Influence Of Hydroxyethyl Starch Research Articles

Hydroxyethyl Starch 130/0.4 Binds to Neutrophils Impairing Their Chemotaxis through a Mac-1 Dependent Interaction.

Several studies showed that hydroxyethyl starch (HES), a synthetic colloid used in volume replacement therapies, interferes with leukocyte-endothelium interactions. Although still unclear, the mechanism seems to involve the inhibition of neutrophils’ integrin. With the aim to provide direct evidence of the binding of HES to neutrophils and to investigate the influence of HES on neutrophil chemotaxis, we isolated and treated the cells with different concentrations of fluorescein-conjugated HES (HES-FITC), with or without different stimuli (N-Formylmethionine-leucyl-phenylalanine, fMLP, or IL-8). HES internalization was evaluated by trypan blue quenching and ammonium chloride treatment. Chemotaxis was evaluated by under-agarose assay after pretreatment of the cells with HES or a balanced saline solution. The integrin interacting with HES was identified by using specific blocking antibodies. Our results showed that HES-FITC binds to the plasma membrane of neutrophils without being internalized. Additionally, the cell-associated fluorescence increased after stimulation of neutrophils with fMLP (p < 0.01) but not IL-8. HES treatment impaired the chemotaxis only towards fMLP, event mainly ascribed to the inhibition of CD-11b (Mac-1 integrin) activity. Therefore, the observed effect mediated by HES should be taken into account during volume replacement therapies. Thus, HES treatment could be advantageous in clinical conditions where a low activation/recruitment of neutrophils may be beneficial, but may be harmful when unimpaired immune functions are mandatory.

Influence of hydroxyethyl starch combined with strengthening anti-platelet therapy on the short-term clinical efficacy, TCD index and recurrence rate of patients with TIA secondary to cerebral artery stenosis

Objective To investigate the influence of hydroxyethyl starch combined with strengthening anti-platelet therapy on the short-term clinical efficacy, TCD index and recurrence rate of patients with TIA secondary to cerebral artery stenosis. Methods 80 patients with TIA secondary to cerebral artery stenosis were chosen, and they were randomly divided into two groups according to the digital table, each group in 40 cases.The control group received strengthening anti-platelet therapy alone, and the observation group received hydroxyethyl starch on the basis of control group.The short-term clinical efficacy, the blood flow velocity of ACA and MCA before and after treatment, the TIA recurrence rate, the incidence of cerebral infarction and adverse reactions of both two groups were compared. Results The short-term effective rates of the control group and observation group were 77.50%, 97.50%, respectively.The short-term effective rate of the observation group was significantly higher than that of the control group(χ2=12.33, P<0.05). The blood flow velocity of ACA and MCA of the control group after treatment were (51.05±9.83)cm/s, (54.88±6.62)cm/s, respectively, which were significantly lower than those of the observation group[(59.12±12.07)cm/s, (62.65±8.09)cm/s, t=3.17, 2.96, 4.03, 4.74, 3.67, 4.05, all P<0.05]. The TIA recurrence rate and the incidence rate of cerebral infarction of the control group were 22.50%, 12.50%, respectively, which were significantly higher than those of the observation group(5.00%, 0.00%, χ2=11.75, 14.06, all P<0.05). The incidence rates of adverse reactions of the control group and observation group were 12.50%, 10.00%, respectively.There was no significant difference in the incidence rate of adverse reactions between the two groups(χ2=1.75, P<0.05). Conclusion Hydroxyethyl starch combined with strengthening anti-platelet therapy in the treatment of patients with TIA secondary to cerebral artery stenosis can efficiently relieve the symptoms of neurological function, higher the level of cerebral blood perfusion, reduce the risk of TIA recurrence and cerebral infarction, and not increase the incidence of adverse reactions. Key words: Cerebral artery diseases; Ischemic attack, transiet; Hydroxyethyl starch

Hydroxyethyl Starch Influences Biochemical Markers of Renal Damage and of Inflammation after Multivessel Coronary Artery Bypass Grafting - A Subgroup Analysis

Objectives: During a prospective, randomized study investigating anticoagulation management in 120 CABG patients (Hoenicka et al., J. Thromb. Haemost. 2015), a pharmacovigilance communication had led to a decreased use of hydroxyethyl starch (HES) during surgery and intensive care. Influence of HES on peri- and postoperative parameters up to 72 hour was evaluated in a subgroup analysis.

