An assessment of the effects on coagulation of midtrimester and final-trimester amniotic fluid on whole blood by Thrombelastograph analysis

The Thrombelastograph((R)) test (TEG; Haemoscope Corporation, Skokie, IL) was used to assess the effects of midtrimester and final-trimester amniotic fluid (AF) on whole blood coagulation. Different volumes of midtrimester and final-trimester AF were added to whole blood from nonpregnant volunteers in a series of TEG tests. The addition of both midtrimester and final-trimester AF resulted in significant decreases in reaction time (P < 0.001) and time from reaction to a fixed level of clot firmness (P < 0.05) and significant increases in angle (P < 0.05) and coagulation index (P < 0.05) values. This reflects accelerated clot initiation and propagation. There was no significant change in the maximal amplitude or % lysis at 30 and 60 min with the addition of either midtrimester or final-trimester AF. There was no significant difference between the effects of midtrimester and final-trimester AF on whole blood TEG. TEG may be an additional useful tool in the treatment of coagulopathy in AF embolism. IMPLICATIONS: We used the Thrombelastograph((R)) test (Haemoscope Corporation, Skokie, IL) to assess the effects of midtrimester and final-trimester amniotic fluid (AF) on whole blood coagulation. Results demonstrate that AF accelerates clot initiation and propagation. The Thrombelastograph((R)) test may be useful in assessing coagulopathy in patients with AF embolism.     

Electron microscopic evaluations of clot morphology during thrombelastography

In this study, we characterized clot morphology with a scanning electron microscope (SEM) at time points corresponding to the commonly used thrombelastography (TEG) variables, illustrating the correlation of the physical clot formation with TEG(R) tracings. The first channel of the TEG analyzer was used to obtain the tracings of clot formation, while the sub-samples for the SEM were obtained from the second TEG channel. Different types of samples were examined, including whole blood, abciximab-treated whole blood, platelet-rich plasma (PRP), and abciximab-treated PRP. The SEM images were obtained at reaction time, different amplitudes (5-30 mm), maximum amplitude (MA), and at amplitude 60 min after MA. In the whole blood, coarse fibrin and activated platelets were observed at reaction time and fibrin strands progressively became more solid and intertwined at amplitude 10 mm and thereafter. Red blood cells were surrounded with fibrin strands at amplitude 30 mm and were tightly packed by fibrin strands at MA. In abciximab-treated whole blood, red blood cell shape was maintained at MA. The process of fibrin formation and platelet activation was also examined in PRP. Abciximab did not block platelet shape change, although the blockage of fibrin binding to platelets was shown on the TEG analyzer. In summary, we have shown structural changes of the forming clot in relation to TEG variables.     

Gerinnungsmonitoring mithilfe der Thrombelastographie bei Lungenembolie

Thrombelastography (TEG) is a bedside method used to determine coagulation parameters such as clot formation, stabilization and lysis. This report describes a case of cardiopulmonary arrest due to fulminant pulmonary embolism in a 42-year-old postpartum patient. We discuss the dynamics of coagulation parameters during CPR and thrombolysis complicated by bleeding, as assessed by TEG.     

Arterial and venous Thrombelastograph variables differ during cardiac surgery

The Thrombelastograph (TEG; Haemoscope Corp., Skokie, IL) coagulation analyzer is an effective point-of-care monitor for routine clinical practice and clinical research. Prior investigators have used either arterial or venous samples of blood for TEG measurements. We conducted this prospective cohort study to determine potential differences in TEG variables between arterial and venous blood samples. Arterial and venous samples were drawn from 40 cardiac surgical patients, yielding 134 pairs for comparison. Twenty-nine comparisons (control) were between arterial and arterial samples and were not significantly different. For the arterial and venous comparisons (n = 105), mean (+/-sd) arterial and venous values were the following: reaction time, 10 +/- 2 mm vs 13 +/- 4 mm, P = 0.004; maximum amplitude, 59 +/- 9 mm vs 49 +/- 12 mm, P < 0.001; alpha angle, 61 +/- 10 degrees vs 51 +/- 14 degrees, P < 0.001; K, 5 +/- 2 mm vs 8 +/- 4 mm, P = 0.007; and lysis, 2.5 +/- 1.7 vs 2.5 +/- 2.0 (not significant), arterial versus venous, respectively. Arterial blood samples demonstrated TEG values reflecting stronger (larger maximum amplitude) and faster (shorter reaction time and K value, wider alpha angle) clot formation. The results suggest that users of TEG coagulation analyzers should be consistent with the site of blood sampling given the potential differences obtained. IMPLICATIONS: Thrombelastograph (TEG) values obtained from venous blood samples differ from values obtained from arterial blood samples. When the TEG coagulation analyzer is used for clinical purposes, it is important to be consistent in the blood collection site.     

