Can the Viscoelastic Parameter α-Angle Distinguish Fibrinogen from Platelet Deficiency and Guide Fibrinogen Supplementation?

Early Goal-Directed Hemostatic Therapy for Severe Acute Bleeding Management in the Intensive Care Unit: A Narrative Review

This is a narrative review of the published evidence for bleeding management in critically ill patients in different clinical settings in the intensive care unit (ICU). We aimed to describe "The Ten Steps" approach to early goal-directed hemostatic therapy (EGDHT) using point-of-care testing (POCT), coagulation factor concentrates, and hemostatic drugs, according to the individual needs of each patient. We searched National Library of Medicine, MEDLINE for publications relevant to management of critical ill bleeding patients in different settings in the ICU. Bibliographies of included articles were also searched to identify additional relevant studies. English-language systematic reviews, meta-analyses, randomized trials, observational studies, and case reports were reviewed. Data related to study methodology, patient population, bleeding management strategy, and clinical outcomes were qualitatively evaluated. According to systematic reviews and meta-analyses, EGDHT guided by viscoelastic testing (VET) has been associated with a reduction in transfusion utilization, improved morbidity and outcome in patients with active bleeding. Furthermore, literature data showed an increased risk of severe adverse events and poor clinical outcomes with inappropriate prophylactic uses of blood components to correct altered conventional coagulation tests (CCTs). Finally, prospective, randomized, controlled trials point to the role of goal-directed fibrinogen substitution to reduce bleeding and the amount of red blood cell (RBC) transfusion with the potential to decrease mortality. In conclusion, severe acute bleeding management in the ICU is still a major challenge for intensive care physicians. The organized and sequential approach to the bleeding patient, guided by POCT allows for rapid and effective bleeding control, through the rational use of blood components and hemostatic drugs, since VET can identify specific coagulation disorders in real time, guiding hemostatic therapy with coagulation factor concentrates and hemostatic drugs with individual goals.

Characteristics of blood clotting on thromboelastography in patients with early burns

BACKGROUND

Thromboelastography (TEG) is a viscoelastic test that may be used to evaluate the hemostatic function of whole blood, and it may be useful for burn patients with multiple hemostatic defects.

METHODS

We retrospectively recruited patients with burns between January 2019 and July 2021. Blood samples were drawn on admission and subjected to coagulation parameter assessment, including conventional coagulation tests and TEG assessment. Receiver operating characteristic (ROC) analysis was performed to predict the occurrence of complications in patients with early burns.

RESULTS

Ninety-three patients with early burns met the inclusion criteria. Patients with minor, moderate, severe, and extremely severe burns accounted for 19.4 %, 36.6 %, 16.1 %, and 27.9 % of all patients, respectively. Compared with the healthy controls, patients with early burns showed significant reductions in the R and K values, and significant elevation in the maximum amplitude (MA), coagulation index (CI), and alpha angle. Compared with minor and moderate burn patients, patients with severe and extremely severe burns had lower K values and thrombin time and higher alpha angle, CI, prothrombin time, international normalized ratio, D-dimer, and fibrin degradation products. Patients with hypercoagulation had lower R and K values, longer MA, longer CI, and greater alpha angle. After ROC analysis, the areas under the ROC curve for acute lung injury, acute kidney injury, and bleeding were 0.789, 0.802, and 0.900, respectively.

CONCLUSION

TEG provides insight into the hemostatic state of patients with early burns, and can predict complications in early burn patients when combined with conventional coagulation tests.

