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 B
Explanation
The nurse should contact the provider before administering furosemide because the patient has a low serum potassium level of 2.8 mEq/L, which is below the normal range of 3.5 to 5.0 mEq/L.Furosemide is a diuretic that can cause potassium loss and worsen hypokalemia, which can lead to cardiac arrhythmias, muscle weakness, and fatigue. The nurse should also monitor the patient’s blood pressure, weight, and urine output, as furosemide can lower blood pressure and cause dehydration.
Choice A. Administer medication is wrong because the nurse should not give furosemide without checking with the provider first, as it could be harmful to the patient with low potassium.
Choice C. Hold medication is wrong because the nurse should not withhold furosemide without a valid reason or an order from the provider, as it could cause fluid overload and worsen the patient’s condition.
Choice D. Give potassium supplement is wrong because the nurse should not give potassium supplement without an order from the provider, as it could cause hyperkalemia or interact with other medications.
Correct Answer is B
Explanation
Class IV antidysrhythmics or calcium channel blockers decrease the flow of calcium ions into cardiac and vascular smooth muscle cells, thus decreasing heart rate and contractions.By reducing the calcium influx, they also decrease the slope of phase 0 and 4 and prolong phase 2 of the cardiac action potential.This results in vasodilation, reduced myocardial oxygen demand, and decreased conduction through the AV node.
Choice A is wrong because calcium channel blockers do not increase blood vessel spasm, but rather cause vasodilation.
Choice C is wrong because calcium channel blockers do not decrease refractory period, but rather prolong it by extending phase 2 of the cardiac action potential.
Choice D is wrong because calcium channel blockers do not increase heart rate, but rather decrease it by slowing down the pacemaker activity and AV nodal conduction.
Normal ranges for heart rate are 60 to 100 beats per minute, and for blood pressure are 120/80 mmHg or lower.
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