In vitro evaluation of the effect of profound haemodilution with hydroxyethyl starch 6%, modified fluid gelatin 4% and dextran 40 10% on coagulation profile measured by thromboelastography

Intravenous Fluid Administration and the Coagulation System

Intravenous fluid administration in veterinary patients can alter coagulation function by several mechanisms. Both crystalloid and colloid fluids cause hemodilution, reducing platelet count and plasma coagulation protein concentrations. Hemodilution is associated with a hypercoagulable effect at low dilutions and a hypocoagulable effect at higher dilutions. Composition of crystalloid fluids likely has a minor effect, primarily dependent on fluid ion composition. Hypertonic crystalloids may also cause hypocoagulability. Colloids, both synthetic and natural, can cause hypocoagulability by several mechanisms beyond the effects of hemodilution. These include impaired platelet function, decreased plasma coagulation factor activity, impaired fibrin formation and crosslinking, and accelerated fibrinolysis. The vast majority of the veterinary literature investigates the hypocoagulable effects of hydroxyethyl starch-containing fluids using in vitro, experimental, and clinical studies. However, results are inconsistent, likely due to the varying doses and physicochemical properties of the specific fluid products across studies. In addition, some evidence exists for hypocoagulable effects of gelatin and albumin solutions. There is also evidence that these colloids increase the risk of clinical bleeding in people. Limitations of the veterinary evidence for the hypocoagulable effects of colloid fluids include a predominance of in vitro studies and in vivo studies using healthy subjects, which exclude the interaction of the effects of illness. Therefore, clinical relevance of these effects, especially for low-molecular-weight hydroxyethyl starch, is unknown. Firm recommendations about the most appropriate fluid to use in clinical scenarios cannot be made, although it is prudent to limit the dose of synthetic colloid in at-risk patients. Clinicians should closely monitor relevant coagulation assays and for evidence of hemorrhage in at-risk patients receiving any type of fluid therapy, especially in large volumes.

Resuscitation Strategies for the Small Animal Trauma Patient

Traumatic injuries in small animals are a common cause for presentation to emergency departments. Severe traumatic injury results in a multitude of systemic responses, which can exacerbate initial tissue damage. Trauma resuscitation should focus on the global goals of controlling hemorrhage, improving tissue hypoperfusion, and minimizing ongoing inflammation and morbidity through the concept of "damage-control resuscitation." This approach focuses on the balanced use of blood products, hemorrhage control, and minimizing aggressive crystalloid use. Although these tenets may not be directly applicable to every veterinary patient with trauma, they provide guidance when managing the most severely injured subpopulation of these patients.

Haemostatic resuscitation in trauma: the next generation

PURPOSE OF REVIEW

To discuss the recent developments in and evolvement of next generation haemostatic resuscitation in bleeding trauma.

RECENT FINDINGS

Mortality from major trauma is a worldwide problem, and massive haemorrhage remains a major cause of potentially preventable deaths. Development of coagulopathy further increases trauma mortality emphasizing that coagulopathy is a key target in the phase of bleeding. The pathophysiology of coagulopathy in trauma reflects at least three distinct mechanisms that may be present isolated or coexist: acute traumatic coagulopathy, coagulopathy associated with the lethal triad, and consumptive coagulopathy. The concepts of 'damage control surgery' and 'damage control resuscitation' have been developed to ensure early control of bleeding and coagulopathy to improve outcome in bleeding trauma. Haemostatic resuscitation aims at controlling coagulopathy and consists of a ratio driven strategy aiming at 1 : 1 : 1, using tranexamic acid according to CRASH-2, and applying haemostatic monitoring enabling a switch to a goal-directed approach when bleeding slows. Haemostatic resuscitation is the mainstay of trauma resuscitation and is associated with improved survival.

SUMMARY

The next generation of haemostatic resuscitation aims at applying a ratio 1 : 1 : 1 driven strategy while using antifibrinolytics, haemostatic monitoring and avoiding critical fibrinogen deficiency by substitution.

In vitro evaluation of the effect of haemodilution with dextran 40 on coagulation profile as measured by thromboelastometry and multiple electrode aggregometry

We evaluated the effects of haemodilution with either dextran 40 or 0.9% normal saline on coagulation in vitro using rotational thromboelastometry (ROTEM®, Pentapharm Co., Munich, Germany) and multiple electrode aggregometry (Multiplate® Platelet Function Analyser, Dynabyte, Munich, Germany). Venous blood samples obtained from 20 healthy volunteers were diluted in vitro with dextran 40 or normal saline by 5%, 10% and 15%. Fibrinogen concentration, ROTEM-EXTEM® (screening test for the extrinsic coagulation pathway), FIBTEM® (an EXTEM-based assay of the fibrin component of clot) parameters including coagulation time, clot formation time, alpha angle, maximum clot firmness and lysis index were measured in the undiluted sample and at each level of haemodilution. Dextran 40 at 15% haemodilution significantly prolonged coagulation time, clot formation time and significantly decreased the alpha angle and maximal clot firmness (EXTEM amplitude at five minutes [A5] and ten minutes [A10]) compared with normal saline. The FIBTEM assay (maximal clot firmness and FIBTEM A5 and A10) showed a marked decrease in maximal clot firmness at all dilutions suggesting impaired fibrinogen activity and a risk of bleeding. Multiple electrode aggregometry did not demonstrate any platelet dysfunction. Haemodilution with dextran 40 causes significant impairment in clot formation and strength compared to saline haemodilution and undiluted blood. At the levels of in vitro haemodilution designed to reflect the clinical use of dextran infusions, no significant fibrinolysis or platelet inhibition was observed.

Safety of gelatin solutions for the priming of cardiopulmonary bypass in cardiac surgery: a systematic review and meta-analysis

This systematic review and meta-analysis was conducted to evaluate the safety of gelatin versus hydroxyethyl starches (HES) and crystalloids when used for cardiopulmonary bypass (CPB)-priming in cardiac surgery. MEDLINE (Pubmed), Embase and CENTRAL were searched. We included only randomized, controlled trials comparing CPB-priming with gelatin with either crystalloids or HES-solutions of the newest generation. The primary endpoint was the blood loss during the first 24 hours. Secondary outcomes included perioperative transfusion requirements, postoperative kidney function, postoperative ventilation times and length of stay on the intensive care unit. Sixteen studies were identified, of which only ten met the inclusion criteria, representing a total of 824 adult patients: 4 studies compared gelatin with crystalloid, and 6 studies gelatin with HES priming. Only 2 of the studies comparing HES and gelatin reported postoperative blood loss after 24 hours. No significant difference in postoperative blood loss was found when results of both studies were pooled (SMD -0.12; 95% CI: -0.49, 0.25; P=0.52). Likewise, the pooled results of 3 studies comparing gelatin and crystalloids as a priming solution could not demonstrate significant differences in postoperative bleeding after 24 hours (SMD -0.07; 95% CI: -0.40, 0.26; P=0.68). No differences regarding any of the secondary outcomes could be identified. This systematic review suggests gelatins to have a safety profile which is non-inferior to modern-generation tetrastarches or crystalloids. However, the grade of evidence is rated low owing to the poor methodological quality of the included studies, due to inconsistent outcome reporting and lack of uniform endpoint definitions.

Effects of in vitro hemodilution with crystalloids, colloids, and plasma on canine whole blood coagulation as determined by kaolin-activated thromboelastography

OBJECTIVE

To investigate the effects of in vitro hemodilution with lactated Ringers solution (LRS), hetastarch (HES), and fresh frozen plasma (FFP) on whole blood coagulation in dogs as assessed by kaolin-activated thromboelastography.

DESIGN

In vitro experimental study.

SETTING

University teaching hospital.

ANIMALS

Six healthy client-owned dogs.

