A nurse is caring for a client admitted to the intensive care unit for a cardiac dysrhythmia. The nurse understands the prescribed calcium channel blocker has which of the following mechanisms of action?
Acts on the beta cells within the heart and lungs to regulate cardiac rhythm
Increases heart rate and increases myocardial contractility
Reduces the contractility and conductivity of the heart
Increase oxygen to the systemic circulation
The Correct Answer is C
A) "Acts on the beta cells within the heart and lungs to regulate cardiac rhythm.": This statement is incorrect because calcium channel blockers do not primarily act on beta cells. Instead, they block calcium channels in cardiac and smooth muscle, which affects heart contractility and conductivity.
B) "Increases heart rate and increases myocardial contractility.": Calcium channel blockers typically do the opposite; they decrease heart rate and myocardial contractility by inhibiting calcium entry into the heart muscle cells. Therefore, this statement does not accurately describe their mechanism of action.
C) "Reduces the contractility and conductivity of the heart.": This statement accurately reflects the action of calcium channel blockers. By blocking calcium entry, these medications decrease myocardial contractility and slow down electrical conduction through the heart, which can help manage dysrhythmias.
D) "Increase oxygen to the systemic circulation.": While calcium channel blockers can improve blood flow and reduce myocardial oxygen demand by decreasing heart workload, their primary action does not directly focus on increasing oxygen delivery to systemic circulation. Their primary role is in managing heart contractility and rhythm.
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Correct Answer is B
Explanation
A) Carvedilol: While carvedilol is a beta-blocker that can be used to treat hypertension, it is not considered a first-line treatment. Beta-blockers are typically used when other first-line agents are not effective or in specific situations such as heart failure or ischemic heart disease.
B) Lisinopril: Lisinopril is an ACE inhibitor and is considered a first-line treatment for hypertension. It effectively reduces blood pressure by inhibiting the angiotensin-converting enzyme, leading to vasodilation and decreased blood volume. Its well-documented efficacy and favorable side effect profile make it a common choice for initial therapy.
C) Clonidine: Clonidine is an alpha-2 adrenergic agonist that can lower blood pressure but is generally not used as a first-line treatment due to its side effects and potential for rebound hypertension if discontinued abruptly.
D) Doxazosin: Doxazosin is an alpha-1 blocker that can be used to treat hypertension but is not typically a first-line choice. It may be used in specific cases, such as in patients with benign prostatic hyperplasia, but other classes of medications are usually preferred for initial hypertension treatment.
Correct Answer is D
Explanation
A) Pulse oximetry of 92%: While a pulse oximetry reading of 92% is slightly below normal, it is not a definitive reason to hold verapamil. This reading indicates mild hypoxemia, but it does not directly contraindicate the use of verapamil. Other factors should be considered before making a decision based solely on this value.
B) Pulse of 78: A pulse rate of 78 beats per minute is within the normal range for adults and does not warrant holding verapamil. This finding alone does not indicate any immediate concerns related to the administration of the medication.
C) Respiratory rate of 12: A respiratory rate of 12 breaths per minute is within the normal range for adults. This finding does not provide any indication that verapamil should be withheld. It is important to consider other clinical factors when assessing the appropriateness of medication administration.
D) History of myocardial infarction a week ago: Verapamil, a calcium channel blocker, can have significant effects on cardiac function. Administering it to a client who recently experienced a myocardial infarction (heart attack) could exacerbate cardiac issues and lead to complications. Therefore, it is crucial to hold the medication and consult with the healthcare provider before proceeding.