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PubMed2004

Heparinase-modified thrombelastography in term and preterm neonates.

UNLABELLED: Thrombelastography (TEG) appears to be a promising test to assess coagulation in infants and children. TEG enables a rapid assessment of hemostatic function with only 300 microL of whole blood and provides information about plasmatic coagulation, platelet function, and fibrinolysis. In this study, we used TEG to assess the coagulation system of preterm and term neonates to determine the effects of their deficient coagulation factor levels on global hemostatic function. Heparinase-modified TEG, platelet and red blood cell count, plasma fibrinogen, and prothrombin time were assessed in four groups of clinically stable infants: severely preterm (gestational age [GA], 27-31 wk), moderately preterm (GA, 32-36 wk), term (GA, 36-40 wk), and former preterm (corrected GA, 34-40 wk). Healthy adult volunteers served as a control group. When compared with the adult group, thromboelastography revealed no defects in coagulation from groups of clinically stable infants, documenting the functional integrity of coagulation despite, in part, decreased conventional coagulation variables. Because clinically stable preterm and term infants show a relatively small incidence of bleeding, despite prolonged conventional coagulation tests, TEG may better reflect the hemostatic potential of these patients compared with conventional coagulation tests. IMPLICATIONS: This study assessed the coagulation of preterm and term infants by thrombelastography and found functional integrity of coagulation despite, in part, decreased conventional coagulation variables.

Adult↗

PubMed2004

The impact of factor XIII on coagulation kinetics and clot strength determined by thrombelastography.

Fibrinogen has been shown to be responsible for most protein-mediated clot strength via thrombelastography. However, factor XIII (FXIII) activity also plays a prominent role in the development of clot strength. Thus, we hypothesized that changes in FXIII activity would significantly increase clot strength. FXIII (0%, 1%, 6.25%, 12.5%, 25%, 50%, and 100% normal activity) was placed in a fixed volume of citrated FXIII-deficient plasma with 1% tissue factor and calcium chloride and underwent thrombelastography for 10 min. We measured the variables reaction time (R; a measurement of clot initiation), alpha (a measure of the rate of clot formation), amplitude (A; a measure of clot strength), and shear elastic modulus (G; a measure of clot strength). FXIII activity significantly decreased R in a pattern of exponential decay (R2 = 0.77; P < 0.001). FXIII activity significantly increased alpha, following a sigmoidal pattern (R2 = 0.88; P < 0.001). Finally, increases in FXIII activity significantly increased A and G in a sigmoidal pattern (R = 0.89; P < 0.001). We concluded that FXHI significantly affects R, alpha, A, and G. Thus, transfusion decision making with protein-mediated thrombelastographic patterns must account for the contribution of both fibrinogen and FXIII.

Blood Coagulation↗

PubMedDate not supplied

Comparison of thrombelastography with common coagulation tests in preeclamptic and healthy parturients.

BACKGROUND AND OBJECTIVES: Epidural analgesia/anesthesia is often beneficial in the management and treatment of preeclampsia. However, some preeclamptic patients have a coagulopathy that is a contraindication to regional anesthesia. A routine coagulation battery (RCB) consisting of prothrombin time, partial thromboplastin time, platelet count, and bleeding time, is commonly performed to assess coagulation status. Thrombelastography (TEG) is a measure of clotting that allows evaluation of overall coagulation activity. The goal of this study was to examine whether TEG can predict normal and abnormal coagulation as diagnosed by RCB in healthy and preeclamptic parturients. METHODS: Forty-seven parturients participated in this prospective study, performed early in the first stage of labor. Twenty healthy parturients (group I), 19 mild (group II), and 8 severe preeclamptic/eclamptic parturients (group III) had RCB and TEG performed. RESULTS: Five patients (1, group I; 3, group II; 1, group III) had a normal RCB, but a mildly abnormal TEG (prolonged K, small alpha) (specificity = 0.88). Five of 27 preeclamptic parturients (1, group II; 4, group III) had abnormal RCBs. Three of these 5 patients had thrombocytopenia with normal bleeding times and TEGs. Two patients had thrombocytopenia and prolonged bleeding times and abnormal TEGs (sensitivity = 0.40). CONCLUSION: Thrombelastography is not an effective means of predicting abnormal coagulation, as diagnosed by RCB, in preeclamptic parturients, using currently defined normal TEG values for nonpregnant patients. However, an abnormal TEG maximum amplitude value always correlated with a prolonged bleeding time. Therefore, TEG may be useful in assessing platelet function in the presence of thrombocytopenia. Further studies are warranted.