INTERVENTIONS

Whole blood was collected and diluted in vitro at a 33% and 67% dilution with either LRS, HES, or FFP.

MEASUREMENTS AND MAIN RESULTS

Kaolin-activated thromboelastography was performed on each sample as well as a control. Thromboelastographic parameters R (min), alpha (deg), K (min), and MA (mm) were measured and compared to the sample control for each dilution using mixed model methodology. Prolongation in coagulation times were seen at both dilutions with LRS and HES. There was no significant difference in R times at the 33% dilution, but R time was significantly prolonged at the 67% dilution with HES (P = 0.004). MA was significantly decreased for LRS at both dilutions (P = 0.013, P < 0.001) and more profoundly decreased for HES (P < 0.001, P = 0.006). No significant difference in any parameter was found for FFP.

CONCLUSIONS

In vitro hemodilution of whole blood with both LRS and HES but not FFP resulted in significant effects on coagulation with HES having a more profound effect. In vivo evaluation of changes in coagulation with various resuscitation fluids is warranted and may be clinically relevant.

In vitro evaluation of canine hemostasis following dilution with hydroxyethyl starch (130/0.4) via thromboelastometry

OBJECTIVE

To assess the effects of in vitro hemodilution of canine blood with a low molecular weight hy-droxyethyl starch (HES 130/0.4) by means of thromboelastometry (TEM).

DESIGN

In vitro experimental study.

SETTING

University Teaching Hospital.

ANIMALS

Ten healthy adult staff-owned dogs were sampled for the purposes of the study. Samples were also collected from 45 clinically normal dogs to establish thromboelastometric reference intervals.

INTERVENTIONS

For each dog whole blood was collected by jugular venipuncture and placed into tubes containing 3.8% trisodium citrate and stored at 37°C. Two standard dilutions (1:4 and 1:10) from canine blood specimens were prepared with HES 130/0.4 and saline 0.9%.

MEASUREMENTS AND MAIN RESULTS

The effects of dilution were studied by TEM. No statistically significant differences were observed between the TEM values of the control samples and the samples diluted with saline solution (ratio 1:10 and 1:4). In contrast, hypocoagulability was observed in the samples treated with HES 130/0.4, with more severe effects at 1:4 dilution than at 1:10 dilution. The 1:4 dilution with HES 130/0.4 produced marked alterations: CT (P = 0.035) and CFT (P = 0.0007) on the ex-TEM profile, CT (P = 0.0005) and ML (P = 0.0017) on the fib-TEM profile and CFT (P = 0.0043) on the in-TEM, were all significantly increased (P < 0.05), whereas MCF (P = 0.0042) and alpha angle (P = 0.002) on the in-TEM and MCF (P = 0.011) and alpha angle (P = 0.001) ex-TEM profiles and MCF (P = 0.0001) on the fib-TEM profile were significantly decreased (P < 0.05).

CONCLUSIONS

Dilution of canine blood with HES 130/0.4 results in a thromboelastometric pattern consistent with hypocoagulation and this effect appears to result from a dose-dependent alteration in fibrinogen concentration and inhibition of platelet function. As this is an in vitro study, further in vivo investigations are necessary to confirm the results.

Current management of massive hemorrhage in trauma

Hemorrhage remains a major cause of potentially preventable deaths. Trauma and massive transfusion are associated with coagulopathy secondary to tissue injury, hypoperfusion, dilution, and consumption of clotting factors and platelets. Concepts of damage control surgery have evolved prioritizing early control of the cause of bleeding by non-definitive means, while hemostatic control resuscitation seeks early control of coagulopathy.Hemostatic resuscitation provides transfusions with plasma and platelets in addition to red blood cells in an immediate and sustained manner as part of the transfusion protocol for massively bleeding patients. Although early and effective reversal of coagulopathy is documented, the most effective means of preventing coagulopathy of massive transfusion remains debated and randomized controlled studies are lacking. Viscoelastical whole blood assays, like TEG and ROTEM however appear advantageous for identifying coagulopathy in patients with severe hemorrhage as opposed the conventional coagulation assays.In our view, patients with uncontrolled bleeding, regardless of it's cause, should be treated with hemostatic control resuscitation involving early administration of plasma and platelets and earliest possible goal-directed, based on the results of TEG/ROTEM analysis. The aim of the goal-directed therapy should be to maintain a normal hemostatic competence until surgical hemostasis is achieved, as this appears to be associated with reduced mortality.

Coagulopathy and hemostatic monitoring in cardiac surgery: an update

OBJECTIVES

Cardiac surgery with cardiopulmonary bypass (CPB) causes severe derangements in the hemostatic system, which in turn puts the patient at risks of microvascular bleeding. Excessive transfusion and surgical re-exploration after cardiac surgery are potentially associated with a number of adverse outcomes including increased mortality.

DESIGN

This review describes coagulopathies occurring in cardiac surgery and the monitoring of these. Viscoelastic hemostatic assays (VHA) have routinely been used in cardiac surgery for more than 25 years and at least 16 studies (involving more than 3250 patients, including three randomized controlled trials) have compared VHA to routine coagulation tests (RCoT) with regards to their ability to predict bleeding and re-do surgery and also with regards to transfusion requirements secondary to hemostatic therapy based on VHA vs. RCoT.

RESULTS

All 16 studies demonstrated superiority with VHA as compared to RCoT both in predicting bleeding and need for re-do surgery and in reducing the total amount of blood transfusions by employing goal-directed administration of blood products based on VHA as compared RCoT based therapy or at the clinicians discretion.

CONCLUSIONS

The different types of coagulopathies observed in patients undergoing cardiac surgery requires adequate and timely hemostatic therapy and real-time monitoring with WHA such as TEG/ROTEM and whole blood platelet aggregometry.

[Resuscitation damage control in the patient with severe trauma]

Severe trauma is the principle cause of death among young people in developed countries, with the main causes being due to road traffic accidents and accidents at work. The principle cause of death in severe trauma is the massive uncontrolled loss of blood. Most of the severe traumas with a massive haemorrhage develop coagulopathy, with some controversy over what is the best treatment for this. Patients with severe trauma are complex patients; they have a high mortality, they consume a significant amount of sources and can require rapid, intensive and multidisciplinary treatment encompassed within the concept of resuscitation damage control. In this article we attempt to present a current view of the pathophysiology of severe trauma and resuscitation damage control that may be applied to these types of patients.

Management of major blood loss: an update

Haemorrhage remains a major cause of potentially preventable deaths. Trauma and massive transfusion are associated with coagulopathy secondary to tissue injury, hypoperfusion, dilution and consumption of clotting factors and platelets. Concepts of damage control surgery have evolved, prioritizing the early control of the cause of bleeding by non-definitive means, while haemostatic control resuscitation seeks early control of coagulopathy. Haemostatic resuscitation provides transfusions with plasma and platelets in addition to red blood cells (RBCs) in an immediate and sustained manner as part of the transfusion protocol for massively bleeding patients. Transfusion of RBCs, plasma and platelets in a similar proportion as in whole blood prevents both hypovolaemia and coagulopathy. Although an early and effective reversal of coagulopathy is documented, the most effective means of preventing coagulopathy of massive transfusion remains debated and randomized controlled studies are lacking. Results from recent before-and-after studies in massively bleeding patients indicate that trauma exsanguination protocols involving the early administration of plasma and platelets are associated with improved survival. Furthermore, viscoelastic whole blood assays, such as thrombelastography (TEG)/rotation thromboelastometry (ROTEM), appear advantageous for identifying coagulopathy in patients with severe haemorrhage, as opposed to conventional coagulation assays. In our view, patients with uncontrolled bleeding, regardless of its cause, should be treated with goal-directed haemostatic control resuscitation involving the early administration of plasma and platelets and based on the results of the TEG/ROTEM analysis. The aim of the goal-directed therapy should be to maintain a normal haemostatic competence until surgical haemostasis is achieved, as this appears to be associated with reduced mortality.

