or ROTEM (EXTEM clot formation time, P &lt; 0.001). Fibrinogen (±FXIII) increased coagulation independently of temperature (33° or 37°C). After infusion of 1000 ml of HES to patients, fibrinogen measured with two Clauss methods and one immunological method decreased to the same extent (29%, 27% and 31%), whereas fibrinogen‐dependent clot strength (ROTEM FIBTEM MCF) decreased more (44%, P &gt; 0.001). Finally, when comparing seven different Clauss methods during cardiac surgery, within‐method variability was low, but between‐method variability was high (mean difference &gt; 0.5 g/l). No difference between pre‐ and post‐weaning from cardiopulmonary by‐pass was seen.ConclusionFibrinogen concentrate increased coagulation more after haemodilution with HA than synthetic colloids, but equal with or less than after crystalloid haemodilution. FXIII had an additional effect to that of fibrinogen. Hypothermia and haemodilution with HES interacted to decrease coagulation. Fibrinogen ± FXIII increased coagulation also at 33°C. Two Clauss methods after in vivo HES haemodilution did not overestimate fibrinogen; however, fibrinogen‐dependent clot strength decreased more than fibrinogen concentration. Between‐method variability with seven Clauss methods was high. These findings support the use of fibrinogen concentrate after resuscitation with HA, also at hypothermia, but question the use of colloids, especially HES, in resuscitation. Clauss fibrinogen methods need to improve.

Effect of synthetic colloid administration on coagulation in healthy dogs and dogs with systemic inflammation.

BackgroundSynthetic colloids are often used during fluid resuscitation and affect coagulation.ObjectiveTo compare the effects of an isotonic crystalloid and synthetic colloid on coagulation in healthy dogs and dogs with systemic inflammation.AnimalsSixteen adult purpose‐bred Beagles.MethodsRandomized, placebo‐controlled, blinded study. Dogs were randomized into one of two groups receiving fluid resuscitation with either 40 mL/kg IV 0.9% NaCl or tetrastarch after administration of lipopolysaccharide or an equal volume of placebo. After a 14‐day washout period, the study was repeated such that dogs received the opposite treatment (LPS or placebo) but the same resuscitation fluid. Blood samples were collected at 0, 1, 2, 4, and 24 hours for measurement of coagulation variables.ResultsAdministration of either fluid to healthy dogs and dogs with systemic inflammation resulted in similar increases in prothrombin time and activated clotting time. In comparison to saline administration, tetrastarch administration resulted in significantly decreased R (P = .017) in healthy dogs, as well as significantly increased activated partial thromboplastin time (P ≤ .016), CL30% (P ≤ .016), and K (P < .001) and significantly decreased platelet count (P = .019), α (P ≤ .001), MA (P < .001), and von Willebrand factor antigen (P < .001) and collagen binding activity (P ≤ .003) in both healthy dogs and dogs with systemic inflammation.Conclusions and Clinical ImportanceTetrastarch bolus administration to dogs with systemic inflammation resulted in a transient hypocoagulability characterized by a prolonged activated partial thromboplastin time, decreased clot formation speed and clot strength, and acquired type 1 von Willebrand disease.

The crystalloid-colloid debate: Consequences of resuscitation fluid selection in veterinary critical care.

To provide a comprehensive review of the current literature in human and veterinary medicine evaluating the impact of resuscitation fluid choice on patient outcome and adverse effects. Prospective and retrospective studies, experimental models, and review articles in both human and veterinary medicine retrieved via PubMed. A series of recent, large, randomized controlled trials in critically ill human patients comparing crystalloid versus colloid driven fluid resuscitation algorithms have demonstrated no outcome benefit with the use of natural or synthetic colloids. Synthetic colloidal solutions are associated with an increased incidence of adverse effects including acute kidney injury, need for renal replacement therapy, and coagulopathies. Further, colloidal solutions demonstrate a larger volume of distribution in the setting of critical illness than hypothesized. These findings have created controversy regarding colloid fluid resuscitation in critically ill patients and challenge current resuscitation strategies. A thorough review of the most influential human data is provided. No veterinary clinical outcome data pertaining to fluid resuscitation choice currently exist. Veterinary data from experimental and small clinical trials evaluating the coagulopathic effects of hydroxyethyl starch solutions are described. Data pertaining to the use of natural colloids and albumin products in clinical veterinary patients are reviewed. In addition, data pertaining to the comparative intravascular volume expansion effectiveness of different fluid types in canine patients are reviewed. Clinical data from critically ill human patients have failed to demonstrate an outcome advantage associated with colloidal fluid resuscitation and indicate that hydroxyethyl starch solutions may be associated with significant adverse effects, including acute kidney injury, need for renal replacement therapy, coagulopathies, and pathologic tissue uptake. The ability to apply these findings to veterinary patients is unknown; however, similar pathophysiology may apply, and critical re-evaluation of resuscitation strategies is justified.