Viscoelastic Testing Methods

Viscoelastic testing methods examine the real-time formation of a clot in a whole blood sample, and include thromboelastography (TEG), rotational thromboelastometry (ROTEM), and several other testing platforms. They allow for concurrent assessment of multiple aspects of clotting, including plasmatic coagulation factors, platelets, fibrinogen, and the fibrinolytic pathway. This testing is rapid and may be performed at the point-of-care, allowing for prompt identification of coagulopathies to guide focused and rational administration of blood products as well as the identification of anticoagulant effect. With recent industry progression towards user-friendly, cartridge-based, portable instruments, viscoelastic testing has emerged in the 21st century as a powerful tool to guide blood transfusions in the bleeding patient, and to identify and treat both bleeding and thrombotic conditions in many operative settings, including trauma surgery, liver transplant surgery, cardiac surgery, and obstetrics. In these settings, the use of transfusion algorithms guided by viscoelastic testing data has resulted in widespread improvements in patient blood management as well as modest improvements in select patient outcomes. To address the increasingly wide adoption of viscoelastic methods and the growing number of medical and laboratory personnel tasked with implementing, performing, and interpreting these methods, this chapter provides an overview of the history, physiology, and technology behind viscoelastic testing, as well as a practical review of its clinical utility and current evidence supporting its use. Also included is a review of testing limitations and the contextual role played by viscoelastic methods among all coagulation laboratory testing.

The Effect of Sepsis and Septic Shock on the Viscoelastic Properties of Clot Quality and Mass Using Thromboelastometry: A Prospective Observational Study

Background

Sepsis is associated with wide variable coagulation abnormalities. Thromboelastography (TEG) effectively measures the viscoelastic properties of the clots. This study aims to illustrate the viscoelastic properties of clot quality and mass in sepsis and septic shock patients using TEG, as an effective tool over standard coagulation tests.

Materials and methods

A single-center, prospective observational study was conducted. 50 patients each meeting the criteria for sepsis and septic shock, and a healthy group of 30 patients was included in the study. Blood samples were obtained and analyzed for standard coagulation tests, platelet count, fibrinogen, and TEG study.

Results

A total of 130 patients were included. Septic shock patients had a higher sequential (sepsis-related) organ failure score. Prothrombin time (PT) and activated partial thromboplastin time (aPTT) were increased significantly as compared to the sepsis and control groups. TEG markers such as alpha angle, and maximum amplitude (MA) were significantly prolonged while reaction time (R time), was significantly shortened in the sepsis group as compared to the healthy group, suggestive of a hypercoagulable state in sepsis patients. While in septic shock patients, MA and Lysis Index 30 (LY 30) were significantly prolonged and, R time was significantly shortened compared to all other groups. Even though LY30 in sepsis patients was found to be within the normal range (p < 0.001), 18% of patients had prolonged LY30 indicating a hypercoagulable state with impaired fibrinolysis.

Conclusion

Thromboelastography, as a point-of-care test combined with conventional coagulation tests can provide additional, clinically relevant information on coagulopathy, and outcome, and thus help guide treatment modality in sepsis and septic shock-induced coagulopathy.

How to cite this article

Mohapatra P, Kumar A, Singh RK, Gupta R, Hussain M, Singh S, et al. The Effect of Sepsis and Septic Shock on the Viscoelastic Properties of Clot Quality and Mass Using Thromboelastometry: A Prospective Observational Study. Indian J Crit Care Med 2023;27(9):625-634.

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.

Association between multiple coagulation-related factors and lymph node metastasis in patients with gastric cancer: A retrospective cohort study

Background

Patients with tumors generally present with accompanying activation of the coagulation system, which may be related to tumor stage. To our knowledge, few studies have examined the activation of the coagulation system in reference to lymph node metastasis within gastric cancer. This study aimed to investigate the correlation between multiple coagulation-related factors and lymph node metastasis in patients with gastric cancer after excluding the influence of tumor T stage.

Materials and methods

We retrospectively evaluated the relationship between lymph node metastasis and coagulation-related factors in 516 patients with T4a stage gastric cancer. We further analyzed influencing factors for lymph node metastasis and verified the predictive value of maximum amplitude (MA, a parameter of thromboelastography which is widely used to assess the strength of platelet-fibrinogen interaction in forming clots) in reference to lymph node metastasis.

