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

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

Synthetic colloid fluids containing hydroxyethyl starch (HES) have been associated with impairment of coagulation in dogs. It is unknown if HES causes coagulation impairment in dogs with naturally occurring critical illness. This study used banked plasma samples from a blinded, randomized clinical trial comparing HES and balanced isotonic crystalloid for bolus fluid therapy in 39 critically ill dogs. Blood was collected prior to fluid administration and 6, 12, and 24 h thereafter. Coagulation biomarkers measured at each time point included prothrombin time, activated partial thromboplastin time, thrombin time, fibrinogen concentration, and the activities of coagulation factors V, VII, VIII, IX, and X, von Willebrand factor antigen, antithrombin, and protein C. Given the links between coagulation and inflammation, cytokine concentrations were also measured, including interleukins 6, 8, 10, and 18, keratinocyte-derived chemokine, and monocyte chemoattractant protein-1. Data were analyzed with linear mixed effects models. No significant treatment-by-time interactions were found for any biomarker, indicating that the pattern of change over time was not modified by treatment. Examining the main effect of time showed significant changes in several coagulation biomarkers and keratinocyte-derived chemokines. This study could not detect evidence of coagulation impairment with HES.

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.

High-dose Factor XIII administration induces effective hemostasis for trauma-associated coagulopathy (TAC) both in vitro and in rat hemorrhagic shock in vivo models

BACKGROUND

Trauma-associated coagulopathy (TAC) is an early and primary complication in severe trauma patients. Factor XIII (FXIII) is reported to stabilize a clot in the late phase of the coagulation cascade. The goal of this study was to investigate whether the administration of FXIII improves the condition of TAC both in vitro and in vivo.

METHODS

We evaluated the effects of different doses, including a very high dose of FXIII (3.6-32.4 IU/mL) on tissue-plasminogen activator-induced hyperfibrinolysis and the combined condition of dilutional coagulopathy and tissue-plasminogen activator-induced hyperfibrinolysis in vitro. The coagulation status was analyzed by rotational thromboelastometry (ROTEM) and Sonoclot. Then, we evaluated the effect of high-dose FXIII (300 IU/kg) for severe coagulopathy in vivo using a rat liver trauma model in which coagulopathy similar to TAC was observed. Survival time and the amount of intra-abdominal bleeding of rats were measured, and a coagulation test was also performed. Histologic evaluations of rats' lung and kidney after FXIII administration were completed.

RESULTS

High-dose FXIII significantly improved clot strength as well as increased resistance to hyperfibrinolysis in vitro which was confirmed by ROTEM. Platelet function on Sonoclot was significantly increased by FXIII in a dose-dependent manner. Factor XIII significantly decreased the total amount of bleeding and prolonged the survival time compared to control (control vs FXIII: 108.9 ± 11.4 vs 32.6 ± 5.5 mL/kg; p < 0.001; 26.0 ± 8.8 vs 120 minutes, p < 0.001) in a rat model. Rotational thromboelastometry parameters and platelet function on Sonoclot were significantly improved in the FXIII (+) group compared to control. No adverse effects of FXIII were detected histologically.

CONCLUSION

Factor XIII not only generated stable clot resistance to hyperfibrinolysis but also enhanced platelet function by facilitating clot retraction. High-dose FXIII administration therapy has significant clinical impact for severe trauma accompanied with TAC.

STUDY TYPE

Human in vitro and rat in vivo experimental study.

Does small-volume resuscitation with crystalloids or colloids influence hemostasis and survival of rabbits subjected to lethal uncontrolled hemorrhage?

BACKGROUND

Prehospital, small-volume resuscitation of combat casualties with a synthetic colloid (6% hydroxyethyl starch [HES] 670/0.75) has been recommended when blood or blood components are unavailable. We studied hemostatic effects of a newer synthetic colloid (6% HES, 130/0.4) compared with either a natural colloid (albumin) or to crystalloids in an uncontrolled hemorrhage model.

METHODS

Spontaneously breathing New Zealand white rabbits (3.4 ± 0.1 kg) were anesthetized, instrumented, and subjected to a splenic injury with uncontrolled bleeding. Fifteen minutes after injury, rabbits were in shock (mean arterial pressure [MAP] = 26 ± 1.3 mm Hg, and received colloids (6% HES, 130/0.4 or 5% albumin at 15 mL/kg), or crystalloids (normal saline at 30 mL/kg or 5% hypertonic saline at 7.5 mL/kg) for resuscitation in two intravenous bolus injections (15 minutes apart) to raise their MAP to 65 mm Hg, n = 9/group. Animals were monitored for 2.5 hours or until death, and blood losses were measured. Blood samples were analyzed for arterial blood gas, complete blood count, and coagulation measures.

