Synthetic Colloids Research Articles

Longer preoperative fluid resuscitation decreased anesthetic fluid interventions in 297 dogs undergoing surgery for gastrointestinal foreign body obstruction.

The objectives were to (1) compare the impact of preoperative fluid resuscitation on anesthetic parameters and interventions and (2) assess the impact of preoperative resuscitation duration on the integrity of intestinal tissue and postoperative complications in dogs with gastrointestinal foreign body obstruction. Medical records from 1 academic hospital were reviewed for 297 client-owned dogs that underwent gastrointestinal foreign body obstruction surgery between May 2017 and August 2022. Data collected included the following: signalment, preoperative fluid resuscitation, surgical findings, anesthetic parameters and interventions, postoperative complications, and timing of the first meal. Variables for preoperative length of fluid resuscitation (hours), total preoperative fluid bolus (mL/kg), and preoperative fluid rate (mL/kg/d) were changed to categorical variables. Associations between anesthetic interventions, postoperative outcomes, preoperative fluid resuscitation length, and total fluid bolus were assessed with ordered logistic regression. Shorter preoperative fluid resuscitation length was associated with higher anesthetic fluid rates (P = .033) and fluid boluses performed (P = .023). Increased total volume of preoperative fluid boluses was associated with anesthetic synthetic colloid use (P = .028). There was insufficient evidence to claim an association between the impact of preoperative fluid resuscitation length and intestinal wall compromise (perforation, P = .912; enterectomy performed, P = .711). Shorter preoperative fluid resuscitation was associated with increased anesthetic fluid interventions but not the need for more complex surgeries. Longer fluid resuscitation periods are associated with fewer anesthetic interventions in dogs.

Hydroxyethyl Starch, a Synthetic Colloid Used to Restore Blood Volume, Attenuates Shear-Induced Distortion but Accelerates the Convection of Sodium Hyaluronic Acid

Hydroxyethyl Starch, a Synthetic Colloid Used to Restore Blood Volume, Attenuates Shear-Induced Distortion but Accelerates the Convection of Sodium Hyaluronic Acid

Discovering dynamic laws from observations: The case of self-propelled, interacting colloids.

Active matter spans a wide range of time and length scales, from groups of cells and synthetic self-propelled colloids to schools of fish and flocks of birds. The theoretical framework describing these systems has shown tremendous success in finding universal phenomenology. However, further progress is often burdened by the difficulty of determining forces controlling the dynamics of individual elements within each system. Accessing this local information is pivotal for the understanding of the physics governing an ensemble of active particles and for the creation of numerical models capable of explaining the observed collective phenomena. In this work, we present ActiveNet, a machine-learning tool consisting of a graph neural network that uses the collective motion of particles to learn active and two-body forces controlling their individual dynamics. We verify our approach using numerical simulations of active Brownian particles, active particles undergoing underdamped Langevin dynamics, and chiral active Brownian particles considering different interaction potentials and values of activity. Interestingly, ActiveNet can equally learn conservative or nonconservative forces as well as torques. Moreover, ActiveNet has proven to be a useful tool to learn the stochastic contribution to the forces, enabling the estimation of the diffusion coefficients. Therefore, all coefficients of the equationof motion of Active Brownian Particles are captured. Finally, we apply ActiveNet to experiments of electrophoretic Janus particles, extracting the active and two-body forces controlling colloids' dynamics. On the one side, we have learned that the active force depends on the electric field and area fraction. On the other side, we have also discovered a dependence of the two-body interaction with the electric field that leads us to propose that the dominant force between active colloids is a screened electrostatic interaction with a constant length scale. We believe that the proposed methodological tool, ActiveNet, might open a new avenue for the study and modeling of experimental suspensions of active particles.

