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PubMed2005

Thrombelastography/thromboelastometry.

The term thrombelastograph (TEG) was used to describe the trace produced from the measurement of the viscoelastic changes associated with fibrin polymerization. Recently the term rotational thromboelastometry has been applied to the output of the ROTEM instrument. Since its first description in 1948, the TEG/ROTEM has been successfully used in the near patient assessment of haemostasis. The greatest use has been the application of TEG-guided transfusion of blood components in hepatic and more widely in cardiac surgery. Recent years have seen a renewed interest in the technology with applications for both pharmaceutical monitoring and patient screening being described. The present review gives a broad overview of the developments and applications related to thrombelastography/thromboelastometry.

Female↗
PubMed2005

Thromboelastography measurements of whole blood from factor VIII-deficient mice supplemented with rFVIII.

The rotational thromboelastography (ROTEG) assay system allows the real-time analysis of clot formation (fibrin formation) in a whole-blood assay format. The ROTEG system provides significant advantages over the current plasma-based assay systems as it includes the important interactions between cellular and plasmatic coagulation factors. We have employed the ROTEG system to characterize clot formation dynamics in factor VIII- deficient mouse whole blood and examined the ability of recombinant FVIII (rFVIII) supplementation to restore the normal phenotype. The ability to generate a clear dose-response relationship by adding rFVIII to FVIII-deficient murine whole blood (FVIII-/-) demonstrates the feasibility of this approach. A dose-response from 1 U to 0.00001 U mL(-1) demonstrates the enhanced sensitivity of the ROTEG system. Further characterization of this experimental approach may provide a potential tool for comparing the activity of FVIII concentrates and/or evaluating FVIII mutants.

Animals↗
PubMed2006

Acquired haemophilia: dynamic whole blood coagulation utilized to guide haemostatic therapy.

Acquired haemophilia is a rare bleeding disorder caused by autoimmune antibodies interacting with factor VIII (FVIII) or factor IX. Anticipating a high degree of heterogeneity amongst cases, we recently initiated systematic recording of whole blood (WB) coagulation dynamic profiles using our recently developed thrombelastographic method employing very small amounts of tissue factor for activation. Six newly diagnosed patients with acquired haemophilia A in our University Hospital were investigated with the purpose to characterize the WB clotting phenotypes in each patient, as well as inspecting the ex vivo and in vivo response to supplementation with various haemostatic agents. Our results show a striking heterogeneity in patients WB clotting profiles, each patient having a particular pattern and an individual type of response to bypassing agents. Profiles in some of patients resembled severe haemophilia A, even if there was a measurable residual FVIII:C activity while others were more similar moderate-to-mild haemophilia. In one case the profile was very close to normal. Each patient seemed to respond individually to bypassing agents. WB clotting profiles assisted us in selecting an optimal treatment modality in each case and whenever possible, we compared the clinical effects of the treatment selected with the appearance of the WB clotting pattern. In one patient, the ex vivo response to FVIII looked promising, and a approximately 200 IU kg-1 per 24 h high-dose programme nearly normalized the clotting profile in 2-week time. Our preliminary small series of data should be concluded with caution. However, it seems that WB clotting profile studies at baseline, with ex vivo addition of haemostasis promoting agents, and during treatment may hold the potential to predict the success of treatment.

Adult↗
PubMed2006

Individualization of bypassing agent treatment for haemophilic patients with inhibitors utilizing thromboelastography.

The treatment of bleeding for haemophilic patients with inhibitors relies on the use of the bypassing agents, recombinant factor VIIa and factor eight inhibitor bypass activity (FEIBA). While both therapies are effective in the majority of bleeding episodes, there is a significant amount of interindividual variability when it comes to the response to therapy. As of yet, there is no reliable laboratory parameter that can predict the response to therapy in the same manner that factor VIII and factor IX levels predict response in non-inhibitor patients. Developing such a laboratory parameter is vital in order to maximize the clinical efficacy of these agents. Thromboelastography (TEG) is a device, which assesses clot formation over time in whole blood and has several characteristics which suggest it may be an effective way to monitor bypass agent therapy. We studied the ability of TEG to individualize the treatment regimens of three patients with high titre inhibitors assessing the response to recombinant factor VIIa, FEIBA, and when both were used sequentially. The TEG allowed for individualization of treatment for each of the three patients and resulted in more effective, convenient and less expensive treatment regimens. We thus believe that TEG is a promising device for monitoring of bypass agent therapy and should be studied further.