RESULTS

There were no differences among groups in baseline measures and initial hemorrhage volume (11.9 ± 0.6 mL/kg) at 15 minutes postinjury. Twenty minutes after fluid resuscitation (1 hour postinjury), MAP was higher, shock indices were lower, and blood pH was higher in colloids versus. crystalloids groups (p < 0.05). Administration of 6% HES 130/0.4 colloid produced the largest hemodilution (54% decrease in hematocrit, p < 0.05 vs. hypertonic saline). Activated partial thromboplastin time increased approximately 35% above baseline in all groups except in 6% HES 130/0.4 group in which it doubled. Clot strength was reduced (15%) only in the 6% HES 130/0.4 group. 6% HES 130/0.4 resuscitation produced the largest blood loss and 33% survival rate that was not different than the crystalloid groups. Albumin produced the best hemostatic and survival outcomes (78%).

CONCLUSION

Small-volume resuscitation with crystalloids appeared inadequate to treat hypovolemic shock and prevent death. 6% HES 130/0.4 was effective hemodynamically but detrimental to hemostasis. Albumin produced the best outcomes consistent with our previous observations. Further studies are needed to prove benefit of albumin solution as a possible resuscitation fluid for treating combat casualties at the point of injury.

Effects of 6% hydroxyethyl starch 130/0.4 on postoperative blood loss and kidney injury in off-pump coronary arterial bypass grafting: A retrospective study

We retrospectively evaluated the effects of 6% hydroxyethyl starch (HES) 130/0.4 on postoperative blood loss and acute kidney injury (AKI) in patients undergoing off-pump coronary artery bypass grafting (OPCAB).Electronic medical records of 771 patients who underwent OPCAB in our hospital between July 2012 and July 2014 were reviewed, and 249 patients without intraoperative HES-exposure (group NoHES) were matched 1:N with intraoperative HES-exposed 413 patients (group HES) based on propensity score. The effects of intraoperative HES on postoperative cumulative blood loss within the first 24 hours, need for bleeding-related reoperation, and occurrence of postoperative AKI (determined by KDIGO and RIFLE criteria) were analyzed.In our propensity score matched cohort, there were no significant differences between groups for median postoperative 24 hours blood loss (525 mL in group HES vs. 540 mL in group NoHES, P = .203) or need for bleeding-related reoperation (OR, 2.44; 95% confidence interval [CI], 0.64-9.34, P = .19). However, postoperative AKI (assessed by 2 criteria) occurred more frequently in group HES than in group NoHES (by KDIGO criteria: 10.7% vs. 3.6%; OR 3.43 [95% CI, 1.67-7.04]; P < .001 and by RIFLE criteria: 9.6% vs. 2%; OR 3.32 [95% CI, 1.34-8.24]; P = .01). The median volume of infused HES per patient weight was 16 mL/kg in group HES.In the patients undergoing OPCAB, intraoperative 6% HES 130/0.4 did not increase postoperative bleeding. However, renal safety remains a concern. Intraoperative use of HES should be determined cautiously during OPCAB.

Controversies in the use of hydroxyethyl starch solutions in small animal emergency and critical care

OBJECTIVES

To (1) review the development and medical applications of hydroxyethyl starch (HES) solutions with particular emphasis on its physiochemical properties; (2) critically appraise the available evidence in human and veterinary medicine, and (3) evaluate the potential risks and benefits associated with their use in critically ill small animals.

DATA SOURCES

Human and veterinary original research articles, scientific reviews, and textbook sources from 1950 to the present.

HUMAN DATA SYNTHESIS

HES solutions have been used extensively in people for over 30 years and ever since its introduction there has been a great deal of debate over its safety and efficacy. Recently, results of seminal trials and meta-analyses showing increased risks related to kidney dysfunction and mortality in septic and critically ill patients, have led to the restriction of HES use in these patient populations by European regulatory authorities. Although the initial ban on the use of HES in Europe has been eased, proof regarding the benefits and safety profile of HES in trauma and surgical patient populations has been requested by these same European regulatory authorities.

