Human immunodeficiency virus (HIV)infection is associated with haematological changes, including thrombocytopaenia. Pregnancy induces a hypercoagulable state. There are limited data on the coagulation status of women with term pregnancy and HIV receiving anti-retroviral medication. Regional anaesthesia is the technique of choice for caesarean section, and is contraindicated in a hypo-coagulable state. We therefore investigated the coagulation status of term pregnant women with HIV, presenting for elective caesarean section(CS). This was a single-centre cross-sectional observational study, using thromboelastography, comparing the coagulation status of HIV negative and -positive women with no other comorbidities, in pregnancy at term. A blood sample was taken immediately prior to spinal anaesthesia, and thromboelastography was performed within 4 minutes. In addition, platelet count, haemoglobin, and fibrinogen level were measured. Blood samples were obtained from 75 patients. There were no between-group differences in obstetric and demographic data, and no difference in platelet count. The mean (SD) fibrinogen level was higher in HIV positive women (3.9 [1.5] vs 3.5 [0.7] g/L) respectively, p=0.04. There were no significant differences in the r-time, alpha-angle, k-time, MA, or LY-30. The results of this thromboelastography study show that in asymptomatic HIV positive pregnant patients on anti-retroviral treatment, there are no significant differences in coagulation parameters when compared with HIV negative patients. This suggests that routine assessment of coagulation is unnecessary before spinal anaesthesia in patients without other co-morbidities. Further studies could demonstrate the incidence of abnormalities in coagulation or platelet function in patients with AIDS defining disease or HIV positive patients with other co-morbidities.

Dogs with pituitary-dependent hyperadrenocorticism (PDH) are at increased risk of thromboembolic disease (TED); however the pathogenesis of thrombosis in these patients is poorly characterized. Thromboelastography (TEG®) is a whole blood hemostatic test that has recently been shown to be capable of detecting hypercoagulability in veterinary patients. A modification of TEG, PlateletMappingTM (TEG-PM) measures platelet response to the agonists arachidonic acid (MAAA) and adenosine diphosphate (MAADP), and compares this to fibrin clot strength in the absence of platelet activation (MAfibrin). This prospective study evaluated dogs with PDH for hypercoagulability using TEG-PM as well as conventional plasma-based coagulation tests (prothrombin time [PT], activated partial thromboplastin time [aPTT], fibrinogen concentration). Hemostatic testing was performed in 40 healthy dogs, 19 dogs with untreated PDH, 16 of the dogs with PDH after 3 months’ treatment and 15 dogs after 6 months’ treatment. Systolic blood pressure (SBP) was also measured in all the dogs with PDH before and during treatment. In addition, urine protein to creatinine ratio (UPCR) and antithrombin activity [AT] were measured in some dogs with PDH. PT was significantly decreased in the dogs with PDH compared to controls, however all of the dogs with PDH had results within the reference interval. Dogs with PDH were hyperfibrinogenemic compared to healthy dogs; fibrinogen concentrations reduced with treatment of PDH but remained significantly elevated. AT activity in the PDH dogs was not significantly decreased despite the majority of dogs tested having significant proteinuria. Approximately half of the dogs with untreated PDH were hypertensive, and blood pressure did not change significantly following resolution of hypercortisolemia. Serum cholesterol was increased in dogs with untreated PDH but normalized following control of PDH. TEG-PM revealed decreased κ, increased α-angle and increased MAthrombin in dogs with PDH in comparison to healthy dogs. Platelet response to AA was significantly increased in dogs with untreated PDH. Following treatment of PDH, the majority of TEG-PM parameters (with the exception of MAthrombin) did not change significantly. In conclusion, dogs with PDH had evidence of hypercoagulability and hypertension, which persisted despite medical treatment of PDH. These factors may explain the association between hyperadrenocorticism and TED. / OVC Pet Trust Fund, Vetoquinol

