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Introduction ( 5 Questions)
A nurse is caring for a client who has a history of coronary thrombosis and is taking warfarin as a long-term anticoagulant therapy. What laboratory test should the nurse monitor to evaluate the effectiveness of warfarin?
Choice A is wrong because activated partial thromboplastin time (aPTT) reflects the activity of the intrinsic and common pathways of coagulation. Heparin is an anticoagulant that enhances the activity of antithrombin, which inhibits factors II, IX, X, XI, and XII, which are involved in these pathways. Therefore, the aPTT is used to monitor the effectiveness of heparin therapy.
The INR is a standardized measure of the prothrombin time (PT), which reflects the activity of the extrinsic and common pathways of coagulation.
Warfarin is an anticoagulant that inhibits the synthesis of vitamin K-dependent clotting factors (II, VII, IX, and X), which are involved in these pathways.
Therefore, the INR is used to monitor the effectiveness of warfarin therapy and adjust the dose accordingly.The target INR range depends on the indication for warfarin, but it is usually between 2 and 3.
Choice C is wrong because platelet count measures the number of platelets in the blood, which are involved in primary hemostasis. Platelet count is not affected by warfarin therapy, but it can be decreased by heparin-induced thrombocytopenia (HIT), a rare but serious complication of heparin therapy.
Choice D is wrong because fibrinogen level measures the amount of fibrinogen in the blood, which is a precursor of fibrin, the main component of blood clots. Fibrinogen level is not affected by warfarin therapy, but it can be decreased by disseminated intravascular coagulation (DIC), a condition where widespread clotting and bleeding occur simultaneously.
The INR is a standardized measure of the prothrombin time (PT), which reflects the activity of the extrinsic and common pathways of coagulation.
Warfarin is an anticoagulant that inhibits the synthesis of vitamin K-dependent clotting factors (II, VII, IX, and X), which are involved in these pathways.
Therefore, the INR is used to monitor the effectiveness of warfarin therapy and adjust the dose accordingly. The target INR range depends on the indication for warfarin, but it is usually between 2 and 3.
Choice A is wrong because activated partial thromboplastin time (aPTT) reflects the activity of the intrinsic and common pathways of coagulation.
Heparin is an anticoagulant that enhances the activity of antithrombin, which inhibits factors II, IX, X, XI, and XII, which are involved in these pathways. Therefore, the aPTT is used to monitor the effectiveness of heparin therapy.
Choice C is wrong because platelet count measures the number of platelets in the blood, which are involved in primary hemostasis. Platelet count is not affected by warfarin therapy, but it can be decreased by heparin-induced thrombocytopenia (HIT), a rare but serious complication of heparin therapy.
Choice D is wrong because fibrinogen level measures the amount of fibrinogen in the blood, which is a precursor of fibrin, the main component of blood clots. Fibrinogen level is not affected by warfarin therapy, but it can be decreased by disseminated intravascular coagulation (DIC), a condition where widespread clotting and bleeding occur simultaneously.
The normal ranges for these tests are as follows:
• INR: 0.8 to 1.2
• aPTT: 25 to 35 seconds
• Platelet count: 150 to 450 x 10^9/L
• Fibrinogen level: 2 to 4 g/L