Viscoelastic testing has applications in a variety of clinical contexts in which optimal patient blood management is essential. This includes in cardiac surgery, where bleeding is a common complication and optimising the management of haemostasis is vital,1 and in interventional cardiology, where the platelet function testing capacities of Plateletmapping® can be used to guide clinical decisions around blood transfusion and timing of surgery.2,3 In the trauma setting, viscoelastic testing can provide rapid and accurate assessment of trauma-induced coagulopathy4 and can also be used to identify platelet dysfunction in patients with traumatic brain injuries.5 The speed and specificity of viscoelastic testing can also be used for monitoring, evaluating and predicting prognosis of patients at risk of stroke,6 as well as assessment of haemostasis in patients with cirrhosis or requiring liver transplant,7,8 and in the management of post-partum haemorrhage.9 Furthermore, viscoelastic testing has applications in the critical care management of patients with a range of conditions, including COVID-19 and sepsis.10,11
Across most of these settings, compared with conventional coagulation testing, viscoelastic testing-guided algorithms have generally been shown to provide earlier diagnosis and are associated with improved survival rates, fewer red blood cell (RBC) transfusions and reduced blood product usage.4, 12-15 However, there are differences between settings where guidelines recommend the use of viscoelastic testing versus those where it is still in research and development.
| Parameter | What it means | What it measures | Normal range value* | What it shows |
|---|---|---|---|---|
| MA | Maximum amplitude | Overall strength + stability of the fibrin clot | 49.7 ─ 72.7 mm | Platelets and fibrin interaction |
| LY30 | Amplitude at 30 minutes | Percentage decrease in amplitude at 30 minutes post-MA | 2.3 ─ 5.77 % | Fibrin breakdown |
| K-value | Kinetics | Time taken to achieve a certain level of clot strength | 0.7 ─ 3.4 min | Fibrinogen availability |
| a-angle | Slope of line between R and K | Speed of fibrin build up and cross-linking, rate of clot formation | 47.8 ─ 77.7° | Fibrinogen availability |
*For healthy volunteers, measured on TEG®5000 device
Viscoelastic testing can be used in cardiac surgery to assess coagulation parameters and fibrinolysis and to reduce bleeding risk, as it is rapid and performed in a near-patient environment.
Major and/or uncontrollable bleeding during and after surgery is a frequent complication in patients undergoing cardiac surgery; therefore, perioperative monitoring is crucial to prevent coagulopathic causes of haemorrhage and to decrease the need for surgical reintervention. There are multiple factors that lead to bleeding during surgery, which cannot always be distinguished by laboratory tests.1
Since the 1980s, the use of viscoelastic testing has become a more widespread practice during surgical procedures that are associated with major blood loss (e.g., cardiac surgery), and in the management of uncontrolled bleeding.16 Several systematic reviews, meta-analyses and randomised controlled trials (RCTs) compared the use of viscoelastic testing to standard of care-guided algorithms and demonstrated that the use of viscoelastic testing decreased the risk of allogeneic blood product exposure after cardiac surgery, and improved survival.17
Viscoelastic testing can rapidly and dynamically evaluate the different components and stages of whole blood coagulation in cardiac patients, at the site of care. TEG® and ROTEM® devices are, therefore, ideally suited to help inform an accurate diagnosis of coagulopathic status and changes in blood product use.18 The early identification and diagnosis of coagulation abnormalities during cardiac surgery can lead to prompt and appropriate treatment, and guide prophylactic treatment after surgery.
