Version July 2025
INTRODUCTION —
Point-of-care viscoelastic test-based transfusion algorithms can provide rapid information about hemostasis and facilitate decision-making regarding the need for targeted transfusion of blood components (algorithm 1). Viscoelastic testing devices are often available in operating rooms where major surgical procedures are performed that may entail rapid significant blood loss (eg, cardiac, liver, and trauma surgery).
This topic discusses the uses and limitations of POC VET in perioperative, critical care, and other settings.
Separate topics discuss:
●Platelet function tests – (See "Platelet function testing".)
●Intraoperative transfusion decisions – (See "Intraoperative transfusion and administration of clotting factors", section on 'Use of a transfusion algorithm or protocol'.)
●Transfusions during cardiac surgery with cardiopulmonary bypass – (See "Achieving hemostasis after cardiac surgery with cardiopulmonary bypass", section on 'Use of transfusion algorithms'.)
●Management of patients with postpartum hemorrhage – (See "Postpartum hemorrhage: Medical and minimally invasive management".)
●Management of acute traumatic coagulopathy – (See "Ongoing assessment, monitoring, and resuscitation of the severely injured patient".)
TERMINOLOGY
●Point-of-care (POC) testing – This is a broad category that refers to testing that can be performed using a device located at or near the location of the patient (eg, operating room, intensive care unit, emergency department), rather than in a central laboratory [1].
The rationale for POC testing is that a more rapid generation of results might improve patient care, although there are few studies evaluating patient-important outcomes relative to central laboratory testing. (See 'Uses in specific settings' below.)
●Viscoelastic testing (VET) – VET, also referred to as global hemostasis testing and viscoelastic hemostatic assays, is a type of POC test that measures the overall properties of whole blood clot formation under low shear stress. The readout includes parameters for clot initiation, clot formation and strength, and clot dissolution. Several specific platforms have been developed; these measure the same parameters and vary according to the mechanics of the test (table 1) [2-5].
Thromboelastography (TEG) and rotational thromboelastometry (ROTEM) are the two main VET platforms, although the use of sonorheometry (Quantra) is increasing. (See 'Technologies and tests' below.)
●Activated whole blood clotting time (ACT) – ACT is a POC test typically used to assess systemic anticoagulation before initiation of cardiopulmonary bypass during cardiac surgery, and during other vascular surgical procedures such as aortic repair, endovascular interventions, and selected procedures in the cardiac catheterization laboratory. (See "Anticoagulation and blood management strategies during cardiac surgery with cardiopulmonary bypass", section on 'Heparin administration and monitoring'.)
TECHNOLOGIES AND TESTS
General principles
Conceptual basis for the tests — The basic principle of all viscoelastic testing (VET) is that an activator of clotting is added to the blood and a mechanical force is applied to the blood as it clots.
●The activator may be kaolin/celite, ellagic acid, tissue factor, or thrombin (in the form of thrombin receptor activating peptide-6 [TRAP]).
●The mechanical force may be from the torque of a pin or a cup, or from ultrasound.
The readout of the amount of force required over a time interval is used to generate a tracing that graphs several parameters, including clot initiation, kinetics of clot formation, eventual clot strength, clot lysis, and clot stability over time. The details regarding how specific tests work vary depending on the platform and technology.
In sonorheometry, shear waves are generated by ultrasound stimulation to produce an acoustic feedback signal that estimates the stiffness of the clot. (See 'Specific testing platforms' below.)
Sample preparation and machinery — VET technologies have evolved to improve standardization. Initial tests used "native" blood (non-anticoagulated whole blood). This process causes variability in some parameters such as the thromboelastography (TEG) reaction time and rotational thromboelastometry (ROTEM) clotting time (table 1), and it requires pipetting blood into the machine or cartridge.
"Native" blood is still used for POC testing performed at the bedside. However, when samples are sent for laboratory-based testing, citrated samples using standard blood collection tubes are used [6]. Such samples can be held for up to four hours prior to testing.