Can hypertonic saline influence platelet P selectin expression and platelet-leukocyte aggregation?

OBJECTIVES

Part of platelet function involves aggregation and activation. Activation leads to platelet P selectin expression and platelet-leukocyte aggregation. Hypertonic saline inhibits platelet aggregation, although the effects of hypertonic saline on platelet activation are not known. We evaluated the effects of hypertonic saline on platelet activation as measured by platelet P selectin expression and platelet-leukocyte aggregation.

METHODS

Blood samples from healthy volunteers (n = 6) were treated in vitro with various solutions including 23.5%, 7.5%, 3%, and 0.9% saline; Ringer's solution; 5% dextrose in water; and 10% hydroxyethyl starch. Blood was diluted with each type of solution to 2.5%, 5%, 10%, 20%, and 30% (vol/vol) dilution. All blood samples were activated with adenosine diphosphate (20 micromol/L), stained with fluorochrome-conjugated antibodies, and analyzed by flow cytometry to measure platelet P selectin expression and platelet-leukocyte aggregation.

RESULTS

The 23.5% saline solution reduced P selectin expression at 20% and 30% dilutions and platelet-leukocyte aggregation at 10%, 20%, and 30% dilutions. The 7.5% solution saline had no effect on P selectin expression and significantly inhibited platelet-leukocyte aggregation only at 30% dilution. Other solutions had no effect on platelet P selectin expression or platelet-leukocyte aggregation.

CONCLUSIONS

Our data suggest that hypertonic saline does not affect platelet P selectin expression or platelet-leukocyte aggregation at therapeutic plasma concentrations but that an inhibitory effect occurs at supratherapeutic doses. Dilutions of other solutions caused the least disturbance of platelet activation.

Development of in situ-forming hydrogels for hemorrhage control

We report the preparation of in situ-forming hydrogels, composed of oxidized dextran (Odex) and amine-containing polymers, for their potential use as a wound dressing to promote blood clotting. Dextran was oxidized by sodium periodate to introduce aldehyde groups to form hydrogels, upon mixing in solution with different polymers containing primary amine groups, including polyallylamine (PAA), oligochitosan and glycol chitosan. A series of experiments were conducted to identify the optimum gelation condition for the Odex-PAA system. The polymer concentration appeared to have a major effect on gelation time and the polymer weight ratio affected the resulting gel content and swelling. Other influencing factors included pH of the buffer used to dissolve each polymer, PAA molecular weight, and the type of individual material. The latter also contributed significantly to gel content and swelling. Thromboelastography was used to examine the effects of the in situ gelation on blood coagulation in vitro, where the Odex-PAA combination was found to be most pro-hemostatic, as indicated by a decrease in clotting time and an increase in clot strength. The results of this study demonstrated that in situ-forming hydrogels could promote clotting in vitro; however, further studies are required to determine if the same hydrogel formulations are effective in controlling hemorrhage in vivo.

Blood products, volume control, and renal support in the coagulopathy of liver disease

Plasma-based products are commonly used in patients who have chronic liver disease to treat perceived coagulopathy despite unproven efficacy and potentially severe risks, such as transfusion-related acute lung injury, which carries a high mortality rate. Moreover, volume expansion may acutely worsen portal hypertension and increase bleeding from the collateral portal vascular bed. Although factor replacement therapy may be warranted in selected situations, its use should be restricted because of the limitations of target tests, such as international normalized ratio, which poorly reflects presence of bleeding diatheses in patients who have cirrhosis. Renal replacement therapies are frequent adjuncts in patients who have cirrhosis and are acutely decompensated, and may correct uremia-related bleeding diathesis and assist in controlling vascular volume, although they are generally limited to use as a bridge to liver transplantation. Novel extracorporeal therapies are emerging and may also have significant interaction with the hemostatic system. Volume contraction and blood conservation therapies are relatively new and promising approaches to reduce use of blood products in liver transplantation.

Effects of albumin 5% and artificial colloids on clot formation in small infants

Albumin is often cited in textbooks as the gold standard for fluid replacement in paediatrics, but in practice artificial colloids are more frequently used. Although one concern with the use of artificial colloids is their intrinsic action on haemostasis, the available data in children are inconclusive for 6% hydroxyethyl starch 130/0.4 (HES) and no data exist for gelatine solution with respect to coagulation. A total of 42 children (3-15 kg) undergoing surgery and needing colloid replacement were randomly assigned to receive 15 mlxkg(-1) of either albumin 5%, 4% modified gelatine solution or 6% hydroxyethyl starch 130/0.4 solution. Standard coagulation tests and modified thrombelastography (ROTEM) were performed. After colloid administration, routine coagulation test results changed significantly and comparably in all groups, although activated partial thromboplastin time values increased more with gelatine and HES. Coagulation time was unchanged in the children who received albumin or gelatine but other activated modified thrombelastography values were significantly impaired in all groups. After gelatine and after albumin the median clot firmness decreased significantly but remained within the normal range. Following HES, coagulation time increased significantly, and clot formation time, alpha angle, clot firmness, and fibrinogen/fibrin polymerisation were significantly more impaired than for albumin or gelatine, reaching median values below the normal range. From a haemostatic point of view it might be preferable to use gelatine solution as an alternative to albumin; HES showed the greatest effects on the overall coagulation process.

Tranexamic acid does not correct the haemostatic impairment caused by hydroxyethyl starch (200 kDa/0.5) after cardiac surgery

We investigated the effect of intravenous tranexamic acid on hydroxyethyl starch (HES)-induced clot strength impairment after cardiac surgery. Patients were randomized to receive either 1 g tranexamic acid or the same volume of 0.9% saline after administration of 15 ml/kg of 6% HES (molecular weight, 200 kDa; degree of substitution, 0.5) in the immediate postoperative period. Modified thromboelastometry (ROTEM) using different activators [intrinsic ROTEM (InTEM), extrinsic ROTEM (ExTEM), fibrinogen ROTEM (FibTEM)] was carried out to evaluate clot formation and lysis. The clot formation time was prolonged, and the maximum clot firmness (MCF) and shear elastic modulus [G = 5000 x MCF / (100-MCF), dynes/cm(2)] decreased (all activators of ROTEM) after completion of HES (P < 0.001, two-factor analysis of variance). These abnormalities in blood coagulation persisted despite tranexamic acid. Maximal lysis (FibTEM), indicative of fibrinolytic activity, was increased after HES but no effect of tranexamic acid was observed. The cumulative chest tube drainage until the first postoperative morning was not different between the groups (1008 +/- 251 and 1081 +/- 654 ml, P = 0.698, respectively). We conclude that after cardiopulmonary bypass, HES-induced impairment in clot formation and strength, or increased fibrinolytic capacity, is not reversed by the administration of tranexamic acid.

The effects of commonly used resuscitation fluids on whole blood coagulation

OBJECTIVES

Evidence on the effect of crystalloid and colloid resuscitation fluids on coagulation is confusing, with contradictory results from previous studies. This study was performed to test the effect on whole blood coagulation of a range of resuscitation fluids in vitro using a single method at a single dilution.

METHODS

Seven resuscitation fluids were tested in vitro at a dilution of 40%. Whole blood coagulation was measured using a Sonoclot analyser.

RESULTS

A crystalloid/colloid split of effect on coagulation in vitro was not seen. The time to clot formation with Gelofusine, dextran and hydroxyethyl starch was a greatly increased, whereas saline and Haemaccel had little effect, or were slightly procoagulant.

CONCLUSIONS

Some resuscitation fluids have a profound effect on coagulation. The confusion in the literature may result from the effect on coagulation being both fluid and dilution dependent, with no simple crystalloid/colloid split.

