Albumin and Hydroxyethyl Starch Modulate Oxidative Inflammatory Injury to Vascular Endothelium

Background: Human serum albumin is used clinically to maintain colloid osmotic pressure and is viewed to serve an antioxidant role in the vascular compartment via binding of redox-active metal complexes, transport of nitric oxide, and the oxidant-scavenging reactions of the single thiol of human serum albumin, cys34. Because of these potentially desirable adjunctive actions, we evaluated the purity and thiol redox state and compared the relative effects of clinically available 25% human serum albumin preparations with a starch-derived colloid, 6% hydroxyethyl starch, in in vitro models of inflammatory vascular injury.

Methods: Bovine aortic endothelial cell responses to chemical, enzymatic, and cell-derived reactive inflammatory mediators in the presence of human serum albumin or hydroxyethyl starch were assessed.

Results: The cys34 thiol of fresh human serum albumin preparations was 70-85% oxidized and contained a population of human serum albumin (approximately 25% of total) having the cys34 resistant to reduction by 2-mercaptoethanol and NaBH4. Treatment of bovine aortic endothelial cells with human serum albumin dose-dependently protected from HOCl-mediated 14C-adenine release, with this protective effect of human serum albumin not dependent on protein thiol status. Addition of human serum albumin to cell media provided no protection from the cytotoxic actions of peroxynitrite and xanthine oxidase-derived reactive species. Binding of activated polymorphonuclear leukocytes to bovine aortic endothelial cells was significantly amplified by hydroxyethyl starch and inhibited by human serum albumin administration. The binding of neutrophil-derived myeloperoxidase to bovine aortic endothelial cells, a mediator of multiple oxidative and nitric oxide-consuming reactions, was also inhibited by human serum albumin and enhanced by hydroxyethyl starch.     

Contrasting effects of colloid and crystalloid resuscitation fluids on cardiac vascular permeability

BACKGROUND: Fluid extravasation may lead to myocardial edema and consequent reduction in ventricular function. Albumin is presumed to interact with the endothelial glycocalyx. The authors' objective was to compare the impact of different resuscitation fluids (human albumin, hydroxyethyl starch, saline) on vascular integrity. METHODS: In an isolated perfused heart model (guinea pig), Krebs-Henseleit buffer was augmented with colloids (one third volume 5% albumin or 6% hydroxyethyl starch 130/0.4) or crystalloid (0.9% saline). Perfusion pressure and vascular fluid filtration (epicardial transudate formation) were assessed at different flow rates. After global, stopped-flow ischemia (37 degrees C, 20 min), hearts were reperfused with the same resuscitation fluid additives. In a second series, the authors applied the respective perfusates after enzymatic digestion of the endothelial glycocalyx (heparinase, 10 U over 15 min). RESULTS: Both 5% albumin and 6% hydroxyethyl starch decreased fluid extravasation versus saline (68.4 +/- 5.9, 134.8 +/- 20.5, and 436.8 +/- 14.7 microl/min, respectively, at 60 cm H(2)O perfusion pressure; P < 0.05), the corresponding colloid osmotic pressures being 2.95, 5.45, and 0.00 mmHg. Digestion of the endothelial glycocalyx decreased coronary integrity in both colloid groups. After ischemia, a transient increase in vascular leak occurred with Krebs-Henseleit buffer containing hydroxyethyl starch and saline, but not with albumin. The authors observed no difference between intravascular and bulk interstitial colloid concentration in the steady state. Notwithstanding, electron microscopy revealed an intact endothelial glycocalyx and no interstitial edema in the albumin group. CONCLUSION: Ex vivo, albumin more effectively prevented fluid extravasation in the heart than crystalloid or artificial colloid. This effect was partly independent of colloid osmotic pressure and may be attributable to an interaction of albumin with the endothelial glycocalyx.     

Contrasting Effects of Colloid and Crystalloid Resuscitation Fluids on Cardiac Vascular Permeability

Background: Fluid extravasation may lead to myocardial edema and consequent reduction in ventricular function. Albumin is presumed to interact with the endothelial glycocalyx. The authors' objective was to compare the impact of different resuscitation fluids (human albumin, hydroxyethyl starch, saline) on vascular integrity.