The use of an appropriate anticoagulation regiment for the treatment of venous thromboembolism (VTE) in patients with concomitant thrombocytopenia is based on anecdotal evidence and the opinions of managing physicians. The current guidelines suggest that therapeutic levels of anticoagulants may be safely administered to patients who have a minimum platelet count of 50 x 109/L. However, it has recently been suggested that the minimal platelet threshold for safe anticoagulation treatment can be provided at a reduced platelet count of 30 x 109/L. Thus, in order evaluate these platelet threshold we used a thromboelastography (TEG) model to evaluate the clotting parameters of whole blood at predefined platelet counts in the presence of unfractionated heparin (UFH) and low-molecular weight heparin (LMWH). Due to the importance of red blood cells on hemostasis a whole blood TEG model was designed in order to mimic in vivo hemostasis. Clotting was initiated using different concentrations of tissue factor for each anticoagulant at therapeutic and prophylactic levels of UFH and LMWH at predefined platelet counts. In the presence of therapeutic concentrations of either UFH or LMWH, there were no significant differences in TEG parameters of whole blood clots between platelet counts of 30 x 109/L and 50 x 109/L when clotting was driven by the extrinsic pathway. At prophylactic levels of LMWH clot formation was less compromised. Furthermore, no significant difference was noted between platelet-depleted blood (PDB; <10 x 109/L) and 30 x 109/L with respect to r-time. This suggests LMWH at prophylactic levels has no significant bearing on clot formation at a lower platelet threshold versus therapeutic levels of LMWH. Overall, it shows that clot formation is similar for UFH and LMWH when platelet counts are reduced from 50 x 109/L to 30 x 109/L. This work provides insight on the potential for anticoagulation at a reduced platelet threshold in thrombocytopenic conditions. / Thesis / Master of Science (MSc)

Objectives: To determine the effects of prednisone and prednisone plus ultralow-dose aspirin on coagulation in healthy dogs, and to determine intra-individual variation in thromboelastography (TEG). Animals: 14 healthy experimental dogs and 10 healthy client-owned dogs Procedures: Prospective, randomized, blinded study. TEG was performed twice three days apart on each experimental dog prior to treatment and intra-individual variation was calculated. Dogs were given prednisone (2 mg/kg/day) plus aspirin (0.5 mg/kg/day) or prednisone (2 mg/kg/day) plus placebo for 14 days, after which TEG and other baseline tests were repeated. Changes from baseline between and within each group were compared using t-tests or Wilcoxon 2 sample tests. Client owned dogs had TEG performed twice three days apart to determine intra-individual variation. Results: Intra-individual variation in TEG parameters were <10% for MA (maximum amplitude) and angle. For experimental dogs, MA and fibrinogen significantly increased from baseline whereas Ly30 (percent lysis 30 minutes after MA) and antithrombin activity significantly decreased within each group. For the prednisone plus placebo group, Ly60 (percent lysis 60 minutes after MA) significantly decreased from baseline. For all parameters, there was no difference between groups for change from baseline. Conclusions and Clinical Relevance: Prednisone caused hypercoagulability in healthy dogs evidenced by increased MA and fibrinogen and decreased antithrombin activity. Concurrent use of ultra-low dose aspirin had no effect on measured TEG parameters. Intra-individual variation in some TEG parameters is high and may preclude routine clinical utility. / Master of Science

