For a client diagnosed with thrombophlebitis receiving heparin sodium IV, which laboratory test should be monitored?

The correct laboratory test to monitor for a client receiving heparin sodium IV is the activated partial thromboplastin time (aPTT). Heparin acts as an anticoagulant by inhibiting several key factors in the clotting cascade. Monitoring the aPTT allows healthcare providers to assess the effectiveness of heparin therapy and ensure the patient is within the therapeutic range for anticoagulation.

The aPTT specifically measures the intrinsic pathway of coagulation, which is primarily affected by heparin. Keeping the aPTT within a target range is crucial to minimize the risk of bleeding while ensuring the appropriate level of anticoagulation for treating conditions like thrombophlebitis.

Monitoring prothrombin time (PT) is more relevant for patients on warfarin therapy, as this test evaluates the extrinsic pathway and the effect of vitamin K-dependent factors. A complete blood count (CBC) can provide useful information about the patient's overall health and detect potential bleeding complications but does not directly monitor the effects of heparin. The international normalized ratio (INR) is also not applicable as it is primarily used to monitor patients on warfarin, not heparin.