Coagulopathy post peritoneovenous shunt.

In 1942, 53% of medically treated patients with cirrhosis were dead 6 months after the onset of ascites. Only 30% survived 1 year. This dismal outlook has improved only slightly with advances in medicine. Yet, some internists reject the peritoneovenous shunt (PVS) for this fatal condition even if they are aware that a diminished blood volume causes the abnormal sodium retention responsible for ascites. Their objections are based on life-threatening complications of PVS, especially post shunt coagulopathy (PSC). Blood shed into the peritoneal cavity becomes incoagulable. Such blood is immediately coagulated by a protocoagulant (soluble collagen) and concurrently lysed by tissue plasminogen activator (TPA) secreted by the peritoneal serosa. Wide zones of lysis surround peritoneal tissue placed on fibrin plates. Large volumes of ascitic fluid infused into circulating blood simulates the fate of blood shed into the peritoneal cavity with lysis playing the major role. Addition of ascitic fluid to normal platelet-rich plasma in vitro initiates clot lysis on thromboelastogram (TEG). Epsilon-aminocaproic acid (EACA) counteracts this lysis. EACA and clotting factors normalize the TEG and arrest PSC. Disposal of ascitic fluid at surgery prevents or ameliorates PSC. Mild PSC was encountered only twice in 150+ consecutive patients (1.3%) with only one case being clinically significant (0.6%). Severe PSC occurred seven times in 98 early shunt patients whose ascitic fluid was not discarded. Severe PSC requires shunt interruption and control of bleeding with clotting factors and EACA. Peritoneal lavage with saline prevents the recurrence of PSC on reopening the shunt. In four patients, EACA and clotting factors were adequate to arrest coagulopathy. Three earlier patients died of PSC before its cause and treatment were understood. Proper management eliminates this life-threatening complication, and PSC cannot be considered a deterrent to PVS. Disseminated intravascular coagulopathy (DIC) is produced in experimental animals only by the injection of thrombin or thromboplastin. PSC is a distinct entity differing from DIC; EACA and not heparin is the antidote for PSC.     

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.     

The effects of vasoactive agents, platelet agonists and anticoagulation on thrombelastography

BACKGROUND: Platelet activation is a critical step in primary hemostasis and clot formation. We tested a hypothesis that platelet stimulating effects of vasoactive agents or platelet agonists could be shown using thrombelastography (TEG) as faster onset or increased clot strength. We further examined if TEG could be modified to evaluate activated platelets as a reversal of anticoagulation in the presence of partial thrombin inhibition. METHODS: Blood samples were obtained from 126 non-cardiac surgical patients. Effects of vasoactive agents on TEG and aggregometry were examined using epinephrine, norepinephrine, vasopressin, desmopressin acetate, milrinone and olprinone (Experiment I). Platelet agonists (epinephrine, ADP and collagen) were separately tested on TEG (Experiment II). Effects of platelet agonists (ADP and collagen) on TEG under anticoagulation in the absence or presence of abciximab were studied (Experiment III). We also tested antiplatelet effects of milrinone and olprinone in the presence of anticoagulants on TEG (Experiment IV). RESULTS: Neither vasoactive agents nor platelet agonists affected TEG or aggregometry results except for milrinone and olprinone on aggregometry (Experiment I, II). Platelet agonists facilitated clotting in the presence of anticoagulants (Experiment III). Abciximab-treated platelets still exhibited procoagulant effects in the presence of heparin, while not in the presence of argatroban (Experiment III). Platelet inhibition on the modified TEG was more extensive with milrinone than olprinone, and it was dose dependent (Experiment IV). CONCLUSION: Modified TEG using heparin or argatroban might delineate the procoagulant effects of platelets by adding platelet specific agonist.     