Adult↗

PubMed1999

Infection and hemostasis in decompensated cirrhosis: a prospective study using thrombelastography.

Bacterial infections are common complications in decompensated cirrhosis, but their relationship with hemostasis has not been studied. We prospectively assessed whether infection affects hemostasis in cirrhosis using routine hemostasis tests and thrombelastography (TEG), a global test of hemostatic function. Eighty-four cirrhotic patients (Child-Pugh B: 26; C: 58) without overt bleeding or blood-product transfusion were prospectively evaluated with routine hemostasis tests and TEG on admission and/or the first day with signs of infection and 5 days later. There were 30 patients with infection; 15 had infection on admission, and 15 developed infection in hospital. In the patients who developed infection in hospital, there was a significant deterioration in all routine hemostasis tests except platelet count (PLT) and in all TEG parameters, on the first day of infection compared with 7 +/- 3 days previously. The same parameters significantly improved from the first day of infection to day 5 and after (P <.02) only in the 22 patients whose infection resolved, while the r, k, and alpha TEG parameters significantly worsened in the 8 patients with persistent infection. In those who developed infection in hospital and were cured (n = 11), the 5-day parameters did not differ from their preinfection values. In conclusion, bacterial infections frequently impair hemostasis in decompensated cirrhotic patients. Successful treatment of infection usually restores hemostasis parameters to preinfection levels in 5 days. Thus, infection may have a role in the bleeding diathesis of cirrhosis.

Adult↗

PubMed1993

Effect of delay and storage on whole-blood clotting analysis as determined by thrombelastography.

The thrombelastogram (TEG) measures the viscoelastic properties of clotting blood, displaying a visual trace of all phases of coagulation and fibrinolysis. Thrombelastography can be performed on whole blood (WBTEG) or on citrated blood or plasma, citrated samples facilitating delayed analysis but requiring recalcification of the sample. The aim of this study was to investigate the effect of delay and storage method on WBTEG measurement. Thrombelastographic analysis of coagulation in whole blood was investigated after delays of 3 and 6 minutes in polystyrene syringes (PS3 and PS6) and 3 minutes in silicone-coated glass tubes (SG3). Thrombelastograms of the delayed samples were compared with those measured immediately. Silicone-coated glass tubes activated coagulation, as seen by shorter r times (p < 0.01), shorter r + k times (p < 0.01), and larger maximum amplitude (ma) values (p < 0.01) compared with TEG values determined immediately after sampling. In the SG3 group, 20% of samples had clotted by 3 minutes, and the use of SG tubes for this purpose cannot be recommended. A delay of 6 minutes in PS had less effect on the activation of clotting in the earlier stages in that the r time was prolonged (p < 0.01). However, there appeared to be some activation later in that k time was shorter (p < 0.01) and ma was wider (p < 0.05). Overall, a 3-minute delay in PS produced the best values.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Coagulation↗

PubMed1991

Monitoring of coagulation status using thrombelastography during paediatric open heart surgery.

Thrombelastography (TEG) has proved useful in identifying coagulopathies (via assessment of clot elasticity properties) during hepatic surgery, but its role in cardiac surgery has as yet not been defined. Twenty-two children [11M, 11F, mean age (range) 4.9 (0.1-16) years] undergoing open heart surgery were investigated [1] preoperatively, [2] 15 min post protamine, [3] 2 h and [4] 24 h postoperatively using TEG. Comparisons were made between pre- and postoperative measurements and haematological indices. The values obtained from the TEG were: R phase (indicative of thrombokinase and thrombin formation disorders), K phase (indicative of fibrinogenesis) and MA phase (providing information on clot stability and platelet function). The patients were divided into two groups based upon 24 h blood loss; Group 1 - blood loss less than 0.7 ml/kg/h and Group 2 - blood loss greater than 0.7 ml/kg/h. In Group 2 there was a highly significant correlation between post-protamine MA phase and platelet number (r = 0.93, p less than 0.001) but there was no correlation in Group 1 (p greater than 0.1). Furthermore, in Group 2 elevated postoperative blood loss was associated with a prolonged K phase (mean [SD] 12.0 [6.0] versus 6.3 [2.1] min, p less than 0.05) and diminished MA phase (37 [12.5] versus 56 [4.9] mm, p less than 0.01) relative to preoperative values. In Group 1, K and MA phase did not alter significantly (p greater than 0.5 and p greater than 0.2, respectively). TEG predicted with 100% (8/8) accuracy increased post-operative bleeding. The specificity of TEG prediction of future bleeding was 73% [8/11]. Alterations in TEG parameters merit further evaluation as markers of postoperative haemorrhage.

