Extreme hemodilution in rabbits: an in vitro and in vivo Thrombelastographic analysis

Reference Range of Kaolin-Activated Thromboelastography (TEG) Values in Healthy Pet Rabbits (Oryctolagus cuniculus)

Thromboelastography (TEG) is a viscoelastic technique that allows the examination of both cellular and plasma protein clotting factors. Thromboelastography helps to investigate the underlying coagulopathy and to monitor therapeutic modalities. Although viscoelastic techniques have been used in human and veterinary medicine, reference ranges in pet rabbits are missing. The objective of this study is to establish the reference-range values of TEG parameters in healthy pet rabbits. 24 healthy pet rabbits of different breeds were included: 16 crossbreeds, four Californians, two lops, one lionhead, and one angora. Four rabbits were less than one year old and 20 were older than one year. Twelve rabbits were neutered females, 10 neutered males, and two were intact females. Health status was assessed through a physical examination, a complete blood work, and a coagulation profile. A TEG 5000 Thromboelastograph Hemostasis System was used with kaolin-activated citrated whole blood. All samples were analysed 30 min postextraction. The TEG reference ranges were reaction time (R) 1.4-6.9 min; clot formation time (K) 0.8-2.2 min; α angle 65.8-82.2 degrees; maximal amplitude (MA) 53.7-73.5 mm; measure of clot strength/firmness (G-value) 5796.6-13,885.9 dyn/cm²; and percentage of clot lysis in 30 min (LY30%) 0-41.5%. This study provides the reference ranges of TEG in pet rabbits.

Thrombin Generation in Cardiac Versus Noncardiac Surgical Cohorts

BACKGROUND

Bleeding can be a significant problem after cardiac surgery. As a result, venous thromboembolism (VTE) or anticoagulation or both following mechanical valve implantation are often delayed in these patients. The calibrated automated thrombin (CAT) generation assay has become the gold standard to evaluate thrombin generation, a critical step in clot formation independent of other hemostatic processes (eg, platelet activation, fibrin cross-linking, and fibrinolysis), and is increasingly used to examine thrombotic and hemorrhagic outcomes. No study has currently used this assay to compare the thrombin generation profiles of cardiac surgical patients to noncardiac surgical patients. We hypothesize that noncardiac patients may be less prone to postoperative changes in thrombin generation.

METHODS

A prospective, observational, cohort study was undertaken using blood samples from 50 cardiac and 50 noncardiac surgical patients preoperatively, immediately postoperatively, and on postoperative days 1 to 4. Platelet-poor plasma samples were obtained from patients preoperatively, on arrival to the postanesthesia care unit (PACU) or intensive care unit (ICU), and daily on postoperative days 1 to 4 if patients remained inpatient. Samples were evaluated for CAT measurements. Patient and surgical procedure characteristics were obtained from the electronic medical record.

RESULTS

The primary outcome variable, median endogenous thrombin potential (ETP), measured in nanomolar × minutes (nM × min), was decreased 100% in cardiac surgical versus 2% in noncardiac patients (P < .001). All parameters of thrombin generation were similarly depressed. Cardiac (versus noncardiac) surgical type was associated with -76.5% difference of percent change in ETP on multivariable regression analysis (95% confidence interval [CI], -87.4 to -65.5; P value <.001).

CONCLUSIONS

Cardiac surgical patients exhibit a profound decrease in thrombin generation postoperatively compared with noncardiac surgical patients evaluated by this study. Hemodilution and coagulation factor depletion likely contribute to this decreased thrombin generation after cardiac surgery.

