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Antithrombotic Decision Support Tool

Antithrombotic Decision Support Tool

1
Patient Info
2
Risk Factors
3
Bleeding Risk
4
Indication
5
Dual Therapy
6
Drug Selection
7
Recommendation
8
Monitoring
9
Surgery
10
References

Step 1: Patient Information

Basic Patient Data

Coagulation Parameters

D-Dimer Values


Note: 1 ยตg/mL = 1000 ng/mL. Confirm whether your lab reports DDU or FEU (FEU โ‰ˆ 2ร— DDU).

Step 2: Thrombotic Risk Factors

Major Risk Conditions

Minor/Moderate Risk Conditions

Virchow's Triad Factors

Active Thrombosis Panel โ–ผ
Hypercoagulability Testing โ–ผ
Hypercoagulability criteria: Either increased MCF/MA OR 2+ of: increased alpha angle, shortened R/CT time, reduced CFT/K time

Step 3: Bleeding Risk Assessment

Evidence of Active or Suspected Bleeding

Surgical / Procedural Risk

If clotting risk is very high (major risk disease present or active thrombosis), antithrombotics may still be used with caution โ€” see CURATIVE guidelines.

Coagulation-Based Bleeding Risk

Mild prolongation of PT/aPTT (<50%) may be consumptive in animals with active thrombosis and does not necessarily contraindicate antithrombotics.

Step 4: Antithrombotic Indication Decision

Step 5: Dual Therapy Decision

Step 6: Drug Selection

Step 7: Final Recommendation & Dosing

Step 8: Monitoring & Discontinuation Guidelines

General Monitoring

  • Clinical assessment for bleeding/thrombotic signs daily while hospitalized
  • Baseline labs: CBC, PT/aPTT, fibrinogen, D-dimer
  • Repeat labs every 24-48 hours while hospitalized
  • Assess response to antithrombotic therapy

Drug-Specific Monitoring

Antiplatelet Agents (Clopidogrel, Aspirin)

  • Monitor for gastrointestinal side effects (vomiting, diarrhea, melena)
  • Platelet function testing if available (PFA-100, Multiplate)
  • No routine coagulation monitoring required

Unfractionated Heparin (UFH)

  • aPTT every 6 hours until stable, then q12-24 hours
  • Target aPTT: 1.5-2ร— baseline
  • Platelet count q48-72 hours to monitor for HIT (heparin-induced thrombocytopenia)
  • Daily clinical assessment for bleeding

Low Molecular Weight Heparin (LMWH) โ€” Enoxaparin, Dalteparin, Fondaparinux

  • Anti-Xa activity 4 hours post-injection (target 0.5-1.0 IU/mL)
  • Platelet count periodically (less HIT risk than UFH)
  • Assess injection sites for hematomas
  • LMWH products are not interchangeable โ€” each has different dosing and pharmacokinetics

Rivaroxaban

  • PT as rough guide (less sensitive than for warfarin)
  • Anti-Xa activity (rivaroxaban-calibrated) if available
  • Monitor for GI upset, bleeding signs

Viscoelastic Testing

  • If available, repeat q24-48 hours
  • Use to assess response to antithrombotic therapy and guide continuation/discontinuation

Discontinuation Guidelines

IMHA

  • Continue at least 2-4 weeks during high-risk period
  • Many clinicians continue 2-3 months until clinical remission confirmed
  • Discontinue when hemolysis resolved and coagulation parameters normal

Feline Cardiomyopathy

  • Often lifelong, especially with HCM and left atrial enlargement
  • Reassess if clinical status changes
  • Discontinuation only if cardiomyopathy resolves (rare)

PLN / PLE

  • Continue while proteinuria/hypoalbuminemia persists
  • Discontinue when coagulation parameters normalized and proteinuria resolved

Acute Thrombotic Events

  • Minimum 2-4 weeks of therapy
  • Reassess underlying thrombotic risk
  • Consider longer duration if multiple risk factors persist

General Principle

  • Discontinue when underlying risk resolved AND hypercoagulable markers (viscoelastic, D-dimer, fibrinogen) normalized
  • Taper when possible rather than abrupt discontinuation
  • Monitor closely for 2-4 weeks post-discontinuation

Step 9: Perioperative Recommendations

Overview

Based on CURATIVE Domain 4: Perioperative management of antithrombotic therapy in dogs and cats with thrombotic disease.