Factor VIII↗
PubMed2006

An audit of red cell and blood product use after the institution of thromboelastometry in a cardiac intensive care unit.

Cardiac surgery is estimated to use 20% of the UK blood supply. However, there has been much interest recently in decreasing red cell and blood product use not only to ease strain on blood stocks or avoid potential transmission of infection but also to decrease post-operative transfusion-related complications. Coagulopathies are not uncommon in cardiac surgical patients, but the time lapse for reporting conventional laboratory results has been highlighted as an obstacle to the appropriate use of blood products. Accordingly, much interest has arisen in rapid near-patient testing of coagulation and, in January 2002, a thromboelastometer (ROTEM, Pentapharm, Germany) was purchased for our unit. This audit sought to assess its impact by retrospective analysis of 990 sequential patients' demographic data and transfusion details covering 6 months prior to its introduction and 6 months after. In the 6 months prior to its introduction, red cells were used in 60% of patients and fresh frozen plasma (FFP) and platelets used in 17 and 16% of patients, respectively. In the following 6 months, red cell use had fallen to 53% and FFP and platelets to 12 and 11%, respectively (P < 0.05). Introduction of thromboelastometry has significantly decreased our use of red cells and blood products.

Aged↗
PubMed2004

Thromboelastography used to assess coagulation during treatment with molecular adsorbent recirculating system.

Coagulopathy is a life-threatening complication of liver cirrhosis. We describe the effect of molecular adsorbent recirculating system (MARS), a cell-free dialysis technique, on the blood coagulation of cirrhotic patients. From February 2002 to July 2002, nine patients--five males (55.5%) and four females (44.4%), age 47-70 yr (median 56)--underwent 12 courses (4-7 sessions each) of MARS. Patients were treated for the following indications: six (66.6%) acute-on-chronic hepatic failure, three (33.3%) intractable pruritus. Platelet count, prothrombin time (PT), international standardized ratio and thromboelastography were measured before and after each MARS session. Coagulation factors II, V, VII, VIII, IX, X, XI, XII, XIII, von Willebrand, lupus anticoagulant, protein C, protein S, antithrombin III, plasminogen, alpha 2 antiplasmin, D-dimer, fibrin monomers, complement, and C(1) inactivator were measured before and at the end of each MARS treatment. We found a statistically significant difference (p < 0.05) in the platelet count, PT, all the thromboelastograph variables (reaction and constant time, alpha angle, and maximal amplitude), factor VIII, von Willebrand, and D-dimer, when measured before and after MARS. Previous reports have shown amelioration of blood coagulation following MARS treatments. However, we document that MARS induces coagulopathy through a platelet-mediated mechanism, whereby platelet may be mechanically destroyed during the passage of blood through the filters and lines. An alternative postulated mechanism is an immune-mediated platelet disruption - coagulopathy.

Aged↗
PubMed2004

Hypercoagulable state associated with kidney-pancreas transplantation. Thromboelastogram-directed anti-coagulation and implications for future therapy.

BACKGROUND: The clinical consequences of type 1 diabetes mellitus (IDDM) include diabetic triopathy: retinopathy, nephropathy, and neuropathy, as well as microangiopathy, accelerated atherosclerotic disease, and hypercoagulability. The etiology of the hypercoagulability is multifactorial, involving various clotting factors or pathways (for example platelets, fibrinogen, individual components of the clotting system and/or fibrinolysis in different studies). The development of end-stage renal disease (ESRD), with the uremia-related platelet effect has the potential to protect from the existing hypercoagulable state. This has important implications for surgery, particularly simultaneous pancreas-kidney (SPK) transplantation, where the pancreas has historically been prone to thrombosis. This has led us to perform intra-operative thromboelastograms (TEG's) to evaluate the patient's current coagulation status. METHODS: A TEG was performed in 85 SPK recipients along with a control group of 54 non-diabetic kidney transplant (KT) recipients. RESULTS: For each of the 4 TEG coagulation parameters, the SPK recipients were significantly more hypercoagulable than the non-diabetic KT recipients. The use of intra-operative heparin is based on the degree of hypercoagulability by TEG and degree of operative hemostasis. There has been one PT lost to thrombosis (1%) in the first week following transplantation during this time. CONCLUSION: The use of TEG is a helpful adjunct to SPK surgery, demonstrating the patient's current coagulation status. Nearly all SPK recipients (type 1 IDDM with ESRD) have been demonstrated to be hypercoagulable. The TEG allows the judicious use of anti-coagulation at the time of surgery, and beyond.

