Class IV antidysrhythmics or calcium channel blockers have what action on the cardiovascular system?
Increase blood vessel spasm.
Decrease flow of calcium ions thus decreasing heart rate and contractions.
Decrease refractory period.
Increase heart rate.
The Correct Answer is B
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.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is A
Explanation
Digoxin is a medication that can help the heart pump more blood and slow down the heart rate in certain conditions, such as heart failure and atrial fibrillation.However, digoxin has a narrow therapeutic range, which means that too much or too little of it can be harmful.The therapeutic range of digoxin levels in the blood is 0.5-2 ng/mL, and the toxic level is >2.4 ng/mL.Digoxin should be held if the resting apical pulse of an infant is <90 bpm, an older child is <70 bpm, or an adult is <60 bpm.A pulse of 48/min in an adult is too low and could indicate digoxin toxicity, which can cause life-threatening arrhythmias. Therefore, the nurse should withhold the dose and notify the health care provider immediately.
Choice B is wrong because notifying the health care provider and monitoring the patient’s vital signs are not enough.
The nurse should also withhold the dose to prevent further exposure to digoxin.
Choice C is wrong because rechecking the pulse, making sure to count for 1 full minute, is not necessary.The nurse should already have counted the pulse for 1 full minute before administering digoxin, as per standard procedure.
Choice D is wrong because administering the dose could worsen the patient’s condition and increase the risk of digoxin toxicity and arrhythmias.
Correct Answer is C
Explanation
Antidigoxin is an antidote for digoxin toxicity that binds and inactivates digoxin, a cardiac glycoside that can cause life-threatening arrhythmias, hyperkalemia, and other symptoms when overdosed.Antidigoxin is also known as digoxin immune Fab or DIGIFab.
Choice A, protamine sulfate, is wrong because it is an antidote for heparin, an anticoagulant that can cause bleeding when overdosed.
Choice B, acetylcysteine, is wrong because it is an antidote for acetaminophen, a painkiller that can cause liver damage when overdosed.
Choice D, activated charcoal, is wrong because it is a nonspecific adsorbent that can reduce the absorption of some drugs or poisons from the gastrointestinal tract, but it is not effective for digoxin toxicity.
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