Haemostatic changes associated with fluid resuscitation in canine parvoviral enteritis

The haemostatic status of dogs with canine parvovirus (CPV) enteritis, within 24 h of admission after initial fluid administration, has been described previously, but the haemostatic status at admission and after standard fluid resuscitation, as well as after initial fluid redistribution, has not been investigated previously. The objective of this study was to characterise the haemostatic status at admission and describe the effect of crystalloid fluid resuscitation on haemostatic variables in dogs with CPV enteritis. Twenty-seven client-owned, hospitalised dogs with confirmed natural CPV infection and 15 healthy age-matched controls were included in a prospective, observational clinical study. The volume of resuscitation fluid, haematocrit (HCT), platelet count, thromboelastography (TEG) variables, antithrombin (AT) activity, fibrinogen- and C-reactive protein (CRP) concentrations were measured in all dogs at admission, after fluid resuscitation and, in 10 dogs, after receiving an additional 3 hours of maintenance-rate crystalloid fluids. For the CPV group at admission, the median TEG reaction time (R) and maximum amplitude (MA) or clot strength, as well as the median HCT, fibrinogen and CRP concentrations, were significantly increased compared to the controls. After fluid resuscitation, median R was significantly shorter, MA significantly increased and HCT and AT activity significantly decreased compared to admission values. The haemostatic variables remained unchanged after 3 h of maintenance-rate crystalloid therapy. The increased clot strength present in dogs with CPV enteritis at admission was exacerbated after fluid resuscitation and persisted for hours after large-volume crystalloid fluid administration.

Moderate plasma dilution using artificial plasma expanders shifts the haemostatic balance to hypercoagulation

Artificial plasma expanders (PEs) are widely used in modern transfusion medicine. PEs do not contain components of the coagulation system, so their infusion in large volumes causes haemodilution and affects haemostasis. However, the existing information on this effect is contradictory. We studied the effect of the very process of plasma dilution on coagulation and tested the hypothesis that moderate dilution with a PE should accelerate clotting owing to a decrease in concentration of coagulation inhibitors. The standard clotting times, a thrombin generation test, and the spatial rate of clot growth (test of thrombodynamics) were used to assess donor plasma diluted in vitro with various PEs. The pH value and Ca⁺² concentration were maintained strictly constant in all samples. The effect of thrombin inhibitors on dilution-induced hypercoagulation was also examined. It was shown that coagulation was enhanced in plasma diluted up to 2.0-2.5-fold with any PE. This enhancement was due to the dilution of coagulation inhibitors in plasma. Their addition to plasma or PE could partially prevent the hypercoagulation shift.

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.

Correction of blood coagulation dysfunction and anemia by supplementation of red blood cell suspension, fresh frozen plasma, and apheresis platelet: results of in vitro hemodilution experiments

PURPOSE

This study aimed to determine the optimal composition and timing for the administration of blood supplements during in vivo blood transfusion with red blood cells suspension (pRBC), fresh frozen plasma (FFP), and apheresis platelet (PLT) administered for the correction of anemia and coagulation dysfunction caused by in vitro hemodilution.

MATERIALS AND METHODS

We collected blood samples from 24 healthy volunteers and prepared various dilutions of whole blood with normal saline: 9:1, 8:2, 7:3, 6:4, 5:5, 4:6, 3:7, 2:8, and 1:9. The diluted blood samples were then supplemented with blood components at various proportions and then analyzed to determine the values of the routine blood indices, coagulation indices, and thromboelastogram measures.

RESULTS

At hemodilutions of 40%, 50%, and 60%, the hemoglobin, coagulation indices, and platelet number and function reached critical levels, necessitating supplementation with pRBC, FFP, and PLT, respectively. When hemodilution was 90%, the supplementation required was approximately 1:1.3:0.9 of pRBC/FFP/PLT.

CONCLUSION

The use of pRBC, FFP, and PLT in appropriate proportions can correct the blood coagulation dysfunction and anemia caused by in vitro hemodilution, and these proportions can be used as guidelines for in vivo massive transfusion.