Results

Platelet counts (P=0.011), fibrinogen levels (P=0.002) and MA values (P=0.006) were statistically significantly higher in patients with T4a stage gastric cancer presenting with lymph node metastasis than in those without lymph node metastasis. Moreover, tumor N stage was statistically significantly and positively correlated with platelet count (P<0.001), fibrinogen level (P=0.003), MA value (P<0.001), and D-dimer level (P=0.010). The MA value was an independent factor for lymph node metastasis (β=0.098, 95% CI: 1.020-1.193, P=0.014) and tumor N stage (β=0.059, 95% CI: 0.015-0.104, P=0.009), and could be used to predict the presence of lymph node metastasis in patients with gastric cancer (sensitivity 0.477, specificity 0.783, P=0.006). The independent influencing factors for MA value mainly included platelet levels, fibrinogen levels, D-dimer and hemoglobin levels; we found no statistically significant correlations with tumor diameter, tumor area, and other evaluated factors.

Conclusion

We conclude that MA value is an independent influencing factor for lymph node metastasis and tumor N stage in patients with T4a stage gastric cancer. The MA value has important value in predicting the presence or absence of lymph node metastasis in patients with gastric cancer.

Clinical trial registration

http://www.chictr.org.cn, identifier ChiCTR2200064936.

Viscoelastic Hemostatic Assays for Orthopedic Trauma and Elective Procedures

The application of viscoelastic hemostatic assays (VHAs) (e.g., thromboelastography (TEG) and rotational thromboelastometry (ROTEM)) in orthopedics is in its relative infancy when compared with other surgical fields. Fortunately, several recent studies describe the emerging use of VHAs to quickly and reliably analyze the real-time coagulation and fibrinolytic status in both orthopedic trauma and elective orthopedic surgery. Trauma-induced coagulopathy—a spectrum of abnormal coagulation phenotypes including clotting factor depletion, inadequate thrombin generation, platelet dysfunction, and dysregulated fibrinolysis—remains a potentially fatal complication in severely injured and/or hemorrhaging patients whose timely diagnosis and management are aided by the use of VHAs. Furthermore, VHAs are an invaluable compliment to common coagulation tests by facilitating the detection of hypercoagulable states commonly associated with orthopedic injury and postoperative status. The use of VHAs to identify hypercoagulability allows for an accurate venous thromboembolism (VTE) risk assessment and monitoring of VTE prophylaxis. Until now, the data have been insufficient to permit an individualized approach with regard to dosing and duration for VTE thromboprophylaxis. By incorporating VHAs into routine practice, orthopedic surgeons will be better equipped to diagnose and treat the complete spectrum of coagulation abnormalities faced by orthopedic patients. This work serves as an educational primer and up-to-date review of the current literature on the use of VHAs in orthopedic surgery.

Coagulation potential in pediatric patients with immunoglobulin A nephropathy

BACKGROUND

Immunoglobulin A nephropathy (IgAN) is the most prevalent primary chronic glomerular disease in children. Understanding the changes in coagulability caused by IgAN is important for clarifying pathophysiology and choice of treatment. The coagulation potential in patients with IgAN remains to be investigated, however. We aimed to assess comprehensive coagulation potential in pediatric patients with IgAN and explore its relationship with pathological disease severity.

METHODS

Fourteen children with IgAN diagnosed by renal biopsy, who were admitted at Nara Medical University Hospital between 2015 and 2020, were analyzed. Rotational thromboelastometry was used to evaluate coagulation potential. Values of rotational thromboelastometry parameters in patients with IgAN were compared with those in control children.

RESULTS

In patients with IgAN (aged median 9.5 year), clotting time plus clot formation time (CT + CFT) was shortened (P = 0.003) and α angle was greater (P < 0.001) than those in controls, indicating a hypercoagulable state. The rate of mesangial hypercellularity of glomeruli correlated with CT + CFT, α, and maximum clot firmness (MCF) (r_s = -0.79, 0.56, and 0.37). The rate of cellular/fibrocellular crescent of glomeruli correlated with CT + CFT, α, and MCF (r_s = -0.41, 0.60, and 0.50). Patients with mesangial hypercellularity ≥80% of glomeruli showed reduced CT + CFT and increased α angle (P = 0.007 and 0.03). Patients with cellular/fibrocellular crescent ≥10% of glomeruli showed decreased CT + CFT and increased α angle (both P = 0.02).

CONCLUSIONS

The hypercoagulable state in pediatric patients with IgAN may be associated with the pathological severity of their disease.