Influence of Hydroxyethyl Starch on Renal Function After Orthotopic Liver Transplantation

BackgroundPostoperative renal impairment (RI) is one of the most common complications in orthotopic liver transplantation (OLT), and it occurs in 17% to 95% of the patients who undergo the surgery. MethodsWe reviewed 394 consecutive patients who underwent OLT. On the basis of the preoperative renal function level (presence of renal failure (RF): SCr >1.5 mg/dL before OLT), the patients were divided into an RF group and a non-RF group. In each group, the patients were subdivided into 4 subgroups according to the type and dosage of the intra-operative use of HES (hydroxyethyl starch). The changing tendency of the SCr (serum creatinine) of each group and the ratio of the change in the SCr within the first postoperative week were compared. ResultsIn total, 139 of 394 patients (35%) had RI within the first week after OLT (RI group); 104 patients (75%) in the RI group and 181 patients (71%) in the non-RI group required HES transfusions. The multivariate logistic regression analysis identified old age, a low pre-operative platelet level, and massive red blood cell transfusions as risk factors for the postoperative development of RI. The changing tendency of the SCr and the ratio of change in the SCr among the different HES subgroups showed no significant difference in the RF group or in the non-RF group. ConclusionsPerioperative use of HES 200/0.5 or HES 130/0.4 has no significant effect on renal function in the first postoperative week in patients undergoing OLT.

Influence of hydroxyethyl starch (HES) 130/0.4 on hemostasis as measured by viscoelastic device analysis: a systematic review

Hydroxyethyl starch solutions (HES) are plasma volume expanders which affect hemostasis. Newer HES 130/0.4 is said to be safer. Reevaluation of published evidence is necessary after the recent retraction of studies. Systematic review of studies assessing HES 130/0.4 effects on hemostasis by thrombelastography (TEG, ROTEM) or Sonoclot (SCR) in comparison with crystalloid or albumin control fluids was performed. Only studies which provided statistical comparisons between study fluids were analyzed. Studies were divided into in vitro or in vivo hemodilution studies. We assessed study quality, HES effects which differed significantly from controls, values outside normal range, degree of hemodilution, and cumulative HES dose. Seventeen in vitro and seven in vivo hemodilution studies were analyzed. Four studies reported quality control measures. Nineteen studies (all 15 ROTEM studies, 3 of 5 in vitro TEG, and 1 of 2 SCR studies) showed a significant hypocoagulatory effect of HES 130/0.4 on clot formation, while clotting time was not uniformly affected. Three in vivo TEG studies with low HES doses or cancer patients found mixed or nonsignificant results. In studies which provided normal ranges (n = 9), more values were outside normal ranges in the HES than in the control groups (87/122 vs. 58/122, p < 0.001). Dose effects were apparent in the in vitro studies, which investigated higher dilutions up to 80%. In vivo studies were fewer and did not investigate doses >40 ml/kg. HES 130/0.4 administration results in a weaker and smaller clot. Until results from well-designed clinical trials are available, safer fluids should be chosen for patients with impaired coagulation.

Influence of hydroxyethyl starch and gelatin versus crystalloids on renal function, fluid balance, and ICU length of stay in patients with severe sepsis

In a smaller sample of patients with severe sepsis, resuscitation with the synthetic colloids hydroxyethyl starch (HES) as well as gelatin (GEL) increased the occurrence of acute kidney injury (AKI) in comparison with crystalloids (CRYS). We now performed the analysis in a large-scale sample with over 1,100 septic patients on our ICU.

