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
Nitroglycerin transdermal patches are used to prevent episodes of angina (chest pain) in people who have coronary artery disease (narrowing of the blood vessels that supply blood to the heart).Nitroglycerin is a vasodilator that works by relaxing the blood vessels so that the heart does not need to work as hard and therefore does not need as much oxygen.However, if nitroglycerin is used continuously, the body may develop tolerance to its effects, meaning that it will not work as well to prevent angina attacks.Therefore, it is important to remove the patch at bedtime and apply a new one in the morning, leaving a 10-12 hour nitrate-free interval.This way, the body can restore its sensitivity to nitroglycerin and avoid angina episodes during the day.
Choice A is wrong because allergic response is not a common reason to remove the patch at night.Although some people may experience skin irritation or rash from the patch, this is usually mild and does not require discontinuation of the medication.If the skin reaction is severe or bothersome, the patch can be applied to a different area of the skin or switched to another form of nitroglycerin.
Choice C is wrong because overdose is unlikely to occur from using the patch as prescribed.Nitroglycerin patches come in doses ranging from 0.1 milligrams per hour to 0.8 mg/hr, and should be placed on clean, dry, and hairless skin for 12-14 hours and removed for 10-12 hours.If a patch loosens or falls off, it should be replaced with a fresh one.Overdose symptoms may include severe headache, dizziness, blurred vision, nausea, vomiting, sweating, chest pain, fast or irregular heartbeat, difficulty breathing, fainting, or seizures.If these occur, the patch should be removed immediately and medical attention should be sought.
Choice D is wrong because management of BPH (benign prostatic hyperplasia) is not related to nitroglycerin use.
BPH is a condition
Correct Answer is B
Explanation
Vitamin K is the antidote for warfarin toxicity because it can reverse the effects of warfarin by restoring the clotting factors.Warfarin is an oral anticoagulant that works by inhibiting vitamin K epoxide reductase, an enzyme that activates vitamin K in the body.Vitamin K is needed for the synthesis of active coagulation factors, such as II, VII, IX and X.By blocking vitamin K, warfarin reduces the blood’s clotting activity and prevents the formation of blood clots.
Choice A is wrong because vitamin B12 is not involved in the coagulation cascade.Vitamin B12 is mainly involved in DNA synthesis, red blood cell production and nerve function.
Choice C is wrong because calcium gluconate is not an antidote for warfarin toxicity.Calcium gluconate is used to treat low blood calcium levels or hypocalcemia.Calcium is also a cofactor for some coagulation factors, but it does not reverse the effects of warfarin.
Choice D is wrong because protamine sulfate is not an antidote for warfarin toxicity.
Protamine sulfate is used to reverse the effects of heparin, another type of anticoagulant that works by inhibiting thrombin and factor Xa.
Protamine sulfate does not affect the vitamin K-dependent coagulation factors that are inhibited by warfarin.
Normal ranges for coagulation tests that are affected by warfarin are:
• Prothrombin time (PT): 11 to 13.5 seconds
• International normalized ratio (INR): 0.8 to 1.2
• Activated partial thromboplastin time (aPTT): 25 to 35 seconds
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