What coagulation labs should be ordered for surgical patients?

Coagulation Labs for Surgical Patients

Routine preoperative coagulation testing should NOT be performed for all surgical patients but should be reserved for specific patient populations with risk factors for bleeding disorders or those undergoing high-risk procedures. 1

When to Order Coagulation Tests

Coagulation testing should be targeted to patients with:

1. Medical conditions associated with impaired hemostasis:

   • Liver disease
   • Diseases of hematopoiesis
   • History of bleeding disorders
   • Renal disease

2. Medication use:

   • Patients taking anticoagulants (warfarin, DOACs, etc.)
   • Patients on antiplatelet therapy

3. Clinical history suggesting coagulation disorder:

   • History of spontaneous bruising
   • History of excessive surgical bleeding
   • Family history of known heritable coagulopathy

4. High-risk surgical procedures:

   • Major vascular surgery
   • Neurosurgery
   • Procedures with anticipated significant blood loss

Recommended Coagulation Tests

When indicated based on the above criteria, the following tests should be ordered:

1. Basic coagulation panel:

   • Prothrombin Time (PT) / International Normalized Ratio (INR)
   • Activated Partial Thromboplastin Time (aPTT)
   • Platelet count
   • Fibrinogen level (in selected cases)

2. Additional tests for specific scenarios:

   • Thromboelastography (TEG) or rotational thromboelastometry (ROTEM) for more comprehensive assessment of coagulation and fibrinolysis
   • Platelet function testing for patients with suspected or drug-induced platelet dysfunction (e.g., clopidogrel)
   • D-dimer for suspected DIC or COVID-19 patients

Interpretation and Management Guidelines

Platelet Count

• <50 × 10^9/L: Platelet transfusion usually indicated in the presence of excessive bleeding 1
• 50-100 × 10^9/L: Consider platelet transfusion based on risk of bleeding into confined space (e.g., brain, eye)
• >100 × 10^9/L: Platelet transfusion rarely indicated in patients with normal platelet function

PT/INR

• PT/INR >1.5 times normal: Consider fresh frozen plasma (FFP) administration if actively bleeding 2
• For patients on warfarin: PT/INR should be determined before any dental or surgical procedure 3

Fibrinogen

• <1.0 g/L: Consider cryoprecipitate or fibrinogen concentrate administration 2

Special Considerations

Cirrhosis Patients

• For patients with stable cirrhosis undergoing common gastrointestinal procedures (paracentesis, thoracentesis, variceal banding, etc.), routine use of blood products for bleeding prophylaxis is not recommended 1

Monitoring During Surgery

• Visual assessment of the surgical field should be jointly conducted by the anesthesiologist and surgeon to determine whether excessive microvascular bleeding is occurring 1
• Intraoperative laboratory monitoring for coagulopathy should include determination of platelet count, PT/INR, and aPTT 1
• Point-of-care testing can provide rapid results (under 5 minutes) compared to central laboratory testing (median 88 minutes) 4

Common Pitfalls to Avoid

1. Indiscriminate preoperative coagulation testing - Current literature suggests unnecessary coagulation testing is rampant with astoundingly low sensitivity (1.0%-2.1%) for detection of clinically significant bleeding disorders 5

2. Relying solely on PT/INR for patients on direct oral anticoagulants (DOACs) - These tests have variable sensitivity to DOACs 2

3. Delayed testing in massive hemorrhage - Early and repeated testing is essential for timely intervention 2

4. Overlooking clinical history - A bleeding history should be obtained from all surgical patients, which is more valuable than routine testing 1

5. Ignoring hemoconcentration - This can mask coagulopathy; assess volume status and consider isotonic fluid administration before interpreting results 2

By following these evidence-based guidelines, clinicians can optimize the use of coagulation testing in surgical patients, avoiding unnecessary tests while ensuring appropriate monitoring for those at genuine risk of bleeding complications.