Fluid therapy in ICU – A review

The most common indications of fluid resuscitation in critical care settings are severe hypovolemia, sepsis, trauma, burns, and perioperative fluid loss. Evaluation of intravascular volume status and the ability for identifying patients who might profit from volume expansion is vital. Traditional markers such as central venous pressure and pulmonary capillary wedge pressure have poor predictive value for fluid responsiveness. Dynamic indices such as pulse pressure variation, stroke volume variation, tidal volume challenge, and passive leg raise test are recommended to predict fluid responsiveness over static markers. The next perplexing part of fluid therapy is the choice of fluid resuscitation. The simplest answer is to provide crystalloids and avoid synthetic colloids (hydroxyethyl startch, gelatin, and dextran). Among the colloids, albumin has a role in certain clinical conditions in critical care settings. Between normal saline and buffered solutions, buffered solutions have the advantage of reducing acid–base disturbances, and chloride burden, and are likely to prevent renal failure. However, the advantage of buffered solutions did not consistently show up in large randomized controlled trials. Although administering fluids is a common therapeutic approach in critical care settings, administering fluids excessively has been linked to fatal outcomes. The resuscitation, optimization, stabilization, and evacuation concept describes the use of a dynamic fluid strategy to optimize benefits and prevent the negative effects of fluid overload. After receiving a patient in an emergency room or intensive care unit with hemodynamic instability, the first thing that comes to mind is whether or not the patient would benefit from fluid administration. How to predict fluid responsiveness? What type of fluids should be administered? When to stop administering fluids and start evacuation are vital questions confronted in day-to-day practice. In this article, we would like to discuss these issues and provide recommendations for current practices.

What is the best treatment for hypotension in healthy dogs during anaesthesia maintained with isoflurane?

Hypotension is a common and potentially life-threatening complication of general anaesthesia in dogs. Due to the combination of cardiovascular side effects of many anaesthetic, sedative and analgesic drugs used peri-operatively hypotension is frequently reported even in healthy dogs undergoing elective procedures. Several treatment options for hypotension have been advocated. Potential treatments include rapid administration of either crystalloid or colloid fluids; pharmacological treatments to increase cardiac output and/or systemic vascular resistance; or reduction in the delivery of the volatile anaesthetic agents. This critical appraisal considers the current evidence for which treatment is the best option for treating hypotension in healthy euvolemic dogs undergoing general anaesthesia maintained with isoflurane. Fourteen relevant studies were appraised, including 12 laboratory studies and two small clinical trials. One study demonstrated that reduction in the delivery of isoflurane may correct hypotension, but this treatment may not always be feasible. In general, rapid administration of fluids did not increase blood pressure and failed to correct hypotension. Synthetic colloids demonstrated some efficacy, but results were inconsistent between studies and large volumes may be required. Infusion of dopamine appears to be the most reliable pharmacological option consistently increasing blood pressure, cardiac output and correcting hypotension.

Chemotactic behavior for a self-phoretic Janus particle near a patch source of fuel.

Many biological microswimmers are capable of chemotaxis, i.e., they can sense an ambient chemical gradient and adjust their mechanism of motility to move towards or away from the source of the gradient. Synthetic active colloids endowed with chemotactic behavior hold considerable promise for targeted drug delivery and the realization of programmable and reconfigurable materials. Here, we study the chemotactic behavior of a Janus particle, which converts "fuel" molecules, released at an axisymmetric chemical patch located on a planar wall, into "product" molecules at its catalytic cap and moves by self-phoresis induced by the product. The chemotactic behavior is characterized as a function of the interplay between the rates of release (at the patch) and the consumption (at the particle) of fuel, as well as of details of the phoretic response of the particle (i.e., its phoretic mobility). Among other results, we find that, under certain conditions, the particle is attracted to a stable "hovering state" in which it aligns its axis normal to the wall and rests (positions itself) at an activity-dependent distance above the center of the patch.

Role of Crystalloids in the Perioperative Setting: From Basics to Clinical Applications and Enhanced Recovery Protocols.

Perioperative fluid management, a critical aspect of major surgeries, is characterized by pronounced stress responses, altered capillary permeability, and significant fluid shifts. Recognized as a cornerstone of enhanced recovery protocols, effective perioperative fluid management is crucial for optimizing patient recovery and preventing postoperative complications, especially in high-risk patients. The scientific literature has extensively investigated various fluid infusion regimens, but recent publications indicate that not only the volume but also the type of fluid infused significantly influences surgical outcomes. Adequate fluid therapy prescription requires a thorough understanding of the physiological and biochemical principles that govern the body's internal environment and the potential perioperative alterations that may arise. Recently published clinical trials have questioned the safety of synthetic colloids, widely used in the surgical field. A new clinical scenario has arisen in which crystalloids could play a pivotal role in perioperative fluid therapy. This review aims to offer evidence-based clinical principles for prescribing fluid therapy tailored to the patient's physiology during the perioperative period. The approach combines these principles with current recommendations for enhanced recovery programs for surgical patients, grounded in physiological and biochemical principles.