When using cartridge-based systems for the newer TEG6s or ROTEM Sigma tests, a small volume of blood (300 to 340 microL depending on the system) is aspirated from a citrate-containing tube and injected into the system into which a cartridge with several different tests has been inserted. Details for each system are discussed below. (See 'TEG' below and 'ROTEM' below.)
Institutions that use these devices in clinical care need to have quality assurance protocols in place to ensure that they are maintained appropriately and that relevant training is provided.
Choice of cartridge(s) — TEG6s and ROTEM Sigma systems use different cartridges designed for specific diagnostic purposes.
●TEG6s system – The TEG6s system includes the following cartridges:
•Kaolin cartridge for whole blood clotting assessment
•Functional Fibrinogen cartridge to determine the fibrinogen contribution to clot strength
•RapidTEG cartridge for rapid results in patients with major bleeding including trauma
•Heparinase cartridge to remove heparin from the sample and assess clotting
The table lists some of these options (table 2).
●ROTEM Sigma system – The ROTEM Sigma system includes the following cartridges listed here and described further below (table 2): (See 'ROTEM' below.)
•INTEM cartridge for evaluating contact activation/intrinsic pathway
•EXTEM cartridge that uses tissue factor to assess the extrinsic pathway and overall clot formation
•FIBTEM cartridge to measure fibrinogen contribution to maximal clot strength
•APTEM cartridge that contains a fibrinolytic inhibitor to evaluate fibrinolysis
•HEPTEM cartridge that contains heparinase to remove heparin
The fibrinogen tests for both instruments use a platelet inhibitor to assess clot strength based on fibrinogen (abciximab for TEG and cytochalasin for ROTEM).
Specific testing platforms — TEG and ROTEM are the most used platforms. The table summarizes the parameters tested and their interpretation (table 1). (See 'TEG' below and 'ROTEM' below.)
Sonorheometry (the Quantra device) uses ultrasound generation and resonance detection to examine viscoelastic properties during clot generation. Quantra measures clot kinetics by different parameters, with the clotting time (CT) being an important metric for the time to form a detectable clot, similar to the TEG reaction time [5,7-10]. (See 'TEG' below.)
Several other systems are under investigation.
TEG — TEG is the most used VET.
●Principle – The principle for TEG involves measuring the torque on a pin dipped into a rotating plastic cup filled with non-anticoagulated whole blood. As a clot begins to form, the torque increases, and with clot breakdown from fibrinolysis, the torque decreases. The resulting tracing has specific parameters that can be compared to reference ranges.
●Mechanics – In the TEG and the related rapid TEG (r-TEG) devices, the clot's physical properties are measured using a cylindrical cup that holds a whole blood sample at 37ºC and is oscillated to and fro with a rotation cycle of 10 seconds. As the clot forms, the torque of the rotating cup is transmitted to an immersed pin. The degree of pin rotation is converted to an electrical signal via a transducer and monitored via a chart recorder. The strength of the developing clot increases the magnitude of the output, whereas during clot lysis, the bonds between the cup and the pin are broken, and the signal decreases.
●Devices – There are several commercially available devices that measure TEG. While the specifics of the devices vary, they all measure the same general parameters.
For the newest TEG system, TEG6s, a cartridge is loaded into the device and approximately 340 microL of blood is injected into the sample port. The TEG6s analyzer mixes the blood with the reagents in the cartridge and measures the parameters listed and defined below. The results are displayed in real-time in the characteristic large tracing examining clot development and characteristics. The shape of the tracing has been likened to a hotdog or a shovel [11].
●Parameters – The figure illustrates the standard TEG tracing (figure 1). The parameters on the tracing are as follows (table 1):
•Clot initiation – Clot initiation is the time from sample placement or activation until the tracing amplitude reaches 2 mm; this measures the time it takes for the coagulation cascade to start thrombin generation and fibrin formation.