Viscoelastic Testing and Coagulopathy of Traumatic Brain Injury

A unique coagulopathy often manifests following traumatic brain injury, leading the clinician down a difficult decision path on appropriate prophylaxis and therapy. Conventional coagulation assays—such as prothrombin time, partial thromboplastin time, and international normalized ratio—have historically been utilized to assess hemostasis and guide treatment following traumatic brain injury. However, these plasma-based assays alone often lack the sensitivity to diagnose and adequately treat coagulopathy associated with traumatic brain injury. Here, we review the whole blood coagulation assays termed viscoelastic tests and their use in traumatic brain injury. Modified viscoelastic tests with platelet function assays have helped elucidate the underlying pathophysiology and guide clinical decisions in a goal-directed fashion. Platelet dysfunction appears to underlie most coagulopathies in this patient population, particularly at the adenosine diphosphate and/or arachidonic acid receptors. Future research will focus not only on the utility of viscoelastic tests in diagnosing coagulopathy in traumatic brain injury, but also on better defining the use of these tests as evidence-based and/or precision-based tools to improve patient outcomes.

Anesthetic Management of Living-Donor Renal Transplantation in a Patient With Epstein Syndrome Using Rotational Thromboelastometry: A Case Report

Epstein syndrome is a myosin heavy chain 9 (MYH9)-related disorder characterized by hearing loss and macrothrombocytopenia with renal failure, which usually requires platelet transfusion during surgery. We report the case of a 22-year-old man who underwent living-donor renal transplantation without platelet transfusion using rotational thromboelastometry (ROTEM) monitoring. His intraoperative laboratory coagulation findings were a platelet count of 28–31 × 10⁹/L based on microscopy and fibrinogen of 256 mg/dL. However, his extrinsic pathway evaluations by ROTEM were normal. The estimated blood loss during the operation was 150 mL, and the patient showed no bleeding complications without platelet transfusion.

Prospective Longitudinal Evaluation of Coagulation with Novel Thromboelastography Technology in Patients After Subarachnoid Hemorrhage: A Pilot Study

BACKGROUND

There is limited knowledge of whether hypercoagulability is present after subarachnoid hemorrhage (SAH) or about its timing of onset, duration, and severity. To conduct a pilot new-generation thromboelastography (TEG) technology (TEG6s)-based and conventional coagulation test-supported longitudinal assessment of coagulation in patients with SAH.

METHODS

We prospectively enrolled patients with nontraumatic SAH on admission from May 2015 to May 2016. We performed TEG6s measurements and conventional coagulation tests on days 1, 2, 3, 5, 7, 10, and 14 and compared them with TEG6s parameters in healthy volunteers.

RESULTS

We studied 14 patients and 72 TEG6s measurements. Of these patients, 10 (71.4%) were admitted to the intensive care unit. Mean age was 57.5 (±14.5) years, Acute Physiology and Chronic Health Evaluation III score 58.2 (±26.6), length of hospital stay was 23 (±11.7) days, and mortality was 14.3%. At baseline, conventional coagulation tests were within normal range. However, TEG6s parameters already showed increased coagulability. Thereafter, alpha angle, reaction time, functional fibrinogen level, and maximum amplitude rapidly and significantly increased (P < 0.01) compared with healthy controls. Ten (71.4%) patients demonstrated a >20% increase in coagulability based on TEG6s parameters from their baseline. Moreover, TEG6s hypercoagulability peaked at day 10 and only showed an initial partial decline towards normal by day 14. Similarly, platelet counts and fibrinogen levels increased over this period (P < 0.01) CONCLUSIONS: Using TEG6s technology, we found significant and progressive hypercoagulability in 70% of patients, with an early dominant contribution from hyperfibrinogenemia and increased fibrin formation and partial contribution from thrombocytosis, beginning on the first day, increasing to peak values by day 10, and then partly declining toward normal by day 14.