Retrospective evaluation of indications, transfusion protocols, and acute transfusion reactions associated with the administration of lyophilized canine albumin: 53 cases (2009-2020).

To describe the administration of lyophilized canine albumin (LCA) and determine the increase in serum albumin concentrations post-LCA transfusion. To describe the incidence and types of acute transfusion reactions (TRs) and associated outcome in dogs presenting to a veterinary teaching hospital. Retrospective and descriptive study from 2009 to 2020. University teaching hospital. Fifty-three client-owned dogs included in the study if they received an LCA transfusion and had vital sign monitoring recorded for at least for 4hours after starting the LCA transfusion. None. The 53 dogs available for study inclusion received 64 LCA transfusions. Signalment; underlying disease; indications for LCA transfusion; pre- and posttransfusion serum albumin concentration; volume, concentration, and dose of LCA; duration of transfusion; administration of other blood products or synthetic colloids; occurrence, timing, and type of TR; length of hospitalization; and outcome were recorded. Serum albumin concentrations increased post-LCA transfusion, with a median dose of 0.56g/kg and a median posttransfusion serum albumin increase of 3g/L (0.3g/dL) (P=0.008). TRs occurred in 13 of 64 (20.3%) transfusion events. Volume per kilogram, dose (g/kg), concentration, duration of transfusion, and additional administration of synthetic colloids were not associated with TRs. Three (23%) TRs were classified as febrile nonhemolytic transfusion reaction, 5 (38.5%) as transfusion-associated dyspnea (development of respiratory distress and limited diagnostics), and 5 (38.5%) had clinical signs that could not be defined by any 1 TR category. Six (46.1%) of 13 events were nonsevere, 5 (38.5%) were severe, and 2 (15.4%) were life-threatening. Administration of LCA can be used to increase serum albumin concentrations, although the clinical implications of this increase are unknown. Acute TRs associated with LCA are relatively frequent and can be life-threatening. Careful monitoring is vital.

Evaluation of a Hydroxyethylstarch Solution for Dimethyl Sulfoxide Removal from Mobilized Peripheral Blood using an Automated System

Background and objectives: This study evaluates the efficacy of synthetic colloid hydroxyethyl starch for use as a washing solution to remove DMSO from hematopoietic stem cells cryopreserved grafts in comparison to a crystalloid based solution. 
 Materials and methods: We evaluated samples of cryopreserved mobilized peripheral blood (MPB) from 6 (six) patients that had not been used for transplant. For comparison, we used two equal bags of the same collection procedure, allowing the analysis of two different solutions simultaneously. Washing solutions were used: a crystalloid solution (solution 1, sodium chloride 0.9%) and a colloidal solution (solution 2, hydroxyethyl starch 6%), both added with human albumin 2.5%. The washes were performed using the SEPAX2™ (Biosafe) system automated methodology, using the CS-600.1 kit (Biosafe), according to the washing protocol established by the manufacturer. 
 Results: The washing solution containing HES showed a statistically significant increase in the recovery of CNT and CD34+/CD45+ cells (p = 0.0313, both), in addition to a greater number of CFU-GM colonies (without statistical significance) when compared to the 0.9% sodium chloride solution. Furthermore, the wash solution containing HES also prevented significant clumping, contrary to what was observed in the wash with 0.9% sodium chloride solution. 
 Conclusion: This work shows that the colloidal washing solution containing hydroxyethyl starch is a good option for DMSO removal procedures in samples of cryopreserved mobilized peripheral blood, maintaining the CD34+ cells viability and functionality and reducing the cell clumping.

Expert Consensus on the Use of Human Serum Albumin in Adult Cardiac Surgery.

Expert Consensus on the Use of Human Serum Albumin in Adult Cardiac Surgery.