Anticoagulants↗
PubMed2005

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

BACKGROUND: Hydroxyethyl starch (HES) solutions impair haemostatic mechanisms. The impact of the degree of substitution (DS) of a HES solution on thromboelastometry tracings is unclear. Therefore we tested the hypothesis of whether the DS has an effect on the haemostatic defect caused by HES, and assessed whole blood coagulation by thromboelastometry coagulation analysis (ROTEM, Pentapharm Co., Munich, Germany) in serial in vitro haemodilutions of colloids. METHODS: Whole blood was withdrawn from 12 volunteers in a crossover study. Six per cent low-molecular weight HES with a high (HES MW 120 kDa/degree of substitution 0.7) and low (HES MW 130 kDa/0.4) degree of substitution, 4% succinylated gelatin (GEL) or 4% albumin (ALB) was added to citrated venous whole blood samples to make 20, 40, 60 vol.% end-concentrations of each of the solutions. Samples were analyzed by ROTEM. RESULTS: There was a comparable decrease in maximum clot firmness (MCF) and shear elastic modulus [G = 5000 x MCF/(100-MCF)] by HES 120/0.7 and HES 130/0.4 at 20 and 40 vol.% dilutions. At 60 vol.% dilution HES 120/0.7 decreased less alpha-angle and MCF than HES 130/0.4 (P < 0.05). With moderate dilutions all colloids shortened coagulation time (CT). At 20, 40 and 60 vol.% dilutions MCF and G were more decreased in both HES groups than in the ALB and GEL groups (P < 0.05). Furthermore, at 40 and 60 vol.% dilutions G deteriorated more in the GEL than in the ALB group (P < 0.05). CONCLUSION: In vitro the impact of the degree of substitution of HES solution on thromboelastometry coagulation analysis was modest. Haemodilution with gelatin and albumin induced fewer coagulation abnormalities than HES. In addition, the haemodilution with gelatin impaired coagulation more than albumin solution.

Adult↗
PubMed2005

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.

Albumins↗
PubMed2006

Moderate superficial hypothermia prolongs bleeding time in humans.

BACKGROUND: In vitro and in vivo studies have shown that mild systemic hypothermia influences platelet adhesion and aggregation and coagulation reactions. We wanted to test the hypothesis that mild local hypothermia in healthy volunteers with preserved core temperature increased bleeding time. A secondary aim was to evaluate if local cooling influenced whole blood coagulation measured by thrombelastograph (TEG) in the same setting. METHODS: Bleeding time was measured at the left volar forearm at a baseline skin temperature of 32 degrees C and after cooling to 30 degrees C and 28 degrees C in a water bath. Skin temperature was continuously measured by contact thermistors. Measurements of coagulation by TEG were performed at baseline skin temperature before cooling and after cooling to 28 degrees C skin temperature. Tympanic membrane temperature was continuously measured. RESULTS: Compared with baseline, bleeding time was significantly prolonged at 30 degrees C skin temperature and further prolonged at 28 degrees C skin temperature. No significant differences were measured in any of the TEG parameters. During the procedure, tympanic membrane temperature did not change. CONCLUSION: Lowering the skin temperature from 32 degrees C to 30 degrees C and 28 degrees C with a preserved core temperature more than doubled the bleeding time. Whole blood coagulation measured by TEG was not influenced by the local cooling. In addition to core temperature, local temperature may offer information in understanding the surgical site of bleeding.

Adult↗
PubMed2006

The contribution of platelets in the production of cryoprecipitates for use in a fibrin glue.