Influence of hydroxyethyl starch 130/0.4 on renal function of injured patients with acute renal failure after Wenchuan earthquake

To retrospectively analyze the use of hydroxyethyl starch (HES) 130/0.4 in injured patients with acute renal failure (ARF) in Wenchuan earthquake, and its influence on the renal function. Critically ill traumatic patients with ARF admitted to intensive care unit (ICU) of West China Hospital within 1 month after Wenchuan earthquake were divided into two groups according to whether or not HES 130/0.4 was used (Y group for having used it and N group for not). The basic clinical data and acute physiology and chronic health evaluation II (APACHE II) score were obtained on admission. Serum blood urea nitrogen (BUN) and creatinine (SCr) on day 1, 3, 7, 14 and 28 were compared between two groups, as well as the time of continuous renal replacement therapy (CRRT) and mechanical ventilation (MV), transfusion amount, and 28-day mortality rate. The usage of HES 130/0.4 was recorded in Y group, including total days, maximum daily amount, total amount and average amount being used. A total of 39 patients were enrolled into the study, 30 in Y group, 9 in N group. No statistical difference was found in basic clinical data and APACHE II score on admission to ICU. Also there was no difference in days of CRRT and MV, or transfusion amount. Serum BUN and SCr on day 1, 3, 7, 14 and 28 after admission to ICU showed no significant difference between two groups, except for SCr concentration on day 1 (P<0.05). In Y group, the mean duration of using HES 130/0.4 was 3 days, mean daily amount was (529.9+/-226.3) ml, maximum daily amount was 2 500 ml, minimum daily amount was 500 ml (none exceeded recommended dosage), total amount used was 500-13 500 ml. The 28-day mortality rate in Y group was 26.7%, no patient died in N group within 28 days. No negative influence on the renal function imparted by HES 130/0.4 is found in critically ill traumatic patients with ARF.

Influence of Hydroxyethyl Starch on Healing of Colonic Anastomosis in a Rat Model of Peritonitis

Background: This study was designed to evaluate the role of different intravascular volume replacement regimens of HES 130/0.4 on wound healing process in left colonic anastomoses in the presence of intra-abdominal sepsis induced by murine model of cecal ligation and puncture (CLP). Methods: The left colonic anastomosis was performed in 40 rats that were divided into five groups (n = 8/group): saline controls (30 ml/kg); CLP plus saline (30 ml/kg); CLP plus HES (7.5, 15, or 30 ml/kg, respectively). Saline or HES was treated before the construction of left colonic anastomosis and on a regular daily basis. Anastomotic bursting pressures were measured in vivo on day 5. Tissue samples were obtained for analyses of hydroxyproline (HP) contents, myeloperoxidase (MPO) acivity, malondialdehyde (MDA), reduced glutathione (GSH) levels, and nuclear factor-κ B (NF-κ B) activation. The plasma levels of tumor necrosis factor (TNF)-α and interleukin (IL)-6 were also measured. Results: Intra-abdominal sepsis led to significant decreases in colonic anastomotic bursting pressures, and perianastomotic tissue HP contents and GSH levels, along with increases in perianastomotic tissue MPO activity, MDA levels and NF-κ B activation and plasma levels of TNF-α and IL-6. After treated with HES, these provoked perianastomotic tissue MPO activity, MDA levels, NF-κ B activation, and plasma levels of TNF-α and IL-6 were suppressed and GSH levels were restored, especially in 15 ml/kg HES group. Without obvious influence on systemic nutritional condition, HES 15 ml/kg but not HES 7.5 ml/kg significantly increased anastomotic bursting pressures, and perianastomotic tissue HP contents. However, HES 30 ml/kg even led to adverse effects on anastomotic bursting pressures. Conclusions: This study showed that moderate doses (15 ml/kg) of HES 130/0.4 administration significantly prevented this intraperitoneal sepsis-induced impaired anastomotic healing of the left colon. It also suggested the possibility of poorer anastomotic healing receiving HES at higher doses (30 ml/kg). Clearly, HES 130/0.4 now should not be recommended to use at a high doses postoperatively in sepsis.