Fluid management in living donor hepatectomy: Recent issues and perspectives.

The importance of the safety of healthy living liver donors is widely recognized during donor hepatectomy which is associated with blood loss, transfusion, and subsequent post-operative morbidity. Although the low central venous pressure (CVP) technique can still be effective, it may not be advantageous concerning the safety of healthy donors undergoing hepatectomy. Emerging evidence suggests that stroke volume variation (SVV), a simple and useful index for fluid responsiveness and preload status in various clinical situations, can be applied as a guide for fluid management to reduce blood loss during living donor hepatectomy. Synthetic colloid solutions are also associated with serious adverse events such as the use of renal replacement therapy and transfusion in critically ill or septic patients. However, it is uncertain whether the intra-operative use of colloid solution is associated with similarly adverse effects in patients undergoing living donor hepatectomy. In this review article we discuss the recent issues regarding the low CVP technique and the high SVV method, i.e., maintaining 10%-20% of SVV, for fluid management in order to reduce blood loss during living donor hepatectomy. In addition, we briefly discuss the effects of intra-operative colloid or crystalloid administration for surgical rather than septic or critically ill patients.

Volume expansion in the first 4 days of shock: a prospective multicentre study in 19 French intensive care units.

To describe the current practices of volume expansion in French intensive care units (ICU). In 19 ICUs, we prospectively observed the prescription and monitoring practices of volume expansion in consecutive adult patients with shock [sustained hypotension and/or need of vasopressor therapy, associated with at least tachycardia and/or sign (s) of hypoperfusion]. Patients were included at the time of prescription of the first fluid bolus (FB). Thereafter, all the FBs administered during the 96 h following shock onset were surveyed. An FB was defined as an intravenous bolus of at least 100 ml of a blood volume expander intended to rapidly improve the patient's circulatory condition. We included 777 patients [age: 63 ± 15 years; female gender: 274 (35 %); simplified acute physiology score II: 55.9 ± 20.6; ICU length of stay: 6 days (interquartile range (IQR) 3-13); ICU mortality: 32.8 %] and surveyed 2,694 FBs. At enrolment mean arterial pressure was 63 mmHg (IQR 55-71). The most frequent triggers of FB were hypotension, low urine output, tachycardia, skin mottling and hyperlactataemia. Amount of fluid given at each FB was highly variable between centres. Crystalloids were used in 91 % (2,394/2,635) and synthetic colloids in 3.3 % (87/2,635) of FBs. Overall, clinicians used any kind of haemodynamic assessment (central venous pressure measurement, predictive indices of fluid responsiveness, echocardiography, cardiac output monitoring or a combination of these) in 23.6 % (635/2,694) of all FBs surveyed, with an important between-centre heterogeneity. High between-centre variability characterised all the aspects of FB prescription and monitoring, but overall haemodynamic exploration to help guide and monitor FB was infrequent.

Choices in fluid type and volume during resuscitation: impact on patient outcomes.