Clinical applicability of rapid thrombelastography and functional fibrinogen thrombelastography to adult liver transplantation

Unlike kaolin thrombelastography (k-TEG), the clinical utility of rapid thrombelastography (r-TEG) and functional fibrinogen thrombelastography (FF-TEG) has not been tested in liver transplantation (LT). These thrombelastography techniques were simultaneously performed at the time of the skin incision (the baseline) and 30 minutes after graft reperfusion (III + 30) for 27 consecutive adult LT patients. k-TEG and r-TEG parameters [alpha angle (α) and maximum amplitude of the clot (MA)] were compared in addition to the assay time. Estimated FF-TEG fibrinogen levels were compared with plasma fibrinogen measurements. At the baseline, the values of Spearman's correlation coefficient (r) between k-TEG and r-TEG were moderate for α (r = 0.40, P = 0.06) and strong for MA (r = 0.90, P < 0.01). At III + 30, r was 0.46 (P < 0.05) for α and 0.80 (P < 0.01) for MA. The average time required to measure MA via r-TEG was decreased in comparison with k-TEG [from 29.7 to 21.6 minutes at the baseline (a 22% reduction) and from 29.6 to 22.9 minutes at III + 30 (a 23% reduction)]. FF-TEG correlated strongly with the plasma fibrinogen level at the baseline (r = 0.90, P < 0.01); however, FF-TEG overestimated the fibrinogen level at III + 30 (r = 0.58, P = 0.01). In conclusion, in adult LT, r-TEG correlates with k-TEG strongly for MA but only moderately for α. FF-TEG estimates the plasma fibrinogen level well at the baseline; however, it must be interpreted with caution because of its overestimation after graft reperfusion when the plasma fibrinogen level often decreases to less than 100 mg/dL.

Effect of hemodilution on coagulation and recombinant factor VIIa efficacy in human blood in vitro

BACKGROUND

This study evaluates the effect of hemodilution by various common resuscitation fluids, and the efficacy of activated recombinant factor VII (rFVIIa) on coagulation parameters in human blood in vitro.

METHODS

Samples from normal healthy volunteers (n = 9) were hemodiluted from 0% to 90% with normal saline, or 0%, 40%, 60%, and 80% with 5% albumin, Hespan, Hextend, normal saline, or lactated Ringer's, and incubated at 37°C ± 1°C for 30 minutes with and without rFVIIa (1.26 μg/mL).

RESULTS

There was a strong correlation between the dilution of hemoglobin (Hb), platelets, or fibrinogen and coagulation parameters. Hemodilution 0% to 90% changed coagulation parameters (prothrombin time [PT], activated partial thromboplastin time [aPTT], and thromboelastography) in an exponential fashion; the greatest changes occurred after hemodilution lowered Hb <6 mg/dL, platelet count < 100,000/mm(3), and fibrinogen concentration <200 mg/dL. PT and aPTT were significantly prolonged after 60% and 80% dilution for all fluids. Hemodilution of 60% and 80% significantly decreased clot strength (maximum amplitude) and the kinetics of clot development (α angle) and increased the clot formation time (K). Hemodilution with Hextend and Hespan decreased maximum amplitude and α angle >5% albumin, lactated Ringer's, or normal saline. rFVIIa significantly improved PT at 60% and 80% dilutions, and aPTT at 80% dilution. There was a significant effect of dilution, but not fluid type, on the efficacy of rFVIIa to change PT and aPTT, and the onset of clotting (R).

CONCLUSIONS

We have strong in vitro evidence that Hb <6 mg/dL, platelet count <100,000/mm(3), and fibrinogen concentration <200 mg/dL can be used as indexes of hemodilution-induced coagulopathy. This study also shows that Hextend and Hespan tend to decrease the clotting ability >5% albumin or the crystalloids. rFVIIa significantly decreased PT at all dilutions and aPTT at the highest dilution. The effectiveness of rFVIIa on PT and aPTT was significantly affected by the degree of dilution, but not by the type of fluid.