Pre-Surgical Assessment

  • Evaluate current antithrombotic regimen
  • Assess bleeding vs thrombotic risk balance
  • Discuss with anesthesia and surgical teams
  • Plan perioperative management strategy

Drug-Specific Perioperative Management

Clopidogrel

  • Elective surgery: Ideally discontinue 5-7 days before procedure
  • Emergency surgery: Be prepared for increased bleeding risk
  • Consider bridging with UFH or LMWH if high thrombotic risk

Aspirin

  • Discontinue 5-7 days before elective surgery if possible
  • For emergency surgery, inform anesthesia/surgery of recent aspirin use

LMWH (Enoxaparin, Dalteparin, Fondaparinux)

  • Hold 12-24 hours before procedure
  • Resume 12-24 hours post-op if hemostasis achieved
  • Monitor injection sites post-op

Unfractionated Heparin (UFH)

  • Discontinue CRI 1-2 hours before procedure (short half-life ~60 min)
  • Can resume 2-3 hours post-op once hemostasis achieved
  • May be used for bridging (discontinue procedural, restart post-op)

Rivaroxaban

  • Hold 24-48 hours before procedure
  • Resume once hemostasis confirmed (typically 12-24h post-op)

Tissue Plasminogen Activator (tPA)

  • Contraindicated with concurrent surgery
  • If thrombolysis ongoing, delay surgery if possible

High Thrombotic Risk Patients Requiring Urgent Surgery

  • Continue antithrombotics with caution
  • The risk of thrombosis may outweigh surgical bleeding risk
  • Discuss thoroughly with surgeon and anesthesia
  • Consider dual therapy post-op if single therapy used pre-op
  • May benefit from viscoelastic-guided hemostasis management

Post-Operative Management

  • Resume antithrombotics as soon as hemostasis is adequate (typically 12-24 hours for most procedures)
  • Monitor surgical site for bleeding and hematoma formation
  • Assess for thrombotic complications (swelling, lameness, dyspnea)
  • Continue monitoring labs per antithrombotic protocol

Step 10: CURATIVE Guidelines References

ACVECC CURATIVE Antithrombotic Guidelines

All recommendations in this tool are based on the peer-reviewed ACVECC CURATIVE guidelines for antithrombotic therapy in dogs and cats:

Initial Guidelines (2019)

1. Goggs et al. (2019) - ACVECC CURATIVE Antithrombotic Consensus Guide: Consensus Document on Antithrombotic Therapy 2. Domain 1 (2019) - Identification of patients at risk of thrombotic disease 3. Domain 2 (2019) - Defining rational antithrombotic therapy 4. Domain 3 (2019) - Monitoring antithrombotic therapy 5. Domain 4 (2019) - Perioperative antithrombotic management 6. Domain 5 (2019) - Termination of antithrombotic therapy 7. Clinical Application (2019) - Clinical application of the CURATIVE guidelines

Updated Guidelines (2022)

8. Domain 1 Update (2022) - Identification of patients at risk of thrombotic disease 9. Domain 6 (2022) - Thrombolytic therapy in dogs and cats with thrombotic disease

How to Use These References

  • Click any reference link to access the full text on the journal website
  • All DOIs link to PubMed Central or the journal for access
  • Contact your veterinary library or institution for full-text access if needed
  • Consider downloading these papers for your reference library

Additional Recommended Resources

  • DeLaforcade et al. reviews on thromboelastography in veterinary medicine
  • Goggs et al. on coagulation abnormalities in critically ill animals
  • Brooks et al. consensus statements on critical coagulopathies
  • Recent publications on feline arterial thromboembolism (FAT CAT studies)
Disclaimer: This tool is for educational and clinical decision support purposes only. It does not replace clinical judgment. All recommendations are based on the ACVECC CURATIVE guidelines, peer-reviewed literature, and the personal clinical experience of the author. Clinicians should always apply their own judgment, consider individual patient factors, and consult with specialists when appropriate. The authors and institution assume no liability for inappropriate use of this tool or adverse outcomes resulting from its application.
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