-Reaction time (R time) – Reaction time or R time is the time for initial fibrin formation that leads to clot formation, typically 2 mm of clot amplitude.
•Clot kinetics
-Clot formation time (K time) – Time elapsed for the clot amplitude on the tracing to go from 2 mm to 20 mm; measures fibrin crosslinking (the final phase of clot formation).
-Clotting time with kaolin – The use of a specific channel treated with kaolin and heparinase allows identification of residual circulating heparin, if appropriate.
-Alpha angle – The alpha (α-) angle is defined as the angle between the middle line of the tracing and a tangential line to the developing body of the tracing.
•Clot strength – Measures maximum clot firmness; describes overall platelet and fibrinogen function and interactions. However, this TEG parameter is not a platelet function assay since the amplitude, which indicates maximum clot firmness, is highly influenced by fibrinogen levels [12].
-Maximum amplitude (MA) – Amplitude measured at peak clot strength; TEG MA reflects clot maximum strength and is an indicator of platelet count and function and fibrinogen levels as key components of clot strength in whole blood.
High MA is associated with hypercoagulable states.
Low MA may be seen in patients with bleeding and may indicate hypofibrinogenemia.
-Clot viscoelasticity (G value; research only) – Calculated value measuring total clot strength based on clot amplitude. G values are used for research purposes.
•Clot lysis – Percentage of loss of amplitude at a fixed time interval after MA; measures clot strength/stability and is affected by fibrinolysis. Clot lysis is primarily used for decision-making in the management of patients with coagulopathy, especially whether to administer an antifibrinolytic agent.
•Ly30 – The percent clot lysis detected 30 minutes after the MA.
The portions of the TEG tracing that partially assess platelet function are the alpha angle and the MA, but these tests are highly dependent on fibrinogen levels.
ROTEM
●Principle – The principle for ROTEM involves measuring the torque on a rotating pin dipped into a stationary plastic cup filled with non-anticoagulated whole blood. As a clot begins to form, the torque increases, and with clot breakdown from fibrinolysis, the torque decreases. The resulting tracing has specific parameters for clot formation, clot strength, and clot dissolution that can be compared to reference ranges.
●Devices – There are several ROTEM systems such as ROTEM Sigma and ROTEM Delta.
●Mechanics – For the ROTEM Sigma, approximately 300 microL of blood is pipetted into the cartridge's designated port, where blood is mixed with the reagents. The parameters measured by ROTEM are listed and defined below.
●Parameters – The figure illustrates the standard ROTEM tracing (figure 1). The parameters on the tracing are as follows (table 1):
•Clot initiation – Time from sample placement or activation until the tracing amplitude reaches 2 mm; measures the time it takes for the coagulation cascade to start thrombin generation and fibrin formation.
-Clot time (CT) – Time for initial fibrin crosslinking (final phase of clot formation), typically 2 mm of clot amplitude.
-Heparinase thromboelastometry clotting time (HEPTEM) – Uses a specific channel treated with heparinase to allow identification of residual circulating heparin, if appropriate (table 2).
•Clot kinetics
-Clot formation time (CFT) – Time elapsed for the clot amplitude on the tracing to go from 2 mm to 20 mm; measures fibrin crosslinking (the final phase of clot formation).
-Alpha (α-) angle – The angle between the middle line of the tracing and a tangential line to the developing body of the tracing.
•Clot strength – Clot strength measures the maximum clot firmness; it describes overall platelet and fibrinogen function and interaction.
-Maximal clot formation (MCF) – Amplitude measured at peak clot strength.
-Maximum clot elasticity (MCE) – Calculated value measuring total clot strength based on clot amplitude.
•Clot lysis – Clot lysis is the percentage of loss of amplitude at a fixed time interval after MCF; it measures clot strength/stability and is affected by fibrinolysis. Clot lysis is primarily used for decision-making in the management of patients with coagulopathy, especially whether to administer an antifibrinolytic agent.