The effects of colloid solutions on hemostasis

PURPOSE

Colloid solutions are widely used to prevent or to correct hypovolemia in surgical patients. Although more efficacious than crystalloids, they are more expensive and can be associated with adverse effects, in particular when they interfere with the hemostatic system.

METHODS

This narrative review focuses on the effects of albumin and synthetic colloids on the biological markers of coagulation and their clinical consequences.

RESULTS

All colloidal plasma substitutes interfere with the physiological mechanisms of hemostasis either through a non-specific effect correlated to the degree of hemodilution or through specific actions of these macromolecules on platelet function, coagulation proteins, and the fibrinolytic system. Albumin has the least effect, while high molecular weight (Mw) dextrans and hydroxyethyl starches (HES) have the most significant effects. Gelatins and medium Mw HES with a low molar substitution ratio have moderate and, probably, comparable effects. The use of dextrans and high in vivo Mw HES may be associated with increased bleeding, while gelatins and low in vivo Mw HES are unlikely to have such an effect.

CONCLUSIONS

In most cases, the clinical consequences of the biological effects of colloids on hemostasis are limited, provided that safety considerations are observed (maximum daily dosage, duration of treatment, patient's hemostatic status, clinical conditions). The implications may be different in patients with hemostatic disorders, either inherited or related to preoperative antiplatelet or anticoagulant treatment. In these patients, crystalloids, gelatins or even albumin solutions should be preferred when hemodilution exceeds 30% of the circulating blood volume.

Effects of hemodilution on outcome after modified Blalock-Taussig shunt operation in children with cyanotic congenital heart disease

OBJECTIVE

Cyanotic congenital heart diseases (CCHD) with secondary polycythemia and hyperviscosity state are associated with a reduction in blood flow, stagnation of blood, and thrombosis. Sufficient hemodilution in cyanotic children results in higher blood flow and significant reductions in perioperative blood loss. The aim of this study was to investigate similar beneficial effects of hemodilution in preventing shunt thrombosis and decreasing postoperative blood loss after modified Blalock-Taussig (BT) shunt operations in children with CCHD.

DESIGN

Prospective, randomized, controlled study.

SETTING

Cardiac center of a tertiary care, referral hospital.

PARTICIPANTS

Fifty children with CCHD undergoing modified BT shunt operations.

INTERVENTIONS

Patients were randomized into 2 groups. The study group (n = 25) received a calculated amount of 6% hydroxyethyl starch (200/0.5) solution to bring down the hematocrit to 45%, whereas the control group (n = 25) received 5% dextrose solution intraoperatively as per the authors' normal protocol.

MEASUREMENTS AND MAIN RESULTS

Effects of hemodilution on shunt patency, postoperative blood loss at 24 hours, blood and blood component usage, and re-exploration rates were recorded. The shunt patency rate was significantly higher in the study group than the control group (100% and 84%, respectively, p < 0.05). Postoperative blood loss at 24 hours was significantly higher in the control group than in the study group (14.4 +/- 11.8 mL/kg and 9.9 +/- 8 mL/kg, respectively, p < 0.05). The number of recipients and the amount of blood and blood components administered were higher in the control group, but they were not statistically significant. The re-exploration rate (for excessive postoperative chest-tube drainage) was significantly higher in the control group than the study group (12% and 0%, respectively, p < 0.05).

CONCLUSION

Hemodilution in CCHD patients undergoing modified BT shunt surgery has beneficial effects including improved shunt patency because of higher blood flow through the graft and less postoperative blood loss, which may be attributed to the lower viscosity produced by hemodilution.

Effects of Hextend Hemodilution on Plasma Coagulation Kinetics in the Rabbit: Role of Factor XIII-Mediated Fibrin Polymer Crosslinking

BACKGROUND

Hydroxyethyl starch administration has been associated with decreases in hemostasis and has recently been demonstrated to decrease fibrinogen (FI)-thrombin-(FIIa)-Factor XIII (FXIII) interactions in vitro in human plasma. Thus, the purpose of the present study was to determine the effect of in vivo hemodilution with Hextend (6% hydroxyethyl starch, mean molecular weight 450 kDa) on plasma coagulation kinetics.

MATERIALS AND METHODS

Eight male, New Zealand White rabbits were intravenously administered with 20 ml/kg of Hextend. Citrated plasma was obtained before, 1 min after, and 1 h after hemodilution. Thrombelastographic analyses were performed, with clot initiation (R, sec), clot propagation (alpha, degrees), and clot strength (shear elastic modulus, G, dynes/cm(2)) determined over 20 min. Samples were celite-activated and had either with addition or without additions of FI, FIIa or activated FXIII (FXIIIa) to restore protein content to prediluted values.

RESULTS

There was no significant difference in R values observed before (229 +/- 30), 1 min after (241 +/- 54), and 1 h after (214 +/- 42) hemodilution. Prediluted alpha values (75.2 +/- 1.9) were significantly decreased 1 min (53.3 +/- 5.9) and 1 h after hemodilution (56.1 +/- 10.2). Prediluted G values (1,992 +/- 434) were significantly reduced 1 min (532 +/- 195) and 1 h after (630 +/- 297) hemodilution. FI, FIIa, and FXIIIa addition significantly decreased R values after hemodilution. alpha and G values were significantly improved by FI and FXIIIa after hemodilution. FIIa addition did not significantly affect alpha or G.

CONCLUSIONS

Hextend hemodilution in rabbits maintains clot initiation by diminishing both FIIa-FI and FXIIIa-fibrin interactions, whereas clot propagation and strength were reduced by diminished FXIIIa-fibrin interactions.

Gelatin and Hydroxyethyl Starch, but Not Albumin, Impair Hemostasis After Cardiac Surgery

We investigated the effect of postoperative administration of colloids on hemostasis in 45 patients after cardiac surgery. Patients were randomized to receive 15 mL kg(-1) of either 4% albumin, 4% succinylated gelatin, or 6% hydroxyethyl starch (molecular weight of 200 kDa/degree of substitution 0.5) as a short-term infusion. There was a comparable decrease in maximum clot firmness of thromboelastometry tracings in gelatin and hydroxyethyl starch groups immediately after completion of the infusion, whereas these values remained unchanged in the albumin group. The impairment in clot strength persisted up to 2 h, although the values partly recovered. Postoperative bleeding correlated inversely with the clot strength in pooled data of the artificial colloids. Fibrin formation (clot formation time, alpha-angle) and fibrinogen-dependent clot strength (maximum clot firmness and shear elastic modulus) were more disturbed in the hydroxyethyl starch group than in the gelatin group. We conclude that after cardiopulmonary bypass surgery, both gelatin and hydroxyethyl starch impair clot strength and fibrin buildup, which may predispose patients to increased blood loss. The greatest impairment in hemostasis was seen after hydroxyethyl starch administration, whereas albumin appeared to have the least effect on hemostatic variables.

The effect of colloidal fluid replacement on wound healing in an experimental sublethal hemorrhagic shock model

OBJECTIVE

The aim of the study was to evaluate the effects of different resuscitation solutions on wound healing in an animal model of sublethal hemorrhagic shock.

METHODS

Sublethal hemorrhagic shock was established by blood withdrawal until the mean arterial pressure fell to 40 mmHg within 15 min. Animals were resuscitated with four different solutions: group I (n=19) 0.9% NaCl, group II (n=20) 10% dextran 40, group III (n=20) 6% hydroxyethyl starch, group IV (n=18) 4% modified fluid gelatin. Following inhalation anesthesia, a full thickness skin incision of 2 cm in length was made on the abdominal wall and sutured primarily. The incision wound on the abdominal wall was excised on the fifth day. The breaking strength of the incision and hydroxyproline content of dry tissue were evaluated.