| Study | Key Outcomes | |
|---|---|---|
 | Meta-analysis of 21 RCTs (n=8,900)19 | Viscoelastic testing was associated with reductions in mortality, reduction in risk of acute kidney injury, as well as risk of blood product transfusion, when compared with standard of care. |
| Meta-analysis of 7 RCTs (n=1,035)20 | Viscoelastic testing algorithms reduced the need for RBC and fresh frozen plasma (FFP) transfusions compared with clinician discretion. There was no difference in platelet transfusion requirements. |
| Meta-analysis of 19 studies including 13 RCTs (n=15,320)12 | Viscoelastic testing-guided transfusion algorithms reduced blood loss volume and relative risk of RBC, platelet and FFP transfusions compared with standard of care. |
| Meta-analysis of 15 RCTs (n=8,737)1 | Viscoelastic testing-guided algorithms reduced RBC and platelet transfusion compared with standard of care. The frequency of severe acute kidney injury was reduced in the viscoelastic testing group in the four trials where this was reported. |
| Meta-analysis of 17 RCTs (n=8,332)21 | Viscoelastic testing-guided algorithms reduced the odds of receiving allogenic blood products and the incidence of thromboembolic events, compared with standard of care in RCTs and observational studies. |
| Meta-analysis of 15 RCTs (n=1,493)22 | Viscoelastic testing-guided transfusion reduced overall mortality compared with transfusion guided by any other method (low quality evidence). |
| RCT (n=7,402)23 | Viscoelastic testing reduced red blood cell transfusions, platelet transfusions and the incidence of major bleeding compared with current standard of care. |
| RCT (n=100)17 | Viscoelastic testing reduced RBC transfusion, FFP and platelet transfusion, and the 6-month mortality rate compared with current standard of care. |
Typical coagulation abnormalities include residual or rebound heparin, clotting factor deficiency, fibrinogen deficiency and platelet deficiency and/or dysfunction. All the following examples are from TEG® 6s US versions, taken from the TEG® manager software.
The TEG® 6s Citrated Multi-channel (CM) cartridge contains four channels that perform the main assays summarised in the Table below:
| Test | What it measures |
|---|---|
| Citrated kaolin (CK) | The use of kaolin stimulates coagulation through the intrinsic pathway – assesses coagulation and clot strength |
| Citrated RapidTEG (CRT) | Quick assessment of clot strength without assessment of clot initiation |
| CK assay with heparinase (CKH) | Combining CK assay with heparinase to assess the effect of heparin on the clot, |
| Citrated functional fibrinogen (CFF) | Provides an assessment of the fibrinogen contribution to the overall clot strength |
A. Heparin effect
An example trace showing the heparin effect observed during cardiac surgery. This can be recognized by the lengthened R-time in the CK trace, which is normalized on the CKH trace. This corresponds to reduced coagulation initiation and slower clotting time.
B. Low fibrinogen
The trace shows an example of acquired hypofibrinogenaemia due to surgical bleeding. The low MA values in the CK and in particular the CFF trace shows reduced clot strength due to lack of fibrinogen and is indicative of low fibrinogen levels.
C. Low platelets
This example is of reduced platelets levels due to acquired clinical bleeding. The low MA value in the CRT trace, in the presence of normal fibrinogen levels shown by the normal MA in the CFF trace, is indicative of low platelets.
Platelet mapping assays enable quantification of platelet function by measuring the activity of the P2Y12 and thromboxane pathways.24 Platelet function can be monitored at the site of care using whole blood platelet function tests, including VerifyNow®, Multiplate®,PFA-100 and the TEG® analyser with the PlateletMapping® assay. The whole blood TEG® assay is capable of testing platelet function via the PlateletMapping® cartridge.25 Platelet function tests determine the level of inhibition caused by the use of platelet function testing in patients undergoing non-surgical or catheter based cardiac interventions can guide clinical decisions.