Larval cyathostominosis: Clinicopathological data and treatment outcomes of 38 hospitalised horses (2009–2020)

SummaryBackgroundThere is limited evidence regarding the treatment and outcomes of larval cyathostominosis.ObjectivesTo describe the presentation, treatment and outcomes of horses with larval cyathostominosis in two equine hospitals.Study designRetrospective, multicentred cohort study.MethodsClinical records were reviewed (2009–2020). Inclusion criteria included a diagnosis of larval cyathostominosis (determined by faecal assessment and/or post‐mortem examination). Data were assessed for normality. Descriptive analysis was performed for frequency results and central tendencies. Statistical analysis between survivors and nonsurvivors was determined by Chi‐square/Fisher's exact test for categorical variables, and Student's t‐test/Mann–Whitney for continuous variables.ResultsOf 38 cases, 21 (55%) were nonsurvivors (3/38 dead on arrival). Nonsurvivors died by 2.9 days ± 2.4. Tachycardia (mean 61 beats/min ± 14), leucocytosis (mean 17.1 × 109/L ± 9.1), neutrophilia (mean 14.1 × 109/L ± 8.5), hypoalbuminaemia (mean 21.6 g/L ± 6.0), hyperfibrinogenaemia (mean 7.4 g/L ± 2.6) and elevated serum amyloid A (SAA) (median 315.0 mg/L, interquartile range [IQR] 117.0–1460.0) were consistent findings. Faecal shedding of Salmonella spp. occurred in four cases. The mean last recorded albumin was 18.6 g/L ± 4.5 and total protein (TP) 52.3 g/L ± 13.6. Crystalloids were administered in 25/35, synthetic colloids in 5/35 and plasma in 17/35 cases. Anthelmintic treatment was administered in 25/35 cases, of which 22 also received corticosteroids. Recumbency prior to admission (p = 0.037) and administration of isotonic fluid therapy (p = 0.027) were associated with nonsurvival. From peripheral blood analysis, lower TP (p = 0.006) and higher SAA (p = 0.050) concentrations at admission as well as lower last recorded TP (p = 0.002) and lower last recorded albumin concentrations (p = 0.028) were associated with nonsurvival.Main limitationsResults may not be applicable to other populations.ConclusionsReferred cases of larval cyathostominosis have a low survival rate. Several variables are associated with reduced survival: history of recumbency, isotonic fluid therapy, elevated SAA at admission, low TP at admission, low last recorded TP and low last recorded albumin.

Retrospective analysis of the use of canine-specific albumin in 125 critically ill dogs.

To describe the clinical use of canine-specific albumin (CSA) in critically ill dogs, report adverse events, and evaluate measurable clinical effects of CSA administration. Retrospective case series from 2019 to 2020. Large, urban, private-practice referral and emergency center. Consecutive sample of 125 client-owned dogs administered CSA transfusions. None. The conditions most commonly associated with the use of CSA were surgical (32/125) and nonsurgical (20/125) gastrointestinal disease. Both serum albumin and total plasma protein concentrations were significantly increased posttransfusion (P<0.001), and 16% albumin transfusions produced the greatest magnitude increase in serum albumin (P=0.0015). Concurrent crystalloid administration did not affect change in albumin. While there was no significant improvement in blood pressure seen in those patients that received albumin, a significant improvement in shock index was identified (P=0.02). Adverse events were uncommon; however, 8 critically ill dogs died during CSA administration. CSA appears to be a relatively safe alternative to synthetic colloids and complementary to crystalloids in critically ill patients. More concentrated solutions may be more effective in raising serum albumin concentration. Further investigation into the indications for and efficacy of CSA will continue to improve our knowledge of this blood product.

Uso de fluidoterapia en la práctica clínica

The use of intravenous fluid therapy must meet a need that cannot be met by oral administration and is not free from risk. No perfectly physiological intravenous solution is currently available. Intravenous solutions are classified into crystalloids and colloids. For the majority of indications, optimal intravenous fluid therapy is based on the use of crystalloids. The choice of fluid therapy must be personalised based on the patient’s characteristics and prior medical history, the current clinical situation, the osmolality and association of hydroelectrolytic imbalances and the acid-base equilibrium. The use of synthetic colloids is subject to significant restrictions given their negative effects on health outcomes, mainly anaphylactic reactions.

Active responsive colloids driven by intrinsic dichotomous noise.

