The nurse anticipates the following laboratory study to assess the therapeutic effect in the client taking heparin intravenously?

Appeared in: GMCH Chandigarh - 2019

Explanation

Intravenous (unfractionated) heparin primarily potentiates antithrombin, which inactivates clotting factors in the intrinsic pathway of the coagulation cascade.
The Activated Partial Thromboplastin Time (aPTT) is the laboratory test that specifically measures the time it takes for a clot to form via the intrinsic pathway.
Therefore, aPTT is the standard for monitoring the therapeutic effect of IV heparin, with a target range typically 1.5 to 2.5 times the baseline control value.

Option A: Prothrombin time (PT), usually reported as INR, measures the extrinsic coagulation pathway.
Option C: Hematocrit measures the percentage of red blood cells in the blood volume. It does not measure clotting factors or the effect of anticoagulants.
Option D: Hemoglobin measures the oxygen-carrying capacity of red blood cells. It does not assess the function of the coagulation cascade.

Clinical Relevance

Nursing practice connection: Use the key finding related to Pharmacology: Monitoring Anticoagulant Therapy to guide bedside assessment, documentation, and the next nursing action.
A core nursing responsibility is ensuring aPTT levels are drawn on time and reported promptly, as heparin has a narrow therapeutic window. Delays can lead to sub-therapeutic clotting or supra-therapeutic bleeding.
Nurses must implement bleeding precautions for any patient on heparin, including monitoring for subtle signs like oozing from IV sites, petechiae, or changes in vital signs (tachycardia, hypotension).
What if? If the patient were on a prophylactic dose of subcutaneous low-molecular-weight heparin (LMWH), such as enoxaparin, routine aPTT monitoring is typically not required because its anticoagulant effect is more predictable and it has a greater effect on Factor Xa than thrombin.

How to Approach the Question

First, identify the key medication in the question: 'heparin intravenously'.
Next, determine the specific task: assess the 'therapeutic effect' of the drug.
Recall the two main laboratory pathways for coagulation monitoring: aPTT for the intrinsic pathway and PT/INR for the extrinsic pathway.
Associate IV heparin with the intrinsic pathway and aPTT.
Evaluate the options. Eliminate Hematocrit and Hemoglobin as they measure blood components and volume, not clotting time. Eliminate Prothrombin time as it is used for warfarin.
Confirm that Activated partial thromboplastin time (aPTT) is the correct test for monitoring IV heparin therapy.

Concept Tested & Keywords

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E6 Pharmacology Nursing Lilley 11e Part 2 p. 125-127

E6 Medicine Harrison 22e Part 1 p. 515-517

Practise the full GMCH Chandigarh - 2019

Attempt every question from this paper in a timed mock, then review the full solution for each one.