Influence of volume reduction and cryopreservation methodologies on quality of thawed umbilical cord blood units for transplantation

Introduction Although there is considerable variability in methodology among umbilical cord blood banks, their common goal is to achieve optimal product quality for transplantation. Cryopreservation is a critical issue for a long-term maintenance of cord blood viability and colony-forming capacities. Materials and methods We designed a prospective study to compare controlled (CRF) vs. non-controlled freezing (URF) of volume-reduced cord blood units. In addition, the influence of hydroxy ethyl starch (HES) on cryopreservation was also assayed. To assess the efficiency of protocols used, cell recoveries were measured and the presence of hematopoietic colony-forming units was quantified. Results In the study phase, we observed similar CB haematopoietc recoveries for CRF and URF strategies, except for TNC recovery that was better for HES volume reduced CB units in the URF group. When we analysed the data of routine processed CB units in samples from satellite cryovials, we found better BFU-E, CFU-GM, CFU-GEMM and CFU recoveries for those units processed with HES than without HES, in an URF manner. Conclusions URF of CB units is a cryopreservation procedure that allows similar hematopoietic progenitor recoveries than CRF with programmed devices. However, our study suggests that those banks that cryopreserve CB units in a URF manner should use HES for volume reduction. On the other hand, for CRF cryopreservation methodology volume reduction with and without HES are equally useful.

Influence of volume therapy with a modern hydroxyethylstarch preparation on kidney function in cardiac surgery patients with compromised renal function: A comparison with human albumin*

There is continuing concern about the influence of hydroxyethylstarch on renal function in patients with compromised kidney function. Prospective, randomized, single-center study. University-affiliated hospital. Fifty patients undergoing elective, first-time coronary artery bypass grafting using cardiopulmonary bypass with a preoperative serum creatinine between 1.5 and 2.5 mg/dL. According to a prospective, randomized sequence, the patients received either hydroxyethylstarch with a low molecular weight (mean molecular weight 130 kD) and a low molar substitution (0.4) (6% hydroxyethylstarch 130/0.4) (n = 25) or 5% human albumin (n = 25). Volume was added to the priming (500 mL) and given perioperatively until the second postoperative day to keep pulmonary artery occlusion pressure or central venous pressure between 12 and 14 mm Hg. Serum creatinine and cystatin plasma levels were measured from arterial blood samples. From urine specimens, N-acetyl-beta-D-glucosaminidase, glutathione transferase-alpha, and neutrophil gelatinase-associated lipocalin were measured. Measurements were performed after induction of anesthesia, at the end of surgery, 5 hrs after surgery, and on the first and second postoperative days. A follow-up after discharge from the hospital (60 days) was also done. Similar amounts of hydroxyethylstarch and albumin were infused. Serum creatinine, glomerular filtration rate, and cystatin C plasma levels were without significant differences between the groups. Concentrations of kidney-specific proteins were elevated at baseline and increased significantly after surgery without showing group differences. Urinary levels of neutrophil gelatinase-associated lipocalin increased more in the albumin- than in the hydroxyethylstarch-treated patients. None of the patients developed acute renal failure requiring renal replacement therapy during the hospital stay and thereafter. A hydroxyethylstarch preparation with a low molecular weight and a low molar substitution given in cardiac surgery patients with preoperative compromised kidney function did not negatively influence kidney integrity compared with a human albumin-based volume replacement strategy.