Effect of induced hypotensive anaesthesia vs isovolaemic haemodilution on blood loss and transfusion requirements in orthognathic surgery: a prospective, single-blinded, randomized, controlled clinical study

Induced hypotensive anaesthesia and isovolaemic haemodilution are well-established blood-sparing techniques in major surgery. This prospective study compared them for blood loss, transfusion requirements, and surgical field quality during standardized orthognathic operations. In a surgeon-blinded trial, 60 healthy patients requiring either Le Fort I osteotomy or bimaxillary surgery were randomly allocated to receive normotensive anaesthesia, induced hypotensive anaesthesia, or induced hypotensive anaesthesia combined with isovolaemic haemodilution. Blood loss and haemoglobin level were measured intraoperatively and calculated on postoperative day 3. The surgeons rated surgical field quality. Mean blood loss was 1021.63, 392.38 (p<0.05) and 1191.65ml in the normotensive, hypotensive and haemodilution groups, respectively. Mean haemoglobin level immediately after surgery was 9.3, 10.3, and 7.4g/dl (p<0.05), respectively. No hypotensive group patients received transfusions; four normotensive group patients required allogenic transfusions; seven haemodilution group patients needed autogenous retransfusions (p<0.05). Surgical field quality was significantly better in the hypotensive than in the normotensive (p<0.05) or haemodilution (p<0.05) groups. In orthognathic surgery, hypotensive anaesthesia significantly reduces blood loss and transfusion requirements and minimizes allogenic transfusions risks. Induced hypotensive anaesthesia combined with isovolaemic haemodilution has no additional blood-sparing effects but impairs surgical field quality.

Balanced hydroxyethylstarch preparations: are they all the same? In-vitro thrombelastometry and whole blood aggregometry

BACKGROUND AND OBJECTIVE

Haemostasis appears to be less altered with balanced than with unbalanced hydroxyethylstarch (HES) preparations. In a blinded in-vitro coagulation study, the effects of two HESs dissolved in different balanced solutions were measured.

METHODS

Blood from 12 healthy young male volunteers was diluted by 10, 30 and 50% by using either a balanced 6% HES 130/0.42 or a balanced 6% HES 130/0.4. Composition of the solvent of the two HES preparations differed. An unbalanced gelatin solution was used as a control. Rotation thrombelastometry was used to assess changes in coagulation, and whole blood aggregometry using three different inductors was used to assess the effects of dilution on platelet function.

RESULTS

Dilutions of 10 and 30% showed no significant changes in thrombelastometry data and platelet aggregation in all three groups. Fifty per cent haemodilution was associated with significantly more pronounced deterioration in clotting time, clot formation time and clot firmness, with the balanced HES 130/0.42 containing calcium than with the balanced HES without calcium. Platelet function was also more impaired by HES not containing calcium than by HES containing calcium. Extreme dilution with gelatin showed similar results to those of balanced HES 130/0.4.

CONCLUSION

Our in-vitro studies showed that extreme haemodilution with HES 130/0.42 dissolved in a balanced solution containing calcium was associated with less negative effects on thrombelastometry and platelet aggregation than HES 130/0.4 prepared in a balanced solution without calcium. Gelatin prepared in a nonbalanced solution showed similar effects on coagulation to balanced HES without calcium.

Effects of acute hypervolemic fluid infusion of hydroxyethyl starch and gelatin on hemostasis and possible mechanisms

OBJECTIVE

The purpose of this study was to investigate the effects of acute hypervolemic fluid infusion (AHFI) of 6% hydroxyethyl starch (HES) 130/0.4 or 4% succinylated gelatin (GEL) on hemostasis and the possible mechanisms.

METHODS

Thirty-six gastric cancer patients were randomized to receive AHFI of either HES, GEL or lactated Ringer's (RL) solution at the rate of 30 mL x kg(-1) x h( -1) from 20 minutes before to 40 minutes after induction of general anesthesia.

RESULTS

Group HES and GEL had significantly prolonged PT and aPTT, decreased VIII:C and vWF immediately after AHFI. Statistically prolonged reaction time and coagulation time, and decreased growth angle were seen immediately after HES infusion. Maximum amplitude decreased significantly in group HES and GEL immediately after and 4 hours after AHFI.