We study the influence of intrinsic noise on the structure and dynamics of responsive colloids (RCs), which actively change their size and mutual interactions. The colloidal size is explicitly resolved in our RC model as an internal degree of freedom (DOF) in addition to the particle translation. A Hertzian pair potential between the RCs leads to repulsion and shrinking of the particles, resulting in an explicit responsiveness of the system to self-crowding. To render the colloids active, their size is internally driven by a dichotomous noise, randomly switching ("breathing") between growing and shrinking states with a predefined rate, as motivated by recent experiments on synthetic active colloids. The polydispersity of this dichotomous active responsive colloid (D-ARC) model can be tuned by the parameters of the noise. Utilizing stochastic computer simulations, we study crowding effects on the spatial distributions, relaxation times, and self-diffusion of dense suspensions of the D-ARCs. We find a substantial influence of the "built-in" intrinsic noise on the system's behavior, in particular, transitions from unimodal to bimodal size distributions for an increasing colloid density as well as intrinsic noise-modified diffusive translational dynamics. We conclude that controlling the noise of internal DOFs of a macromolecule or cell is a powerful tool for active colloidal materials to enable autonomous changes in the system's collective structure and dynamics towards the adaptation of macroscopic properties to external perturbations.

Association of red cell distribution width/albumin ratio with intraoperative blood transfusion in cervical cancer patients.

Although minimally invasive surgical techniques have reduced intraoperative bleeding, the risk of transfusion exists. However, few studies have evaluated risk factors for transfusion in radical hysterectomy. We aimed to evaluate the association between preoperative red cell distribution width/albumin ratio (RDW/albumin) and transfusion in cervical cancer patients. We analyzed 907 patients who underwent radical hysterectomy between June 2006 and February 2015. Logistic regression and Cox regression analyses were performed to determine the risk factors for transfusion and mortality at 5-year and overall. Net reclassification improvement (NRI) and integrated identification improvement (IDI) analyses were performed to verify the improvement of the intraoperative transfusion model upon the addition of RDW/albumin. RDW/albumin was an independent risk factor for transfusion (odds ratio [OR]: 1.34, 95% confidence interval [CI]: 1.02-1.77, p = 0.035). Additionally, body mass index, operation time, laparoscopic surgery, total fluids, and synthetic colloid were risk factors for transfusion. RDW/albumin was an independent risk factor for 5-year mortality (hazard ratio [HR]: 1.51, 95% CI: 1.07-2.14, p = 0.020), and overall mortality (HR: 1.48, 95% CI: 1.06-2.07, p = 0.021). NRI and IDI analyses showed the discriminatory power of RDW/albumin for transfusion (p<0.001 and p = 0.046, respectively). RDW/albumin might be a significant factor in transfusion and mortality in cervical cancer patients.

Multi-scale organization in communicating active matter

The emergence of collective motion among interacting, self-propelled agents is a central paradigm in non-equilibrium physics. Examples of such active matter range from swimming bacteria and cytoskeletal motility assays to synthetic self-propelled colloids and swarming microrobots. Remarkably, the aggregation capabilities of many of these systems rely on a theme as fundamental as it is ubiquitous in nature: communication. Despite its eminent importance, the role of communication in the collective organization of active systems is not yet fully understood. Here we report on the multi-scale self-organization of interacting self-propelled agents that locally process information transmitted by chemical signals. We show that this communication capacity dramatically expands their ability to form complex structures, allowing them to self-organize through a series of collective dynamical states at multiple hierarchical levels. Our findings provide insights into the role of self-sustained signal processing for self-organization in biological systems and open routes to applications using chemically driven colloids or microrobots.

Low-Fouling Zwitterionic Polymeric Colloids as Resuscitation Fluids for Hemorrhagic Shock.

Colloids, known as volume expanders, have been used as resuscitation fluids for hypovolemic shock for decades, as they increase plasma oncotic pressure and expand intravascular volume. However, recent studies show that commonly used synthetic colloids have adverse interactions with human biological systems. In this work, a low-fouling amine(N)-oxide-based zwitterionic polymer as an alternative volume expander with improved biocompatibility and efficacy is designed. It is demonstrated that the polymer possesses antifouling ability, resisting cell interaction and deposition in major organs, and is rapidly cleared via renal filtration and hepatic circulation, reducing the risk of long-term side effects. Furthermore, in vitro and in vivo studies show an absence of adverse effects on hemostasis or any acute safety risks. Finally, it is shown that, in a head-to-head comparison with existing colloids and plasma, the zwitterionic polymer serves as a more potent oncotic agent for restoring intravascular volume in a hemorrhagic shock model. The design of N-oxide-based zwitterionic polymers may lead to the development of alternative fluid therapies to treat hypovolemic shock and to improve fluid management in general.