Effects of hydroxyethyl starch administration on renal function in critically ill patients

The influence of hydroxyethyl starch (HES) solutions on renal function is controversial. We investigated the effect of HES administration on renal function in critically ill patients enrolled in a large multicentre observational European study. All adult patients admitted to the 198 participating intensive care units (ICUs) during a 15-day period were enrolled. Prospectively collected data included daily fluid administration, urine output, sequential organ failure assessment (SOFA) score, serum creatinine levels, and the need for renal replacement therapy (RRT) during the ICU stay. Of 3147 patients, 1075 (34%) received HES. Patients who received HES were older [mean (SD): 62 (SD 17) vs 60 (18) years, P = 0.022], more likely to be surgical admissions, had a higher incidence of haematological malignancy and heart failure, higher SAPS II [40.0 (17.0) vs 34.7 (16.9), P < 0.001] and SOFA [6.2 (3.7) vs 5.0 (3.9), P < 0.001] scores, and less likely to be receiving RRT (2 vs 4%, P < 0.001) than those who did not receive HES. The renal SOFA score increased significantly over the ICU stay independent of the type of fluid administered. Although more patients who received HES needed RRT than non-HES patients (11 vs 9%, P = 0.006), HES administration was not associated with an increased risk for subsequent RRT in a multivariable analysis [odds ratio (OR): 0.417, 95% confidence interval (CI): 0.05-3.27, P = 0.406]. Sepsis (OR: 2.03, 95% CI: 1.37-3.02, P < 0.001), cardiovascular failure (OR: 6.88, 95% CI: 4.49-10.56, P < 0.001), haematological cancer (OR: 2.83, 95% CI: 1.28-6.25, P = 0.01), and baseline renal SOFA scores > 1 (P < 0.01 for renal SOFA 2, 3, and 4 with renal SOFA = 0 as a reference) were all associated with a higher need for RRT. In this observational study, haematological cancer, the presence of sepsis, cardiovascular failure, and baseline renal function as assessed by the SOFA score were independent risk factors for the subsequent need for RRT in the ICU. The administration of HES had no influence on renal function or the need for RRT in the ICU.

Influence of hydroxyethyl starch 130/0.4 in pulmonary neutrophil recruitment and acute lung injury during polymicrobial sepsis in rats

Acute lung injury (ALI) is a progressive syndrome associated with significant mortality in sepsis patients. Neutrophils are key cells in the inflammatory response that characterizes ALI. This study was designed to explore the effects of hydroxyethyl starch (HES) 130/0.4 (a novel plasma substitute) on pulmonary neutrophil recruitment and associated ALI in a rat sepsis model induced by cecal ligation and puncture (CLP). Animals were randomly assigned to six groups [saline control; CLP and saline; CLP and HES (7.5, 15 and 30 ml/kg); and HES control], subjected to CLP and infused with or without HES 130/0.4 4 h after CLP. Six hours later, the pulmonary capillary permeability (PCP), myeloperoxidase (MPO) activity, lung histological changes, tumor necrosis factor-alpha, interleukin-1beta and cytokine-induced neutrophil chemoattractant levels, P-selectin mRNA expression and nuclear factor-kappa B (NF-kappaB) activation were measured. Resuscitation with HES 130/0.4 significantly attenuated the CLP-induced increase in PCP, MPO activity, cytokine/chemokine levels, mRNA expression of P-selectin and NF-kappaB activation, all of which are involved in the recruitment of neutrophils. Groups receiving the higher doses of HES 130/0.4 (15 and 30 ml/kg) were more adequately resuscitated. HES 130/0.4 can inhibit CLP-induced neutrophil recruitment and subsequent ALI by attenuating cytokines/chemokines, adhesion molecule-mediated inflammation and NF-kappaB activation.

