What lab value should be monitored when administering continuous IV heparin for venous thrombosis?

When administering continuous IV heparin for the management of venous thrombosis, monitoring the activated partial thromboplastin time (aPTT) is crucial. Heparin works as an anticoagulant, primarily affecting the intrinsic pathway of the coagulation cascade. The aPTT test specifically evaluates the efficacy of this pathway, making it the most relevant laboratory value for assessing the therapeutic effect of heparin therapy.

In clinical practice, the aPTT measures the time it takes for blood to clot and helps determine whether the heparin dosage is within the desired therapeutic range. This is typically maintained at approximately 1.5 to 2.5 times the normal aPTT value, thereby reducing the risk of thrombosis while minimizing the potential for bleeding complications. Regular monitoring ensures that adjustments can be made to the heparin infusion rate as needed to maintain this therapeutic range.

The other lab values mentioned serve different purposes. The prothrombin time (PT) and international normalized ratio (INR) are primarily used to monitor oral anticoagulants like warfarin, not heparin. A complete blood count (CBC) can provide information on platelet levels and other blood components but is not specific for monitoring heparin therapy