This dissertation describes the effects of tetrastarch (130/0.4) on serum colloid osmotic pressure and thromboelastography variables in healthy pony mares. Additional variables assessed during this study included markers of haemodilution (PCV, TS) and serum creatinine and bile acid concentrations. Six clinically healthy Nooitgedacht pony mares were utilized in a crossover study design. Tetrastarch (130/0.4) was administered at 10, 20 and 40 ml/kg bwt to each mare in a random sequence with a two week washout period between each of the treatments. Packed cell volume (PCV), plasma total solids (TS), serum colloid osmotic pressure (COP), and platelet count were measured and thromboelastography (TEG) was performed before treatment (baseline), immediately after infusion (time 0), and 1, 6, 12, 24, 48, and 96 h after tetrastarch infusion. All TEG variables remained within reference range in all treatment groups. Administration of tetrastarch at 40 ml/kg bwt resulted in a prolonged K-time at 6 h post-infusion, and decreased maximum amplitude at 0, 1, 6, 24 and 48 h post-infusion compared to baseline. Administration of tetrastarch increased mean COP values above baseline in all three treatment groups, persisting to 24, 6 and 48 h after treatment with 10, 20 and 40 ml/kg of tetrastarch respectively. This study concluded that, although values remained within established reference ranges, the administration of tetrastarch (130/0.4) at 40 ml/kg bwt is more likely to induce changes in TEG variables than doses of 20 ml/kg or less. Tetrastarch increased COP in healthy horses at all evaluated dose rates. / Dissertation (MMedVet)--University of Pretoria, 2014. / gm2014 / Companion Animal Clinical Studies / unrestricted

Coagulopathy, a condition in which blood coagulation is impaired, can be inherited or result from a variety of conditions including severe trauma, illness or surgery. Perioperative monitoring of a patient’s coagulation status is important to identify coagulopathic patients. Thromboelastography or TEG remains the gold standard for whole blood coagulation monitoring. However, TEG suffers from certain well-documented drawbacks such as contact containment and manipulation of the blood sample, large and uncontrolled strain, and the inability to distinguish the contribution of elasticity and viscosity during blood coagulation. We developed a non-contact blood rheometer which uses a single drop of blood to measure its viscoelastic properties. Small sample size (typically 5-15 μL), low shear strain (linear viscoelasticity), and non-contact manipulation and containment of samples make this technique unique for real-time monitoring of blood coagulation. In the first part of this work, we addressed the development of the technique, benchmarking the results against known material properties standards. We observed large amplitude oscillations of the levitated drop results in multiple resonance modes and excessive dissipation. We suggested upper bound limits for drop oscillation amplitudes required to satisfy the Lamb theoretical expressions for drop frequency and damping. In the second part, we applied our technique to study sickle-cell disease. Our technique showed that the shape oscillation of blood drops was able to assess an abnormally increased viscosity in sickle cell patients when compared with normal controls over a range of hematocrit. Furthermore, the technique was sensitive enough to detect viscosity changes induced by hydroxyurea treatment. The third part of this work focused on blood coagulation monitoring. The technique showed sensitivity to coagulation parameters, such as platelet count, calcium ion concentration, and hematocrit. A comparison of the results with TEG showed coagulation started sooner in the levitation technique, but with a lower rate and lower maximum stiffness. Thus, the technique developed can be used as a monitoring tool to assess blood mechanical properties sensitively enough to be of use in clinical diagnostic settings. / 2020-06-04T00:00:00Z

The complement system is a long and complicated event of reactions where activation leads to cleavage of different factors and ends with either inflammation or cell lysis.     Recent studies have shown that the complement system and coagulation have some elements in common. Therefore in this study it was relevant to look at the inhibition of the complement system in two different whole blood analyses of coagulation activation, thromboelastography and impedance aggregometry. Thromboelastography, or TEG®, measures the clot forming properties of whole blood and the impedance aggregometry, or Multiplate®, measures platelets’ ability to adhere and aggregate to an electrode. Four different inhibitors where used: Eculizumab, C1 inhibitor, Compstatin and OMS721, which all inhibits different parts of the complement system.     The curves from Multiplate® was presented in standard deviation and the number of reduction, while the results from TEG® was presented in before and after added inhibitor in graphs.     In conclusion, impedance aggregometry show a more specific and secure results of the inhibitors effect, which was seen by that both C1 inihibitor and Compstatin had a major influence on the area under the curve (AUC). In TEG® there were no detectable difference, which could mean TEG® is not specific enough for platelets efficiency, which is affected by the complement inhibition.