A new approach for freezing of aqueous solutions under active control of the nucleation temperature

An experimental setup for controlled freezing of aqueous solutions is introduced. The special feature is a mechanism to actively control the nucleation temperature via electrofreezing: an ice nucleus generated at a platinum electrode by the application of an electric high voltage pulse initiates the crystallization of the sample. Using electrofreezing, the nucleation temperature in pure water can be precisely adjusted to a desired value over the whole temperature range between a maximum temperature T n max close to the melting point and the temperature of spontaneous nucleation. However, the presence of additives can inhibit the nucleus formation. The influence of hydroxyethylstarch (HES), glucose, glycerol, additives commonly used in cryobiology, and NaCl on T n max were investigated. While the decrease showed to be moderate for the non-ionic additives, the hindrance of nucleation by ionic NaCl makes the direct application of electrofreezing in solutions with physiological salt concentrations impossible. Therefore, in the multi-sample freezing device presented in this paper, the ice nucleus is produced in a separate volume of pure water inside an electrode cap. This way, the nucleus formation becomes independent of the sample composition. Using electrofreezing rather than conventional seeding methods allows automated freezing of many samples under equal conditions. Experiments performed with model solutions show the reliability and repeatability of this method to start crystallization in the test samples at different specified temperatures. The setup was designed to freeze samples of small volume for basic investigations in the field of cryopreservation and freeze-drying, but the mode of operation might be interesting for many other applications where a controlled nucleation of aqueous solutions is of importance.

The influence of HES on the filtration properties of capillary membrane plasmaseparation.

Plasmaseparation is a treatment under discussion for critically ill patients, especially in sepsis and multiorgan failure. These patients receive a variety of different fluid substitutes, including hydroxyethylstarch (HES). HES is known to influence rheological properties, but nothing is known about the possible interactions between HES and the plamaseparation procedure. We used an in vitro plasmaseparation circuit with heparinized porcine blood. Before priming the system, 2 liters of blood were supplemented by adding 100 ml of either NaCl 0.9% or HES (n=6 in each group). We monitored the transmembrane (TMP) and the filtration pressure (PF) and measured free plasma hemoglobin (free Hb) and platelet counts before and after the two hours plasmaseparation procedure. The final transmembrane pressure was significantly higher with HES substitution. In the HES group we found negative filtration pressures from the very beginning with a significant further decrease toward the end of the experiments. A significant increase in free Hb and decrease in platelet counts were noted only in the HES group. Volume substitution with HES leads to impaired filtration properties and deteriorated hemocompatibility in in vitro plasmaseparation. Further studies have yet to evaluate whether or not the effects described also occur under clinical conditions.

The Effect of Hydroxyethyl Starch on Platelet Aggregation In Vitro

The effect of hydroxyethyl starch (HES) on hemostasis seems to be minimal when it is used in recommended amounts.A number of studies have investigated the effect of HES on platelet function when administered in vivo, but there has been no study investigating the effect on the isolated platelet function when administered in vitro. A photometrical method to assess platelet function in platelet-rich plasma (approximately 250 x 109 platelets/L) was used with platelet aggregation induced using either collagen, epinephrine, adenosine diphosphate, or ristocetin. We found a dose-dependent decrease of platelet aggregation in vitro with either collagen or epinephrine, but not with adenosine diphosphate or ristocetin. However, the changes of HES on platelet aggregation were detected only in doses larger than those routinely used in the clinical setting. Therefore, we conclude that the influence of HES at the recommended doses on initial platelet aggregation may not be clinically relevant. Implications: The effect of hydroxyethyl starch on platelet function and coagulation is discussed. This study showed no influence on platelets in clinically relevant doses in an in vitro model. (Anesth Analg 1998;86:1318-21)

The effect of hydroxyethyl starch on platelet aggregation in vitro.

The effect of hydroxyethyl starch (HES) on hemostasis seems to be minimal when it is used in recommended amounts. A number of studies have investigated the effect of HES on platelet function when administered in vivo, but there has been no study investigating the effect on the isolated platelet function when administered in vitro. A photometrical method to assess platelet function in platelet-rich plasma (approximately 250 x 10(9) platelets/L) was used with platelet aggregation induced using either collagen, epinephrine, adenosine diphosphate, or ristocetin. We found a dose-dependent decrease of platelet aggregation in vitro with either collagen or epinephrine, but not with adenosine diphosphate or ristocetin. However, the changes of HES on platelet aggregation were detected only in doses larger than those routinely used in the clinical setting. Therefore, we conclude that the influence of HES at the recommended doses on initial platelet aggregation may not be clinically relevant. The effect of hydroxyethyl starch on platelet function and coagulation is discussed. This study showed no influence on platelets in clinically relevant doses in an in vitro model.