Methods: In an isolated perfused heart model (guinea pig), Krebs-Henseleit buffer was augmented with colloids (one third volume 5% albumin or 6% hydroxyethyl starch 130/0.4) or crystalloid (0.9% saline). Perfusion pressure and vascular fluid filtration (epicardial transudate formation) were assessed at different flow rates. After global, stopped-flow ischemia (37[degrees]C, 20 min), hearts were reperfused with the same resuscitation fluid additives. In a second series, the authors applied the respective perfusates after enzymatic digestion of the endothelial glycocalyx (heparinase, 10 U over 15 min).

Results: Both 5% albumin and 6% hydroxyethyl starch decreased fluid extravasation versus saline (68.4 +/- 5.9, 134.8 +/- 20.5, and 436.8 +/- 14.7 [mu]l/min, respectively, at 60 cm H2O perfusion pressure; P < 0.05), the corresponding colloid osmotic pressures being 2.95, 5.45, and 0.00 mmHg. Digestion of the endothelial glycocalyx decreased coronary integrity in both colloid groups. After ischemia, a transient increase in vascular leak occurred with Krebs-Henseleit buffer containing hydroxyethyl starch and saline, but not with albumin. The authors observed no difference between intravascular and bulk interstitial colloid concentration in the steady state. Notwithstanding, electron microscopy revealed an intact endothelial glycocalyx and no interstitial edema in the albumin group.     

Endothelial Glycocalyx as an Additional Barrier Determining Extravasation of 6% Hydroxyethyl Starch or 5% Albumin Solutions in the Coronary Vascular Bed

Background: The impact on the endothelial glycocalyx for the extravasation of colloidal infusion solutions has not been investigated sufficiently.

Methods: Isolated guinea pig hearts were perfused with Krebs-Henseleit buffer in a Langendorff mode. Solutions of 0.9% saline, 5% albumin (70 kd), or 6% hydroxyethyl starch (200 kd) were infused into the coronary system for 20 min at a rate of one third of the coronary flow, also during reperfusion after 15 min of ischemia, and after enzymatic digestion of the endothelial glycocalyx by heparinase. Net coronary fluid filtration was assessed directly by measuring the formation of transudate on the epicardial surface, and solute extravasation was assessed by measuring albumin and hydroxyethyl starch in the coronary effluent and transudate. Hearts were perfusion fixed to visualize the endothelial glycocalyx using transmission electron microscopy.

Results: Only infusion of hydroxyethyl starch, not infusion of albumin, significantly decreased net coronary fluid filtration. Heparinase application without ischemia increased coronary leak by 25% but did not accelerate the passage of colloids. Ischemia alone did not alter permeability. However, there was a large (approximately +200%), transient (approximately 4 min) increase in permeability for water, albumin, and hydroxyethyl starch after ischemia with heparinase application. Also, histamine (10-6m) only increased permeability after pretreatment of the hearts with heparinase. The thickness of the glycocalyx after colloid administration was 0.2-0.3 [mu]m. No glycocalyx could be detected after application of heparinase.     

Acid-base changes caused by 5% albumin versus 6% hydroxyethyl starch solution in patients undergoing acute normovolemic hemodilution: a randomized prospective study

BACKGROUND: Preoperative acute normovolemic hemodilution (ANH) is an excellent model for evaluating the effects of different colloid solutions that are free of bicarbonate but have large chloride concentrations on acid-base equilibrium. METHODS: In 20 patients undergoing gynecologic surgery, ANH to a hematocrit of 22% was performed. Two groups of 10 patients each were randomly assigned to receive either 5% albumin or 6% hydroxyethyl starch solutions containing chloride concentrations of 150 and 154 mm, respectively, during ANH. Blood volume (double label measurement of plasma and red cell volumes), pH, Paco2, and serum concentrations of sodium, potassium, chloride, lactate, ionized calcium, phosphate, albumin, and total protein were measured before and 20 min after completion of ANH. Strong ion difference was calculated as serum sodium plus serum potassium minus serum chloride minus serum lactate. The amount of weak plasma acid was calculated using a computer program. RESULTS: After ANH, blood volume was well maintained in both groups. ANH caused slight metabolic acidosis with hyperchloremia and a concomitant decrease in strong ion difference. Plasma albumin concentration decreased after hemodilution with 6% hydroxyethyl starch solution and increased after hemodilution with 5% albumin solution. Despite a three-times larger decrease in strong ion difference after ANH with 6% hydroxyethyl starch solution, the decrease in pH was nearly the same in both groups. CONCLUSIONS: ANH with 5% albumin or 6% hydroxyethyl starch solutions led to metabolic acidosis. A dilution of extracellular bicarbonate or changes in strong ion difference and albumin concentration offer explanations for this type of acidosis.     