RESULTS

Differences in breaking strength values were observed between groups I-III and I-IV (P<0.05). Hydroxyproline values were significantly lower in group IV (58.47 microg/ml) and group II (69.17 microg/ml) (P<0.05). The gelatin-resuscitated group had lower breaking strength and hydroxyproline values than the other groups.

CONCLUSION

It can be concluded that resuscitation with modified fluid gelatin may have detrimental effects on wound healing in an experimental model of sublethal hemorrhagic shock.

Effects of PentaLyte and Voluven hemodilution on plasma coagulation kinetics in the rabbit: role of thrombin-fibrinogen and factor XIII-fibrin polymer interactions

BACKGROUND

Hydroxyethyl starch (HES) administration has resulted in decreased hemostasis and fibrinogen (FI)-thrombin-(FIIa)-Factor XIII (FXIII) interactions. I proposed to determine the hemostatic effect of hemodilution with PentaLyte (6% HES, mean molecular weight 220 kDa) and Voluven (6% HES, 130 kDa).

METHODS

Rabbits were intravenously administered 20 ml/kg PentaLyte or Voluven (n = 8 per fluid) over 10 min. Plasma was obtained prior to, 1 min and 1 h after hemodilution. Thrombelastography was performed, with clot initiation (R, sec), clot propagation (alpha, degrees), and clot strength (shear elastic modulus, G, dynes/cm2) determined over 20 min. Celite-activated samples had either no additions or addition of FI, FIIa or activated FXIII (FXIIIa) to restore protein content to pre-diluted values.

RESULTS AND CONCLUSIONS

While there were no significant differences between the groups, R significantly decreased 1 h after hemodilution compared with values observed before and 1 min after hemodilution, whereas alpha and G significantly decreased 1 min after hemodilution and then significantly, but only partially, increased 1 h after hemodilution compared with pre-dilution values. Addition of FI, FIIa and FXIIIa significantly decreased R in both groups. alpha and G 1 min after hemodilution were significantly enhanced by FI, FIIa, FXIIIa in both groups; however, 1 h after hemodilution, rabbits administered PentaLyte had alpha and G enhanced only by FI and FXIIIa addition, whereas animals administered Voluven had alpha and G significantly enhanced by FI addition. PentaLyte and Voluven hemodilution initially diminishes FIIa-FI and FXIIIa-fibrin, but within an hour primarily inhibit FXIIIa-fibrin interactions in the rabbit.

Colloids decrease clot propagation and strength: role of factor XIII-fibrin polymer and thrombin-fibrinogen interactions

Colloid-mediated hypocoagulability is clinically important, but the mechanisms responsible for coagulopathy have been incompletely defined. Thus, my goal was to elucidate how colloids decrease plasma coagulation function. Plasma was diluted 0% or 40% with 0.9% NaCl, three different hydroxyethyl starches (HES, mean molecular weight 450, 220 or 130 kDa), or 5% human albumin. Samples (n=6 per condition) were activated with celite, and diluted samples had either no additions or addition of fibrinogen (FI), thrombin (FIIa) or activated Factor XIII (FXIIIa) to restore protein function to prediluted values. Thrombelastographic variables measured included clot propagation (angle, alpha), and clot strength (amplitude, A; or shear elastic modulus, G). Dilution with 0.9% NaCl significantly decreased alpha, A and G-values compared to undiluted samples. Supplementation with FI, but not FIIa or FXIIIa, resulted in 0.9% NaCl-diluted thrombelastographic variable values not different from those of undiluted samples. FI supplementation of HES 450, HES 220, HES 130 and albumin-diluted samples only partially restored alpha, A and G-values compared to undiluted samples. FIIa addition only improved clot propagation and strength in albumin-diluted samples. FXIIIa supplementation improved propagation in samples diluted with HES 450, HES 220 and albumin, and clot strength improved in HES 450 and albumin-diluted plasma. Considered as a whole, these data support compromise of FIIa-FI and FXIIIa--fibrin polymer interactions as the mechanisms by which colloids compromise plasma coagulation. Investigation to determine if clinical enhancement of FXIII activity and/or FI concentration (e.g. fresh-frozen plasma, cryoprecipitate) can attenuate colloid-mediated decreases in hemostasis is warranted.

A triple-blinded randomized trial comparing the hemostatic effects of large-dose 10% hydroxyethyl starch 264/0.45 versus 5% albumin during major reconstructive surgery

In Canada, hydroxyethyl starch 264/0.45 (HES 264/0.45; molar weight 264 kDa, molar substitution 0.45) has largely replaced albumin as the colloidal fluid of choice for perioperative intravascular volume expansion. The maximum recommended dose of HES 264/0.45 is 28 mL/kg; however, there are no clinical data supporting this limit. In this study we compared the hemostatic effects of HES 264/0.45 versus 5% albumin in doses up to 45 mL/kg over 24 h during major reconstructive head and neck surgery. Fifty patients were randomized to receive HES 264/0.45 or 5% human albumin from the induction of anesthesia until 24 h thereafter. Both albumin and HES 264/0.45 effectively maintained physiologic variables in the perioperative and postoperative periods. The partial thromboplastin time and international normalized ratio were significantly increased in the HES 264/0.45 group compared with the albumin group after infusion of 30 mL/kg and 45 mL/kg (P < 0.05). Factor VIII activity and von Willebrand factor level were significantly reduced in the HES 264/0.45 group compared with the albumin group after infusion of 15 mL/kg, 30 mL/kg, and 45 mL/kg (P < 0.05). Significantly more subjects in the HES 264/0.45 group received allogeneic red blood cell transfusions (P < 0.02). We conclude that HES 264/0.45 infusions >30 mL/kg over 24 h impair coagulation to a greater extent than albumin, possibly leading to more allogeneic transfusions.

In vitro effects of gelatin solutions on platelet function: a comparison with hydroxyethyl starch solutions

The aim of this study was to investigate the effects of various gelatin and hydroxyethyl starch solutions on platelet reactivity. Citrated whole blood was obtained from 20 healthy volunteers. Expression of glycoprotein (GP) IIb-IIIa and p-selectin were determined using whole blood flow cytometry on both resting and agonist-activated platelets before and after in vitro haemodilution (20% and 40%) using oxypolygelatin, modified gelatin, urea-linked gelatin, hydroxyethyl starch (HES) 130 (mean molecular weight in kDa), HES 200, HES 450 and HES 550. High degrees of haemodilution using oxypolygelatin had no significant effect, similar to HES 130, whereas modified gelatin inhibited GP IIb-IIIa expression, similar to HES 200 and HES 450. Urea-linked gelatin significantly increased the expression of GP IIb-IIIa, similar to HES 550. p-selectin expression remained unchanged in all samples. The present in vitro study indicates that chemical characteristics of colloidal solutions modulate their influence on platelet reactivity.

Perioperative fluid management and clinical outcomes in adults

The administration of IV fluid to avoid dehydration, maintain an effective circulating volume, and prevent inadequate tissue perfusion should be considered, along with the maintenance of sleep, pain relief, and muscular relaxation, a core element of the perioperative practice of anesthesia. Knowledge of the effects of different fluids has increased in recent years, and the choice of fluid type in a variety of clinical situations can now be rationally guided by an understanding of the physicochemical and biological properties of the various crystalloid and colloid solutions available. However, there are few useful clinical outcome data to guide this decision. Deciding how much fluid to give has historically been more controversial than choosing which fluid to use. A number of clinical studies support the notion that an approach based on administering fluids to achieve maximal left ventricular stroke volume (while avoiding excess fluid administration and consequent impairment of left ventricular performance) may improve outcomes. In this article, we review the available fluid types and strategies of fluid administration and discuss their relationship to clinical outcomes in adults.