Influence of hydroxyethylstarch and dextran on TNF-α-production and procoagulant activity of monocytes in vitro

Our results show no influence of both artifical colloids, HES and DX, on the PBMC's basal or LPS-stimulated in-vitro cytocine production and TF-expression. The data give no evidence that LPS-signal-transduction by MNC's is impaired by HES or DX.

Influence of hydroxyethyl starch on humoral and cell‐mediated immune responses in mice

The immunotoxicity of hydroxyethyl starch (HES), a reagent used in leukocytapheresis or as a plasma expander, was assessed. HES did not significantly alter host resistance to Listeria monocytogenes or Streptococcus pneumoniae. HES (4-32 ml/kg), as well as a physiological saline solution (32 ml/kg), did inhibit the in vitro lymphoproliferation of spleen cells from mice intravenously injected 1 hour prior to removal of the spleens; the proliferation induced by a T-cell and B-cell mitogen was suppressed. However, this suppression was transient, in that, HES and saline injections given 4 and 24 hours prior to removal of the spleens produced no significant inhibition. Unlike the HES effects on lymphoproliferation, HES did suppress the in vivo humoral immune response to sheep erythrocytes (SRBC) when given 24 hours prior to antigen, but this inhibition was obtained only with the 32 ml per kg dose. Interestingly, a similar dose of mouse albumin significantly enhanced the response. In vitro analysis of humoral and cell-mediated immune responsiveness with in vivo treated spleen cells produced results that were not dose dependent. Although HES was more suppressive than saline, both saline and HES were inhibitory. The lack of a dose-dependent effect suggests that the in vitro analysis of in vivo treated cells was not a good index of their in vivo reactivities. The greater variability and apparent sensitivity of the in vitro analysis probably reflect the transient effects of in vivo dilution of serum factors by relatively large intravenous injections and/or the transient effects of injection trauma.

The influence of hydroxyethyl starch on ice formation in aqueous solutions

Differential scanning calorimetry, and, in some supplementary experiments, X-ray diffractometry and cryomicroscopy, were applied to study the influence of concentration (< 70 wt%) and cooling/warming rates (< 320 K/min) on ice formation in aqueous solutions of HES. The calorimetric measurements of the quantity of crystallizing water indicated that a mass fraction ϑ = 0.522 (i.e., grams water per gram HES) remained unfrozen. These results are in good agreement with our earlier extrapolations from ternary phase diagram data and tend to support the proposed cryoprotective mechanism. The value of ϑ determined during warming was essentially independent of composition up to the corresponding saturation concentration. It was observed that solutions containing 60 wt% HES or more remained wholly amorphous during cooling even at rates as low as 2.5 K/min (down to 120 K). Such glassy solutions are subject to devitrification at temperatures T d which depend on the warming rate. The concentrations close to 55 wt% HES mark a transitional range exhibiting two crystallization peaks, probably due to different mechanisms of nucleation, the portion of ice formed during cooling being related to the imposed cooling rate. All samples showed a recrystallization transition at 257.5 K which was also observed cryomicroscopically. Glass transitions, however, could not be detected by the methods applied in this study. The X-ray diffraction patterns contained the structure of only one solid phase, namely hexagonal ice. A comparison of various modifications of HES, PEG, and PVP involving bound water and melting temperature did not reveal marked differences. Minimum initial HES concentrations preventing lethal salt enrichment were computed for both binary and ternary mass fractions of NaCl as biologically relevant parameters, yielding 24.1 and 10.8 wt% HES, respectively.