Endothelial glycocalyx as an additional barrier determining extravasation of 6% hydroxyethyl starch or 5% albumin solutions in the coronary vascular bed

BACKGROUND: The impact on the endothelial glycocalyx for the extravasation of colloidal infusion solutions has not been investigated sufficiently. METHODS: Isolated guinea pig hearts were perfused with Krebs-Henseleit buffer in a Langendorff mode. Solutions of 0.9% saline, 5% albumin (70 kd), or 6% hydroxyethyl starch (200 kd) were infused into the coronary system for 20 min at a rate of one third of the coronary flow, also during reperfusion after 15 min of ischemia, and after enzymatic digestion of the endothelial glycocalyx by heparinase. Net coronary fluid filtration was assessed directly by measuring the formation of transudate on the epicardial surface, and solute extravasation was assessed by measuring albumin and hydroxyethyl starch in the coronary effluent and transudate. Hearts were perfusion fixed to visualize the endothelial glycocalyx using transmission electron microscopy. RESULTS: Only infusion of hydroxyethyl starch, not infusion of albumin, significantly decreased net coronary fluid filtration. Heparinase application without ischemia increased coronary leak by 25% but did not accelerate the passage of colloids. Ischemia alone did not alter permeability. However, there was a large (approximately +200%), transient (approximately 4 min) increase in permeability for water, albumin, and hydroxyethyl starch after ischemia with heparinase application. Also, histamine (10 m) only increased permeability after pretreatment of the hearts with heparinase. The thickness of the glycocalyx after colloid administration was 0.2-0.3 microm. No glycocalyx could be detected after application of heparinase. CONCLUSION: The endothelial glycocalyx acts as a competent barrier for water and colloids. Only after its destruction do changes in endothelial morphology (postischemic reperfusion or histamine application) become effective determinants of coronary extravasation.     

Acid-Base Changes Caused by 5% Albumin versus 6% Hydroxyethyl Starch Solution in Patients Undergoing Acute Normovolemic Hemodilution: A Randomized Prospective Study

Background: Preoperative acute normovolemic hemodilution (ANH) is an excellent model for evaluating the effects of different colloid solutions that are free of bicarbonate but have large chloride concentrations on acid-base equilibrium.

Methods: In 20 patients undergoing gynecologic surgery, ANH to a hematocrit of 22% was performed. Two groups of 10 patients each were randomly assigned to receive either 5% albumin or 6% hydroxyethyl starch solutions containing chloride concentrations of 150 and 154 mm, respectively, during ANH. Blood volume (double label measurement of plasma and red cell volumes), pH, Paco2, and serum concentrations of sodium, potassium, chloride, lactate, ionized calcium, phosphate, albumin, and total protein were measured before and 20 min after completion of ANH. Strong ion difference was calculated as serum sodium plus serum potassium minus serum chloride minus serum lactate. The amount of weak plasma acid was calculated using a computer program.

Results: After ANH, blood volume was well maintained in both groups. ANH caused slight metabolic acidosis with hyperchloremia and a concomitant decrease in strong ion difference. Plasma albumin concentration decreased after hemodilution with 6% hydroxyethyl starch solution and increased after hemodilution with 5% albumin solution. Despite a three-times larger decrease in strong ion difference after ANH with 6% hydroxyethyl starch solution, the decrease in pH was nearly the same in both groups.     