We summarize the emerging new literature regarding the pathophysiological principles underlying the beneficial and deleterious effects of fluid administration during resuscitation, as well as current recommendations and recent clinical evidence regarding specific colloids and crystalloids. This systematic review allows us to conclude that there is no clear benefit associated with the use of colloids compared to crystalloids and no evidence to support the unique benefit of albumin as a resuscitation fluid. Hydroxyethyl starch use has been associated with increased acute kidney injury (AKI) and use of renal replacement therapy. Other synthetic colloids (dextran and gelatins) though not well studied do not appear superior to crystalloids. Normal saline (NS) use is associated with hyperchloremic metabolic acidosis and increased risk of AKI. This risk is decreased when balanced salt solutions are used. Balanced crystalloid solutions have shown no harmful effects, and there is evidence for benefit over NS. Finally, fluid resuscitation should be applied in a goal-directed manner and targeted to physiologic needs of individual patients. The evidence supports use of fluids in volume-responsive patients whose end-organ perfusion parameters have not been met.

Radionuclide desorption kinetics on synthetic Zn/Ni-labeled montmorillonite nanoparticles

Sorption/desorption kinetics for selected radionuclides (99Tc(VII), 232Th(IV), 233U(VI), 237Np(V), 242Pu and 243Am(III)) under Grimsel (Switzerland) ground water conditions (pH 9.7 and ionic strength of ∼1mM) in the presence of synthetic Zn or Ni containing montmorillonite nanoparticles and granodiorite fracture filling material (FFM) from Grimsel were examined in batch studies. The structurally bound Zn or Ni in the octahedral sheet of the synthetic colloids rendered them suitable as colloid markers. Only a weak interaction of the montmorillonite colloids with the fracture filling material occurs over the experimental duration of 10,000h (∼13months). The tri- and tetravalent radionuclides are initially strongly associated with nanoparticles in contrast to 99Tc(VII), 233U(VI) and 237Np(V) which showed no sorption to the montmorillonite colloids. Radionuclide desorption of the nanoparticles followed by sorption to the fracture filling material is observed for 232Th(IV), 242Pu and 243Am(III). Based on the conceptual model that the driving force for the kinetically controlled radionuclide desorption from nanoparticles and subsequent association to the FFM is the excess in surface area offered by the FFM, the observed desorption kinetics are related to the colloid/FFM surface area ratio. The observed decrease in concentration of the redox sensitive elements 99Tc(VII), 233U(VI) and 237Np(V) may be explained by reduction to lower oxidation states in line with Eh-pH conditions prevailing in the experiments and thermodynamic considerations leading to (i) precipitation of a sparingly soluble phase, (ii) sorption to the fracture filling material, (iii) possible formation of eigencolloids and/or (iv) sorption to the montmorillonite colloids. Subsequent to the sorption/desorption kinetics study, an additional experiment was conducted investigating the potential remobilization of radionuclides/colloids attached to the FFM used in the sorption/desorption kinetic experiments by contacting this FFM with pure Grimsel groundwater for 7days. A positive correlation of 242Pu, 232Th(IV) and 237Np was observed with the Zn and Ni concentrations in the desorption experiments indicating a remobilization of sorbed montmorillonite colloids. The results of the study in hand highlight (i) the novel use of structural labeled colloids to decrease the uncertainties in the determination of nanoparticle attachment providing more confidence in the derived radionuclide desorption rates. Moreover, the data illustrate (ii) the importance of radionuclide colloid desorption to be considered in the analysis and application of colloid facilitated transport both in laboratory or in-situ experiments and numerical model simulations and (iii) a possible remobilization of sorbed colloids and associated radionuclides by desorption from the matrix material (FFM) under non-equilibrium conditions.

Fluid resuscitation in sepsis: a systematic review and network meta-analysis.