CONCLUSION

Gelatin reduced clot quality associated with derangements of fibrin polymerization and HES 130/0.4 delayed initiation of sufficient thrombin generation to convert fibrinogen to fibrin and impaired platelet function.

A new plasma-adapted hydroxyethylstarch preparation: in vitro coagulation studies using thrombelastography and whole blood aggregometry

BACKGROUND

The lack of acceptance of hydroxyethylstarch (HES) for intravascular volume replacement is most likely due to reports of abnormal coagulation. In a blinded in vitro study, we compared the effects on hemostasis of a new HES, prepared in a balanced solution, with a conventional HES preparation and Ringer's lactate solution.

METHODS

Blood was taken from 10 healthy young male volunteers. Blood was diluted by 10%, 30%, and 50% using either 6% HES 130/0.42 prepared in a balanced solution, a conventional nonbalanced 6% HES 130/0.4 or Ringer's lactate solution. Rotation thrombelastography, was performed after adding two activators (thromboplastin-phospholipid to monitor the intrinsic system; tissue factor to monitor the extrinsic system). Whole blood aggregometry adding adenosine diphosphate, collagen, and thrombin receptor-activating protein was used to assess changes of platelet function.

RESULTS

Dilution of blood (30% and 50%) resulted in clot formation time that was significantly more prolonged in the nonbalanced than in the balanced HES group. In the 50% diluted sample using the unbalanced HES, maximum clot firmness was significantly more reduced than by 50% dilution using the balanced HES. In the 50% diluent using the nonbalanced HES, adenosine diphosphate-, collagen-, and thrombin receptor activating protein-induced aggregometry was more reduced than in the balanced HES group.

CONCLUSIONS

A balanced HES preparation showed fewer negative effects on thrombelastographic data and platelet aggregation than a nonbalanced HES preparation, especially when using higher degrees of dilution. Future clinical studies may show a decreased influence of balanced HES solutions on coagulation.

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.

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.

The Effect of Dilution on Plasma Coagulation Kinetics Determined by Thrombelastography Is Dependent on Antithrombin Activity and Mode of Activation

Hemodilution-associated hypercoagulability has been the focus of several investigations because significant morbidity and mortality have been associated with perioperative thrombophilia. Because most investigations implicate imbalances in procoagulant/anticoagulant activity as the etiology of hemodilution-associated hypercoagulability, we determined the effects of dilution on coagulation kinetics and clot strength with thrombelastography (TEG(R)). Control plasma (+/-celite activation) and antithrombin (AT)-deficient (<10% activity) plasma were diluted 0%, 10%, 20%, and 30% with saline. TEG(R) variables measured included time to clot initiation (reaction time, R), speed of clot propagation (angle, alpha), and clot strength (amplitude, A; or shear elastic modulus, G). Dilution of control plasma (10%-30%) resulted in a significant (P < 0.05) 16% decrease in R values, no change in alpha values, and decrease in A and G values. AT-deficient plasma had significantly smaller R values compared with control, and dilution did not change R values in AT-deficient plasma. Celite activation eliminated dilution-associated changes in R values in control plasma but resulted in linear decreases (R(2) = 0.88-0.96, P < 0.0001) in alpha, A, and G in response to dilution. Thus, our data indirectly support the concept that decreases in AT activity cause dilution-mediated hypercoagulability in plasma. Finally, celite activation permits quantification of dilution with TEG.

Effect of in vitro hemodilution with hydroxyethyl starch and dextran on the activity of plasma clotting factors

OBJECTIVE

A recent thrombelastography study indicated a compromised in vitro blood coagulation after 10:10 (equal parts of blood and infusion) and 10:4 (10 parts blood to four parts infusion) hemodilution with several plasma substitutes. Oncovertin N (Oncovertin) (a 10% dextran 40 solution) had the strongest anticoagulant effect of all solutions tested, and HAES-sterile 10% (HAES) (a 10% hydroxyethyl starch 200/0.5 solution) showed the strongest effect of five different hydroxyethyl starch preparations. The aim of this study was to determine how in vitro hemodilution with HAES and Oncovertin affects the activity of coagulation factors.