Calcium supplementation of saline-based colloids does not produce equivalent coagulation profiles to similarly balanced salt preparations

OBJECTIVES: The primary objective of this study was to test the hypothesis that calcium alone does not account for the observed coagulation differences between saline-based and balanced electrolyte IV fluid preparations. DESIGN: Controlled, nonblinded, in vitro observational study. SETTING: University-based anesthesia research laboratory. PARTICIPANTS: Ten healthy volunteers. INTERVENTIONS: The volunteers donated fresh blood for in vitro 40% and 60% dilution with 6 intravenous fluid preparations (lactated Ringer's solution, human albumin solution, and 4 hydroxyethyl starch preparations). All saline-based fluids were supplemented with calcium chloride to obtain ionized concentrations >or=1.0 mmol/L. MEASUREMENTS AND MAIN RESULTS: After dilution of the fresh blood with the study fluids, samples were analyzed by using the Thrombelastograph. Three colloid preparations produced minimal coagulation derangement, even at 60% dilution (human albumin solution, tetrastarch in saline, and pentastarch in balanced electrolyte solution), whereas pentastarch in saline and hetastarch in balanced electrolyte produced a mildly hypocoagulable state at 60% dilution. CONCLUSIONS: The different coagulation profiles between the 2 pentastarch preparations, as well as similar profiles of pentastarch in saline and hetastarch in balanced electrolyte solution, suggest that calcium is not solely responsible for previously observed effects.     

Renal impact of fluid management with colloids: a comparative review

BACKGROUND AND OBJECTIVES: Colloids such as hydroxyethyl starch (HES), gelatin, dextran and albumin are useful for maintaining renal perfusion and function. The comparative renal effects of colloids have not been previously reviewed. METHODS: Computer searches of the MEDLINE and EMBASE bibliographic databases and the Cochrane Library were conducted using the search terms: colloids; hetastarch; gelatin; dextrans; serum albumin; kidney failure; cardiac surgical procedures; and kidney transplantation. Relevant studies were also sought through hand searching and examination of reference lists. Results of identified studies were qualitatively summarized with account taken for potential confounding factors. RESULTS: The three artificial colloids HES, gelatin and dextran all exhibited troublesome renal side-effects. Randomized trials have demonstrated adverse renal effects of HES in sepsis and surgery. Undesirable renal effects are common to all available HES solutions regardless of molecular weight, substitution or C2/C6 ratio. While some of its effects may be less severe than those of HES, gelatin also can adversely affect the kidney. A negative renal impact of dextran is well-established, although this colloid is now less extensively used than formerly. As the normal endogenous colloid, albumin exhibits a wide margin of renal safety, although albumin overdose needs to be avoided. Albumin also appears to exert protective effects on the kidney such as inhibition of apoptosis and scavenging of reactive oxygen species. CONCLUSIONS: Colloids display important differences in their actions on the kidney. These contrasting renal effects should be considered in making fluid management decisions.     

Albumin, HES 120 and dextran 70 as adjuvants to red blood cell concentrates: a study on colloid osmotic pressure changes in vitro

An in vitro model of surgical bleeding was developed to simulate continuous blood loss and replacement therapy with plasma substitutes and red cell concentrates. The model was used to determine the lowest colloid concentration in vitro for each of the plasma substitutes that sustains colloid osmotic pressure above 2.4 kPa (or 18 mmHg) when used up to the recommended maximal total dose. Plasma, supernatant separated from red cell concentrates and dextran 70, hydroxyethyl starch 120 or albumin were mixed to create dilutions imitating plasma composition in the course of clinical blood loss and replacement therapy. The relative volume of each component was calculated according to the model when the bleeding was equal to multiples of 10% of blood volume up to a blood loss of 120%. Our measurements indicate that the colloid concentrations of 5.0% for albumin, 4.0% for hydroxyethyl starch 120 and 3.5% for dextran 70 preserve colloid osmotic pressure above 2.4 kPa.     

Colloid osmotic pressure of plasma replacement fluids

Colloid osmotic pressure (COP) of some of the most frequently used plasma replacement fluids was measured with a colloid osmometer. COP of 4% human albumin solutions was only half that of normal human serum (13.6±0.6 vs. 27.5 ± 2.7 mmHg (1.8±0.1 vs. 3.7±0.4 kPa)) (mean±s.d.), whereas COP of 20% human albumin solutions was eight times higher (196.0±12.3 mmHg (26.1 ± 1.6 kPa)). Enhancing the protein concentration from 4% to 20% in the human albumin solutions increased COP 14-fold, reflecting the exponential relationship between protein concentration and COP of a solution. Fresh donor plasma furnished by the hospital blood-bank had a COP about 30% below normal human serum (18.1 ± 1.3 mmHg (2.4 ± 0.2 kPa)), due to dilution during preparation. Dextran 70 (6%) had a COP more than twice, and RingerDextran 60 (3%) about 75% of that of normal human serum. Dextran 40 (10%) and gelatin (3.5%, Haemaccel) leaked markedly through the membrane of the colloid osmometer, making acceptable measurements impossible. Seven different hydroxyethyl starch (HES) solutions were measured, and the COP varied between half and 3 times that of normal human serum, depending on molecular weight and concentration of the HES.     

