Which laboratory test measures the effectiveness of warfarin?
PTT.
PT/INR.
aPTT.
ACT.
The Correct Answer is B
PT stands for prothrombin time, which is a measure of how long it takes the blood to clot.
INR stands for international normalized ratio, which is a way of standardizing the PT results across different laboratories.
Warfarin is a blood thinner that works by inhibiting the production of vitamin K-dependent clotting factors in the liver.
Therefore, warfarin prolongs the PT and increases the INR. The PT/INR test is used to monitor the effectiveness of warfarin therapy and adjust the dose accordingly.
Choice A is wrong because PTT stands for partial thromboplastin time, which is another measure of blood clotting time, but it reflects the activity of different clotting factors than PT. PTT is used to monitor heparin therapy, not warfarin therapy.
Choice C is wrong because aPTT stands for activated partial thromboplastin time, which is a variation of PTT that uses an activator to speed up the clotting time. Like PTT, aPTT is used to monitor heparin therapy, not warfarin therapy.
Choice D is wrong because ACT stands for activated clotting time, which is a measure of the whole blood clotting time. ACT is used to monitor high-dose heparin therapy during certain procedures, such as cardiac bypass surgery or angioplasty.
The normal ranges for these tests may vary depending on the laboratory and the method used, but generally, they are:
• PT: 10 to 13 seconds
• INR: 0.8 to 1.2 (without warfarin) or 2.0 to 3.0 (with warfarin)
• PTT: 25 to 35 seconds
• aPTT: 30 to 40 seconds
• ACT: 70 to 120 seconds
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is C
Explanation
Digoxin is a cardiac glycoside that increases the force of heart contractions (positive inotropy) and decreases the heart rate (negative chronotropy) by inhibiting the sodium-potassium ATPase pump in the cardiac cell membranes and affecting the autonomic tone.This helps to improve the symptoms of heart failure and to control the ventricular rate in atrial fibrillation.
Choice A is wrong because positive chronotropy means increasing the heart rate, which is the opposite of what digoxin does.
Choice B is wrong because negative inotropy means decreasing the force of heart contractions, which is also the opposite of what digoxin does.
Choice D is wrong because positive inotropy and positive chronotropy would both increase the workload of the heart, which is not desirable in heart failure or atrial fibrillation.
Normal ranges for digoxin are 0.5 to 2 ng/mL for heart failure and 0.8 to 2 ng/mL for atrial fibrillation.Digoxin has a narrow therapeutic window and can cause serious side effects if overdosed or underdosed.
Correct Answer is D
Explanation
Choice A is wrong because calcium channel blockers (CCBs) are a class of drugs that prevent calcium from entering the cells of the heart and blood vessels, causing them to relax and lower blood pressure.
Examples of CCBs include amlodipine, diltiazem, verapamil, and nifedipine.CCBs are used to treat hypertension, angina, and arrhythmias.
Choice B is wrong because beta blockers are a class of drugs that reduce the heart rate and force of contraction, lowering the cardiac output and blood pressure.
Examples of beta blockers include atenolol, metoprolol, propranolol, and bisoprolol.Beta blockers are used to treat hypertension, angina, heart failure, and arrhythmias.
Choice C is wrong because platelet inhibitors are a class of drugs that prevent platelets from clumping together and forming blood clots.
Examples of platelet inhibitors include aspirin, clopidogrel, ticagrelor, and prasugrel.Platelet inhibitors are used to prevent or treat cardiovascular events such as heart attack or stroke.
Choice E is wrong because ACE inhibitors are a class of drugs that inhibit the enzyme that converts angiotensin I to angiotensin II, reducing the production of this vasoconstrictor hormone.
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