BACKGROUND AND OBJECTIVES: Cryoprecipitate has a wide application for use as a fibrin glue. In some situations, platelets are added to the preparation in order to enhance the fibrin glue. MATERIALS AND METHODS: Fresh plasma was collected by apheresis from the same donor to produce 250 ml of platelet-rich plasma (PRP) or platelet-poor plasma (PPP) (n = 12 each). Cryoprecipitate was then produced following the standards of the American Association of Blood Banks and resuspended to a total volume of 8 ml, from which aliquots were removed and assayed. Clot formation was measured using the thromboelastogram. RESULTS: The protein content of the two preparations was identical for PRP and PPP. Results for fibrinogen (PPP 475 +/- 220 mg; PRP 399 +/- 215 mg), Factor VIII (PPP 186 +/- 67 IU; PRP 175 +/- 70 IU) and von Willebrand Factor (PPP 260 +/- 104 IU; PRP 221 +/- 88 IU) were not significantly different. The concentration of platelet-derived growth factor was markedly higher (a 100-fold increase at 3778 +/- 1036 ng) when platelets were added to the plasma. There was a small, but not statistically significant, difference in the rate of clot formation (R = 2.3 for PPP and 3.8 for PRP) and clot strength (MA = 63.4 for PPP and 56.6 for PRP) between PPP and PRP cryoprecipitates when measured using the thromboelastogram. CONCLUSIONS: Platelets do not significantly increase the concentration of the usual constituents of cryoprecipitate; however, the levels of platelet-derived growth factor are markedly enhanced. Therefore, there are advantages for using PRP to enhance the growth of new tissue.

Blood Platelets↗
PubMed2004

The use of recalcified citrated whole blood -- a pragmatic approach for thromboelastography in children.

BACKGROUND: Thromboelastography (TEG) is an established way of monitoring the coagulation status of children and adults requiring blood products during surgery. Serial measurements are performed using a nearside machine and blood product prescription may be titrated against changes in TEG. There may also be useful applications when the patient is remote from the TEG machine but these are limited because TEG is usually performed on fresh native whole blood within 6 min of venepuncture. Citrated whole blood can be used for TEG if transport time is more than 6 min. We wished to establish whether TEG parameters for citrated whole blood were comparable with those of native whole blood in healthy children. METHODS: Blood was obtained from 14 healthy children undergoing minor surgical procedures, at the time of intravenous cannula insertion for anaesthesia. Each sample was divided: TEG was performed on part of the sample in its fresh native state at 6 min and second portion of the sample was citrated, kept at room temperature and TEG was performed at 30 min after recalcification. RESULTS: There was a significant difference in TEG parameters (r, k, alpha, MA and LY30) for fresh native whole blood and recalcified citrated whole blood (paired t-test). CONCLUSIONS: The normal range for fresh native whole blood TEG parameters is well established, which is routinely used in practice. There was a significant difference between TEG parameters for fresh native whole blood and citrated whole blood. We recommend that a specific normal range be established for citrated whole blood to enable it to be used in clinical practice.

Adolescent↗
PubMed2004

Whole blood clot formation phenotypes in hemophilia A and rare coagulation disorders. Patterns of response to recombinant factor VIIa.

Until now, no routinely used clotting assay has demonstrated the power to reflect significantly a patient's response to recombinant factor (rF)VIIa. Adopting a thrombelastographic principle, profiles of continuous whole blood (WB) coagulation were studied in minimally altered WB activated with a small amount of tissue factor (TF). Investigation of the WB clotting profile was performed before and after ex vivo addition of rFVIIa 20 nm to WB from 26 patients with hemophilia A, two patients with severe hemophilia B, and individuals with deficiencies of FV, FX, FXI, and FXIII. In five patients with hemophilia plus inhibitors, the response to ex vivo added rFVIIa and to activated complex concentrate (APCC) was studied. Patients with severe and moderate hemophilia A demonstrated remarkable variance in the hemostatic characteristics at baseline, even in groups with the same FVIII:C activity levels. The response to rFVIIa at 20 nm also varied extensively, the effect correlating with the continuous WB coagulation phenotype at baseline. This indicates that the efficacy of rFVIIa may be optimized by tailoring the dose according to the hemostatic response to varying doses tested prior to in vivo administration. In patients with inhibitors against FVIII and factor IX, rFVIIa and APCC substitution resulted in quite similar response patterns that appeared to be dose dependent. In severe FV, FX, and FXIII-deficient WB, rFVIIa addition induced minor changes only. In FXI deficiency, rFVIIa normalized the dynamic properties of clotting, although a reduced clot firmness remained unchanged. In conclusion, the thrombelastographic analysis of WB clotting, as activated with a minute amount of TF, seems an interesting method that detects phenotypic variation amongst hemophilia patients. The method appears useful for assessment of the hemostatic capacity and it seems a promising tool for evaluation of the individual response to rFVIIa or APCC before and during in vivo administration.

Adult↗