A systematic review of the comparative safety of colloids

HYPOTHESIS: Safety differences exist among colloids widely used for fluid management in acutely ill patients, as judged according to the comparative incidence of adverse events. DATA SOURCES: Colloid safety data for human subjects were sought, without language or time period restrictions, by means of computer searches of bibliographic and clinical trial databases, hand searches of medical journals and Index Medicus, inquiries with investigators and colloid suppliers, and examination of reference lists. Search terms included "colloids", "morbidity", and "mortality". STUDY SELECTION: Controlled trials, cohort studies, pharmacovigilance studies, and prior meta-analyses were independently selected by 2 unblinded investigators. Of 189 candidate studies, 113 were included, with safety data encompassing 1.54 x 10(6) patients and 1.09 x 10(8) colloid infusions. DATA EXTRACTION: Two unblinded investigators independently extracted data. Study limitations and confounding factors were tabulated. DATA SYNTHESIS: With albumin as the reference colloid, the incidence rate ratio for anaphylactoid reactions was 4.51 (95% confidence interval, 2.06-9.89) after hydroxyethyl starch administration, 2.32 (95% confidence interval, 1.21-4.45) after dextran, and 12.4 (95% confidence interval, 6.40-24.0) after gelatin. Pruritus occurrence was significantly increased by hydroxyethyl starch exposure (odds ratio, 1.78; 95% confidence interval, 1.23-2.58). Artificial colloid administration was consistently associated with coagulopathy and clinical bleeding, most frequently in cardiac surgery patients receiving hydroxyethyl starch. On the basis of large-scale pharmacovigilance study results, albumin infusion resulted in a low rate of both total adverse events (3.1 to 8.6 per 10(5) infusions) and serious adverse events (1.29 per 10(6) infusions). CONCLUSIONS: Significant safety differences exist among colloids. Therefore, conclusions regarding the clinical usefulness of colloids as a fluid class should be formed with caution.     

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

OBJECTIVE: Hypothermic cardiopulmonary bypass is associated with increased fluid extravasation. This study aimed to compare whether iso-oncotic priming solutions, in contrast to crystalloids, could reduce the cold-induced fluid extravasation during cardiopulmonary bypass in piglets. METHODS: Three groups were studied: the control group (CT group; n = 10), the albumin group (Alb group; n = 7), and the hydroxyethyl starch group (HES group; n = 7). Prime (1000 mL) and supplemental fluid were acetated Ringer solution, 4% albumin, and 6% hydroxyethyl starch, respectively. After 1 hour of normothermic cardiopulmonary bypass, hypothermic cardiopulmonary bypass (cooling to 28 degrees C within 15 minutes) was initiated and continued to 90 minutes. Fluid needs, plasma volume, changes in colloid osmotic pressure in plasma and interstitial fluid, hematocrit levels, and tissue water content were recorded, and protein masses and fluid extravasation rates were calculated. RESULTS: Colloid osmotic pressure in plasma decreased immediately after the start of cardiopulmonary bypass in the CT group but remained stable in the Alb and HES groups. Colloid osmotic pressure in interstitial fluid tended to decrease in the CT group and remained unchanged in the Alb group, whereas a slight increase was observed in the HES group. Immediately after the start of cooling, fluid extravasation rates increased from 0.15 +/- 0.10 to 0.64 +/- 0.12 mL . kg -1 . min -1 in the CT group, whereas no such increase was observed in the Alb and HES groups. The changes in fluid extravasation rates were reflected by corresponding changes in tissue water content. CONCLUSION: The use of albumin or hydroxyethyl starch as prime to preserve the colloid osmotic pressure during cardiopulmonary bypass causes a reduction in the cold-induced fluid extravasation compared with that seen with crystalloids. Albumin seems more effective than hydroxyethyl starch to limit cold-induced fluid shifts during cardiopulmonary bypass.     