-Lysis index at 30 minutes (LI30) – Lysis index at 30 minutes after MCF is reached.
-Maximal lysis (ML) – Maximum lysis expressed as a percentage of MCF.
●Specialized cartridges (table 2)
•FIBTEM (tissue factor + cytochalasin D) – FIBTEM is the ROTEM assay for fibrinogen measurement. It uses a platelet inhibitor, cytochalasin, to inhibit platelet-mediated clot formation. FIBTEM amplitude after five minutes (FIBTEM A5) is an early indicator of hypofibrinogenemia in a rapidly bleeding patient and is available sooner than using the MCF. A FIBTEM A5 <10 mm has been suggested as a way to detect the progression of bleeding from mild to severe hemorrhage in patients with postpartum hemorrhage (PPH). (See 'Postpartum hemorrhage' below.)
•EXTEM (tissue factor) – EXTEM is the ROTEM assay that assesses the tissue factor-activated pathway (extrinsic pathway) and subsequent clot formation that occurs. The initial clot formation, termed clot time, is a similar initial test that measures initial coagulation as measured by prothrombin time (PT) in standard laboratory testing, and then subsequent clot activation as described.
•INTEM (ellagic acid) – INTEM is the ROTEM assay that assesses the contact activation pathway (intrinsic pathway). The clot time that initially occurs is similar to that measured by activated partial thromboplastin time (aPTT) in standard laboratory testing, with subsequent additional clot formation due to additional components of the hemostatic cascade.
BENEFITS AND LIMITATIONS
Potential benefits — VET platforms are standalone automated machines that are often used on-site in the operating room or emergency department trauma bay, with results that are available in 10 to 15 minutes. Clinicians have direct access to the results without having to wait for a report from the central laboratory.
VET results reflect the continuum of hemostasis over time, with information about all aspects of clotting from clot initiation, kinetics of clot formation, clot strength, and fibrinolysis.
Information from VET may be comparable to standard tests and/or clinical judgment during clinically significant blood loss, where assessments of coagulopathy facilitate initial clinical decision-making to allow more immediate appropriate treatment of the likely coagulation disorders, such as with VET-directed transfusion algorithms (algorithm 1 and table 3).
VET can also be repeated following transfusions or administration of hemostatic agents to facilitate rapid assessment of responses [13]. However, standard laboratory tests of clotting, fibrinogen levels, and platelet count are also obtained, as these provide additional information [2].
Available evidence supporting the use of VET includes the following:
●Thromboelastography (TEG) has been validated against standard laboratory tests and thrombin-antithrombin complex levels [14-16]. (See 'TEG' above.)
●Rotational thromboelastometry (ROTEM) has also been validated against standard laboratory tests, thrombin-antithrombin complex levels, and euglobin clot lysis times [17]. (See 'ROTEM' above.)
●Quantra has been validated in clinical settings and is able to predict hypofibrinogenemia and thrombocytopenia [5,7-10]. (See 'Specific testing platforms' above.)
●For patients who may have residual heparin levels after systemic heparinization (eg, for cardiopulmonary bypass), any of the available VET technologies can be performed in the presence of specific clotting activators or inhibitors to determine if residual heparin is present [18].
●In general, randomized trials and observational studies in surgical patients have noted that, compared with standard care based on standard laboratory coagulation testing and/or clinical judgment, the use of VET (with or without a transfusion algorithm (algorithm 1)) reduces allogeneic transfusions [4,19-56].
However, data suggesting clear benefits are not consistent, particularly in non-cardiovascular surgical procedures. Evidence presented in meta-analyses has been limited by heterogeneity among studies due to the use of institution-specific VET parameters to guide transfusion in an algorithm or protocol, as well as the high risk of bias, imprecision, and/or indirectness in most studies [20-25,44,46,47].
Potential limitations — VET technology has the following limitations:
●The value of VET for evaluation of platelet function is unclear, especially as clot strength is highly dependent on fibrinogen as well as red blood cells [4,12].
