Protein C and S pathway – Mnemonic

Mnemonic: Time To Play Counter Strike (CS) at 5 and 8 o’clock

Factor Va and VIIIa are different in coagulation cascade. They are the co-factors for factor Xa and IXa respectively.

Another mnemonic: protein C Cuts Coagulation by Cutting Cofactors (Va and VIIIa)

Protein S is cofactor for protein S.

Protein C and S pathway using the mnemonic:

  1. Time To: Thrombin (factor IIa) – Thrombomodulin complex
  2. Play Counter Strike: Protein C and S
  3. 5 and 8 o’clock: Va and VIIIa
Joe D [CC BY-SA 3.0], via Wikimedia Commons

Clinical implications:

a. Factor V leiden mutation: Factor V resistant to inhibition by activated protein C (APC) leading to hypercoagulability.

b. Warfarcin induced Paradoxical hypercoagulability: The half-life of protein C is relatively short 6-8 hours. With inhibition of vitamin K, level of protein C falls before that of vitamin K dependent pro-coagulant factors like II, VII, IX and X, which have a half life of 5-7 days. This results in loss of protein C anticoagulant effect before inhibition of coagulation pathway achieved, and for a short time the patient becomes paradoxically more hypercoagulable.

  • This can lead to skin or subcutaneous necrosis secondary to thrombosis.
  • Heparin is co-administered with warfarin initially in cases of DVT to prevent this complication.

Review simplified coagulation cascade.

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