Effect of 6% hydroxyethyl starch 130/0.4 on kidney and haemostatic function in cardiac surgical patients: a randomised controlled trial

Whether third-generation hydroxyethyl starch solutions provoke kidney injury or haemostatic abnormalities in patients having cardiac surgery remains unclear. We tested the hypotheses that intra-operative administration of a third-generation starch does not worsen postoperative kidney function or haemostasis in cardiac surgical patients compared with human albumin 5%. This triple-blind, non-inferiority, clinical trial randomly allocated patients aged 40–85 who underwent elective aortic valve replacement, with or without coronary artery bypass grafting, to plasma volume replacement with 6% starch 130/0.4 vs. 5% human albumin. Our primary outcome was postoperative urinary neutrophil gelatinase-associated lipocalin concentrations, a sensitive and early marker of postoperative kidney injury. Secondarily, we evaluated urinary interleukin-18; acute kidney injury using creatinine RIFLE criteria, coagulation measures, platelet count and function. Non-inferiority (delta 15%) was assessed with correction for multiple comparisons. We enrolled 141 patients (69 starch, 72 albumin) as planned. Results of the primary analysis demonstrated that postoperative urine neutrophil gelatinase-associated lipocalin (median (IQR [range])) was slightly lower with hydroxyethyl starch (5 (1–68 [0–996]) ng.ml⁻¹) vs. albumin (5 (2–74 [0–1604]) ng.ml⁻¹), although not non-inferior [ratio of geometric means (95%CI) 0.91 (0.57, 1.44); p = 0.15] due to higher than expected variability. Urine interleukin-18 concentrations were reduced, but interleukin-18 and kidney injury were again not non-inferior. Of 11 individual coagulation measures, platelet count and function, nine were non-inferior to albumin. Two remaining measures, thromboelastographic R value and arachidonic acid-induced platelet aggregation, were clinically similar but with wide confidence intervals. Starch administration during cardiac surgery produced similar observed effects on postoperative kidney function, coagulation, platelet count and platelet function compared with albumin, though greater than expected variability and wide confidence intervals precluded the conclusion of non-inferiority. Long-term mortality and kidney function appeared similar between starch and albumin.     

Relative purity of thrombin-based hemostatic agents used in surgery

BACKGROUND: Hemostatic agents used in surgery contain thrombin isolated from either a bovine or human source. The use of thrombin derived from a bovine source has been associated with the development of an abnormal immune response, but a study of the immunoreactivity of the various commercially available thrombin preparations has not been conducted. This study determined the relative purity of commercially available thrombin preparations, if humans have natural antibodies that recognize these preparations, and if elicited antibodies against bovine thrombin cross-react with other bovine or human hemostatic agents. STUDY DESIGN: The purity of hemostatic agents was determined by protein and substrate assays, electrophoresis, and immunoblotting. The natural antigenicity and cross-reactivity of elicited antibodies were measured by ELISA using serum samples from 82 donors from the Red Cross and serum collected from patients exposed to bovine thrombin, respectively. RESULTS: All of the bovine thrombin preparations were found to contain the xenogeneic carbohydrate galactosealpha1-3galactose. The natural antigenicity of the bovine thrombin preparations was greater than that of a human thrombin preparation and similar to that of porcine aortic endothelial cells. Antibodies elicited against bovine thrombin were found to cross-react with other bovine preparations and other xenoantigens but not with human hemostatic preparations. CONCLUSIONS: All patients have antibovine thrombin antibodies, even before exposure to bovine thrombin-containing hemostatic agents. The cross-reactivity of elicited antibovine thrombin antibodies indicates that if a patient has been sensitized to a bovine product, it is likely safer to use a human-derived product in lieu of a bovine product.     