Artificial colloids impair haemostasis. An in vitro study using thromboelastometry coagulation analysis

BACKGROUND

Hydroxyethyl starch (HES) solutions impair haemostatic mechanisms. The impact of the degree of substitution (DS) of a HES solution on thromboelastometry tracings is unclear. Therefore we tested the hypothesis of whether the DS has an effect on the haemostatic defect caused by HES, and assessed whole blood coagulation by thromboelastometry coagulation analysis (ROTEM, Pentapharm Co., Munich, Germany) in serial in vitro haemodilutions of colloids.

METHODS

Whole blood was withdrawn from 12 volunteers in a crossover study. Six per cent low-molecular weight HES with a high (HES MW 120 kDa/degree of substitution 0.7) and low (HES MW 130 kDa/0.4) degree of substitution, 4% succinylated gelatin (GEL) or 4% albumin (ALB) was added to citrated venous whole blood samples to make 20, 40, 60 vol.% end-concentrations of each of the solutions. Samples were analyzed by ROTEM.

RESULTS

There was a comparable decrease in maximum clot firmness (MCF) and shear elastic modulus [G = 5000 x MCF/(100-MCF)] by HES 120/0.7 and HES 130/0.4 at 20 and 40 vol.% dilutions. At 60 vol.% dilution HES 120/0.7 decreased less alpha-angle and MCF than HES 130/0.4 (P < 0.05). With moderate dilutions all colloids shortened coagulation time (CT). At 20, 40 and 60 vol.% dilutions MCF and G were more decreased in both HES groups than in the ALB and GEL groups (P < 0.05). Furthermore, at 40 and 60 vol.% dilutions G deteriorated more in the GEL than in the ALB group (P < 0.05).

CONCLUSION

In vitro the impact of the degree of substitution of HES solution on thromboelastometry coagulation analysis was modest. Haemodilution with gelatin and albumin induced fewer coagulation abnormalities than HES. In addition, the haemodilution with gelatin impaired coagulation more than albumin solution.

Thrombelastographic whole blood clot formation after ex vivo addition of plasma substitutes: improvements of the induced coagulopathy with fibrinogen concentrate

BACKGROUND

Plasma substitutes such as hydroxyethyl starch (HES) and various dextrans may compromise the haemostatic system, thereby causing potentially dangerous bleeding. Whilst several mechanisms have been advanced to explain the nature of the coagulopathy induced by this colloid, there has been comparably little interest in devising ways to optimize haemostasis after a relative colloid overdose.

METHODS

Real-time whole blood (WB) clot formation profiles were recorded using a thrombelastographic method employing activation with tissue factor. The coagulation tracings were transformed into dynamic velocity profiles of WB clot formation. WB from healthy individuals (n=20) was exposed to haemodilution of approximately 55% with isotonic saline, HES 200/0.5, HES 130/0.4, and dextran 70, respectively. Possible modalities for improvement of the induced coagulopathy were explored, in particular ex vivo addition of a fibrinogen concentrate.

RESULTS

WB coagulation profiles changed significantly with decreased clot strength, and a compromised propagation phase of clot formation. The duration of the initiation phase of WB coagulation was unchanged. No statistical differences were detected amongst the HES solutions and dextran 70. However, dextran 70 returned a more suppressed clot development and strength compared with the HES solutions. Ex vivo haemostatic addition of washed platelets (75 x 10(9) litre(-1)) and factor VIII (0.6 IU ml(-1)) produced insignificant changes in clot initiation, propagation, and in the clot strength. In contrast, ex vivo addition of a fibrinogen concentrate (1 g litre(-1)) improved the coagulopathy induced by all of the three individual plasma expanders tested.

CONCLUSION

Coagulopathy induced by haemodilution with either HES 200/0.5, HES 130/0.4, and dextran 70 may be improved by fibrinogen supplementation.

Low-molecular-weight dextran infusion is more effective for the treatment of hemoconcentration due to severe ovarian hyperstimulation syndrome than human albumin infusion

The most severe complication of ovarian hyperstimulation syndrome (OHSS) is thromboembolism, which is related to hemoconcentration. Dextran 40 infusion has greater effectiveness for the treatment of hemoconcentration due to OHSS than does human albumin infusion.

The role of the intestine in the pathophysiology and management of severe acute pancreatitis

BACKGROUND

The outcome of severe acute pancreatitis has scarcely improved in 10 years. Further impact will require new paradigms in pathophysiology and treatment. There is accumulating evidence to support the concept that the intestine has a key role in the pathophysiology of severe acute pancreatitis which goes beyond the notion of secondary pancreatic infection. Intestinal ischaemia and reperfusion and barrier failure are implicated in the development of multiple organ failure.

DISCUSSION

Conventional management of severe acute pancreatitis has tended to ignore the intestine. More recent attempts to rectify this problem have included 1) resuscitation aimed at restoring intestinal blood flow through the use of appropriate fluids and splanchnic-sparing vasoconstrictors or inotropes; 2) enteral nutrition to help maintain the integrity of the intestinal barrier; 3) selective gut decontamination and prophylactic antibiotics to reduce bacterial translocation and secondary infection. Novel therapies are being developed to limit intestinal injury, and these include antioxidants and anti-cytokine agents. This paper focuses on the role of the intestine in the pathogenesis of severe acute pancreatitis and reviews the implications for management.

The effects of hydroxyethyl starch solutions on thromboelastography in preoperative male patients

BACKGROUND

Hydroxyethyl starches (HES) have been shown to decrease clot strength and to increase coagulation times assessed by thromboelastography (TEG). HES with minimal anticoagulant side-effects is beneficial for plasma volume expansion in the perioperative setting. A comparison of the in vivo effects of high, middle and low molecular weight HES solutions on TEG variables has not been performed so far.

METHODS

Blood was obtained before and after intravenous infusion (10 ml kg-1) of either saline, HES 70/0.5/4 (molecular weight in kDa/degree of substitution/C2:C6 ratio), HES 130/0.4/9, HES 200/0.6/9.4, or HES 450/0.7/4.6 in 50 otherwise healthy patients. Thromboelastography was performed in 360 micro l of 1% celite activated citrated whole blood after recalcification.

RESULTS

HES 450/0.7/4.6 prolonged reaction time indicating impairment of the plasmatic coagulation system. TEG parameters indicative for platelet function, including angle alpha, maximum amplitude and coagulation time, deteriorated after infusion of HES 450/0.7/4.6 and HES 70/0.5/4. HES 200/0.6/9.4 and HES 130/0.4/9 impaired platelet contribution to hemostasis only partially, decreasing two or one TEG platelet parameters, respectively.

CONCLUSION

Infusion of HES 450/0.7/4.6 compromises TEG parameters more than the other solutions tested, whereas HES 130/0.4/9 has the smallest effect. Further outcome-related studies are needed in order to assess the clinical relevance of our findings.

The in vitro effects of crystalloids and colloids on coagulation

Classically haemodilution is regarded as causing coagulopathy. However, haemodilution with saline seems to cause a hypercoagulable state both in vivo and in vitro. The aim of the present study was to measure the effect of mild to severe haemodilution using thrombelastography. Blood samples were taken in 12 healthy volunteers and divided into seven aliquots. One aliquot was undiluted and acted as control. The other six were diluted with normal saline, Ringer Acetate, 4% albumin, Dextran 70, 6% and 10% hydroxyethylstarch to 10%, 20%, 40%, 50% and 60% dilution. The dilution was checked by measuring the haemoglobin concentration. Each aliquot was placed in a temperature-controlled thrombelastography channel. Increased coagulation activity, as measured by thrombelastography changes, was detected at low and medium levels of dilution with all the tested solutions. At more than 40% dilution, coagulation returned to normal while in the case of dextran and hydroxyethylstarch coagulopathy developed. For crystalloids and albumin,dilution had to exceed 50% before coagulation was impaired. If these findings can be reproduced in vivo, they may have implications for transfusion practice and prophylaxis against thrombosis.