Viscoelastic Signals for Optimal Resuscitation in Trauma: Kaolin Thrombelastography Cutoffs for Diagnosing Hypofibrinogenemia (VISOR Study)

BACKGROUND

Acute traumatic coagulopathy is common in trauma patients. Prompt diagnosis of hypofibrinogenemia allows for early treatment with cryoprecipitate or fibrinogen concentrate. At present, optimal cutoffs for diagnosing hypofibrinogenemia with kaolin thrombelastography (TEG) have not been established. We hypothesized that kaolin kaolin-TEG parameters, such as kinetic time (K-time), α-angle, and maximum amplitude (MA), would accurately diagnose hypofibrinogenemia (fibrinogen <200 mg/dL) and severe hypofibrinogenemia (fibrinogen <100 mg/dL).

METHODS

Adult trauma patients (injury severity score >15) presenting to our trauma center between October 2015 and October 2017 were identified retrospectively. All patients had a traditional plasma fibrinogen measurement and kaolin-TEG performed within 15 minutes of each other and within 1 hour of admission. Some patients had additional measurements after. Receiver operating characteristic (ROC) curve analysis was performed to evaluate whether K-time, α-angle, and MA could diagnose hypofibrinogenemia and severe hypofibrinogenemia. Area under the ROC curve (AUROC) was calculated for each TEG parameter with a bootstrapped 99% confidence interval (CI). Further, ROC analysis was used to estimate ideal cutoffs for diagnosing hypofibrinogenemia and severe hypofibrinogenemia by maximizing sensitivity and specificity. In addition, likelihood ratios were also calculated for different TEG variable cutoffs to diagnose hypofibrinogenemia and severe hypofibrinogenemia.

RESULTS

Seven hundred twenty-two pairs of TEGs and traditional plasma fibrinogen measurements were performed in 623 patients with 99 patients having additional pairs of tests after the first hour. MA (AUROC = 0.84) and K-time (AUROC = 0.83) better diagnosed hypofibrinogenemia than α-angle (AUROC = 0.8; P = .03 and P < .001 for AUROC comparisons, respectively). AUROCs statistically improved for each parameter when severe hypofibrinogenemia was modeled as the outcome (P < .001). No differences were found between parameters for diagnosing severe hypofibrinogenemia (P > .05 for all comparisons). The estimated optimal cutoffs for diagnosing hypofibrinogenemia were 1.5 minutes for K-time (95% CI, 1.4-1.6), 70.0° for α-angle (95% CI, 69.8-71.0), and 60.9 mm for MA (95% CI, 59.2-61.8). The estimated optimal cutoffs for diagnosing severe hypofibrinogenemia were 2.4 minutes for K-time (95% CI, 1.7-2.8), 60.6° for α-angle (95% CI, 57.2-67.3), and 51.2 mm for MA (95% CI, 49.0-56.2). Currently recommended K-time and α-angle cutoffs from the American College of Surgeons had low sensitivity for diagnosing hypofibrinogenemia (3%-29%), but sensitivity improved to 74% when using optimal cutoffs.

CONCLUSIONS

Kaolin-TEG parameters can accurately diagnose hypofibrinogenemia and severe hypofibrinogenemia in trauma patients. Currently recommended cutoffs for the treatment of hypofibrinogenemia are skewed toward high specificity and low sensitivity. Many patients are likely to be undertreated for hypofibrinogenemia using current national guidelines.

Viscoelastic Monitoring to Guide the Correction of Perioperative Coagulopathy and Massive Transfusion in Patients with Life-Threatening Hemorrhage

The resuscitation of patients with traumatic hemorrhage remains a challenging clinical scenario. The appropriate and aggressive support of the patient's coagulation is of critical importance. Conventional coagulation assays present several shortcomings in this setting. The integration of viscoelastic monitoring in clinical practice has the potential to result in significant improvements. In order to be successful, the provider must understand basics of the methodology, read outs, and the limitations of the technique.

Viscoelastic Monitoring to Guide Hemostatic Resuscitation in Liver Transplantation Surgery

Coagulopathic bleeding must be anticipated during liver transplantation (LT) surgery. Patients with end-stage liver disease (ESLD) often present with disease-related hematologic disturbances, including the loss of hepatic procoagulant and anticoagulant clotting factors and thrombocytopenia. Transplantation surgery itself presents additional hemostatic changes, including hyperfibrinolysis. Viscoelastic monitoring (VEM) is often used to provide targeted, personalized hemostatic therapies for complex bleeding states including cardiac surgery and major trauma. The use in these coagulopathic conditions led to its application to LT, although the mechanisms of coagulopathy in these patients are quite different. While VEM is often used during transplant surgeries in Europe and North America, evidence supporting its use is limited to a few small clinical studies. The theoretical and clinical applications of the standard and specialized VEM assays are discussed in the setting of LT and ESLD.

