PT-INR Blood Test Lecture Notes

Introduction

• Presenter: Sarah, a registered nurse from RN.com
• Topic: PT-INR blood test
• Resources: Free quiz available after watching the video

What is a PT-INR?

• Purpose: Assesses how fast blood clots
• Process: Blood is drawn from a patient's vein, placed in a tube, and sent to a lab
• Components:
  • PT: Prothrombin (clotting factor 2)
  • INR: International Normalized Ratio

Importance of PT-INR

• Warfarin Monitoring: Important for patients on warfarin (Coumadin)
  • Warfarin: Anticoagulant that prolongs clot formation
  • INR Calculation: Based on PT level; used to adjust warfarin dosage
• Diagnosing Bleeding Disorders: Looks at the extrinsic pathway of coagulation cascade

Coagulation Cascade

• Prothrombin: Clotting factor 2
  • Turns into thrombin with the help of factor 5
  • Converts fibrinogen into fibrin to form a clot
• Vitamin K: Essential for production of clotting factors; produced in the liver

Liver and Vitamin K

• PT-INR Levels: Can indicate liver issues (e.g., vitamin K deficiency)
• Warfarin: Vitamin K antagonist, prolongs clot formation

Coagulation Pathways

• Extrinsic Pathway: Activated by external injury, checked by PT-INR
• Intrinsic Pathway: Activated by internal vascular injury, checked by APTT
• Common Pathway: Where intrinsic and extrinsic pathways meet to form a clot

Clotting Factors Checked by PT-INR

• Factors: 1, 2, 5, 7, and 10

PT-INR Test Interpretation

• PT Level: Measured in seconds; normal range is 10-12 seconds
• Potential Issues:
  • High PT Level: Clotting disorder, vitamin K deficiency, cancer, liver disease, anticoagulant use
• INR Level:
  • Normal INR: Less than 1.1
  • Therapeutic INR for Warfarin: 2 to 3
  • Risks:
    • INR < 2: Risk of clot development
    • INR > 3: Risk of excessive bleeding

Conclusion

• Summary of PT-INR's role in understanding blood clotting
• Importance of monitoring levels in patients on anticoagulants
• Encouragement to take the quiz for better comprehension

This summary provides a comprehensive overview of the PT-INR blood test and its clinical implications, as covered in the lecture by Sarah.