Overview
Definition:
Rotational thromboelastometry (ROTEM) is a viscoelastic hemostasis analysis method that assesses the dynamic properties of clot formation and lysis in whole blood
It provides a comprehensive picture of the patient's coagulation status, including clot initiation, amplification, stabilization, and fibrinolysis, using different activators to mimic specific coagulation pathways and platelet functions
This bedside test is crucial in managing bleeding patients, especially in surgical settings.
Epidemiology:
Coagulopathy is a significant complication in surgical patients, particularly in trauma, major orthopedic, cardiothoracic, and hepatic surgeries
Postoperative bleeding affects up to 5-10% of major surgical procedures, leading to increased morbidity, mortality, and resource utilization
The incidence of needing blood transfusions varies widely by procedure, but can be as high as 50% in complex surgeries
Identifying and managing coagulopathy promptly with tools like ROTEM can mitigate these risks.
Clinical Significance:
Accurate and rapid interpretation of ROTEM is vital for guiding hemostatic therapy in surgical patients at risk of or experiencing bleeding
It allows for a more targeted approach to transfusion compared to conventional coagulation tests (PT/INR, aPTT), which reflect only specific components of the coagulation cascade and are less sensitive to global hemostatic function
This evidence-based approach helps optimize blood product usage, reduce transfusion-associated complications, and improve patient outcomes in the perioperative period.
Diagnostic Approach
History Taking:
Obtain a detailed history of bleeding diathesis, anticoagulant/antiplatelet use, liver disease, renal disease, and previous surgical bleeding episodes
Inquire about the onset, severity, and nature of current bleeding, as well as any recent infections or sepsis.
Physical Examination:
Perform a thorough physical examination, focusing on signs of bleeding (e.g., ecchymoses, petechiae, hematomas), vital signs (hypotension, tachycardia), and signs of organ dysfunction (e.g., jaundice, ascites, encephalopathy)
Assess for signs of shock or hypovolemia.
Investigations:
ROTEM analysis using various activators (INTEM, EXTEM, FIBTEM, APTEM) is central
INTEM assesses the intrinsic pathway, EXTEM the extrinsic pathway, FIBTEM evaluates fibrinogen contribution to clot strength, and APTEM detects hyperfibrinolysis
Reference ranges for key parameters include: CT (Clotting Time), CFT (Clot Formation Time), MCF (Maximum Clot Formation), and ML (Maximum Lysis)
Conventional labs like PT, aPTT, platelet count, fibrinogen levels, and D-dimers are also important for comprehensive assessment.
Differential Diagnosis:
Differential diagnoses for bleeding in surgical patients include: acquired coagulopathy (dilutional coagulopathy, disseminated intravascular coagulation (DIC), liver disease, vitamin K deficiency, anticoagulant/antiplatelet effects), inherited bleeding disorders, thrombocytopenia, platelet dysfunction, and surgical bleeding (e.g., anastomotic leak, uncontrolled hemorrhage from operative site)
ROTEM helps differentiate between these by assessing the specific defects in clot formation and lysis.
Rotem Parameters And Interpretation
Intem Analysis:
INTEM (Intrinsic Pathway Activation): Assesses the overall coagulation potential
Long CT suggests deficiencies in factors of the intrinsic pathway or severe anticoagulation
Reduced MCF indicates impaired clot strength due to factors or platelets
High ML suggests hyperfibrinolysis
Reference CT: 15-30 sec, CFT: 40-120 sec, MCF: 50-72 mm, ML: 0-15%.
Extem Analysis:
EXTEM (Extrinsic Pathway Activation): Primarily assesses the contribution of tissue factor and the common pathway
Long CT suggests deficiencies in factors of the extrinsic or common pathway, or anticoagulants
Reduced MCF indicates impaired clot strength
High ML suggests hyperfibrinolysis
Reference CT: 15-30 sec, CFT: 40-120 sec, MCF: 50-72 mm, ML: 0-15%.