Thrombelastograph (TEG) analysis of platelet gel formed with different thrombin concentrations

Autologous blood transfusion is the safest and most successful way to decrease transfusion-related risks such as postoperative infections, allo-immunization, and short- and long-term immunosuppression. In addition, these fibrin sealants are known to provide coagulation support at the surgical site and act as an adjunct to the control of postoperative bleeding. The physical formation of autologous platelet fibrin gel clot is dependent on both the common pathway of the coagulation cascade and platelet activation. Platelet gel can help provide control of intraoperative and postoperative bleeding. The Thrombelastograph Hemostasis Analyzer (TEG) measures the viscoelastic properties of a clot as it forms. Based on the information that the TEG provides, it promises to be a good choice for point of care measurement of the integrity of thrombus formed by platelet gels. Bovine blood from a single donor was sequestered into platelet-rich plasma and was made into platelet gel using calcium and three different concentrations of thrombin. The platelet gel samples were then analyzed with the TEG analyzer. The results for MA, tMA, CI, and angle were recorded and statistical analysis was performed to accept or reject the null hypothesis, which is: There is no difference between TEG parameters when analyzing platelet gels formed with calcium chloride, platelet-rich plasma and three different concentrations of thrombin A one-way analysis of variance test was performed between thrombin concentrations for MA (p = 0.19), tMA (p = 0.443), CI (p = 0.257), and angle (p = 0.323). The results showed that thrombin concentration did not affect the MA, tMA, CI, or angle as measured by the TEG analyzer. The null hypothesis was accepted. Based on a one-way analysis of variance test for MA, tMA, CI, and angle there was no significant statistical difference for the TEG samples in this experiment as reported with a 95% confidence interval.     

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.     

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.     

Hemostatic assessment of patients undergoing intraaortic balloon pump therapy

Patients undergoing intraaortic balloon pump (IABP) therapy are at risk for developing coagulopathies due to the adverse effects of prolonged exposure of the synthetic surface of the polyurethane balloon to blood components. Hemorrhagic risk has been attributed to a number of factors including thrombocytopenia, vascular injury, and/or platelet degranulation which increase the potential of receiving autogeneic blood transfusions. The present study is a prospective evaluation of coagulation using a viscoelastic monitor (Thrombelastograph--TEG) that measures functional aspects of clot development and stabilization in patients being treated with IABP therapy. Following Institutional Review Board approval, six patients undergoing IABP therapy for hemodynamic instability were enrolled in this study. Blood samples were taken prior to balloon insertion, at 8, 16, 24, 48, 72, and 96 hours on IABP therapy, and 24 hours following the removal of the balloon when applicable. Samples were incubated with heparinase to degrade heparin and TEG profiles were subsequently determined in duplicate. Measured parameters on the TEG included R-time, K-time, maximum amplitude, alpha angle, and lysis at 30 and 60 minutes with calculation of the TEG index. Mortality was 33% following IABP discontinuation. Transfusion of packed red blood cells occurred in 50% of the patients during their balloon pump therapy. Patients demonstrated a significant deviance in fibrinolytic potential from pre-IABP lysis (1.6% +/- 1.8) at both 24 hours (18.8% +/- 22.9) and 48 hours (21.9% +/- 28.5) of therapy (p < 0.05) which returned to baseline shortly after balloon removal. Activation of coagulation factors appeared evident by a steadily increasing alpha angle from pre-IABP data (3.1 +/- 9.2) throughout the duration of therapy and 24 hour recovery (53 +/- 14; p < .005), and by a steadily trending increase in the TEG index pre-IABP (.251 +/- 1.4) to post-IABP (2.6 +/- 1.7; p < 0.05). The results indicate that IABP therapy induces an increase in fibrinolytic potential at 24 to 48 hours of balloon pump therapy with a paradoxical trend toward increased coagulability, potentially predisposing the patient to hemorrhagic risk.     

