How to correct a low R time on thromboelastography (TEG) with activated coagulation (CK)?

Correcting Low R Time on TEG with Activated Coagulation (CK)

To correct a low R time on thromboelastography (TEG) with activated coagulation (CK), administer prothrombin complex concentrate (PCC) and intravenous vitamin K, especially if the patient is on vitamin K antagonists. 1

Understanding Low R Time on TEG

• R time (reaction time) measures the time to initial fibrin formation, representing clot initiation 2
• A shortened R time indicates hypercoagulability, which may increase thrombotic risk 2
• Normal R time typically ranges from 5-10 minutes, with values below this range suggesting hypercoagulability 2
• Low R time on TEG with activated coagulation (CK) is often associated with anticoagulant therapy, particularly with direct oral anticoagulants (DOACs) or vitamin K antagonists (VKAs) 1

Diagnostic Approach

• Confirm the low R time finding with repeat testing if clinically appropriate 2
• Consider concurrent abnormalities in other TEG parameters that may indicate additional coagulation issues 2
• Assess the patient's medication history, particularly for anticoagulants 1
• For patients on DOACs, specific assays may provide additional information:
  • Dabigatran: diluted thrombin time (dTT) or ecarin clotting time (ECT) 3
  • Rivaroxaban/apixaban: anti-Xa activity 1

Treatment Algorithm for Low R Time

1. For patients on vitamin K antagonists (VKAs):

   • Administer prothrombin complex concentrate (PCC) along with intravenous vitamin K 1
   • Dosing should be guided by INR level and clinical urgency 1

2. For patients on direct oral anticoagulants (DOACs):

   • For dabigatran: Consider idarucizumab (Praxbind) 3
   • For factor Xa inhibitors (rivaroxaban, apixaban): Consider andexanet alfa or PCC 1

3. For patients not on anticoagulants with hypercoagulability:

   • Consider prophylactic anticoagulation based on thrombotic risk assessment 1
   • Low molecular weight heparin (LMWH) may be appropriate in many cases 1

Monitoring Response

• Repeat TEG 15-30 minutes after intervention to assess response 2
• Target normalization of R time (typically 5-10 minutes) 2
• Monitor for signs of bleeding or thrombosis 1

Special Considerations

• In trauma patients, viscoelastic tests like TEG may guide more targeted blood product use 4
• In pregnancy, baseline R times are typically shortened due to physiologic hypercoagulability 1
• In liver disease, viscoelastic tests like TEG may provide more valuable information than standard coagulation tests 2

Pitfalls to Avoid

• Do not rely solely on conventional coagulation tests (PT, aPTT) as they may not correlate well with TEG parameters 2
• Standard TEG is insensitive to antiplatelet agents and cannot reliably detect platelet dysfunction 2
• Anemia can paradoxically show hypercoagulable TEG results due to decreased blood viscosity, potentially masking coagulopathy 2
• Results vary between devices and are not interchangeable between TEG and ROTEM 2
• Proper training and regular calibration are essential for accurate TEG interpretation 2