DESIGN

HAES and Oncovertin were tested to determine the intrinsic effect of colloid molecules, as opposed to hemodilution. Normal saline (NaCl) and nonlactated Ringer solution were used as noncolloidal controls.

SETTING

University research institute.

PATIENTS

Six healthy volunteers.

INTERVENTIONS

Twenty milliliters of blood was obtained from each subject.

MEASUREMENTS AND MAIN RESULTS

Prothrombin index, activated partial prothrombin time, soluble fibrin monomers, and the activity of coagulation factors I, II, V, VII, VIII, IX, X, XI, and XII were measured with the Behring Chromotimer according to the manufacturer's instructions. Two dilution ratios of citrated blood to infusion were used: 10:10 (equal parts of blood and infusion) and 10:4 (10 parts blood to four parts infusion). Baseline was undiluted. Hemodilution with NaCl at both 10:4 and 10:10 influenced the coagulation variables measured. The activities of factors I, VII, and soluble fibrin monomers were less influenced than expected by hemodilution alone. The activities of factors II, V, IX, and XI were significantly (p <.04) lower with both 10:4 and 10:10 dilution with NaCl. In the assays for factors IX, XI, and XII, clots formed immediately after adding the appropriate reagents in the presence of Ringer solution at 10:10 hemodilution, so that the activities of those factors could not be measured. For the other factors and for 10:4 dilution, the outcome after Ringer solution was similar to that of NaCl. The activities were less influenced after 10:4 hemodilution with both HAES and Oncovertin than after dilution with NaCl and Ringer solution, with no significant differences from baseline. At 10:10 hemodilution with both HAES and Oncovertin, several factor activities were significantly (p <.04) lower than baseline.

CONCLUSIONS

Both NaCl and Ringer solution cause measurable effects on coagulation factors at 10:4 hemodilution that can be explained by hemodilution alone. The effects on clotting factors of 10:4 hemodilution with HAES and Oncovertin were not significant. Even at 10:10 hemodilution with HAES or Oncovertin, the reduction in factor activities, although significantly (p <.04) different from baseline, was less than what was expected by dilution alone.

Hemodilution with albumin, but not Hextend, results in hypercoagulability as assessed by Thrombelastography in rabbits: role of heparin-dependent serpins and factor VIII complex

Isovolemic hemodilution (IVHD) has been advocated as an effective method of reducing the need for transfusion but has been associated with hypercoagulability. We tested the hypothesis that IVHD enhances hemostatic function by decreasing circulating antithrombin activity in rabbits. Furthermore, it was determined whether different replacement solutions would affect hemostasis. Sedated rabbits were randomly assigned to groups that underwent IVHD (40% blood volume removed) with 5% human albumin (n = 10) or a 6% hetastarch solution (Hextend). Antithrombin and Factor VIII complex (VIII:C) activities were determined, and thrombelastography(R) was performed with or without platelet inhibition. IVHD resulted in a significant (P < 0.05) decrease in antithrombin (32%-39%) without fluid-specific differences observed. VIII:C did not change in the albumin group, whereas the hetastarch group had a significant (P < 0.05) decrease (43%) in VIII:C that was also significantly (P < 0.05) less than the albumin group. The time to clot initiation was decreased, and the rate of clot formation increased significantly via thrombelastography(R) in albumin animals. No significant change in clot kinetics was observed in hetastarch animals. In rabbits, the primary determinant of hemostasis after IVHD was the interaction of changes in antithrombin activity and VIII:C. These data serve as a rational basis to determine whether IVHD-mediated hypercoagulability encountered clinically may be attenuated or exacerbated by the choice of colloid administered.