Fluid resuscitation is the cornerstone of sepsis treatment. However, whether balanced or unbalanced crystalloids or natural or synthetic colloids confer a survival advantage is unclear. To examine the effect of different resuscitative fluids on mortality in patients with sepsis. MEDLINE, EMBASE, ACP Journal Club, CINAHL, HealthSTAR, the Allied and Complementary Medicine Database, and the Cochrane Central Register of Controlled Trials through March 2014. Randomized trials that evaluated different resuscitative fluids in adult patients with sepsis or septic shock and death. No language restrictions were applied. Two reviewers extracted data on study characteristics, methods, and outcomes. Risk of bias for individual studies and quality of evidence were assessed. 14 studies (18916 patients) were included with 15 direct comparisons. Network meta-analysis at the 4-node level showed higher mortality with starches than with crystalloids (high confidence) and lower mortality with albumin than with crystalloids (moderate confidence) or starches (moderate confidence). Network meta-analysis at the 6-node level showed lower mortality with albumin than with saline (moderate confidence) and low-molecular-weight starch (low confidence) and with balanced crystalloids than with saline (low confidence) and low- and high-molecular-weight starches (moderate confidence). These trials were heterogeneous in case mix, fluids evaluated, duration of fluid exposure, and risk of bias. Imprecise estimates for several comparisons in this network meta-analysis contribute to low confidence in most estimates of effect. Among patients with sepsis, resuscitation with balanced crystalloids or albumin compared with other fluids seems to be associated with reduced mortality. The Hamilton Chapter of the Canadian Intensive Care Foundation and the Critical Care Medicine Residency Program and Critical Care Division Alternate Funding Plan at McMaster University.

Hydroxyethyl starch: a review of pharmacokinetics, pharmacodynamics, current products, and potential clinical risks, benefits, and use.

To review and summarize the pharmacokinetics and pharmacodynamics of hydroxyethyl starch (HES), as well as reported risks and benefits of HES infusion, and to provide administration and monitoring recommendations for HES use in dogs and cats. Veterinary and human peer-reviewed medical literature, including scientific reviews, clinical and laboratory research articles, and authors' clinical experience. HES solutions are the most frequently used synthetic colloid plasma volume expanders in human and veterinary medicine. The majority of research in human medicine has focused on the adverse effects of HES infusion, with emphasis on acute kidney injury and coagulation derangements. The studies often differ in or fail to report factors, such as the type, amount, interval, and concentration of HES administered; the patient population studied; or concurrent fluids administered. Currently, there is no definitive clinical evidence that the reported adverse effects of HES use in human medicine occur in veterinary species. There is little information available on HES administration techniques or simultaneous administration of additional fluids in human and veterinary medicine. The rationale for HES use in small animals has been largely extrapolated from human medical studies and guidelines. A controlled approach to intravenous fluid resuscitation using crystalloid and HES volumes titrated to reach desired resuscitation end point parameters is outlined for small animal practitioners. The extrapolation of data from human studies directly to small animals should be done with the knowledge that there may be species variations and different pharmacokinetics with different HES solutions. Veterinary reports indicate that bolus and continuous rate infusions of 6% hetastarch solutions at moderate doses are well tolerated in feline and canine subjects. Further research in domesticated species is necessary to better define and expand the knowledge regarding use of HES solutions in small animal medicine.

Management of acute kidney injury with continuous venovenous haemodiafiltration in a cat.

Continuous renal replacement therapy is an emerging technique for the treatment of acute kidney injury (AKI). Data regarding its use in cats are limited. This report describes the use of a novel continuous renal replacement therapy (CRRT) system for the treatment of AKI in a cat. A 1.3-year-old cat developed uraemic signs following the administration of a non-steroidal anti-inflammatory agent for the treatment of a suspect traumatic episode. CRRT was provided with a Prismaflex Gambro machine used in continuous venovenous haemodiafiltration mode, with an AN-69 surface-treated membrane, synthetic colloid priming and heparin anticoagulation. Two treatment cycles were performed, totalling 51 h of CRRT. The treatment was effective in controlling uraemic signs, and no major complications were noted. Owing to financial constraints the owners declined further CRRT treatments, and on day 8 of hospitalisation, owing to the lack of significant clinical improvement, humane euthanasia was performed. The set-up detailed in this report provides a viable option for the initial treatment of cats with AKI.

Albumin-Beyond Fluid Replacement in Cardiopulmonary Bypass Surgery: Why, How, and When?