Surveillance de l'hémostase au cours de la transplantation hépatique : apport du thromboélastogramme

Monitoring of coagulation is mandatory during liver transplantation (LT). Standard coagulation tests may be routinely used. However, they give static information and may be inadequate in case of severe coagulation defect. Interest has been recently focused on thromboelastography (TEG) which could give more suitable and rapid information in these cases. Few studies have evaluated the clinical interest of TEG compared to conventionnal tests. This comparison was the aim of the present study, performed in 89 patients scheduled for LT. The anaesthetic management as well as procedure of transfusion were similar in all patients. Before unclamping, 5000 KUI · kg⁻¹ of aprotinin were injected. Routine tests and TEG were performed at the beginning and end of both preanhepatic and anhepatic phases, and 5, 30, 60, and 120 min after the revascularisation of the new liver. A phase of hypocoagulability was observed after unclamping. Biological signs included an increase in activated thromboplastin time, a reduction of α angle and maximum amplitude on TEG with a lengthening of its r + k component. A strong correlation existed between maximum amplitude and platelets, maximum amplitude and fibrinogen, α and fibrinogen at each time of the surgical procedure. Euglobulin lysis time decreased significantly after clamping, whereas fibrin degradation products increased at the same time. However, typical fibrinolysis with a clot lysis index (CLI) below 55 % was only observed in 15 patients. Twelve of them had a CLI value reaching 0 %, associated with severe generalized oozing. Aprotinin (200 000 to 600 000 KIU) corrected these abnormalities. These results show that TEG may not be very helpful to determine whether platelets or fibrinogen are involved in the phase of hypocoagulability detected after unclamping. However, TEG allows the actual diagnosis of fibrinolysis and guides therapy. Moreover, it may have a predictive value in some limited cases.     

Altered fibrin clot properties in patients on long-term haemodialysis: relation to cardiovascular mortality.

BACKGROUND: Haemodialysis patients are at an increased risk of cardiovascular (CV) morbidity and mortality. Both end-stage renal disease (ESRD) and thromboembolic coronary events have been shown to be associated with the formation of dense fibrin clots resistant to fibrinolysis. The aim of the present study was to investigate the effect of long-term haemodialysis on clot structure/function and analyse an influence of markers of inflammation, oxidative stress and lipoprotein(a). We sought also to investigate if clot features might be related to CV events and mortality in haemodialysis patients. Subjects and methods. In 33 patients (19 males, 14 females), aged 27 to 89 years, on long-term haemodialysis and 33 age- and sex-matched apparently healthy controls, we investigated fibrin clot properties and susceptibility to lysis using recombinant tissue plasminogen activator by using permeation and turbidity assays. RESULTS: Haemodialysis patients produced fibrin clots that had less porous structure (P < 0.0001) were less susceptible to fibrinolysis (P < 0.0001), began fibrin protofibril formation more quickly (P < 0.0001) and showed increased overall fibre thickness (P < 0.0001) compared with controls. Clot permeability and lysis time correlated with F2-isoprostanes (P < 0.01), Lp(a) (P < 0.0001) and fibrinogen (P < 0.01). None of the clot variables showed associations with the duration of haemodialysis treatment or the cause of ESRD. During a 36-month follow-up, 10 CV deaths were recorded. Mortality was associated with reduced clot permeability (P < 0.0001), prolonged lysis time (P < 0.0001), faster fibrin protofibril formation (P = 0.0004), thicker fibres (P < 0.0001) and increased fibrin clot mass (P < 0.0001). CONCLUSIONS: Unfavourably altered clot properties can be detected in haemodialysis patients and may be associated with increased CV mortality.     