IMPLICATIONS

Isovolemic hemodilution (IVHD) is associated with hypercoagulability. Rabbits hemodiluted with albumin, but not Hextend, became hypercoagulable secondary to a loss of antithrombin activity with simultaneous maintenance of Factor VIII complex activity (VIII:C). Hextend-treated animals had proportionate decreases in both antithrombin activity and VIII:C. IVHD-mediated hypercoagulability encountered clinically may be attenuated or exacerbated by the choice of colloid administered.

Coagulation effects of in vitro serial haemodilution with a balanced electrolyte hetastarch solution compared with a saline-based hetastarch solution and lactated Ringer's solution

The hydroxyethyl starches are a group of compounds that has been associated with impairment of coagulation when large volumes are administered. The thrombelastograph is commonly used to assess point-of-care whole blood coagulation. Little is known about the dose-response relationships of haemodilution, and it is reasonable to assume that a linear association exists. This may not be the case with altered electrolyte compositions of the fluids used for haemodilution. We have therefore conducted an in vitro study of haemodilution of human whole blood using lactated Ringer's solution and two high molecular weight hetastarches, one in a balanced salt solution, the other in a 0.9% saline solution. The thrombelastograph, commonly used for the assessment of the coagulation effects of synthetic colloids, was used as the coagulation assessment device. Serial haemodilution with hetastarch in a balanced salt solution demonstrated a biphasic response (of r-times and k-times, as well as alpha angles), with haemodilution in the 20-40% range causing enhanced coagulation, and higher degrees of dilution causing a decrease in overall coagulation performance. A similar picture was observed with lactated Ringer's solution, but only significantly so in alpha angles. Hetastarch in saline did not display this initial increased coagulability at mild to moderate dilutions. This biphasic response of lactated Ringer's solution and hetastarch in a balanced salt solution reflects the complex interaction of fluids and the coagulation system, and that these effects cannot be attributed to simple haemodilution. On the other hand, there was a linear decrease in maximum amplitude with haemodilution. Maximum amplitude was particularly affected by both starches, which is an expected finding in view of the known interaction between the hydroxyethyl starches and von Willebrand's factor.

Are lactated Ringer's solution and normal saline solution equal with regard to coagulation?

Crystalloids represent an attractive strategy to alleviate intravascular volume deficits. Crystalloid hemodilution was associated with hypercoagulability in in vitro and in vivo studies. The influence of different crystalloids on coagulation in the surgical patient is not well studied. In a prospective, randomized study in patients undergoing major abdominal surgery, we used either lactated Ringer's solution (RL) (n = 21) or 0.9% saline solution (SS) (n = 21) exclusively for intravascular volume replacement over 48 h to maintain central venous pressure between 8 and 12 mm Hg. Activated thrombelastography (TEG) using different activators (intrinsic TEG, extrinsic TEG, heparinase TEG, aprotinin TEG) was used to measure coagulation time, clot formation time, and maximum clot firmness. Measurements were performed after induction of anesthesia (T0), immediately after surgery (T1), 5 h after surgery (T2), and on the morning of the first (T3) and second (T4) postoperative days. RL 18,750 +/- 1890 mL and 17,990 +/- 1790 mL of SS were infused during the study period. Acidosis was seen only in the SS-treated group. Blood loss was not different between the groups. Fibrinogen and antithrombin III decreased similarly at T1 and T2 in both groups, most likely because of hemodilution. Differences in TEG data from normal baseline were seen only immediately after surgery and 5 h thereafter, indicating mild hypercoagulability in the intrinsic TEG (RL, from 147 +/- 130 s to 130 +/- 11 s; SS, from 146 +/- 12 s to 131 +/- 12 s). There were no differences in coagulation between RL- and SS-treated patients. We conclude that in major abdominal surgery intravascular volume replacement with crystalloids resulted in only moderate and abbreviated changes in coagulation. No differences in activated TEG and blood loss were seen between an RL- and an SS-based intravascular volume replacement regimen.