Blood Coagulation↗

PubMed1988

Material thrombelastography: an assessment of phosphorylcholine compounds as models for biomaterials.

The use of phosphorylcholine (PC) containing compounds as possible biomaterials has been evaluated by material thrombelastography (MTEG). The detailed analysis of the MTEG technique is discussed. A remarkable reduction of thrombogenicity by compounds containing the PC group is demonstrated. The results observed with a polymerised PC-lipid indicate potential use of such substances as biomaterials with minimal thrombogenicity.

1,2-Dipalmitoylphosphatidylcholine↗

PubMed1989

New haemocompatible polymers assessed by thrombelastography.

Mimicry of the nonthrombogenic surface of the erythrocyte has been advocated as the starting point for the development of nonthrombogenic biomaterials. Phosphorylcholine forms 88% of the outer surface of the erythrocyte, and so materials containing it should be nonthrombogenic. We have evaluated the thrombogenicity of such materials and compared them with Dacron and PTFE. Three materials containing phosphorylcholine were used: a naturally occurring phospholipid (dipalmitoylphosphatidylcholine, DPPC), a polymerized phospholipid (diacetylenic phosphatidylcholine, DAPC) and a polyester polyurethane (Polyester G). The thrombogenic potential of these materials was assessed by material thrombelastography (MTEG). This technique uses human whole blood at 37 degrees C, without an air interface, and records the elasticity of the blood clot produced. Since each material is evaluated with a control surface, extraneous differences due to factors other than the test material are eliminated. Analysis, and examples of the MTEG traces are shown and discussed. The phosphorylcholine containing materials were found to have a reduced amount of clotting factor activation, but only DPPC was better than Dacron and PTFE. MTEG demonstrated the known thrombogenicity of Dacron towards platelets. A striking reduction in platelet activation was shown for the three phosphorylcholine containing materials. These three materials show only 25% of the platelet activation of PTFE. These materials warrant further investigation as potentially very useful biomaterials.

Biocompatible Materials↗

PubMed2005

Normal values for thrombelastography (ROTEM) and selected coagulation parameters in porcine blood.

The pig is a suitable animal model for researching blood coagulation and fibrinolysis. The present study therefore aimed to investigate in porcine blood the applicability of commercially available tests of coagulation and thrombelastography (ROTEM) and above all to determine normal values for coagulation parameters (e.g. prothrombin time (PT), activated partial thromboplastin time (aPTT), thrombin-antithrombin complexes (TAT), fibrinogen, antithrombin III (AT III), D-dimers, protein C). Except for the FibTEM and aPTT tests, all commercially available coagulation tests used were fully applicable for porcine blood. Normal values and reference intervals for porcine blood are given. As compared to the human reference intervals for the coagulation parameters investigated, porcine blood was found to be hypercoagulable.

Animals↗

PubMed2001

Changes in coagulability as measured by thrombelastography following surgery for proximal femoral fracture.

The effect of surgery for femoral neck fracture on whole blood coagulation and the relationship of altered coagulation to deep venous thrombosis were investigated in 250 patients. Whole blood coagulation was measured using thrombelastography preoperatively, in the early postoperative period and at 6-week review. Significant hypercoagulability was demonstrated after surgery and persisted to 6-week review. A significant correlation between hypercoagulability and the development of deep venous thrombosis is demonstrated. Hypercoagulability is shown to be a major factor in thrombosis formation following proximal femoral neck fracture surgery.

