Maternity Nursing: Postpartum Q 13
A nurse is caring for a postpartum (PP) client with a diagnosis of DVT who is receiving a continuous intravenous infusion of heparin sodium. Which of the following laboratory results will the nurse specifically review to determine if an effective and appropriate dose of the heparin is being delivered?
A. Prothrombin time
B. International normalized ratio
C. Activated partial thromboplastin time
D. Platelet count
Correct Answer: C. Activated partial thromboplastin time.
Anticoagulation therapy may be used to prevent the extension of thrombus by delaying the clotting time of the blood. Activated partial thromboplastin time should be monitored, and a heparin dose should be adjusted to maintain a therapeutic level of 1.5 to 2.5 times the control. Anticoagulants derive their effect by acting at different sites of the coagulation cascade. Some act directly by enzyme inhibition, while others indirectly, by binding to antithrombin or by preventing their synthesis from the liver (vitamin K dependent factors).
Option A: This is the initial test used to identify defects in secondary hemostasis. It is the time taken for blood to clot and generates thrombin. A delay in the PT or aPTT indicates the presence of either a deficiency or inhibitor of the clotting factor, except for the antiphospholipid antibody, which can result in delayed aPTT. The normal range for PT levels is approximately 11 to 13 seconds, although levels may vary depending on the laboratory.
Option B: The INR are used to monitor coagulation time when warfarin (Coumadin) is used. The clotting time is the time it takes for plasma to clot after the addition of different substrates in vitro under standard conditions using the capillary method. The average clotting time is between 8 to 15 minutes. Some studies have disputed the use of clotting time as a screening test.
Option D: Although thrombocytopenia increases bleeding risk, it has been shown to predispose patients to venous thromboembolism. Heparin-induced thrombocytopenia is antibody-mediated with complications that include pulmonary embolism, acute myocardial infarction, and ischemic limb necrosis. Therefore, estimation of the bleeding risk before initiation of anticoagulation is essential. The use of argatroban, lepirudin, or danaparoid is recommended over other non-heparin anticoagulants.