VETERINARY DATA SYNTHESIS

The veterinary literature is limited mostly to experimental studies and clinical investigations with small populations of patients with short-term end points and there is insufficient evidence to generate recommendations.

CONCLUSIONS

Currently, there are no consensus recommendations regarding the use of HES in veterinary medicine. Veterinarians and institutions affected by the HES restrictions have had to critically reassess the risks and benefits related to HES usage based on the available information and sometimes adapt their procedures and policies based on their reassessment. Meanwhile, large, prospective, randomized veterinary studies evaluating HES use are needed to achieve relevant levels of evidence to enable formulation of specific veterinary guidelines.

Fibrinogen concentrate improves survival during limited resuscitation of uncontrolled hemorrhagic shock in a Swine model

The purpose of this study was to evaluate the effect of fibrinogen concentrate, as a hemostatic agent, on limited resuscitation of uncontrolled hemorrhagic shock. We use a swine model of hemorrhagic shock with free bleeding from a 4-mm aortic tear to test the effect of adding a one-time dose of fibrinogen concentrate given at the onset of limited fluid resuscitation. Immature female swine were anesthetized and subjected to catheter hemorrhage and aortic tear to induce uniform hemorrhagic shock. Animals (n = 7 per group) were then randomized to receive (i) no fluid resuscitation (neg control) or (ii) limited resuscitation in the form of two boluses of 10 mL/kg of 6% hydroxyethyl starch solution given 30 min apart (HEX group), or (iii) the same fluid regimen with one dose of 120-mg/kg fibrinogen concentrate given with the first hydroxyethyl starch bolus (FBG). Animals were then observed for a total of 6 h with aortic repair and aggressive resuscitation with shed blood taking place at 3 h. Survival to 6 h was significantly increased with FBG (7/8, 86%) versus HEX (2/7, 29%) and neg control (0/7, 0%) (FBG vs. HEX, Kaplan-Meier log-rank P = 0.035). Intraperitoneal blood loss adjusted for survival time was increased in HEX (0.4 mL/kg per minute) when compared with FBG (0.1 mg/kg per minute, P = 0.047) and neg control (0.1 mL/kg per minute, P = 0.041). Systemic and cerebral hemodynamics also showed improvement with FBG versus HEX. Fibrinogen concentrate may be a useful adjunct to decrease blood loss, improve hemodynamics, and prolong survival during limited resuscitation of uncontrolled hemorrhagic shock.

Hextend-perfluorocarbon cocktail inhibits mean arterial pressure response in a rabbit shock model

BACKGROUND

Hextend (HEX) is standard of care resuscitation fluid for combat-related traumatic hemorrhage. Because HEX has limited oxygen-carrying capacity, combination therapy with oxygen therapeutics could improve oxygen delivery after hemodynamic shock. We hypothesized that addition of perfluorocarbon (PFC) to HEX would improve hemodynamics and oxygen delivery marker response in a rabbit model of hemorrhagic shock.

METHODS

Anesthetized New Zealand rabbits (n = 23) were randomly allocated to resuscitation with fresh whole blood (FWB), HEX, or HEX plus PFC (HEX + PFC) after 60 min of hemorrhagic hypotension. Mean arterial pressure (MAP) was sampled every 2-3 min for 120 min postinfusion; MAP profiles were modeled by a one-compartment pharmacokinetic model to determine peak MAP (Pmax), time to peak MAP (tmax), and postinfusion MAP persistence. Arterial blood was sampled every 15 min to examine pH, blood gases PO2 and pCO2, metabolites lactate and glucose, methemoglobin (metHb), and electrolytes.

RESULTS

Compared with FWB and HEX, HEX + PFC administration resulted in delayed peak MAP and less persistent (P < 0.0001) MAP elevation; metHb was significantly elevated (P < 0.0001) compared with FWB and HEX. There were no significant differences in PO2, pCO2, or pH. Glucose, hematocrit, and hemoglobin of both HEX and HEX + PFC were significantly lower relative to FWB. Lactate clearance was modest and transient for all treatments; base deficit was significantly more negative for HEX + PFC.

CONCLUSIONS

Addition of PFC to HEX did not improve hemodynamics or acidosis. Further dose- and volume-range studies are required to test efficacy of PFC in combination with HEX for hemorrhagic shock.