●VET is insensitive to aspirin or platelet P2Y12 inhibitors such as clopidogrel. Since thrombin generation in the VET assays causes platelet activation, these platelet inhibitors do not affect routine VET parameters [57-59].
●Specific VET tests termed "platelet mapping" have been developed, but these do not consistently compare favorably with light transmission aggregometry [60]. (See "Platelet function testing", section on 'Platelet aggregometry'.)
●VET is not available in every institution [4,61].
●Use of VET does not eliminate the need for standard laboratory coagulation tests to confirm findings [2]. The machines are not easily portable; they are too heavy to routinely move for assessing military or civilian casualties in the field.
●VET requires specialized training and quality control procedures that are unlikely to be as rigorous as tests performed in a clinical laboratory setting [4]. Many clinicians are unfamiliar with the interpretation of results and with specific interventions (transfusions, hemostatic therapies) that would be indicated for specific abnormalities on the VET tracing.
USES IN SPECIFIC SETTINGS —
VET can be used in several settings to assess different aspects of clotting and clot breakdown, with VET-guided transfusion protocols [6]. However, it is not used to diagnose specific factor deficiencies, which are evaluated using specific factor assays.
Detection of fibrinolysis — Fibrinolysis is a normal final stage of hemostasis involving clot breakdown. (See "Overview of hemostasis", section on 'Clot dissolution and fibrinolysis'.)
There are several clinical settings with abnormal fibrinolysis (eg, severe trauma, liver transplantation), especially hyperfibrinolysis. VET can be used to facilitate rapid diagnosis of these alterations, especially in patients with acute bleeding (figure 2A-C) [62-71]. The clot lysis parameters (ie, thromboelastography [TEG]: lysis at 30 minutes [LY30], rotational thromboelastometry [ROTEM]: lysis index at 30 minutes [LI30]) are used to assess fibrinolytic abnormalities (table 1). Transfusion protocols may recommend the use of an antifibrinolytic agent such as tranexamic acid (TXA) if the parameter is high (table 3). (See "Thrombotic and hemorrhagic disorders due to abnormal fibrinolysis", section on 'General hyperfibrinolytic states'.)
Evidence for the use of VET in fibrinolytic disorders includes:
●Hyperfibrinolysis – Hyperfibrinolysis may be seen in severe trauma or liver transplantation and is associated with increased mortality [63,64,72-75]. Hyperfibrinolysis appears to be primarily due to an increase in tissue plasminogen activator (tPA) release without a compensatory increase in plasminogen activator inhibitor-1 (PAI-1) [76,77]. Preclinical models suggest that hyperfibrinolysis is mechanistically related to the degree of shock.
In a single-center prospective observational study of 73 critically injured trauma patients meeting the criteria for massive transfusion protocol, an LY30 ≥3 percent was associated with massive transfusion in 91 percent, whereas an LY30 <3 percent was only associated with massive transfusion in 30 percent [78]. The risk of hemorrhagic death was also higher in those with the higher LY30 (46 versus 5 percent with LY30 <3 percent).
Another study in trauma patients also found that LY30 ≥3 percent was associated with increased mortality (44 percent) versus 3 percent in individuals with LY30 <3 percent; the increased mortality was primarily due to exsanguination [79].
Some guidelines suggest using an LY30 of >5 percent as a trigger for administering antifibrinolytic therapy; the manufacturer cites the upper bound of normal as >7.5 percent (table 3 and figure 1).
●Fibrinolytic shutdown – Fibrinolytic shutdown can occur in certain elective surgical procedures and in trauma patients; its mechanisms and clinical implications are an active area of investigation [80-82].