Aged↗

PubMed1997

Management of a postpartum coagulopathy using thrombelastography.

Thrombelastography (TEG), which evaluates the elastic properties of whole blood and provides a global assessment of hemostatic function, is useful in managing peripartum coagulopathy. A case of severe bleeding after vaginal delivery, in which TEG was used successfully to manage hemostatic defects, is presented.

Adult↗

PubMed2004

Dose-response relationship between plasma ionized calcium concentration and thrombelastography.

OBJECTIVES: To establish the threshold value for calcium at which coagulation commenced and to investigate the range over which changes in ionized calcium influenced coagulation. DESIGN: Controlled, nonblinded, in vitro observational study. SETTING: The study was conducted in a university-based laboratory. PARTICIPANTS: Blood was obtained from healthy volunteers. INTERVENTIONS: One hundred samples of citrated blood were recalcified using varying quantities of 10% calcium chloride solution. Heparinized samples from the recalcified blood were obtained for measurement of ionized calcium concentration (Ca(2+)). MEASUREMENTS AND RESULTS: Coagulation of the recalcified samples was analyzed using thrombelastography. The ionized calcium concentration in recalcified blood was measured using a calcium electrode in a blood gas analyzer. No sample with a Ca(2+) < 0.33 mmol/L showed any clot formation. Normal coagulation measures were obtained in almost all samples in which the Ca(2+) was >0.56 mmol/L. Final clot strength appeared to be independent of Ca(2+) once the threshold value of 0.33 mmol/L was exceeded. CONCLUSIONS: Ca(2+) of <0.33 mmol/L is necessary to prevent coagulation. Ca(2+) > 0.56 is unlikely to be the cause of coagulation abnormalities during surgical procedures in which calcium metabolism is deranged. Between these values, Ca(2+) may exert an effect on the rate of clot formation, but final clot strength should be unaffected.

Blood Coagulation↗

PubMed2004

Does homeopathically potentized antimony stimulate coagulation? A summary of previous findings and results of an in vitro pilot study by means of thrombelastography.

BACKGROUND: Potentized antimony is traditionally used in anthroposophic medicine to enhance hemostasis in bleeding disorders, but evidence of its effectiveness is scarce. On the other hand, non-toxic and economic additional therapeutic options for hemostatic disorders are desirable. OBJECTIVES: We examined all available literature on the subject and performed a controlled pilot in vitro study to test the procoagulatory potency of antimony D 5. DESIGN: Freshly drawn citrated whole blood of 12 healthy volunteers and 12 patients with bleeding disorders was equally distributed into 344 portions, after which it was mixed with antimony D 5, or its potentized vehicle (lactose D 5) as control solution and tested with thrombelastography. The paired t-test and the Wilcoxon signed rank test were used for statistical analysis. In 5 of the 12 healthy donors, a second blood sample was drawn to assess individual variability and increase the total number of replicates. Thus three separate calculations were performed: for the 12 patients, the 12 healthy donors, and the 5 later samples from the same donors. The analysis was exploratory, and no Bonferroni correction was applied. RESULTS: In the antimony D5 samples of the 12 healthy subjects, but not the patients, there was a tendency toward a shorter clotting time (CT) (p = 0.074) and a trend for an increased clot firmness, expressed as maximal amplitude (MA) (p = 0.058). The increase of MA was significant (p = 0.011) when the later samples were included. No statistical difference was detected for the clot formation time and the clot lysis index. CONCLUSION: The exploratory results of this pilot study are inconclusive as to whether antimony D5 has a procoagulatory effect in vitro, although the results suggest an effect on MA and possibly CT. More research is warranted.

Adult↗

PubMed1995

Thrombelastography reveals two causes of haemorrhage in HELLP syndrome.

We describe the use of thrombelastography in HELLP syndrome (Haemolysis, Elevated Liver Enzymes, Low Platelets). It differentiated between two possible causes of significant haemorrhage and revealed an accompanying underlying fibrinolysis. This allowed specific therapy to be directed at both abnormalities and, we believe, helped prevent this patient from undergoing radical surgery to curb blood loss.