In non-surgical patients with acute coronary syndrome on DAPT, pre-operative platelet mapping has been used to investigate haemostatic alterations, and to guide decisions around blood transfusion and timing of surgery. 2,3
Cardiology patients scheduled for cardiopulmonary bypass or CABG are often on antiplatelet therapy, which will need to be ceased prior to surgery to prevent increased risk of bleeding. However, when coming off therapy, patients are at risk of thrombosis or ischaemic events, and it is therefore important to monitor platelet aggregation in decision-making for timing of cardiac surgery or other invasive procedures after discontinuation of antiplatelet therapy.27 The European 2018 ESC/EACTS clinical guidelines on myocardial revascularisation state that platelet function testing should be used to inform DAPT de-escalation in patients coming off therapy prior to surgery.28
PlateletMapping® assays allow cardiologists to monitor antiplatelet drugs and antithrombotics, including DAPT to help reduce thromboembolic complications. The PlateletMapping® assay is a modification of the TEG®, measuring percentage platelet aggregation and inhibition in the presence of adenosine diphosphate (ADP) or arachidonic acid (AA).24 It was designed to be used for evaluating the therapeutic inhibitory effect of antiplatelet therapy on platelet aggregation. Using pre-operative platelet function testing for cardiac surgery can potentially reduce waiting times for patients receiving dual DAPT3 and may reduce bleeding and hospital length of stay.29 Such a reduction in waiting time for cardiac surgery was seen in P2Y12 inhibitor non-responders.30 The TEG® PlateletMapping® assay can assess the platelet function of the ADP receptor, allowing CABG surgery to be scheduled earlier, with a 50% reduction in time to surgery.3 Use of pre-operative platelet function testing algorithms (including TEG® PlateletMapping®) in patients undergoing CABG surgery also results in a reduction in RBC transfusion and FFP transfusion.31
TEG® device-guided algorithms are being investigated to detect low and high responsiveness to DAPT and to aid in escalating DAPT in patients receiving this treatment after percutaneous coronary intervention.13 The potential to provide individualised treatment with the use of TEG® devices could improve clinical outcomes by optimising DAPT use to reduce the risk of major adverse cardiovascular events or reduce the risk of DAPT-induced bleeding events.
| Study | Key Outcomes | |
|---|---|---|
| Systematic review of 113 articles32 | TEG® PlateletMapping® was comparable to other platelet function tests in predicting ischaemic risk and monitoring patient responses to DAPT. |
| CREATIVE RCT (n=1,078)13
| The use of TEG® PlateletMapping® and intensified antiplatelet therapies in percutaneous coronary intervention reduced the risk of major bleeding versus standard antiplatelet therapies. |
| RCT (n=306)33
| Modifying clopidogrel maintenance doses according to platelet reactivity in percutaneous coronary intervention reduced the rate of major adverse cardiovascular events compared with the use of fixed doses. |
The PlateletMapping® assay cartridge provides four channels of dried reagents, KHH (kaolin with heparinase), ActF (Activator F), ADP (adenosine-5’- diphosphate), and AA (arachidonic acid).
A. TEG® PlateletMapping® trace can be used to monitor the patient response to antiplatelet therapy. This trace shows a normal MA for the ADP-induced channel, but low MA in the AA-induced channel, suggesting inhibition of AA, which is sensitive to aspirin.
B. This trace shows low MA for both the ADP- and AA-induced channel suggesting inhibition of both AA and ADP, caused by aspirin and ADP receptor antagonists, respectively.
Major bleeding following traumatic injury is a leading cause of morbidity and mortality,34,35 and viscoelastic testing can be used to detect and monitor trauma-induced coagulopathy.36 TEG®PlateletMapping® can also be used to identify platelet dysfunction in patients with traumatic brain injury5, as well as those with more minor injuries.37
The prompt detection and stabilisation of coagulopathy is important in the management of severe bleeding as a result of trauma.36 However, diagnosis of major bleeding is difficult and is often based on clinical measures that can lack sensitivity,36 and pre-existing therapy with DOAC can also complicate matters.37 The turnaround time of standard laboratory tests is frequently too slow for an emergency situation, and the ability of standard laboratory tests to predict major bleeding and allow for pre-emptive treatment is also limited.36 In addition , platelet inhibition is common in both minor as well as major injuries,5,38 which mat be complicated by any pre-injury antiplatelet therapy.5
The use of viscoelastic testing can provide a rapid and accurate assessment of blood product requirements in the management of trauma-induced coagulopathy.4 Whilst conducting RCTs in the trauma setting is logistically difficult,39 the available data suggest that TEG-guided management in the trauma setting improves survival and can decrease the use of blood products (Table 5).
Viscoelastic testing can rapidly and dynamically evaluate the different components and stages of whole blood coagulation in trauma patients at the site-of-care and is thus highly reliable for use in this setting.35 TEG® analysis provides results more quickly than standard laboratory tests and provides more comprehensive results,40 making it more suitable for assessing coagulation status and blood product needs in an emergency.