Targeted Thromboelastographic (TEG) Blood Component and Pharmacologic Hemostatic Therapy in Traumatic and Acquired Coagulopathy

Trauma-induced coagulopathy (TIC) is a recently described condition which traditionally has been diagnosed by the common coagulation tests (CCTs) such as prothrombin time/international normalized ratio (PT/INR), activated partial thromboplastin time (aPTT), platelet count, and fibrinogen levels. The varying sensitivity and specificity of these CCTs have led trauma coagulation researchers and clinicians to use Viscoelastic Tests (VET) such as Thromboelastography (TEG) to provide Targeted Thromboelastographic Hemostatic and Adjunctive Therapy (TTHAT) in a goal directed fashion to those trauma patients in need of hemostatic resuscitation. This review describes the utility of VETs, in particular, TEG, to provide TTHAT in trauma and acquired non-trauma-induced coagulopathy.

The effectiveness of 10 years of interventions to control postoperative bleeding in adult cardiac surgery

Objectives

Postoperative bleeding in cardiac surgery remains an important complication, leading to increased morbidity and mortality. Different interventions are possible to prevent/treat postoperative bleeding. The present study aims to investigate the effectiveness of these interventions in a real-world scenario.

Methods

This is a retrospective study based on 19 670 consecutive adult cardiac surgery patients operated from 2000 to 2015. During the study period, the following interventions have been applied and tested for effectiveness with a before versus after analysis: thromboelastography (TEG)-based diagnosis and treatment in actively bleeding patients; platelet function tests (PFTs); timing of surgery based on PFTs; fresh frozen plasma (FFP)-free strategy using prothrombin complex concentrate and fibrinogen concentrate.

Results

TEG-based diagnostic and therapeutic approach resulted in a significant (P = 0.006) reduction of postoperative bleeding and significant (P = 0.001) increase in platelet concentrate transfusion rate. Timing of surgery based on PFTs resulted in a significant reduction of postoperative bleeding (P = 0.001), surgical re-exploration rate (P = 0.002), FFP (P = 0.001) and platelet concentrate (P = 0.016) transfusion rate. FFP-free strategy was associated with a significant decrease in postoperative bleeding (P = 0.005) and FFP transfusions (P = 0.001). The combination of all the interventions was associated with a significant (P = 0.001) reduction in postoperative bleeding, surgical re-exploration rate and FFP transfusions, whereas platelet concentrate transfusion rate was significantly (P = 0.001) higher.

Conclusions

Despite a continuous increase in the bleeding risk profile, the application of a bundle of interventions is effective in controlling postoperative bleeding and related complications. Platelet transfusions remain unreplaceable in the present scenario.

Quasi-static acoustic tweezing thromboelastometry

Essentials Blood coagulation measurement during contact with an artificial surface leads to unreliable data. Acoustic tweezing thromboelastometry is a novel non-contact method for coagulation monitoring. This method detects differences in the blood coagulation state within 10 min. Coagulation data were obtained using a much smaller sample volume (4 μL) than currently used.