[Effects of plasma substitutes on hemostasis]

OBJECTIVE

Data synthesis on haemostasis effects of cristalloids and colloids and clinical implications for their use for plasma volume replacement.

DATA SOURCES

Data were searched in the Medline database from 1954 to 2000 using the following key-words: cristalloids, colloids, albumin, gelatin, dextran, hydroxyethyl starch, haemostasis, von Willebrand disease, haemodilution.

DATA EXTRACTION

Publications from 1954 to 1990 were selected depending on the quality of their methodology. Most of articles published after 1990 and all types including case report were accepted.

DATA SYNTHESIS

Cristalloids induces a moderate hypercoagulable state with 10 to 30% haemodilution. Hypocoagulation is observed above 50% haemodilution. Albumin does not impair hemostasis except with a 50% or more haemodilution where hypocoagulation is observed. Dextran dramatically impairs haemostasis and fibrinolysis. With increasing dose, a progressive decrease of all von Willebrand multimers, mostly the largest, is observed. Till 50% haemodilution, gelatin has a moderate impact on hemostasis, but platelet aggregation is moderately modified. However this moderate impairment of haemostasis may potentiate the haemostatic effect of other colloids when used in association with gelatin. More than 30% haemodilution with hydroxyethyl starch (HES) has a serious effect in vitro on platelet function and fibrinoformation. In most studies in human, less than 20 ml.kg-1 plasma volume replacement has no clinical impact, but in some evaluations postoperative bleeding is more important with HES, particularly HES 450, in comparison to other colloids. With HES 450 and HES 200 highly substituted (0.6 of degree of substitution) intravascular cumulation of large molecules leads to type I von Willebrand syndrome when doses overtake 80 ml.kg-1. Dextran and HES are prohibited in patients with impaired haemostasis due to congenital disease (haemophilia and von Willebrand disease) or acquired defect (thrombocytopenia). Caution is required in patients with renal failure or receiving antithrombotic or non-steroidal anti-inflammatory agents. Patients without a haemorrhagic diathesis must not received more than 1.5 g.kg-1.j-1 of dextran and restrictive conditions of use must be respected with HES.

CONCLUSION

Except isotonic cristalloids, all colloids induce haemostastic changes particularly for haemodilution over 30%. Effects are more pronounced with HES and dextran.

In vivo effect of haemodilution with saline on coagulation: a randomized controlled trial

BACKGROUND

Previous studies have shown that 10-30% haemodilution with crystalloid may induce a hypercoagulable state demonstrable by using the Thrombelastograph (TEG). While most are in vitro studies, the few in vivo studies are limited by confounding surgical or 'environmental' factors. We conducted this randomized controlled study to evaluate the coagulation changes associated with in vivo haemodilution.

METHODS

Twenty patients undergoing major hepatobiliary surgery were randomly allocated to one of two study groups. Group H (n = 10) had 30% blood volume withdrawn over 30 min and replaced with saline. Group C (n = 10) did not have any blood withdrawn. Blood samples were taken in both groups at 10, 20 and 30 min. Native TEG, complete blood count, coagulation profile, fibrinogen, antithrombin III, protein C and thrombin-antithrombin complex concentrations were measured.

RESULTS

Compared with Group C, Group H patients had significantly greater shortening of r-time at 30 min (-30% vs +36%), greater shortening of k-time at all time points (-36% vs +17% at 10 min; -37% vs +44% at 20 min; -45% vs +49% at 30 min), and greater widening of alpha at 30 min (+71% vs +4%). The decrease in antithrombin III and other natural procoagulants and anticoagulants closely followed that of haematocrit, with the exception of thrombin-antithrombin complex.

CONCLUSION

In vivo haemodilution of up to 30% with saline can induce a hypercoagulable state. The mechanism remains unclear as disproportionate dilution of natural anticoagulants was not detected. Thrombin-antithrombin complex concentration remained stable despite haemodilution in Group H, which may suggest increased thrombin generation.

Resuscitation fluids

BACKGROUND AND OBJECTIVES

The aim of this review was to summarize the properties of the commonly available resuscitation fluids and highlight where knowledge of the characteristics of individual fluids might guide their use in clinical practice. Some of the current controversies surrounding resuscitation fluids are also discussed. Blood or blood products, or strategies of fluid administration, are not focused upon.

CONCLUSIONS

The clinical trial data does not support the concept of a therapeutic advantage for either crystalloids or colloids, despite claimed theoretical advantages for both classes of fluid. The available colloid solutions have quite distinct profiles of activity, both in terms of their plasma volume expansion profile and other physiological and pharmacological properties. Recent data suggests that physiologically balanced crystalloid and colloid solutions may improve clinical outcomes when compared with saline-based fluids.

Monitoring the Hematologic Complications of Cardiopulmonary Bypass

Patients undergoing cardiopulmonary bypass (CPB) procedures have a variety of hemostatic defects that lead to bleeding and the frequent need for transfusion of allogeneic blood products. Dilution of the patient's blood volume by the extracorporeal circuit priming so lution causes depletion of platelets and coagulation factor levels. Contact of blood with the extracorporeal circuit induces a hemorrhagic diathesis through a vari ety of mechanisms. Contact activation causes the for mation of kallikrein, bradykinin, and complement acti vation, leading to a whole-body inflammatory reaction. Intrinsic coagulation is stimulated, leading to subse quent activation of the fibrinolytic system. Platelet dys function caused by the effects of the extracorporeal circuit on platelet membrane integrity and the effects of circulating platelet inhibitors have also been described. The use of high-dose heparin for CPB mitigates these effects but does not completely eliminate them. Prota mine, administered to antagonize heparin's effects, has antiplatelet properties and anticoagulant effects when given in excess. Because of the numerous hemostatic insults incurred during and after CPB, complex moni toring techniques are necessary to ensure adequate anticoagulation, adequate heparin neutralization, and normal platelet function. Coagulation monitoring has allowed more specific identification of particular distur bances of hemostasis and has been linked with a reduc tion in hemorrhagic complications after CPB. Copyright © 2001 by W.B. Saunders Company.

Influence of a new hydroxyethylstarch preparation (HES 130/0.4) on coagulation in cardiac surgical patients

OBJECTIVE

To compare volume therapy with HES 130/0.4, a new hydroxyethylstarch (HES) solution with a gelatin-based fluid replacement strategy.

DESIGN

Prospective, randomized, safety study.

SETTING

Urban, university-affiliated hospital (single institution).

PARTICIPANTS

Forty-two patients undergoing elective cardiac surgery.

INTERVENTIONS

Patients were prospectively randomized into 2 groups: In group 1 (n = 21), gelatin was given perioperatively for volume support until the 1st postoperative day to keep the central venous pressure (CVP) between 10 and 14 mmHg; in group 2 (n = 21) HES 130/0.4 was administered using the same protocol as in group 1.

MEASUREMENTS AND MAIN RESULTS

Standard coagulation variables and modified thromboelastography (TEG) were used. Using different activators for extrinsic and intrinsic activation and heparin inactivation by heparinase, the onset of coagulation (coagulation time), kinetics of clot formation (clot formation time), and maximum clot firmness were measured. Measurements were performed after induction of anesthesia (T0), at the end of surgery (T1), 4 hours after surgery (T2), and on the morning of the 1st postoperative day (T3). A total of 3310 +/- 810 mL of gelatin and 3070 +/- 570 mL of HES 130/0.4 were used in the 2 groups during the study period. The 2 groups did not differ with regard to postoperative bleeding or in use of packed red blood cells or fresh frozen plasma. Standard coagulation variables were similar between the 2 groups. All TEG variables were within the normal range at baseline. Coagulation time and clot formation time data were significantly elevated after surgery and in the intensive care unit, without showing specific differences between the 2 volume replacement groups. Intrinsic TEG and heparinase TEG clot formation times remained significantly higher until the end of the study period. No differences were seen between HES-treated and gelatin-treated patients.