A prospective study from 2015 involving 2540 traumatically injured patients reported that fibrinolysis shutdown was the most common phenotype (46 percent), followed by physiologic fibrinolysis (36 percent) and hyperfibrinolysis (18 percent) [83]. Overall mortality was 21 percent. Hyperfibrinolysis defined by LY30 ≥3 percent was associated with the highest mortality (34 percent), followed by fibrinolysis shutdown (defined by LY30 ≤0.8 percent; mortality 22 percent). Physiologic fibrinolysis had the lowest mortality (14 percent). After adjustment for age, injury severity score, mechanism of injury, head injury, and blood pressure, the risk of mortality remained increased for hyperfibrinolysis (odds ratio [OR] 3.3, 95% CI 2.4-4.6) and fibrinolytic shutdown (OR 1.6, 95% CI 1.3-2.1) [83].
Another prospective study from 2014 with >180 traumatically injured patients noted similar results [79].
Trauma resuscitation — VET is well suited to assess coagulopathy after traumatic injury and to monitor its response to transfusions and interventions and resolution [84].
VET-based goal-directed resuscitation is suggested by the Eastern Association for the Surgery of Trauma (EAST) for trauma patients requiring massive blood transfusion if the technology is available [56,85]. This recommendation was based on a 2020 systematic review and meta-analysis that reported VET-guided transfusion was associated with a lower rate of transfusion, lower number of transfused units of red blood cells (RBCs), lower number of patients and units of transfused fresh frozen plasma (FFP), and less need for interventional procedures to manage bleeding (angioembolization, endoscopy, surgery) [56]. (See "Initial management of moderate to severe hemorrhage in the adult trauma patient" and "Massive blood transfusion".)
In addition to the detection of hyperfibrinolysis as discussed above (see 'Detection of fibrinolysis' above), thromboelastography (TEG) has been used to diagnose the later-appearing hypercoagulability that occurs in some patients after moderate traumatic injury despite having normal-range values on standard coagulation tests [86,87]. TEG parameters have also been used to predict mortality in trauma patients, although it is not clear that the use of VET technology can improve survival rates [73,84,88-91]. (See "Ongoing assessment, monitoring, and resuscitation of the severely injured patient".)
Major surgical procedures with risk for significant blood loss — VET can be used in addition to standard laboratory coagulation tests to assess overall coagulation function during major surgical procedures that are anticipated to have a blood loss ≥500 mL (eg, cardiovascular procedures, liver transplantation surgery) [13,20-25,54,55,61,92].
For surgical patients with clinically significant bleeding, various society guidelines recommend the use of a goal-directed protocol or algorithm based on VET results, if available, for decision-making regarding blood product transfusion, in addition to standard laboratory tests (algorithm 1 and table 1 and table 3) [2,3,19,56,93-99].
Further discussion is presented separately:
●General surgery – (See "Intraoperative transfusion and administration of clotting factors", section on 'Point-of-care tests' and "Intraoperative transfusion and administration of clotting factors", section on 'Use of a transfusion algorithm or protocol'.):
●Cardiac surgery – (See "Achieving hemostasis after cardiac surgery with cardiopulmonary bypass", section on 'Use of transfusion algorithms'.)
●Liver transplantation – (See "Liver transplantation: Anesthetic management", section on 'Management of coagulopathy'.)
●Abdominal or thoracic aortic surgery – (See "Anesthesia for open abdominal aortic surgery", section on 'Blood salvage and transfusion' and "Anesthesia for open descending thoracic aortic surgery", section on 'Management of anticoagulation, bleeding, and hemostasis'.)
Perioperative uses of VET are evolving, and the technology is sometimes used in other major surgical procedures if clinically significant blood loss is expected (eg, joint arthroplasty, spine surgery, some major abdominal or urologic procedures) [100-102].
The use of VET technology may also be helpful postoperatively. For example, if a patient with clinically significant postoperative bleeding has VET test parameters that are within normal ranges, a surgical source is the most likely cause. This knowledge facilitates decisions to return to an operating room. (See "Perioperative blood management: Strategies to minimize transfusions", section on 'Postoperative strategies'.)