Comparison of viscoelastic measures of coagulation after cardiopulmonary bypass

Postoperative hemorrhage remains a major cause of morbidity after cardiopulmonary bypass (CPB). Treatment remains empiric because of the need for immediate correction and the lack of availability of rapid intraoperative coagulation monitoring (except for ACT) at most institutions. Thrombelastography (TEG) and Sonoclot analysis (SCT) are measures of viscoelastic properties of blood which allow rapid intraoperative evaluation of coagulation factor and platelet activity as well as overall clot integrity from a single blood sample. Routine coagulation tests (RCT) including activated clotting time (ACT), prothrombin time (PT), partial thromboplastin time (PTT), fibrinogen level (FIB), and platelet count (PLT) were determined and compared to TEG and SCT to assess which best predicted clinical hemostasis after CPB. Forty-two patients prospectively felt to be at high risk for excessive post-CPB bleeding had blood obtained for RCT, TEG, and SCT analysis before systemic heparinization and 30 min after protamine administration. Nine of 42 patients had excessive chest tube drainage, but no reoperations were required. After CPB, mean values for RCT were normal, but there were abnormalities in TEG and SCT parameters that reflect platelet-fibrin interaction. Both TEG and SCT were 100% accurate in predicting bleeding in these nine patients and, overall, both tests were significantly better predictors of postoperative hemorrhage than RCT. We conclude that viscoelastic determinants of clot strength may be abnormal after CPB and that SCT and TEG are, therefore, more useful than RCT for the detection and management of coagulation defects associated with CPB.     

The effect of hemopure on coagulation in clinically relevant concentrations

Hemopure is a new colloidal blood substitute that may influence coagulation. We designed this study to examine the influence of this product on in vitro coagulation of whole blood by using the thrombelastograph (TEG). Blood samples from 20 volunteers were obtained. Hemopure was added to blood samples to obtain 0.5, 1, and 2 g/dL mixtures of Hemopure in blood. Control consisted of an undiluted sample and, for comparison, two samples diluted with volumes of lactated Ringer's solution (LR) equivalent to the two higher Hemopure dilutions. TEG with Hemopure at a concentration of 2 g/dL showed significantly shorter reaction and clot formation k times and an increased alpha angle compared with control. LR dilution with equivalent volume to 2 g/dL Hemopure solution also resulted in significantly shorter reaction and k times, as well as an increased alpha angle. Coagulation in samples with Hemopure at concentrations of 0.5 and 1 mg/dL did not vary significantly from control. Maximum amplitude did not vary significantly from control in any samples. The effect of Hemopure on TEG measures of coagulation is not significantly different from that of LR at clinically relevant concentrations.     

Effects of hypothermia on thrombelastography in patients undergoing cardiopulmonary bypass

Thrombelastography (TEG) correlates with postoperative chest drain output in patients undergoing cardiopulmonary bypass (CPB). In vitro incubation with heparinase allows TEG monitoring during CPB, despite heparin anticoagulation. Hypothermia impairs coagulation, but these effects cannot be assessed by standard coagulation tests performed at 37 degrees C. The aim of this study was to assess the effects of hypothermia on TEG. Therefore, we have compared normothermic and temperature-adapted TEG in 30 patients undergoing CPB. Our data showed significantly impaired reaction time (r), kinetic time (k), and angle alpha (alpha) in temperature-adapted compared with normothermic TEG. Maximum amplitude (MA), reflecting absolute clot strength, was not affected at temperatures of 33-37 degrees C. These findings indicate a decrease in the speed of clot formation, but not absolute deterioration in clot quality. Furthermore, heparinase-modified TEG indicated that there were nine cases in which heparin effects persisted after heparin reversal with protamine, providing a rational guide to protamine therapy.      

Coagulation effects of a recently developed hydroxyethyl starch (HES 130/0.4) compared to hydroxyethyl starches with higher molecular weight

