Thromboelastometry and Thrombelastography Analysis under Normal Physiological Conditions - Systematic Review

Review of Thromboelastography (TEG): Medical and Surgical Applications

Thromboelastography (TEG) is a laboratory assay utilized to evaluate hemostatic properties of blood, identify coagulopathy, and guide blood product administration. While the clinical use of TEG started in the care of surgical patients, the assay has now been incorporated more routinely in the care of the medical patient as well. In this review, we explore the evolution of TEG from the historical perspective of its inception to the current state of the art of the assay. The TEG procedure and its measurements are illustrated along with a table that summarizes recommendations from across the medical and surgical literature. After each section, we review salient learning points to provide the busy clinician with information that can be immediately integrated at the bedside. We conclude with a series of summary questions to check for comprehension and direct the reader to additional resources to improve their knowledge of TEG.

Role of Human-Computer Interaction Healthcare System in the Teaching of Physiology and Medicine

With the increasingly severe aging of the population, the difficult and expensive medical treatment problems are becoming more and more prominent; the salary level of domestic doctors is not high, but the cost of training doctors is high, coupled with doctors' work pressure and mental pressure; the number of candidates for medical school is decreasing year by year; medical talent is rare; and the allocation of medical staff is scarce. Health care is the basic guarantee for people's good life, and the shortage of medical staff will have many impacts on health care. Human-computer interaction (HCI) is the study of people, computers, and their interaction. HCI refers to the communication between the user and the computer system, which is the two-way information exchange of various symbols and actions between the human and the computer. The purpose of this paper is to study a healthcare system with human-computer interaction through the client, apply the system to the teaching of physiology and medicine, and analyze its effects and functions in combination with various evaluation indicators. This paper selects teaching content, ease of use of human-computer interaction design, technical services, and user subjective satisfaction as evaluation indicators, and constructs an evaluation model for this. And it builds the physiology and medicine teaching system framework and healthcare system, and conducts tests and statistics on the teaching system. This paper combines online questionnaires, in-app survey feedback, and field visits to collect feedback from users and administrators. The final data show that the teaching system meets the requirements in four evaluation indicators: teaching content, ease of use of human-computer interaction design, technical services, and user subjective satisfaction. User satisfaction with these four aspects reached 86.33%, 95.17%, 63.83%, and 81.87%, respectively. It shows that the system is more popular and can meet the needs of most users.

Thromboelastography: a review for radiologists and implications on periprocedural bleeding risk

Thromboelastography (TEG) and rotational thromboelastometry are emerging technologies that are gaining increasing acceptance in the medical field to evaluate the coagulation status of patients on an individual level by assessing dynamic clot formation. TEG has been proven to reduce blood product use as well as improve patient outcomes in a variety of medical settings, including trauma and surgery due to the expediated nature of the test as well as the ability to determine specific deficiencies present in whole blood that are otherwise undetectable with traditional coagulation studies. Currently, no guidelines or recommendations are in place for the utilization of TEG in interventional or diagnostic radiology although access to TEG has become increasingly common in recent years. This manuscript presents a review of prior literature on the technical aspects of TEG as well as its use in various fields and explains the normal TEG-tracing parameters. Common hemodynamic abnormalities and their effect on the TEG tracing are illustrated, and the appropriate treatments for each abnormality are briefly mentioned. TEG has the potential to be a useful tool for determining the hemodynamic state of patients in both interventional and diagnostic radiology, and further research is needed to determine the value of these tests in the periprocedural setting.

Sulfated non-anticoagulant low molecular weight heparin in the prevention of cancer and non-cancer associated thrombosis without compromising hemostasis

INTRODUCTION

Cancer-associated thrombosis (CAT) accounts for about 20% of all cases of Venous Thromboembolism (VTE). Tissue factor (TF) is documented to be highly expressed on cancer cells and pathological angiogenic endothelial cells. Here, we used a novel oxidized sulfated ultra-LMWH, S-NACH, which is devoid of anti-factor Xa and IIa activities with limited to no systemic anticoagulant effects. This sulfated form has enhanced binding to vascular endothelial cells (EC) and releases and potentiates the action of tissue factor pathway inhibitor (TFPI). S-NACH binds with high affinity to EC, releases and binds to EC TFPI, and promotes vascular antithrombotic effect with limited to no risk of bleeding complications.

MATERIALS AND METHODS

We investigated the effects of S-NACH on clot kinetics in vitro and in vivo. Also, we investigated the effects of S-NACH on CAT mediated by human acute leukemia cells (K562) and human pancreatic cancer cells (SUIT2).