SUMMARY

Background Thromboelastography is widely used as a tool to assess the coagulation status of critical care patients. It allows observation of changes in material properties of whole blood, beginning with early stages of clot formation and ending with clot lysis. However, the contact activation of the coagulation cascade at surfaces of thromboelastographic systems leads to inherent variability and unreliability in predicting bleeding or thrombosis risks. Objectives To develop acoustic tweezing thromboelastometry as a non-contact method for perioperative assessment of blood coagulation. Methods Acoustic tweezing is used to levitate microliter drops of biopolymer and human blood samples. By quasi-statically changing the acoustic pressure we control the sample drop location and deformation. Sample size, deformation and location are determined by digital imaging at each pressure. Results Simple Newtonian liquid solutions maintain a constant, reversible location vs. deformation curve. In contrast, the location/deformation curves for gelatin, alginate, whole blood and blood plasma uniquely change as the samples solidify. Increasing elasticity causes the sample to deform less, leading to steeper stress/strain curves. By extracting a linear regime slope, we show that whole blood or blood plasma exhibits a unique slope profile as it begins to clot. By exposing blood samples to pro- or antithrombotic agents, the slope profile changes, allowing detection of hyper- or hypocoagulable states. Conclusions We demonstrate that quasi-static acoustic tweezing can yield information about clotting onset, maturation and strength. The advantages of small sample size, non-contact and rapid measurement make this technique desirable for real-time monitoring of blood coagulation.

Preoperative thromboelastometry for the prediction of increased chest tube output in cardiac surgery: A retrospective study

Bleeding following cardiac surgery is a serious event with potentially life-threatening consequences. Preoperative recognition of coagulation abnormalities and detection of cardiopulmonary bypass (CPB) related coagulopathy could aid in the start of preventive treatment strategies that minimize perioperative blood loss. Most algorithms that analyze thromboelastometry coagulation tests in elective cardiac surgery do not include test results performed before surgery. We evaluated preoperative rotational thromboelastometry test results for their ability to predict blood loss during and after cardiac surgery.A total of 114 adult patients undergoing cardiac surgery with CPB were included in this retrospective analysis. Each patient had thromboelastometry tests done twice: preoperatively, before the induction of anesthesia and postoperatively, 10 minutes after heparin reversal with protamine after decannulation.Patients were placed into 1 of 2 groups depending on whether preoperative thromboelastometry parameters deviated from reference ranges: Group 1 [N = 29; extrinsically activated test (EXTEM) or INTEM results out of normal range] or Group 2 (N = 85; EXTEM and INTEM results within the normal range). We observed that the total amount of chest tube output was significantly greater in Group 1 than in Group 2 (700 mL vs 570 mL, P = .03). At the same time, the preoperative values of standard coagulation tests such as platelet count, aPTT, and INR did not indicate any abnormalities of coagulation.Preoperative coagulation abnormalities diagnosed with thromboelastometry can predict increased chest tube output in the early postoperative period in elective adult cardiac surgery. Monitoring of the coagulation system with thromboelastometry allows rapid diagnosis of coagulation abnormalities even before the start of the surgery. These abnormalities could not always be detected with routine coagulation tests.

Endothelial Cell-derived Extracellular Vesicles Size-dependently Exert Procoagulant Activity Detected by Thromboelastometry

Endothelial cells (ECs) are major modulators of hemostasis by expressing and releasing pro- and anticoagulant mediators into the circulation. Previous studies showed that cultured ECs release procoagulant mediators into cell culture supernatants as evidenced by the reduction of viscoelastic clotting time. This effect was reversed with an anti-tissue factor antibody. Here, we aimed to investigate whether tissue factor (TF) was released by endothelial-derived extracellular vesicles (EVs) and which portion of the released vesicles displays the most prominent procoagulant properties. After stimulation of ECs with tumor-necrosis factor-α (TNF-α) the supernatants of EC cultures were subjected to differential centrifugation steps to collect larger and smaller EVs which were then characterised by nanoparticle tracking analysis (NTA) and flow cytometry. Mixed with fresh human blood and analysed by thromboelastometry EVs exerted a significant procoagulant stimulus, which could be partly reversed by addition of an anti-TF antibody. Moreover, TF activity was confirmed in the centrifuged fractions. In summary, our results provide evidence of the procoagulant potential of smaller and larger endothelial-derived EV fractions detected by thromboelastometry. The observed effect is most likely due to the release of TF-bearing EVs of different dimensions, which are released upon TNF-α stimulation of endothelial cell cultures.

Implementing a Statistical Model for Protamine Titration: Effects on Coagulation in Cardiac Surgical Patients

OBJECTIVES

To implement a statistical model for protamine titration.

DESIGN

Prospective randomized trial.

SETTING

University hospital.