In patients with traumatic brain injuries, TEG® and TEG®PlateletMapping® can be used to characterise coagulopathy patterns,41 and TEG®PlateletMapping® assays may reduce platelet transfusions without a concurrent increase in clinically significant hematoma expansion in patients prescribed pre-injury antiplatelet therapy.5
| Study | Key Outcomes | |
|---|---|---|
| RCT (n=396)34 | There was no difference in proportion of subjects alive and free of massive transfusion 24 hours after injury when using major haemorrhage protocols based on viscoelastic haemostatic assays instead of conventional coagulation tests. |
| RCT (n=111)4 | The use of a goal-directed, TEG®-guided massive transfusion protocol improved survival compared with a protocol guided by conventional coagulation tests. There were also reductions in plasma and platelet transfusions. |
| Prospective, observational study (n=301)42 | Resuscitation algorithms based on TEG® were associated with reduced mortality (25% vs 11% at 30 days, p=0.002) and blood product wastage and were cost neutral compared with standard coagulation tests. |
The use of viscoelastic testing-guided algorithms in trauma is recommended by the European Multidisciplinary Task Force for Advanced Bleeding Care in Trauma in addition to or instead of standard coagulation tests.43 They also suggest the use of point-of-care platelet function devices as an adjunct to standard laboratory and/or point-of-care coagulation monitoring in patients with suspected platelet dysfunction. The British Society for Haematology advises that point-of-care viscoelastic testing has practical advantages for monitoring major haemorrhage, including speed of results and a set of parameters that assesses a global coagulation profile.36 However, they also state that, at present, the evidence base to guide practice is limited. The American College of Surgeons Trauma Quality Improvement Program massive transfusion in trauma guidelines recommend switching to a laboratory or point-of-care-based transfusion once major bleeding has been controlled and the rate of transfusion has slowed.44 In addition, the Eastern Association for the Surgery of Trauma provides a conditional recommendation for viscoelastic testing-guided transfusions over traditional coagulation parameters in adult trauma patients with ongoing haemorrhage and concern for coagulopathy;45 Finally, the French Working Group on Perioperative Haemostasis proposes that, in the setting of severe trauma, viscoelastic testing can be used for the early diagnosis of coagulopathy, and to indicate haemostatic treatment and to make clinical staff more aware of the severity of trauma.46
A. Low clot strength
An example of low clot strength due to traumatic haemorrhage. The low MA values observed in the CK and CRT traces are not normalized in the CKH trace, indicating the hypocoagulable profile observed is not due to heparin, but to low platelet count/function. Low MA value in the CFF trace is indicative of low fibrinogen.
B. Low platelets and fibrinogen
Low platelet counts and low fibrinogen due to traumatic haemorrhage. The low MA value observed in the CK trace is indicative of low platelet count/activity, and the low MA value in the CFF trace is indicative of low fibrinogen.
Patients who have undergone AIS are at higher risk for stroke recurrence, especially in the case of anti-platelet resistance, and prompt treatment is important.
AIS is related to hypercoagulability – the hypercoagulable state exists in 29–38% of AIS patients48 – and clinical guidelines recommend dual antiplatelet therapy DAPT for patients with a risk of stroke.49 However, DAPT and anticoagulant therapy are associated with an increased risk for haemorrhage, and there is also a high risk of stroke recurrence in patients with anti-platelet resistance. Clinical antiplatelet resistance, or failure, is defined as the inability to prevent ischemic stroke or major vascular events despite the use of antiplatelet therapy.50 Therefore, it is important to predict and identify populations at high risk of haemorrhage and to provide timely interventions.