RESULTS

S-NACH was associated with ~3-fold increase of TFPI 2 levels within 3 h. Also, S-NACH reversed the hypercoagulability state that is associated with cancer cells in vitro. In vivo, S-NACH at 20 mg/kg subcutaneously (SC) had no effect on bleeding time compared to both tinzaparin and enoxaparin at 5 mg/kg SC. S-NACH did not show any anti-IIa or anti-Xa activities in comparison to tinzaparin and enoxaparin (p < 0.001).

CONCLUSION

Data suggest the importance of S-NACH through its EC binding, EC TFPI release and its interaction with TFPI in enhancing its activity in the prevention of cancer and non-cancer associated thrombosis with limited to no bleeding complications.

A prospective study on the correlation between thromboelastometry and standard laboratory tests - influence of type of surgery and perioperative sampling times

This prospective study aimed at investigating the influence of surgery type and perioperative sampling times on the correlations between rotational thromboelastometry (ROTEM) parameters and standard laboratory coagulation tests assessing comparable coagulation phases. Patients undergoing glioblastoma multiforme resection (GBR group, n = 60) or laparoscopic colon cancer resection (CCR group, n = 40) were prospectively included. Blood samples for ROTEM and laboratory assessments were consecutively drawn within 24-hours prior to surgery (baseline), and at 2, 24 and 48-hours after surgery. Correlations between perioperative ExTEM clotting-time (CT-exTEM) and prothrombin time (PT), and between FibTEM maximum clot firmness (MCF-fibTEM) with and plasma fibrinogen (pFB) concentration (Clauss method), were evaluated using the Spearman's rho test. The efficiency of recommended cut-offs of CT-exTEM (>75 s) and MCF-fibTEM (<10 mm) for predicting a prolonged PT (>15 s) or a low pFB (<2 g/L), respectively, was assessed using Receiver-Operator Characteristic curves. Correlations between CT-exTEM and PT were weak in GBR (rho = 0.25 [0.12-0.38], p < .01), and very weak in CCR (rho = 0.06 [-0.12-0.27]). Those between MCF-fibTEM and pFB, were strong in both GBR (rho = 0.69 [0.61-0.76], p < .01) and CCR (rho = 0.70 [0.60-0.78], p < .01). These correlations remained largely unchanged over the studied perioperative period in both groups. Recommended CT-exTEM and MCF-fibTEM cut-offs had poor sensitivity for predicting a prolonged PT (17% [8-31]) or a low pFB (46% [32-62]), without group-related differences. Neither the type of surgery nor the perioperative sampling times had a significant influence on the correlations between ROTEM parameters and standard laboratory tests. ClinicalTrials.gov ID: NCT02652897.

Coagulation parameters during the course of severe postpartum hemorrhage: a nationwide retrospective cohort study

We describe the pattern of change in coagulation parameters during the course of severe postpartum hemorrhage in a retrospective cohort study among 1312 women experiencing severe postpartum hemorrhage necessitating blood transfusion. Levels of hemoglobin, hematocrit, platelet count, fibrinogen, activated partial thromboplastin time (aPTT) and prothrombin time (PT) per categorized volume of blood loss during severe postpartum hemorrhage were described and compared between women with and without the composite adverse outcome. Need for surgical intervention, severe acute maternal morbidity, and maternal mortality were jointly considered the composite adverse outcome. Of the 1312 women, 463 (35%) developed the composite adverse outcome. The incidence of a fibrinogen level <2 g/L was 26% (342 per 1312). Low fibrinogen and prolonged aPTT during the first 2 L of hemorrhage were associated with a subsequent composite adverse outcome; median fibrinogen and aPTT among women with and without the composite end point after 1.5 to 2 L of hemorrhage were 1.5 g/L (interquartile range [IQR], 1.0-1.9) vs 2.7 g/L (IQR, 1.9-3.4) and 39 s (IQR, 30-47) vs 32 s (IQR, 28-36), respectively. PT and platelet count as assessed during the first 2 L of hemorrhage were not associated with morbidity or mortality. Our results suggest that detection of low levels of fibrinogen and elevated aPTT levels during early postpartum hemorrhage can contribute to the identification of women that may benefit from targeted hemostatic treatment. Essential in this identification process is the moment of reaching a level of fibrinogen of <2 g/L during the course of postpartum hemorrhage.