PARTICIPANTS

Sixty (n = 30+30) patients scheduled for elective coronary artery bypass surgery were randomly assigned to 2 groups.

INTERVENTIONS

Protamine dose calculated according to an algorithm established from a statistical model or to a fixed protamine-heparin dose ratio (1:1).

MEASUREMENTS AND MAIN RESULTS

Both groups demonstrated comparable patient demographics and intraoperative data. Coagulation effects were evaluated using rotational thromboelastometry. Using the statistical model reduced (p<0.01) the protamine dose from 426±43 mg to 251±66 mg, followed by significantly (p<0.01) shorter intrinsic clotting time (208±29 seconds versus 244±52 seconds) and stronger clot firmness (p = 0.01), and effects on indices of extrinsic or fibrinogen coagulation pathways were insignificant. Test of residual heparin was negative in all patients after protamine administration, aligned with insignificant (p = 0.27) intergroup heparinase-verified clotting time differences.

CONCLUSIONS

The statistical model for protamine titration is clinically feasible and protects the patient from exposure to excessive doses of protamine, with advantageous effects on coagulation as measured using rotational thromboelastometry. Significance regarding clinical outcome is yet to be defined.

[Rotational thromboelastometry for the diagnosis of coagulation disorders]

BACKGROUND

Compared to conventional coagulation assays, as prothrombin time (PT) or activated partial thromboplastin time (aPTT), viscoelastic methods of coagulation analysis, including rotational thromboelastometry (ROTEM®, Tem International GmbH, Munich, Germany), yield prognostic benefits. Results of ROTEM® in citrated whole blood could be generated within 10-12 min and allow for a qualitative and semiquantitative characterisation of clot kinetics. Based on ROTEM® results, the switch between empiric approaches of treating coagulopathy to a goal-directed approach could be accelerated. Introduction of ROTEM® reduces transfusion requirements and the need for single factor concentrates. Thus, ROTEM® reduces transfusion-related adverse events, and additionally implement therapeutic cost effectiveness.

OBJECTIVES

This review provides a short introduction in the methodology of ROTEM®, showing how the combination of assays with different commercially available ROTEM® reagents allows for rapid differential diagnosis of common coagulopathies in clinical practice. Furthermore, prognostic benefits and limitations of ROTEM® diagnostics are described. Finally, we discuss the potential fields of ROTEM® application in different surgical settings.

CONCLUSION

ROTEM® appears to be a contemporary, applicable and effective method in diagnosing coagulopathy and for subsequent algorithm-based goal-directed therapy.

Reduction in blood transfusion in a cohort of infants having cardiac surgery with cardiopulmonary bypass after instituting a goal-directed transfusion policy

BACKGROUND

Current trends in pediatric cardiac surgery and anesthesiology include goal-directed allogeneic blood transfusion, but few studies address the transfusion of platelets and cryoprecipitate. We report a quality improvement initiative to reduce the transfusion of platelets and cryoprecipitate in infants having cardiac surgery with cardiopulmonary bypass (CPB).

METHODS

Data from 50 consecutive patients weighing four to ten kilograms having cardiac surgery with CPB were prospectively collected after the institution of a policy to obtain each patient's platelet and fibrinogen levels during the rewarming phase of CPB. Data from 48 consecutive patients weighing four to ten kilograms having cardiac surgery with CPB prior to the implementation of the policy change were retrospectively collected. Demographics, laboratory values and blood product transfusion data were compared between the groups, using the Chi-square/Fisher's exact test or the T-Test/Wilcoxon Rank-Sum test, as appropriate.

RESULTS

The results showed more total blood product exposures in the control group during the time from bypass through the first twenty-four post-operative hours (median of 2 units versus 1 unit in study group, p=0.012). During the time period from CPB separation through the first post-operative day, 67% of patients in the control group received cryoprecipitate compared to 32% in the study group (p=0.0006). There was no difference in platelet exposures between the groups.

CONCLUSION

Checking laboratory results during the rewarming phase of CPB reduced cryoprecipitate transfusion by 50%. This reproducible strategy avoids empiric and potentially unnecessary transfusion in this vulnerable population.