Biomarkers of Coagulation and Inflammation in Dogs after Randomized Administration of 6% Hydroxyethyl Starch 130/0.4 or Hartmann’s Solution

Simple SummaryCritically ill dogs often require intravenous fluid therapy to improve circulation and treat life-threatening shock. Standardly, a balanced electrolyte solution called a crystalloid is prescribed. Some veterinarians also prescribe colloid fluids like hydroxyethyl starch (HES), which are crystalloids that contain large starch molecules, as more of the volume delivered stays in circulation compared to crystalloid. However, there is concern that colloids may impair blood clot formation and increase the risk of serious bleeding. To better understand this risk, this study compared the function of individual clotting components within blood samples collected over time from critically ill dogs that received either crystalloids or HES. The blood samples were saved from a previous clinical trial where critically ill dogs requiring intravenous fluids were randomized to receive HES or crystalloids. Blood was collected before fluid therapy and then 6, 12, and 24 h after the start of the intervention fluid. The results did not provide evidence that HES impaired clotting more than crystalloids. However, considering the small sample size and variability between dogs, this result does not provide evidence that HES is safe. Larger or more targeted studies are required to further assess the effect of HES on blood clotting in dogs.Synthetic colloid fluids containing hydroxyethyl starch (HES) have been associated with impairment of coagulation in dogs. It is unknown if HES causes coagulation impairment in dogs with naturally occurring critical illness. This study used banked plasma samples from a blinded, randomized clinical trial comparing HES and balanced isotonic crystalloid for bolus fluid therapy in 39 critically ill dogs. Blood was collected prior to fluid administration and 6, 12, and 24 h thereafter. Coagulation biomarkers measured at each time point included prothrombin time, activated partial thromboplastin time, thrombin time, fibrinogen concentration, and the activities of coagulation factors V, VII, VIII, IX, and X, von Willebrand factor antigen, antithrombin, and protein C. Given the links between coagulation and inflammation, cytokine concentrations were also measured, including interleukins 6, 8, 10, and 18, keratinocyte-derived chemokine, and monocyte chemoattractant protein-1. Data were analyzed with linear mixed effects models. No significant treatment-by-time interactions were found for any biomarker, indicating that the pattern of change over time was not modified by treatment. Examining the main effect of time showed significant changes in several coagulation biomarkers and keratinocyte-derived chemokines. This study could not detect evidence of coagulation impairment with HES.

Perioperative fluid management in children: an updated review

Background: Perioperative fluid management in children has been a major topic for debate. Objectives: Our aim is to review the current evidence on perioperative fluid management in children including: type of fluid, administration rates, preoperative fluid intake and monitoring techniques. Design: Narrative review. Method: Following the PRISMA-S guidelines we performed a search (2010-March 2022) in databases Medline (through PubMed) and Cochrane Library. 4297 citations were found and screened by two independent researchers. After screening, 64 articles were withheld for our review. Results: The perioperative administration of isotonic fluids is safer than hypotonic solutions, concerning the development of hyponatremia. A balanced isotonic solution with 1-2,5% glucose should be used as perioperative maintenance IV fluid in children (1 month to 18 years). Colloids can be used in children when inadequate effect in volume correction is achieved with crystalloids. The preferred synthetic colloid for children is a third generation HES in a balanced solution. To date, most clinicians use the “4-2-1 rule” for calculating fluid rate. This may not be the optimal fluid rate, as little research has been done. Preoperative fasting for clear fluids should be limited to 1 hour, children should even be encouraged to drink up until 1 hour before induction. Respiratory variation of aortic blood flow peak velocity (ΔVpeak) with echocardiography is currently the most reliable technique for evaluating fluid responsiveness in children.

Synthetic Colloids should not be Put out of the Shelves of Intensive Care Unit

Synthetic Colloids should not be Put out of the Shelves of Intensive Care Unit