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

OBJECTIVE

To review and summarize the pharmacokinetics and pharmacodynamics of hydroxyethyl starch (HES), as well as reported risks and benefits of HES infusion, and to provide administration and monitoring recommendations for HES use in dogs and cats.

DATA SOURCES

Veterinary and human peer-reviewed medical literature, including scientific reviews, clinical and laboratory research articles, and authors' clinical experience.

SUMMARY

HES solutions are the most frequently used synthetic colloid plasma volume expanders in human and veterinary medicine. The majority of research in human medicine has focused on the adverse effects of HES infusion, with emphasis on acute kidney injury and coagulation derangements. The studies often differ in or fail to report factors, such as the type, amount, interval, and concentration of HES administered; the patient population studied; or concurrent fluids administered. Currently, there is no definitive clinical evidence that the reported adverse effects of HES use in human medicine occur in veterinary species. There is little information available on HES administration techniques or simultaneous administration of additional fluids in human and veterinary medicine. The rationale for HES use in small animals has been largely extrapolated from human medical studies and guidelines. A controlled approach to intravenous fluid resuscitation using crystalloid and HES volumes titrated to reach desired resuscitation end point parameters is outlined for small animal practitioners.

CONCLUSION

The extrapolation of data from human studies directly to small animals should be done with the knowledge that there may be species variations and different pharmacokinetics with different HES solutions. Veterinary reports indicate that bolus and continuous rate infusions of 6% hetastarch solutions at moderate doses are well tolerated in feline and canine subjects. Further research in domesticated species is necessary to better define and expand the knowledge regarding use of HES solutions in small animal medicine.

Initial resuscitation with plasma and other blood components reduced bleeding compared to hetastarch in anesthetized swine with uncontrolled splenic hemorrhage

BACKGROUND

Damage control resuscitation recommends use of more plasma and less crystalloid as initial resuscitation in treating hemorrhage. The purpose of this study was to evaluate resuscitation with either blood components or conventional fluids on coagulation and blood loss.

STUDY DESIGN AND METHODS

Isofluorane-anesthetized, instrumented pigs (eight per group) underwent controlled hemorrhage of 24 mL/kg, 20-minute shock period, splenic injury with 15-minute initial bleeding, and hypotensive fluid resuscitation. Lactated Ringer's (LR) was infused at 45 mL/kg while hetastarch (high-molecular-weight hydroxyethyl starch 6%, Hextend, Hospira, Inc., Lake Forest, IL) and blood component (fresh-frozen plasma [FFP], 1:1 FFP:[red blood cells] RBCs, 1:4 FFP : RBCs, and fresh whole blood [FWB]) were infused at 15 mL/kg. Postresuscitation blood loss (PRBL), hemodynamics, coagulation, hematocrit, and oxygen metabolism were measured postinjury for 5 hours.

RESULTS

Resuscitation with any blood component reduced PRBL of 52% to 70% compared to Hextend, with FFP resulting in the lowest PRBL. PRBL with LR (11.5 ± 3.0 mL/kg) was not significantly different from Hextend (17.9 ± 2.5 mL/kg) or blood components (range, 5.5 ± 1.5 to 8.6 ± 2.6 mL/kg). The volume expansion effect of LR was transient. All fluids produced similar changes in hemodynamics, oxygen delivery, and demand despite the oxygen-carrying capacity of RBC-containing fluids. Compared with other fluids, Hextend produced greater hemodilution and reduced coagulation measures, which could be caused by an indirect dilutional effect or a direct hypocoagulable effect.

CONCLUSIONS

These data suggest that blood products as initial resuscitation fluids reduced PRBL from a noncompressible injury compared to Hextend, preserved coagulation, and provided sustained volume expansion. There were no differences on PRBL among RBCs-to-FFP, FWB, or FFP in this nonmassive transfusion model.

Effect of haemodilution, acidosis, and hypothermia on the activity of recombinant factor VIIa (NovoSeven)

Background

A range of plasma volume expanders is used clinically, often in settings where haemostasis may already be impaired. The haemostatic agent, recombinant activated factor VII (rFVIIa, NovoSeven^®), may be used to improve haemostasis but potential interactions with different volume expanders are poorly understood.