CONCLUSIONS

Volume replacement with the new HES preparation was as safe as gelatin-based volume replacement with regard to coagulation in cardiac surgical patients. HES 130/0.4 is an alternative plasma substitute to treat volume deficits.

Effects of different plasma substitutes on blood coagulation: a comparative review

OBJECTIVE

To compare the effects of different colloid plasma substitutes on blood coagulation and postoperative blood loss.

DATA SOURCES

Relevant studies were obtained from the medical literature.

STUDY SELECTION

Articles were selected that provided data on the effects of colloids on hemostasis and postoperative blood loss in humans. Studies comparing different colloids were looked for using MEDLINE and by searching through the references of studies as they were collected.

DATA SYNTHESIS

Articles were reviewed and relevant data were extracted and partly presented in comparative tables.

CONCLUSIONS

Dextran, gelatin, and hydroxyethyl starch (HES) all can induce a specific decrease of von Willebrand factor and factor VIII:c. Blood coagulation is most impaired by dextran and high molecular weight HES, both associated with increased postoperative blood loss. The effects of HES on blood coagulation have been shown to depend on its molecular weight and rate of elimination. Detrimental effects have been shown for high molecular weight HES. Medium molecular weight (MMW)-HES with a high degree of substitution (HES 200/0.62) and MMW-HES with high C2/C6 hydroxyethylation ratio (HES 200/0.5/13) are slowly degradable and have been shown to impair blood coagulation after repeated administration. Rapidly degradable HES 200/0.5/6 and gelatin-based plasma expanders appear not to impair hemostasis. However, based on the reviewed literature, all artificial colloids could potentially induce increased bleeding tendency after infusion of very large volumes and especially when given to patients with even mild forms of von Willebrand disease. In those circumstances, crystalloid solutions or alternatives such as plasma or albumin, although associated with other serious complications, could be considered.

The influence of intravascular volume therapy with a new hydroxyethyl starch preparation (6% HES 130/0.4) on coagulation in patients undergoing major abdominal surgery

A new hydroxyethyl starch (HES) preparation with a mean molecular weight of 130,000 daltons and a degree of substitution of 0.4 shows favorable pharmacokinetic properties. We conducted a study of the influence of the new HES specification on coagulation and compared it with another colloidal intravascular volume replacement regimen using gelatin. According to a prospective, random sequence, 42 patients undergoing major abdominal surgery received either HES 130/0.4 (n = 21) or gelatin (n = 21) until the first postoperative day (POD) to keep central venous pressure between 10 and 14 mm Hg. From arterial blood samples, standard coagulation variables were measured, and modified thrombelastogram (TEG) measurements using different activators were performed. A total of 2830 +/- 350 mL of gelatin and 2430 +/- 310 mL of HES 130/0.4 were administered until the morning of the first POD. The use of allogeneic blood/blood products and standard coagulation variables did not differ significantly between the two groups. After induction of anesthesia, all TEG data for both groups were within normal range. Coagulation time and maximum clot firmness did not change significantly in any TEG measurements during the study period. The kinetics of clot formation (clot formation time) significantly increased immediately after surgery, but without showing significant group differences. On the morning of the first POD, the clot formation time returned to almost normal levels, except for aprotinin-activated TEG(R). We conclude that administration of moderate doses of the new HES 130/0.4 preparation in patients undergoing major abdominal surgery results in similar coagulation alterations as those after using an established gelatin-based volume-replacement regimen.

IMPLICATIONS

We compared the effects of infusion of a new hydroxyethyl starch preparation (6% hydroxyethyl starch; mean molecular weight 130,000 daltons; degree of substitution 0.4) on coagulation with a gelatin-based intravascular volume replacement regimen in patients undergoing major abdominal surgery. After moderate doses of hydroxyethyl starch (2430 +/- 310 mL until the morning of the first postoperative day), coagulation monitoring, including modified thrombelastography, did not show impaired hemostasis.

Sonoclot coagulation analysis of in-vitro haemodilution with resuscitation solutions

The colloid and crystalloid solutions used for resuscitation should preferably be free from effects on coagulation. In 10 volunteers, the effects of haemodilution with various concentrations of 0.9% sodium chloride and 4% succinylated gelatin were assessed by Sonoclot analysis, which describes the whole coagulation process. Small and moderate haemodilution (up to 40%) with 0.9% sodium chloride promoted coagulation. Similar haemodilution with 4% succinylated gelatin impaired coagulation, and at 60% haemodilution coagulation was very poor. These findings need to be confirmed in vivo and their clinical relevance determined.

The effect of hydroxyethyl starch 200 kD on platelet function

We evaluated the effects of hydroxyethyl starch with a molecular weight of 200 kD (HES 200 kD) on platelets to gain insight into the potential mechanisms involved in the anticoagulant effects of HES 200 kD. Blood was obtained before and after an IV infusion (10 mL/kg) of either saline (n = 15) or HES 200 kD (n = 15) in otherwise healthy patients scheduled for minor elective surgery. Flow cytometry was used to assess the expression of glycoprotein (GP) IIb-IIIa, GP Ib, and P-selectin on agonist-activated platelets. Overall platelet function was evaluated by assessing thromboelastographic maximum amplitude (MA) in celite-activated blood and platelet function analyzer-closure times by using collagen/adenosine diphosphate cartridges. Saline infusion had no effects on platelet variables, whereas HES 200 kD reduced GP IIb-IIIa expression and MA and prolonged platelet function analyzer-closure times, without affecting the expression of P-selectin and GP Ib. In vitro experiments extended these observations by a concentration-related inhibiting effect of HES 200 kD on GP IIb-IIIa expression. This study demonstrates that cellular abnormalities with decreased availability of platelet GP IIb-IIIa are involved in the anticoagulant effects of HES 200 kD.

Influence of different colloids on molecular markers of haemostasis and platelet function in patients undergoing major abdominal surgery

Synthetic colloids have been reported to cause haemorrhagic complications. The effects of perioperative volume replacement with 4% gelatin (n = 20), 6% low-molecular weight (LMW) hydroxyethyl starch (HES) (Mw: 70,000 dalton; HES 70/0.5; n = 20) and 6% medium-molecular weight (MMW) HES (Mw: 200,000 dalton; HES 200/0.5; n = 20) on haemostasis were assessed in patients undergoing major abdominal surgery. Volume was administered to keep central venous pressure (CVP) between 10 and 14 mm Hg. Conventional global coagulation tests, molecular markers of coagulation, and platelet function (using a platelet function analyser (PFA-100) with ADP as inductor) were monitored prior to surgery (T0), at the end of surgery (T1), 4 h after the end of surgery (T2), and on the morning of the first postoperative day (T3). Significantly more gelatin (2900 (SD 320) ml) than HES 200 (2150 (312) ml) was given during the study period. Bleeding and the use of allogeneic blood-blood products were similar in all groups. Markers of thrombin generation (F1 + 2), of thrombin neutralization (TAT III complex), and of fibrin formation and its degradation (D-dimer) increased significantly during and after surgery without showing significant group differences. Factor VIII and von Willebrand factor (vWF) also increased in all groups beyond the normal range, showing the significantly highest increase in the gelatin-treated group (VIII: from 173 (36) to 266 (33) U dl-1; vWF: from 164(33) to 238 (31) U dl-1). Platelet function remained within the normal range and without group differences throughout the study period. We can conclude that all three solutions can be used safely in patients undergoing major abdominal surgery with regard to the haemostatic process.