Fibtem Analysis:
FIBTEM (Fibrinogen Contribution to Clot Strength): Uses aprotinin to inhibit intrinsic and extrinsic pathways, isolating the role of fibrinogen
A reduced MCF (especially compared to EXTEM MCF) indicates hypofibrinogenemia or dysfunctional fibrinogen
Reference MCF: >15 mm
Low MCF is indicative of fibrinogen deficiency.
Aptem Analysis:
APTEM (Activated Plasminogen Pathway): Assesses fibrinolysis by adding an aprotinin inhibitor to EXTEM
Significant clot lysis (high ML) in EXTEM that is reduced in APTEM suggests pathological fibrinolysis
Reference ML: 0-15%
Elevated ML in EXTEM and normalized or reduced ML in APTEM suggests hyperfibrinolysis.
Management Strategies Guided By Rotem
Hypocoagulability And Hypofibrinogenemia:
A prolonged CT in INTEM/EXTEM with a reduced MCF suggests factors deficiency or impaired thrombin generation
A low FIBTEM MCF (e.g., <15mm) points to hypofibrinogenemia
Management involves fibrinogen concentrate (e.g., 4-6g), and potentially prothrombin complex concentrate (PCC) or fresh frozen plasma (FFP) for factor deficiencies.
Platelet Dysfunction Or Thrombocytopenia:
A normal or near-normal CT and CFT but significantly reduced MCF in EXTEM/INTEM, with a normal FIBTEM MCF, suggests platelet issues
Management focuses on platelet transfusions (e.g., 1-2 apheresis units or 6-8 pooled units).
Hyperfibrinolysis:
High ML in EXTEM/INTEM that is significantly reduced in APTEM indicates hyperfibrinolysis
Management includes tranexamic acid (e.g., 1-2g IV) and potentially cryoprecipitate if fibrinogen is also low.
Dilutional Coagulopathy:
Common in massive transfusion
Characterized by prolonged CT/CFT and reduced MCF, often with low fibrinogen and platelet counts
Management involves rapid administration of blood products, including packed red blood cells, FFP, platelets, and fibrinogen concentrate in appropriate ratios (e.g., 1:1:1 or 1:1:2 PRBC:FFP:Platelets, plus fibrinogen)
ROTEM guides the specific product needed.
Complications
Early Complications:
Thromboembolic events (if procoagulant therapy is overused), persistent bleeding, acute kidney injury, multi-organ dysfunction syndrome, transfusion-related acute lung injury (TRALI), and transfusion-associated circulatory overload (TACO).
Late Complications:
Postoperative adhesions, incisional hernias, surgical site infections, and chronic organ damage due to prolonged hypoperfusion.
Prevention Strategies:
Proactive identification and management of coagulopathy using ROTEM, adherence to transfusion guidelines, careful surgical technique, adequate fluid management, and early recognition of complications.
Key Points
Exam Focus:
ROTEM is a viscoelastic method providing dynamic coagulation assessment
Understand the different activators (INTEM, EXTEM, FIBTEM, APTEM) and their specific roles
Key parameters: CT, CFT, MCF, ML
Low FIBTEM MCF signifies hypofibrinogenemia
High ML reduced by APTEM indicates hyperfibrinolysis
Differentiate between factor deficiencies, platelet dysfunction, and fibrinogen issues.
Clinical Pearls:
Always interpret ROTEM in the context of the clinical scenario and other laboratory findings
Aim for specific product replacement rather than empirical transfusion
Normalization of ROTEM parameters guides discontinuation of therapy
Consider patient's anticoagulant/antiplatelet status when interpreting results.
Common Mistakes:
Over-reliance on conventional coagulation tests without considering dynamic hemostasis
Misinterpreting hyperfibrinolysis (failure to use APTEM)
Not differentiating between platelet issues and fibrinogen deficiency
Incorrectly applying ROTEM results without considering patient history and surgical context.