Maintaining vascular barrier competence, preventing interstitial edema, and keeping microcirculation intact is crucial to achieve an optimal outcome in cardiopulmonary bypass surgery (CPB). Blood contact with roller pumps and foreign surfaces during CPB induces shear stress and a pressure drop across the pump boot that leads to transient systemic activation of the inflammatory and hemostatic systems. Moreover, patients after CPB often need volume resuscitation using the smallest possible amount of colloid solution because of fluid overload. For this purpose, human-derived albumin may be preferred over synthetic colloids because CPB priming with albumin preserves oncotic pressure, prevents platelet adhesion, and likely induces less consumption of coagulation factors. In patients with increased bleeding or renal failure, albumin is a safe alternative because of its minimal side effects. Large, randomized clinical trials comparing the benefit of albumin versus other fluids are warranted in the future to define albumin's distinct role in select high-risk surgical populations.

Effect of synthetic colloid administration on hemodynamic and laboratory variables in healthy dogs and dogs with systemic inflammation.

To compare the effects of administering equal volumes of isotonic crystalloids and synthetic colloids on hemodynamic and laboratory variables in healthy dogs and dogs with systemic inflammation. Randomized, placebo-controlled, blinded study. Comparative clinical research facility. Sixteen adult purpose-bred Beagles. Dogs were first randomized to receive either lipopolysaccharide (LPS; 5 μg/kg, IV) or an equal volume of placebo (0.9% NaCl, IV). Dogs were then randomized into 1 of 2 groups receiving fluid resuscitation with either 40 mL/kg IV isotonic crystalloid (0.9% NaCl) or synthetic colloid (tetrastarch). After a 14-day washout, the study was repeated such that dogs received the opposite treatment (LPS or placebo) and the same resuscitation fluid regimen. Vital signs (heart rate (HR), oscillometric blood pressure) were measured and blood samples were collected for PCV, total plasma protein (TPP), serum lactate concentration, and colloid osmotic pressure (COP) measurements. Healthy (placebo) dogs had similar decreases in PCV and TPP after administration of either fluid. Tetrastarch administration was associated with a larger increase in HR, systolic blood pressure, and mean blood pressure. Dogs with systemic inflammation had similar increases in systolic blood pressure and decreases in PCV, TPP, and lactate after administration of either fluid. Tetrastarch administration caused greater immediate increase in HR and mean blood pressure compared to 0.9% NaCl. In all dogs, 0.9% NaCl administration decreased COP and tetrastarch administration increased COP. Resuscitation with equal volumes of 0.9% NaCl and tetrastarch caused similar changes in hemodynamic and laboratory variables in dogs with LPS-induced systemic inflammation; however, larger increases in HR and blood pressure were seen within the first 2 hours following tetrastarch administration compared to 0.9% NaCl. Tetrastarch administration increased COP in all dogs, despite a decrease in TPP.

Iron colloids reduce the bioavailability of phosphorus to the green alga Raphidocelis subcapitata

Phosphorus (P) is a limiting nutrient in many aquatic systems. The bioavailability of P in natural waters strongly depends on its speciation. In this study, structural properties of iron colloids were determined and related to their effect on P sorption and P bioavailability. The freshwater green alga Raphidocelis subcapitata was exposed to media spiked with radiolabelled 33PO4, and the uptake of 33P was monitored for 1 h. The media contained various concentrations of synthetic iron colloids with a size between 10 kDa and 0.45 μm. The iron colloids were stabilised by natural organic matter. EXAFS spectroscopy showed that these colloids predominantly consisted of ferrihydrite with small amounts of organically complexed Fe. In colloid-free treatments, the P uptake flux by the algae obeyed Michaelis–Menten kinetics. In the presence of iron colloids at 9 or 90 μM Fe, corresponding to molar P:Fe ratios between 0.02 and 0.17, the truly dissolved P (<10 kDa) was between 4 and 60% of the total dissolved P (<0.45 μm). These colloids reduced the P uptake flux by R. subcapitata compared to colloid-free treatments at the same total dissolved P concentration. However, the P uptake flux from colloid containing solutions equalled that from colloid-free ones when expressed as truly dissolved P. This demonstrates that colloidal P did not contribute to the P uptake flux. It is concluded that, on the short term, phosphate adsorbed to ferrihydrite colloids is not available to the green alga R. subcapitata.