TEG® PlateletMapping® can assess platelet function and detect the effectiveness of antiplatelet drugs at point of care. Conventional coagulation tests might delay the decision making in the emergency setting of AIS. In contrast, time-efficient monitoring of coagulation homeostasis could help identify AIS patients at risk of adverse events such as haemorrhage. Firstly, the availability and speed of the VHA point-of-care device allows quick decision-making during treatment. Secondly, monitoring continuously with a point-of-care device allows risk factors to be assessed. Finally, the use of platelet function tests through TEG® PlateletMapping® can detect the presence and effect of antiplatelet drugs and guide treatment. Therefore, the time delay in waiting for the results of conventional coagulation tests might be problematic and viscoelastic testing could be used to predict DAPT-related haemorrhagic events in these patients.5
However, there is a lack of RCTs on the application of viscoelastic testing to monitor AIS patients and evaluate treatment and further research is warranted, Whether the ClotPro® device can be used to predict prognosis has also not been demonstrated. A systematic review of five artucles showed no change in bleeding of the thromboembolic events between use of TEG® PlateletMapping® versus conventional care in ischaemic stroke patients.51
A. Hypercoagulable state
Hypercoagulable state typically observed in patients during/after an AIS. The low R value in the CK and CRT trace, alongside the high MA value is indicative of a hypercoagulable state and of high clot strength/clotting activity.
Viscoelastic testing has several hepatic-related applications, including in patients with cirrhosis undergoing invasive procedures or experiencing active bleeding, and in liver transplant surgery.
Platelet dysfunction can occur in patients with liver disease for a number of reasons, including increased production of nitric oxide and prostaglandin,52, 53 and because of renal dysfunction that often accompanies liver failure.54 Cirrhosis can often cause pro-haemorrhagic and pro-thrombotic imbalances in haemostasis, with an associated increased risk in haemorrhage and thrombosis.7 Standard coagulation tests are not able to accurately predict bleeding risk in these patients.7, 55 In patients requiring liver transplant, the coagulation abnormalities associated with hepatic disease represent a significant complication for an intervention that already has a high bleeding risk.56
Viscoelastic testing is routinely used in liver transplantations and can lead to reductions in blood product use, adverse events, and mortality versus conventional laboratory testing (Table 6). TEG® may also have the capacity to provide rapid assessment of haemostasis and a more comprehensive coagulation assessment in addition to standard coagulation tests in patients with cirrhosis.7,8 Evidence from randomised controlled trials shows examples of the use of viscoelastic testing in patients with cirrhosis undergoing invasive procedures, or invasive treatment procedures.
| Study | Key Outcomes | |
|---|---|---|
 | Meta-analysis of 5 RCTs (n=302)7 | Transfused platelet units were 5x lower with viscoelastic testing versus standard practice. Pooled results showed a significant reduction in the use of any blood product, combined FFP and platelets, and cryoprecipitate. |
| Meta-analysis of 8 RCTs (n=388) and 9 retrospective cohort studies (n=1,365)14 | There was a significant reduction with viscoelastic testing versus standard coagulation testing in the number of patients requiring transfusion with packed red blood cells, platelets and FFP, and a significant reduction in the number of units transfused. Total bleeding events and intraoperative bleeding during liver transplantation were also significantly decreased. |
| Meta-analysis of 7 RCTs (n=421)58 | Treatment algorithms based on viscoelastic testing instead of standard coagulation tests decreased the rates of FFP and platelet transfusion and the number of units transfused for FFP, platelets and cryoprecipitate. Transfusion-related adverse events were also reduced. |
| RCT (n=60)55 | The overall use of blood products, FFP, and platelets was significantly lower with use of a TEG® assay bleeding management algorithm compared with standard of care, even in patients undergoing procedures with a high risk of bleeding. |
| RCT (n=28)59 | TEG® monitoring was associated with the use of fewer units of FFP during orthotopic liver transplantation compared with standard laboratory measures of blood coagulation. |
The use of TEG®is very common in liver transplantation and the French Working Group on Perioperative Haemostasis states that they can be an aid in liver transplant by limiting the transfusion of labile blood products.46 Furthermore, the Society of Critical Care Medicine recommends using viscoelastic testing over standard tests in critically ill patients with acute liver failure or acute on chronic liver failure,60 and the International Society on Thrombosis and Haemostasis suggests that it may be useful in confirming that haemostasis is “normal” in patients with cirrhosis.61 However, the exact role of viscoelastic testing-guided treatment in cirrhosis and liver transplantation has yet to be fully defined, and further study is needed to determine appropriate cut-offs for therapeutic intervention.46,62
A. Pre-operative pre-anhepatic trace
The low MA in the CFF trace is indicative of low fibrinogen levels. This trace is suggestive of reduced clot strength and fibrinogen contribution, which is typically seen in liver disease.
