Anticoagulants

• Anticoagulants are used to interfere with hemostasis (stop bleeding) and prevent the formation of thrombi. They suppress coagulation by reducing the formation of fibrin
• Fibrin is a tough protein that forms a mesh around the clot and solidifies it
• Indications for anticoagulants

  • treat DVT and PE
  • prevent VTE and thrombosis with atrial fibrillation and prosthetic heart valves
  • prevent complications with MI
• Anticoagulant act on the third step of hemostasis. Coagulation is when fibrin forms a mesh that traps red blood cells and platelets, forming the clot
• There are 2 factors in hemostasis:

  • factors affected by warfarin (vitamin K dependent clotting factor)
  • factor affected by heparin (factor that can be inactivated by antithrombin)
• Fibrinolysis is a mechanism by which formed thrombi are lysed. Anticoagulants do not lyse thrombi, they prevent them from bigger
• There are 4 types of anticoagulants

  • unfractioned heparin (heparin)
  • low molecular weight heparin (dalteparin, enoxaparin and tinzaparin)
  • vitamin K antagonist (warfarin)
  • direct oral anticoagulants (thrombin inhibitors like dabigatran) and factor Xa inhibitors like apixaban)
• Action of unfractioned heparin: enhance the activity of antithrombin by inactivating thrombin and factor Xa and reducing the production of fibrin
• Unfractioned heparin is only administered by injection. Its therapeutic response is to prevent DVT and PE and permit adequate anticoagulation
• Adverse effects of unfractioned and LMW heparin

  • bleeding
  • heparin induced thrombocytopenia (low level of platelets increasing the risk of bleeding)
  • antidote: protamine sulfate
• Anticoagulants are not indicated for patients with thrombocytopenia since it increases the risk of bleeding
• Unfractioned heparin needs aPTT monitoring, a blood test measuring the time it takes for the blood to clot. Heparin increases aPTT to around 60 to 80 seconds
• Administration of heparin and LMW heparin

  • independent double verification
  • favor abdomen as injection site
  • rotate sites at each injection
  • do not massage injection site
• LMW heparin enhances the activity of antithrombin by inactivating factor Xa over thrombin (predictable response) and reducing fibrin production
• Manifestations of bleeding are bleeding gums, petechiae (type of rash), ecchymosis, black tarry stools, hematuria, low BP and low hematocrit
• LMW heparin like dalteparin does not require aPTT since plasma levels are highly predictable
• Vitamin K angonist inhibitis the synthesis of vitamin K dependent clotting factors and reduces fibrin production
• Bridging atnicoagulants means administering 2 anticoagulants at the same time while warfarin (vitamin K antagonist) reaches its peak
• Warfarin labatory monitoring is done with PT (prothrombin time) and INR (international normalized ratio). Target INR is 2-3 for VTE and 3 for mechanical mitral valve. It is measured frequently initially to allow dosage adjustment
• Adverse affects of warfarin

  • bleeding
  • antidote is vitamin K
• Direct oral anticoagulants direct the inhibition thrombin and factor Xa (reduction of fibrin)
• Dabigatran is a thrombin inhibitor vs apixaban is a factor Xa inhibitor. They are used to prevent or treat VTE and to prevent strokes
• Direct anticoagulant adverse effects

  • bleeding
  • antidote is praxbind or ondexxya
• Direct oral anticoagulant do not require anticoagulant monitoring since plasma levels are highly predictable
• Nursing implications of anticoagulants

  • monitor for signs of bleeding
  • rotate injection sites
  • education on soft toothbrush and electric razor
  • notify if invasive procedure
  • for warfarin: maintain constant intake of vitamin K
• Effects of diet on warfarin

  • little vitamin K: more time to clot
  • high vitamin K: less time to clot
  • less clotting factors means more bleeding