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 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
Correct Answer is D
Explanation
Report any muscle pain or weakness to the healthcare provider.This is because simvastatin This is because simvastatin can cause a rare but serious side effect of muscle damage (rhabdomyolysis), which can lead to kidney failure.Muscle pain or weakness can be signs of muscle breakdown and kidney damage, and should be reported to the healthcare provider as soon as possible.
Choice A is wrong because changing position slowly when rising from a chair is not related to simvastatin.This is a precaution for people who take medications that lower blood pressure, such as diuretics or beta blockers, to prevent dizziness or fainting.
Choice B is wrong because maintaining a steady intake of green leafy vegetables is not specific to simvastatin.This is a general dietary recommendation for people who take anticoagulants, such as warfarin, to prevent bleeding complications.
Choice C is wrong because consuming no more than 1 L/day of fluid is not advised for people who take simvastatin.This is a restriction for people who have heart failure or kidney disease, to prevent fluid overload.People who take simvastatin should drink enough fluids to stay hydrated and avoid dehydration, which can increase the risk of kidney damage.
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