BACKGROUND: Hydroxyethyl starches (HES) are known to interfere with blood coagulation according to molecular weight, the degree of substitution and the C2/C6 ratio. A recently developed low molecular hydroxyethyl starch (HES 130/0.4) was designed to reduce the blood compromising potency. METHODS: In this study, effects of a 30% in vitro haemodilution with the new HES preparation (HES 130/0.4) in comparison to HES 200/0.5, HES 450/0.7 and sodium chloride solution were investigated using intrinsic and extrinsic activated thrombelastography (TEG) and plasmatic coagulation tests. RESULTS: Whereas plasmatic tests revealed no prolongation of coagulation by HES in comparison to sodium chloride, the TEG variables clotting time, clot formation time and maximal clot firmness showed a significant (P<0.05) inhibition by all the HES preparations. The inhibition was most pronounced in HES 450 (P<0.05 vs HES 130) while HES 130 did not show a statistically significant difference in extrinsic activated maximal clot firmness when compared to sodium chloride. CONCLUSION: These in vitro results demonstrate that hydroxythyl starches especially compromise clot polymerisation. The new preparation HES 130/0.4 seems to inhibit platelet function to a lesser extent than hydroxyethyl starch preparations with a higher molecular weight and degree of substitution.     

The influence of crystalloid and colloid replacement solutions in acute normovolemic hemodilution: a preliminary survey of hemostatic markers

Acute normovolemic hemodilution (ANH), in which blood for autologous use is collected immediately before the onset of surgical blood loss, is a recommended autologous blood procurement technique for blood conservation. Both crystalloid and colloid replacement fluids have been used to maintain normovolemia during ANH, but few data are available to justify the use of a particular replacement fluid. Therefore, we designed a prospective, randomized study to determine if the replacement fluid choice affects various coagulation variables and perioperative blood loss. Forty adult patients, ASA physical status 1-3, scheduled for ANH during radical prostatectomy were randomly assigned to one of four replacement fluid groups: (a) Ringer's lactate, (b) 5% albumin, (c) 6% dextran 70 (DEX), or (d) 6% hetastarch (HES). After the induction of a standardized general anesthetic, all patients underwent ANH to a final hemoglobin level of 9 g/dL. Complete blood count, prothrombin time, partial thromboplastin time, fibrinogen, factors V and VIII levels, bleeding time, and thromboelastography (TEG measurements were obtained at similar time points in the procedure. When compared with baseline, activated partial thromboplastin time decreased and factor VIII levels increased in the postanesthesia care unit in both the Ringer's lactate and 5% albumin groups. The DEX and HES groups demonstrated a decrease in TEG maximum amplitude between preoperative and postanesthesia care unit measurements and TEG alpha (angle) was decreased from baseline in the DEX group. The changes in factor VIII, activated partial thromboplastin time, and TEG measurements indicate that HES and DEX may attenuate the hypercoagulability related to surgery.     

Technical report: Analysis of citrated blood with thromboelastography: comparison with fresh blood samples

PURPOSE: Thromboelastography (TEG) evaluates the visco-elastic properties of whole blood to assess clot formation and hemostasis. When blood cannot be analyzed immediately, it is stored in citrated tubes to be analyzed after recalcification. In this study, we evaluated the results of TEG analysis performed on citrated blood and compared these results to values obtained from activated (kaolin and tissue factor) and non activated, fresh blood samples, obtained at various time intervals (one, two, and three hours). METHODS: Four blood samples were collected from each of ten healthy volunteers. The following TEG analyses were performed on each sample: reaction time (r), k time (k), alpha angle (alpha), and maximum amplitude (MA). Studies were done using fresh, non citrated blood, obtained within five minutes of collection, and using citrated blood, one, two, and three hours after collection. Samples were analyzed, with and without activation, using kaolin and tissue factor. RESULTS: Tissue factor activated and non activated, citrated samples had shorter r and k times (P=0.03, P=0.008, P<0.0001, and P<0.0001, respectively) and higher alpha angle and MA values (P<0.0001, P<0.0001, P=0.79, and P=0.03, respectively) compared to fresh, non citrated samples. These findings were consistent with a hypercoagulable state. Conversely, citrated samples, activated with kaolin, yielded results similar to those obtained from fresh, non citrated samples. The TEG measurements were similar among citrated samples stored from one to three hours. CONCLUSIONS: Our results demonstrate that TEG measures, performed on citrated blood samples, yield results that are consistent with a hyperocoagulable state. Using kaolin to activate citrated samples, on the other hand, yields results similar to those obtained from non citrated, fresh blood samples.