Adult↗

PubMed1996

Thrombelastography changes in pre-eclampsia and eclampsia.

We have measured platelet count, bleeding time and thrombelastography (TEG) variables and the correlation between these variables in 49 pregnant patients presenting with pre-eclampsia or eclampsia. Eighteen patients (37%) had a platelet count < or = 150 x 10(9) litre-1 and seven (14%) had a platelet count < or = 100 x 10(9) litre-1. Bleeding time was prolonged > 9.5 min in 13 (27%) patients and the TEG was abnormal in four (8%). The TEG variables, k time and maximum amplitude (MA) had a strong correlation with platelet count (k time-platelet count < or = 150 x 10(9) litre-1, r = -0.68, P = 0.003, platelet count < or = 100 x 10(9) litre-1, r = -0.84, P = 0.02; MA--platelet count < or = 150 x 10(9) litre-1, r = 0.72, P = 0.001, platelet count < or = 100 x 10(9) litre-1, r = 0.78, P = 0.04). There was no correlation between bleeding time and thrombocytopenia (platelet count < or = 150 x 10(9) litre-1, r = -0.18, ns; platelet count < or = 100 x 10(9) litre-1, r = 0.09, ns). There was no correlation between bleeding time and any measured TEG variable. Of the 10 (20%) patients with an adequate platelet count (> 100 x 10(9) litre-1) but prolonged bleeding time, the TEG was normal, suggesting adequate haemostasis. An MA of 53 mm, which is the lower limit for normal pregnancy, correlated with a platelet count of 54 x 10(9) litre-1 (95% confidence limits 40-75 x 10(9) litre-1). Although the number of patients with severe thrombocytopenia was small, a platelet count of 75 x 10(9) litre-1 should be associated with adequate haemostasis.

Anesthesia, Conduction↗

PubMed1996

Heparinase-guided thrombelastography in an anticoagulated parturient.

We describe the use of heparinase-guided thrombelastography in the assessment of a parturient who had been anticoagulated with heparin for suspected thromboembolic disease. Reversal of the heparin effect in the heparinase-treated sample facilitated administration of protamine and successful subarachnoid analgesia for delivery.

Adult↗

PubMed1998

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.

Adult↗

PubMed2005

Effects of protamine and heparin can be detected and easily differentiated by modified thrombelastography (Rotem): an in vitro study.

BACKGROUND: Precise coagulation monitoring might help prevent heparin-protamine mismatch and thus decrease postoperative blood loss. We therefore measured coagulation time (CT) by modified thrombelastography (Rotem) as a possible differential monitor of the effects of heparin and protamine. METHODS: Undiluted and diluted blood samples from 26 healthy volunteers were spiked with increasing concentrations of heparin (0.1, 0.2, 0.4, 0.8 and 1 U ml(-1)). In addition, undiluted blood was spiked with protamine hydrochloride (0.1, 0.2, 0.4, 0.8 and 1.6 U ml(-1)), and we tested the effect of protamine on the reversal of heparin 0.4 U ml(-1). Heparin-containing samples were analysed using the heparin-sensitive INTEM test and the heparinase-containing HEPTEM test; protamine series were also analysed with the EXTEM test (tissue factor activation). RESULTS: CT by the INTEM test [CT-INTEM; median (min/max)] increased significantly and dose-dependently with increasing concentrations of heparin [control, 175 s (146/226); heparin, 1.0 U ml(-1) 1320 s (559/2100); P<0.001] and protamine [control, 172 s (150/255); protamine, 1.6 U ml(-1) 527 s (300/1345); P<0.0001]. Up to heparin concentrations of 0.4 U ml(-1), results were similar in undiluted and diluted blood samples. As expected, CT-HEPTEM remained within the normal range for all tested heparin concentrations (median 180-183 s), but increased similarly to CT-INTEM for increasing protamine concentrations. CONCLUSION: CT measurement using the Rotem technique appears to be a valuable tool for heparin-protamine management. For detection of heparin alone, protamine alone and the two combined, the ratio of CT-INTEM:CT-HEPTEM can be used to distinguish the effects of heparin excess (CT-INTEM:CT-HEPTEM>1) from those of protamine excess (CT-INTEM:CT-HEPTEM=1).

Adult↗