B. Post-anhepatic phase
The high LY30 value in the CK trace indicates fibrinolysis (excessive clot breakdown). There is also evidence of the heparin effect, as shown by the difference between the R time in the CK and CKH traces, which is typical following liver transplant.
The gynaecologic and obstetric applications of viscoelastic testing include the management of PPH and identifying hypercoagulability as a potential risk factor for miscarriage.
Alterations to haemostasis are common in pregnancy, and both pro-haemorrhagic and pro-thrombotic coagulation changes can occur during pregnancy.63 Globally, PPH is a major cause of maternal morbidity and mortality,9,64 and its incidence is increasing in many countries.65,66 Validated methods for the early identification of PPH are vital to avoid progression to massive haemorrhage and the associated use of blood products.9
Fibrinogen has been shown to be a marker of progression to severe haemorrhage, and laboratory tests may take too long to guide rapid clinical decision making.64,65 Point-of-care testing with viscoelastic assays can provide real-time assessment of patient coagulopathy.9,63,64
Evidence from RCTs and cohort studies has shown that viscoelastic testing-guided protocols can potentially be useful in the management of PPH to predict the risk of bleeding/coagulopathy and may reduve the need for blood transfusions and the use of other blood products (Table 7). However, there is a need for further large scale RCTs on the effect of clinical outcomes in obstetric patients.
| Study | Key outcomes | |
|---|---|---|
 | Retrospective cohort study (n=86)67 | Point-of-care viscoelastic testing was associated with significantly fewer transfusions of packed RBCs, FFP and platelets in patients with severe PPH, as well as significantly lower estimated blood loss, incidence of caesarean hysterectomy, post-operative ICU admission and shorter length of hospitalisation. |
| Retrospective cohort study (n=98)64 | Viscoelastic testing parameters allowed a rapid diagnosis of hypofibrinogenemia and/or thrombocytopenia during PPH and predicted severe haemorrhage. |
| Systematic review of 93 studies9 | Viscoelastic testing may be used to guide transfusion therapy for PPH and to detect the hypercoagulable changes associated with pregnancy, but further large prospective high-quality studies with standardised protocols are needed. |
| Prospective cohort study (n=255)15 | There was a significant reduction in both the number of units and the total volume of blood products transfused when using viscoelastic testing to guide component therapy instead of administering a shock pack at onset of major haemorrhage. There was also a significant reduction in transfusion-associated circulatory overload. |
| RCT (n=55)65 | Infusion of fibrinogen concentrate triggered by a moderate reduction in fibrinogen, as measured by FIBTEM A5, did not significantly reduce blood product transfusion or blood loss versus placebo. |
The use of viscoelastic testing to guide PPH treatment algorithms is recommended as an alternative to laboratory testing by the International Society on Thrombosis and Haemostasis68 and the Network for the Advancement of Patient Blood Management, Haemostasis and Thrombosis.69 The European Society of Anaesthesiology also advises that viscoelastic testing can identify obstetric coagulopathy, and recommends a viscoelastic testing-guided intervention protocol in severe PPH.70 Furthermore, the British Society for Haematology recommends that viscoelastic haemostatic assays may be used as part of an agreed algorithm to manage PPH when the local institution’s major obstetric haemorrhage protocol is activated.36 However, the National Institute for Health and Care Excellence’s 2014 guidance recommended that further research was needed on the clinical benefits and cost effectiveness of viscoelastometric point-of-care testing for the detection, management and monitoring of haemostasis in the emergency control of bleeding during PPH.71
A. Hypercoagulable trace during the third trimester
Potential hypercoagulability typically seen during the third trimester of pregnancy due to high fibrinogen levels. This is indicated by the elevated MA value in the CK and particularly the CFF trace.
B. Post-partum hyperfibrinolysis
The low MA value in the CK trace is indicative of low platelet count/activity and the low MA value in the CFF trace is indicative of low fibrinogen.