Methods

Clot formation was measured by thromboelastography (TEG) using blood from healthy volunteers. In vitro effects of rFVIIa with haemodilution, acidosis, and hypothermia were examined. Conditions were induced by dilution with NaCl (0.9%), lactated Ringer's solution, albumin 5%, or hydroxyethyl starch (HES) solutions [MW (molecular weight) 130–670 kDa]; by adjusting pH to 6.8 with 1 M HEPES (N-2-hydroxyethylpiperazine-N′-2-ethanesulphonic acid) buffer; or by reducing temperature to 32°C. We also studied the effect of low vs high MW HES (MW 200 vs 600 kDa) and rFVIIa on in vivo bleeding time (BT) in rabbits.

Results

Haemodilution progressively altered TEG parameters. rFVIIa improved TEG parameters in the presence of acidosis, hypothermia or 20% haemodilution (P<0.05). At 40% haemodilution, the rFVIIa effect was diminished particularly with high MW HES. In vivo, rFVIIa shortened the BT (P<0.05) with low but not high MW HES.

Conclusions

Efficacy of rFVIIa was affected by the degree of haemodilution and type of volume expander, but not by acidosis or hypothermia.

Hydroxyethyl starch enhances fibrinolysis in human plasma by diminishing α2-antiplasmin–plasmin interactions

Hydroxyethyl starch (HES) solutions are effective volume expanders but are also associated with poorly understood coagulopathy. Enhanced fibrinolysis following dilution with HES has been demonstrated. This investigation sought to identify the interactions of HES with critical fibrinolytic/antifibrinolytic enzymes. Normal plasma or plasmas deficient in factor XIII, thrombin activatable fibrinolysis inhibitor or alpha2-antiplasmin were either not diluted or were diluted 20% with 0.9% NaCl, 5% human albumin, high-molecular-weight HES (HES 450) or low-molecular-weight HES (HES 130). Plasma was activated with celite and exposed to 75 IU/ml tissue-type plasminogen activator. Coagulation growth/disintegration kinetics were determined with thrombelastography. Compared with undiluted plasma, diluted plasma had a significant decrease in the clot lysis time and the time to maximum rate of lysis in all plasma types except in alpha2-antiplasmin-deficient plasma. The hierarchy of the decrease in clot lysis time and time to maximum rate of lysis was HES 450 = HES 130 > 5% human albumin = 0.9% NaCl. In conclusion, HES dilution enhances fibrinolysis by diminishing alpha2-antiplasmin-plasmin interactions. Further laboratory and clinical investigation is warranted to better define the mechanisms by which HES enhances clot disintegration and to find new therapeutic roles for HES to either prevent or treat thrombosis.

Hemostatic Changes After Crystalloid or Colloid Fluid Administration During Major Orthopedic Surgery: The Role of Fibrinogen Administration

BACKGROUND

To explore whether disturbed fibrin polymerization is the main problem underlying dilutional coagulopathy and can be reversed by fibrinogen administration, we conducted a prospective study using modified thrombelastography (ROTEM).

METHODS

Sixty-six orthopedic patients randomly received modified gelatin solution, hydroxyethyl starch 130/0.4, or exclusively Ringer lactate solution. ROTEM analysis was performed, concentrations of coagulation factors and markers of thrombin generation were measured. Fibrinogen concentrate (Hemocomplettan) was administered (30 mg/kg) when thrombelastographically measured fibrinogen polymerization was critically decreased.

RESULTS

The alpha angle, clot firmness, and fibrinogen polymerization (median [min to max]) significantly decreased in the patients receiving hydroxyethyl starch (area under the curve minus baseline (-5 [-9 to -2]), followed by gelatin solution (-3 [-8 to 0]), with the least reductions seen for Ringer lactate solution (-2 [- 4 to 1]) (colloids versus Ringer lactate P < 0.0001). Thirteen patients in the colloid groups but none in the Ringer lactate group needed fibrinogen concentrate to maintain borderline clot firmness. Activity of FVII, FVIII, FIX, and von Willebrand ristocetin activity decreased significantly with colloids. Thrombelastographically measured coagulation time, molecular markers of thrombin generation, and activity of all other coagulation factors were comparable in all groups.

CONCLUSION

Disturbance of fibrinogen/fibrin polymerization is the primary problem triggering dilutional coagulopathy during major orthopedic surgery. The magnitude of clot firmness reduction is determined by the type of fluid used, with hydroxyethyl starch showing the most pronounced effects. These undesirable effects of intravascular volume therapy can be reversed by increasing fibrinogen concentration by administering fibrinogen concentrate, even during continuing blood loss and intravascular volume replacement.