Replacement of major surgical blood loss by hypo-oncotic or conventional plasma substitutes

The purpose of the study was to examine the effects of hypooncotic 4% hydroxyethyl starch 120/0.7, 3% dextran 70, 5% albumin and hyperoncotic 6% hydroxyethyl starch 120/0.7 on the perioperative colloid osmotic pressure (COP), albumin and protein concentrations and fluid balance.
The plasma substitutes were used with red cell concentrates to replace blood loss with equal volume in sixty major abdominal or urological surgeries. A special effort was made to keep replacements and losses at even volumes constantly and to avoid fluctuation of blood volume. The blood specimen were obtained before induction, after each 20% blood loss, at the end of the recovery room phase and on the three following postoperative mornings.
There were significant differences in the peroperative and immediate postoperative COPs. However, these differences had vanished by the first postoperative morning. COP was preserved above 16 mmHg in all groups throughout the study. The identical peroperative albumin and protein concentrations of the synthetic colloid groups suggests that their volume effect was the same, regardless of the varying COP. During the observation period there were no significant differences among the groups concerning the diuresis and the fluid balances. We conclude, that the hypooncotic 4% HES 120 and 3% dextran 70 solutions provide the same clinical effect as 6% HES 120 solution. Consequently less colloid is needed, which allows the use of greater volumes of the dilute colloid solutions in replacement therapy.     

Effects of physiologic albumin and hespan levels on hepatocytes in vitro

BACKGROUND: Although albumin and hydroxyethyl starch (HES) are routinely used in critically ill, hypoalbuminemic patients, no studies have tested the effect of supplemental albumin and HES on hepatocyte function. METHODS: In this study, the effects of these agents were evaluated by using stable, rat hepatocyte cultures in a collagen sandwich configuration. Hepatocyte synthesis of albumin, urea, and intracellular triglycerides was monitored in Dulbecco's modified Eagle medium (supplemented with fetal bovine serum, hydrocortisone, L-proline, gentamycin, and insulin) without supplemental colloid (control cultures) and with supplemental 2% bovine serum albumin (BSA), 4% BSA, 2% HES, or 4% HES. RESULTS: The albumin secretion in control cultures rose from 31.03 microg/day per 10(6) cells on day 3 to 154.17 microg/day per 10(6) cells by day 12 and remained constant. In contrast, the level of albumin synthesis in the 2% and 4% BSA groups rose from significantly higher initial values (p < 0.05) of 71.25 microg/day per 10(6) cells and 73.27 microg/day per 10(6) cells, respectively, to 127.61 microg/day per 10(6) cells and 107.95 microg/day per 10(6) cells by day 7, then declined rapidly to 58.98 microg/day per 10(6) cells and 41.28 microg/day per 10(6) cells by day 12 when cell disruption was present. HES also reduced albumin synthesis. The urea genesis in the control groups and in the treatment groups was found to be comparable throughout the study. The BSA supplemented groups accumulated large amounts of intracellular lipid droplets during the experiment. The intracellular triglycerides analysis found the 4% BSA group to be significantly (p < 0.05) higher than the 4% HES. CONCLUSION: BSA, added to a collagen sandwich hepatocyte preparation, causes reduced hepatocyte synthesis by day 8, probably a result of intracellular triglyceride accumulation, whereas HES reduces synthesis through unidentified mechanisms.     

Synthetic Colloids Attenuate Leukocyte-Endothelial Interactions by Inhibition of Integrin Function

Background: It has been suspected that synthetic colloids may interfere with leukocyte adhesion by down-regulation of endothelial cell adhesion molecules. Although inhibition of endothelial inflammation might reduce leukocyte-related tissue injury, the same mechanism may be detrimental for host defense during severe infection. Regarding the widespread use of colloids, the authors performed a laboratory investigation to determine the mechanisms by which synthetic colloids interfere with leukocyte-endothelial interactions.

Methods: Adhesion molecule expression on native and cytokine-activated endothelium from umbilical veins was measured after pretreatment with gelatin and various preparations of dextran or hydroxyethyl starch. Inhibition of neutrophil adhesion to activated endothelium was examined in a flow chamber by perfusion of untreated and colloid-treated neutrophils over colloid-pretreated endothelium at 2 dyn/cm2. Comparisons were made between untreated controls, colloid-pretreated endothelium, and colloid-cotreated neutrophils.

Results: Intercellular adhesion molecule 1, vascular cell adhesion molecule 1, E-selectin, and P-selectin were not attenuated by any colloid. Accordingly, colloid pretreatment of endothelium alone did not reduce neutrophil adhesion. In contrast, when neutrophils were cotreated by addition of colloids to the perfusate immediately before perfusion, adhesion decreased by 31-51% (P < 0.05) regardless of the colloid type. As indicated by the twofold increased rolling fractions, this reduction was due to an inhibition of neutrophil integrins.     