Postpartum hemorrhage — TEG and ROTEM have been used to facilitate appropriate management of bleeding in patients with postpartum hemorrhage (PPH) and to provide guidance for transfusion of blood products and assessment of responses to hemostatic interventions [96,103-112].
Hypofibrinogenemia is the most common hemostatic abnormality in PPH. It is identified by FIBTEM (table 2) or clot strength (ie, maximum clot firmness [MCF]) for ROTEM, or functional fibrinogen or maximal amplitude (MA) for TEG.
Randomized trials and observational studies have reported that VET is useful in directing early therapy for hypofibrinogenemia in PPH using fibrinogen concentrate or FFP. Supporting data and specific recommendations are presented separately. (See "Postpartum hemorrhage: Medical and minimally invasive management".)
SOCIETY GUIDELINE LINKS —
Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: General issues of trauma management in adults".)
SUMMARY AND RECOMMENDATIONS
●Terminology – Viscoelastic testing (VET), also referred to as global hemostasis testing and viscoelastic hemostatic assays, is a point-of-care (POC) method of testing whole blood clotting. Thromboelastography (TEG) and rotational thromboelastometry (ROTEM) are the two main VET platforms; sonorheometry (Quantra) is less commonly used. (See 'Terminology' above.)
●Technology – VET is done on citrated blood in standard blood collection tubes, using a machine in the operating room or emergency department trauma bay. The readout is a single tracing that contains information about hemostasis and clot lysis, including clot initiation, kinetics of clot formation and strength, and clot dissolution over time (figure 1 and table 1 and table 2). (See 'Technologies and tests' above.)
●Benefits and limitations – VET may provide comparable information to standard coagulation tests in a timelier manner (typical results in 10 to 15 minutes) and an easily accessible format that can be linked to a transfusion algorithm (algorithm 1). However, it does not directly evaluate platelet function and is insensitive to platelet inhibitors including aspirin. It requires specialized training and quality control procedures, is not available in every institution, and carries significant costs. Even in institutions that do use POC tests, standard laboratory coagulation tests are obtained to provide additional information. (See 'Potential benefits' above and 'Potential limitations' above.)
●Specific uses
•Trauma resuscitation – Trauma can cause injury-related fibrinolytic phenotypes (excessive hyperfibrinolysis or fibrinolytic shutdown) that can be diagnosed and monitored during transfusions using VET (table 3). (See 'Detection of fibrinolysis' above and 'Trauma resuscitation' above and "Initial management of moderate to severe hemorrhage in the adult trauma patient" and "Ongoing assessment, monitoring, and resuscitation of the severely injured patient".)
•Major surgical procedures with significant anticipated blood loss – A transfusion algorithm guided by POC VET can aid decision-making regarding the transfusion of blood products during major surgical procedures (algorithm 1). Specific indications are discussed in separate topic reviews such as the following:
-General surgery – (See "Intraoperative transfusion and administration of clotting factors", section on 'Point-of-care tests' and "Intraoperative transfusion and administration of clotting factors", section on 'Use of a transfusion algorithm or protocol'.)
-Cardiopulmonary bypass – (See "Achieving hemostasis after cardiac surgery with cardiopulmonary bypass", section on 'Use of transfusion algorithms'.)
-Liver transplantation – (See 'Detection of fibrinolysis' above and "Liver transplantation: Anesthetic management", section on 'Management of coagulopathy'.)
-Abdominal and thoracic aortic surgery – (See "Anesthesia for open abdominal aortic surgery", section on 'Blood salvage and transfusion' and "Anesthesia for open descending thoracic aortic surgery", section on 'Management of anticoagulation, bleeding, and hemostasis'.)
•Postpartum hemorrhage – Hypofibrinogenemia is the most common clotting abnormality in postpartum hemorrhage, and this can be continuously monitored with VET. (See 'Postpartum hemorrhage' above and "Overview of postpartum hemorrhage".)