The Use of Thromboelastography in Evaluation of Coagulation in Females with Physiological or Pathological Pregnancy MUDr. Ferdinand Polák Abstract Introduction: The target of this study was to compare thromboelastography coagulation parameters in the following three groups: a) healthy pregnant women, b) healthy non-pregnant women and c) pregnant women with pathological pregnancy and also to compare it to reference limits for the common population. If appropriate, we would propose recommendations for new reference ranges for pregnant women in their third trimester. Materials and methods: Prospective observational study, comparing, by using thromboelastography, the blood samples of 60 healthy women in their third trimester of pregnancy (group GRAV) to the samples of the control group of 43 healthy non-pregnant fertile women (group NON-GRAV) and to the samples of 50 women with pathological pregnancy (preeclampsia, fetal death) in their third trimester (group PATOL). Selective percentiles were used to determine new reference limits. Results and conclusions: We found statistically significant differences between groups GRAV and NON-GRAV. Therefore, we established, based on our results, new thromboelastography reference limits for pregnant women. Coagulation changes during pathological pregnancy are less...

The Use of Thromboelastography in Evaluation of Coagulation in Females with Physiological or Pathological Pregnancy MUDr. Ferdinand Polák Abstract Introduction: The target of this study was to compare thromboelastography coagulation parameters in the following three groups: a) healthy pregnant women, b) healthy non-pregnant women and c) pregnant women with pathological pregnancy and also to compare it to reference limits for the common population. If appropriate, we would propose recommendations for new reference ranges for pregnant women in their third trimester. Materials and methods: Prospective observational study, comparing, by using thromboelastography, the blood samples of 60 healthy women in their third trimester of pregnancy (group GRAV) to the samples of the control group of 43 healthy non-pregnant fertile women (group NON-GRAV) and to the samples of 50 women with pathological pregnancy (preeclampsia, fetal death) in their third trimester (group PATOL). Selective percentiles were used to determine new reference limits. Results and conclusions: We found statistically significant differences between groups GRAV and NON-GRAV. Therefore, we established, based on our results, new thromboelastography reference limits for pregnant women. Coagulation changes during pathological pregnancy are less...

<p>The management of thrombosis in the presence of thrombocytopenia is challenging because the inherent risk of bleeding associated with anticoagulant use may increase due to low platelet counts. Guidelines regarding anticoagulant use in this situation are based mainly on expert opinions and anecdotal data. We developed an <em>in-vitro</em> model to study the effect of anticoagulants on plasma clot formation in the presence of low platelet counts. We used thromboelastography (TEG) to measure global viscoelastic properties of clot formation and scanning electron microscopy (SEM) to observe and quantify changes in the fibrin clot structure. Experiments were conducted in plasma with varying platelet concentrations from <10 >– 150 × 10⁹/L. Clotting was activated with tissue factor (TF) and calcium, in the presence of factor XIIa inhibitor, corn trypsin inhibitor. One of the following anticoagulants at therapeutic concentration was added to the mixture: unfractionated heparin (UFH), dalteparin, fondaparinux, rivaroxaban or dabigatran. We found clotting had different sensitivity to TF concentration depending on the anticoagulant present. Effects on TEG parameters varied at a fixed TF concentration with each anticoagulant. UFH had the greatest influence, delaying clotting significantly at low platelet counts. The factor-specific anticoagulants had the least impact on TEG parameters. SEM revealed that UFH had the greatest impact on clot structure. UFH caused significant increase in porosity and fibrin widths and had significantly less fibers when platelets decreased. In conclusion, this study may provide fundamental data to understand clot formation in the presence of anticoagulants at low platelet counts. At low platelets the anticoagulants can jeopardize clot formation, especially UFH. The mechanism of each anticoagulant may contribute to the variation in response to TF initiated clotting. AT-dependent anticoagulants compromised plasma clotting more than the newer factor specific anticoagulants, possibly related to the multiple, non-specific inhibition of coagulation factors.</p> / Master of Science (MSc)