Hyperuricemia induces endothelial dysfunction

BACKGROUND: Hyperuricemia has been linked to cardiovascular and renal diseases, possibly through the generation of reactive oxygen species (ROS) and subsequent endothelial dysfunction. The enzymatic effect of xanthine oxidase is the production of ROS and uric acid. Studies have shown that inhibiting xanthine oxidase with allopurinol can reverse endothelial dysfunction. Furthermore, rat studies have shown that hyperuricemia-induced hypertension and vascular disease is at least partially reversed by the supplementation of the nitric oxide synthase (NOS) substrate, L-arginine. Therefore, we hypothesized that uric acid induces endothelial dysfunction by inhibiting nitric oxide production. METHODS: Hyperuricemia was induced in male Sprague-Dawley rats with an uricase inhibitor, oxonic acid, by gavage; control rats received vehicle. Allopurinol was placed in drinking water to block hyperuricemia. Rats were randomly divided into four groups: (1) control, (2) allopurinol only, (3) oxonic acid only, and (4) oxonic acid + allopurinol. Rats were sacrificed at 1 and 7 days, and their serum analyzed for serum uric acid and nitrites/nitrates concentrations. The effect of uric acid on nitric oxide production was also determined in bovine aortic endothelial cells. RESULTS: Oxonic acid induced mild hyperuricemia at both 1 and 7 days (P < 0.05). Allopurinol reversed the hyperuricemia at 7 days (P < .001). Serum nitrites and nitrates (NO(X)) were reduced in hyperuricemic rats at both 1 and 7 days (P < .001). Allopurinol slightly reversed the decrease in NO(X) at 1 day and completely at 7 days (P < .001). There was a direct linear correlation between serum uric acid and NO(X) (R(2)= 0.56) and a trend toward higher systolic blood pressure in hyperuricemic rats (P= NS). Uric acid was also found to inhibit both basal and vascular endothelial growth factor (VEGF)-induced nitric oxide production in bovine aortic endothelial cells. CONCLUSION: Hyperuricemic rats have a decrease in serum nitric oxide which is reversed by lowering uric acid levels. Soluble uric acid also impairs nitric oxide generation in cultured endothelial cells. Thus, hyperuricemia induces endothelial dysfunction; this may provide insight into a pathogenic mechanism by which uric acid may induce hypertension and vascular disease.     

Synthetic colloids attenuate leukocyte-endothelial interactions by inhibition of integrin function

BACKGROUND: It has been suspected that synthetic colloids may interfere with leukocyte adhesion by down-regulation of endothelial cell adhesion molecules. Although inhibition of endothelial inflammation might reduce leukocyte-related tissue injury, the same mechanism may be detrimental for host defense during severe infection. Regarding the widespread use of colloids, the authors performed a laboratory investigation to determine the mechanisms by which synthetic colloids interfere with leukocyte-endothelial interactions. METHODS: Adhesion molecule expression on native and cytokine-activated endothelium from umbilical veins was measured after pretreatment with gelatin and various preparations of dextran or hydroxyethyl starch. Inhibition of neutrophil adhesion to activated endothelium was examined in a flow chamber by perfusion of untreated and colloid-treated neutrophils over colloid-pretreated endothelium at 2 dyn/cm. Comparisons were made between untreated controls, colloid-pretreated endothelium, and colloid-cotreated neutrophils. RESULTS: Intercellular adhesion molecule 1, vascular cell adhesion molecule 1, E-selectin, and P-selectin were not attenuated by any colloid. Accordingly, colloid pretreatment of endothelium alone did not reduce neutrophil adhesion. In contrast, when neutrophils were cotreated by addition of colloids to the perfusate immediately before perfusion, adhesion decreased by 31-51% (P < 0.05) regardless of the colloid type. As indicated by the twofold increased rolling fractions, this reduction was due to an inhibition of neutrophil integrins. CONCLUSIONS: This study shows that synthetic colloids inhibit neutrophil adhesion by a neutrophil-dependent mechanism rather than interfering with endothelial cell activation. This suggests that inhibition of leukocyte sequestration by volume support is a common and transient phenomenon depending on the colloid concentration in plasma.