Application value of thromboelastography in perioperative clinical blood transfusion and its effect on the outcome of patient

Application value of thromboelastography (TEG) in perioperative clinical blood transfusion and its effect on the outcome of patient were investigated. Seventy-four patients, admitted to The Surgical Department of the First Hospital of Zibo from March 2015 to March 2018, were selected for this study. Among them, 34 patients took only the traditional coagulation function testing method as the blood transfusion guide during the perioperative period and they were regarded as the control group. The other 40 patients used TEG as the blood transfusion guide during the perioperative period, and they were regarded as the TEG group. The coagulation function indicators in 2 h before the operation and in 24 h after the operation, the transfusion amount and blood loss during the operation, the condition of the blood transfusion during the perioperative period, the occurrence rate of the postoperative rebleeding, the length of hospital stay and mortality of the patients in the two groups were compared. The coagulation function indicators of the patients in the two groups in 2 h before the operation and in 24 h after the operation showed that there was no significant difference between the two groups (P>0.050). However, APTT and Pt of the patients in the two groups both increased when compared with those before the treatment (P<0.050) and Hb, Hct, Plt and Fib all decreased (P<0.050). The suspended erythrocytes, Plt, fibrinogen and plasma in the TEG group were both significantly lower than those in the control group (P<0.001). Compared with the traditional coagulation function test, TEG was more accurate for estimating the coagulation function of patient and was more suitable for estimating the condition of blood transfusion of patient in the perioperative period; also, it could shorten the recovery period of patient and it is worthwhile to promote it in the clinic.

Next generation viscoelasticity assays in cardiothoracic surgery: Feasibility of the TEG6s system

BACKGROUND

Viscoelastic near-patient assays of global hemostasis have been found useful and cost-effective in perioperative settings. Shortcomings of current systems include substantial laboratory intensity, user-dependent reproducibility, relatively large sample volumes, sensitivity to ambient vibration and limited comparability between techniques and devices. The aim of this study was to assess feasibility of a new, resonance-based viscoelastic whole blood methodology (TEG6s) in cardiac surgery with cardiopulmonary bypass (CPB) and to compare the parameters this system produces with the ROTEM delta system and standard coagulation tests.

METHODS

In a prospective evaluation study, twenty-three consecutive cardiac surgery patients underwent hemostasis management according to current guidelines, using the ROTEM delta system and standard coagulation tests. Blood samples were collected prior to CPB before anesthetic induction (pre-CPB), during CPB on rewarming (CPB), and 10 minutes after heparin reversal with protamine (post-CPB). ROTEM and standard coagulation test results were compared with TEG6s parameters, which were concurrently determined using its multi-channel microfluidic cartridge system.

RESULTS

TEG6s provided quantifiable results pre-CPB and post-CPB, but only R (clotting time) of CKH (kaolin with heparinase) was measurable during CPB (full heparinization). Spearman's correlation coefficient (rs) was 0.78 for fibrinogen levels and MA CFF (functional fibrinogen). Correlation of several TEG6s parameters was good (0.77 to 0.91) with MCF FIBTEM, and poor (<0.56) with prothrombin time and activated partial thromboplastin time (<0.44). Rs with platelet count was moderate (0.70, MA CK; 0.73, MA CRT). Accuracy of MA CFF for detection of fibrinogen deficiency < 1.5 g/L was high (ROC-AUC 0.93).

CONCLUSIONS

The TEG6s system, which is based on resonance viscoelastic methodology, appears to be feasible for POC hemostasis assessment in cardiac surgery. Its correlations with standard coagulation parameters are quite similar to those of ROTEM and there is good diagnostic accuracy for fibrinogen levels lower than 1.5 g/L. During full heparinization, TEG6s testing is limited to R measurement. Larger studies are needed to assess superiority over other POC systems.

Viscoelasticity and structure of blood clots generated in-vitro by rheometry: A comparison between human, horse, rat, and camel

BACKGROUND

Although the coagulation system is evolutionary well preserved, profound species differences exist in viscoelastic as well as in common laboratory tests of coagulation.

OBJECTIVE

Evaluating differences in clot formation and material characterisation of clots of four mammalian species on macro-, micro- and nanoscales by the means of rheometry, scanning electron microscopy (SEM) and small angle x-ray scattering (SAXS).

METHODS

Blood samples were collected from healthy human volunteers, laboratory rats (HL/LE inbred strain), warmblood horses and dromedary camels. Clot formation was observed by oscillating shear rheometry until plateau formation of the shear storage modulus G', at which point selected clots were prepared for scanning electron microscopy. SEM images were analysed for fibre diameter and fractal dimension. Additionally, scattering profiles for plasma and whole blood samples were obtained with SAXS.

RESULTS

Viscoelasticity of clots showed great interspecies variation: clots of rats and horses exhibited shorter clotting times and higher G' plateau values, when compared to human clots. Camel clots showed unique clotting characteristics with no G' plateau formation in the timeframe observed. Less differentiating features were found with SEM and SAXS, although the rat fibre network appears to be more convoluted and dense, which resulted in a higher fractal dimension.

CONCLUSION

Clotting kinetic differs between the species, which is not only of clinical interest, but could also be an important finding for animal models of blood coagulation.