Applications of viscoelastic testing in the intensive care setting include in the management of clinical conditions such as sepsis, haemorrhage, and COVID-19.
Haemorrhagic or thrombotic complications are common in critically ill patients, and coagulopathy is often multifactorial. Coagulopathies in critically ill patients include platelet dysfunction, thrombocytopenia, and hyperfibrinolysis.72 Coagulopathy is common in patients with sepsis, and coagulation abnormalities can range from increased bleeding to hypercoagulopathy, with disseminated intravascular coagulopathy a particular concern.73,74 COVID-19 is associated with a high rate of thromboembolic complications, but the underlying mechanisms of this are not well defined.75,76 Early and accurate diagnosis of coagulation abnormalities is vital in these settings to determine the correct management strategy, and standard laboratory tests only provide information on part of the clinical picture.72,74
Viscoelastic testing can give a quicker and more complete picture of a patient's haemostatic status than conventional laboratory tests.72 There have been various studies conducted on the use of viscoelastic testing in patients critically ill with COVID-19, in which TEG® assay parameters have been associated with thromboembolic risk (Figure 1 and Table 8), as well as in patients with septic shock (Table 8). There are also applications for viscoelastic testing in the critical care management of patients undergoing cardiovascular surgery77 and liver transplantation78, as well as in neonatal intensive care79 and in trauma patients. 72
The dotted line represents a healthy subject and the solid line represent a typical prothrombotic patient with COVID‐19. The TEG® parameters for the patient with COVID‐19 were R=5.5 minutes, K=78.8°, MA=88.8 mm.
| Study | Key Outcomes | |
|---|---|---|
| Observational study; COVID-19 (n=109)81 | TEG® 5000 was used to determine the frequency of venous thromboembolism in critically ill patients. |
| Observational study; COVID-19 (n=44)82 | Fibrinolytic shutdown (D-dimer >2,600 ng/mL and no clot lysis at 30 minutes) on TEG® predicted thromboembolic events and the need for haemodialysis. |
| Observational study; COVID-19 (n=40)75 | Combined analysis of ROTEM® maximum lysis and D-dimer concentrations had high sensitivity and specificity for predicting thromboembolic risk. |
| Systematic review; COVID-19 (15 studies)10 | Viscoelastic testing identified hypercoagulability and predicted thrombotic complications, suggesting that its use can lead to improvements in the clinical diagnosis of hypercoagulability and management of patients with COVID-19. |
| Systematic review; COVID-19 (44 studies)83 | The heterogeneity in testing systems and reagents, and patients’ illness severity made interpretation difficult. Only some studies found an association of viscoelastic testing with thrombotic events. |
| Prospective observational study; septic shock (n=764)11 | A hypocoagulable state, as defined by the TEG® profile of K >3 min, α <53° and MA <50 mm, was independently associated with an increased mortality rate in septic shock patients with normal PT and aPTT. |
| Retrospective observational study; septic shock (n=295)84 | A TEG® MA value of <64 mm was independently associated with an increased risk of disseminated intravascular coagulation development in septic shock patients. |
| Cohort study; COVID-19 (n=24)80 | Thromboelastographic results in patients with COVID‐19 denoted a state of hypercoagulability. R and K values were shorter than controls in 50% and 90% of patients with COVID‐19, respectively, and K and MA values were higher than controls in 77% and 87%, respectively. LY30 was lower than controls in all patients with COVID‐19. |
A. TEG® 6s tracing in a COVID-19 patient
This COVID-19 patient shows extremely high levels of fibrinogen (evidenced by the high MA value in the CFF trace) and considerable heparin effect (long R time in the CKH trace, but hypercoagulable on CRT-R). VET can measure systemic hypercoagulability as well as lysis.
B. TEG® 6s tracing in a patient undergoing extracorporeal membrane oxygenation (ECMO)
This TEG PlateletMapping® result shows the patient is responsive to aspirin (AA-MA is 21.4 and patient is 80% inhibited) but not clopidogrel (ADP-MA is 52.6mm, 12.2% inhibition).