IMPLICATIONS

In 42 patients undergoing major abdominal surgery, either lactated Ringer's solution or 0.9% saline solution were exclusively used for volume therapy for 48 h. Activated thrombelastography revealed some mild hypercoagulability after surgery. No differences in coagulation were seen between the two intravascular volume replacement strategies.

Resuscitation with Hextend decreases endogenous circulating heparin activity and accelerates clot initiation after hemorrhage in the rabbit

Hemorrhagic shock can result in a hypercoagulable state and has been associated with both hemorrhagic and thrombotic complications in the perioperative period. The author hypothesized that hemorrhage and resuscitation could result in a hypercoagulable state via changes in the heparin-antithrombin III anticoagulant mechanism in rabbits. Rabbits sedated with ketamine underwent sham operation (n = 8) or hemorrhage (25 mL/kg blood shed) for 60 min, followed by resuscitation with an equal volume of 5% human albumin (n = 8) or Hextend (n = 8). Coagulation analysis with the Thrombelastograph analyzer and determination of endogenous heparin and antithrombin III activity were performed on arterial blood samples obtained before hemorrhage and 30 min after resuscitation. The reaction time significantly decreased by 34% after hemorrhage and resuscitation with Hextend, whereas no other significant changes in Thrombelastograph variables were noted. Antithrombin III activity was significantly less in the Albumin (83% +/- 8% of control, mean +/- SD) and Hextend (88% +/- 8%) Resuscitated groups compared with the Sham-Operated animals. Of interest, only the Hextend-Resuscitated animals demonstrated a significant decrease in heparin activity (53.4 +/- 13.6 mU/mL before hemorrhage, 42.3 +/- 5.6 mU/mL after resuscitation). A Hextend)-mediated decrease of both heparin and antithrombin III activity may explain the acceleration of clot initiation compared with albumin administration after hemorrhage in the rabbit.

IMPLICATIONS

Hemorrhage may result in a hypercoagulable state after resuscitation. Decreases in both endogenous heparin and antithrombin III activity after hemorrhage and Hextend resuscitation in rabbits resulted in a significantly decreased time to clot coagulation analysis initiation without a significant change in the rate of clot formation or final clot strength.

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.

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.

Thoracic aorta occlusion-reperfusion decreases hemostasis as assessed by thromboelastography in rabbits

Perioperative hemorrhage and thrombosis are serious complications associated with major vascular surgery. We hypothesized that thoracic aortic occlusion-reperfusion in rabbits would adversely affect hemostasis as assessed by thromboelastographic variables (reaction time, alpha angle and G [a measure of clot strength]). Isoflurane-anesthetized rabbits underwent either sham operation (n = 10) or 30 min of aortic occlusion followed by 90 min of reperfusion (n = 10). Blood samples (350 microL) were exposed to 10 microL of either 0.9% NaCl or cytochalasin D (a platelet inhibitor, 10 microM final concentration) and analyzed for 1 h by using thromboelastography after 30 min of postpreparation equilibration and at 30 and 90 min of reperfusion. Aortic occlusion-reperfusion resulted in a significant (P: < 0.05) increase in reaction time, decrease in alpha angle, and decrease in G at 30 and 90 min of reperfusion compared with the sham-operated group. The decrease in hemostatic function after aortic occlusion-reperfusion was observed to the same degree in samples with or without platelet inhibition. There were no significant differences in platelet concentration between the sham-operated and aortic occlusion-reperfusion groups. Aortic occlusion-reperfusion decreased hemostatic function in rabbits primarily by decreasing the coagulation factor-dependent, platelet-independent contribution to clotting.

IMPLICATIONS

Thoracic aortic occlusion-reperfusion decreased hemostatic function in rabbits primarily by decreasing the coagulation factor-dependent, platelet-independent contribution to clotting. This decrease in hemostatic function may contribute to hemorrhagic complications associated with major vascular surgery.