What is the target International Normalized Ratio (INR) range for a patient who had a mechanical heart valve replacement and is on Warfarin (Coumadin)?
1.5-2.5.
2.0-3.0.
2.5-3.5.
0.8-1.2. —
The Correct Answer is C
Choice A rationale
An INR of 1.5–2.5 is subtherapeutic for mechanical valve prostheses. This range provides inadequate anticoagulation to prevent thrombus formation on artificial valve surfaces, where turbulent blood flow predisposes to platelet activation and fibrin deposition. Such inadequate anticoagulation increases the risk of valve thrombosis and systemic embolization, including stroke or arterial occlusion, making this INR unsuitable for prosthetic valve recipients requiring higher targets.
Choice B rationale
An INR of 2.0–3.0 is therapeutic for atrial fibrillation or venous thromboembolism but insufficient for mechanical heart valves. Mechanical prostheses have greater thrombogenic potential than biological valves, requiring stronger anticoagulation intensity. Maintaining INR below 2.5 increases the risk of thromboembolic events; therefore, this target range is used for less thrombogenic conditions rather than for mechanical valve replacement patients.
Choice C rationale
An INR of 2.5–3.5 is the appropriate target for mechanical heart valves due to elevated thrombotic risk. Warfarin inhibits hepatic synthesis of vitamin K-dependent clotting factors II, VII, IX, and X, prolonging prothrombin time. Maintaining INR within this range ensures optimal anticoagulation while minimizing hemorrhagic risk. The standard therapeutic range reflects the need to balance prevention of mechanical valve thrombosis against potential bleeding complications associated with over-anticoagulation.
Choice D rationale
An INR of 0.8–1.2 represents the normal range for individuals not receiving anticoagulants. This physiologic baseline reflects normal coagulation factor activity and provides no thromboembolic protection. Such INR levels indicate ineffective warfarin dosing in patients with prosthetic valves, predisposing to thrombus formation, mechanical obstruction, and systemic emboli. Therefore, this value range is far below therapeutic targets required for safe long-term anticoagulation management.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is B
Explanation
Choice A rationale
An Implantable Cardiac Defibrillator (ICD) is an electronic device designed to monitor the heart's electrical activity for dangerous rhythms and deliver therapy. Monitoring respirations is the function of a respiratory monitor or pulse oximetry, not the primary and specialized function of the ICD device.
Choice B rationale
The principal function of an ICD is to continuously monitor the heart rhythm, detect life-threatening ventricular tachyarrhythmias (VT or VF), and automatically deliver a high-energy electrical shock (defibrillation/cardioversion) to terminate the dysrhythmia and restore a perfusing rhythm.
Choice C rationale
While an ICD does monitor the heart rate to detect tachycardia and bradycardia, simply monitoring the heart rate is a secondary function. Its defining therapeutic role is the delivery of electrical therapy to treat life-threatening ventricular dysrhythmias, a capability standard pacemakers lack.
Choice D rationale
An ICD does not directly regulate systemic blood pressure; this is achieved through autonomic nervous system regulation, fluid volume management, or vasoactive medications. While treating a lethal dysrhythmia will secondarily stabilize blood pressure, its primary mechanism is electrical, not hemodynamic.
Correct Answer is D
Explanation
Choice A rationale
Ordering a breathing treatment, such as a bronchodilator, is appropriate for a patient with documented bronchospasm or underlying reactive airway disease. Since CABG patients are generally high-risk for atelectasis due to incisional pain, a more generalized and preventative measure like an incentive spirometer is the priority intervention.
Choice B rationale
Giving adequate pain medication is crucial because post-surgical pain leads to shallow breathing and splinting, which directly increases the risk of atelectasis and pneumonia. However, while pain control facilitates respiratory efforts, the direct and most effective intervention to prevent collapse of the alveoli is mechanical lung inflation.
Choice C rationale
Applying oxygen via nasal cannula is used to treat or prevent hypoxemia by increasing the fraction of inspired oxygen (FiO_2). Unless the patient's oxygen saturation is low (normal SpO_2 is 95-100%), this is not a primary intervention to prevent respiratory mechanical compromise like atelectasis; it merely treats the resulting hypoxemia.
Choice D rationale
Incentive spirometry is the most crucial mechanical intervention for preventing postoperative respiratory complications in CABG patients. It encourages maximal inspiratory effort, which helps re-expand collapsed alveoli, preventing atelectasis and subsequent pneumonia caused by shallow, painful post-sternotomy breathing. —.
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