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 D
Explanation
A. "Depending on the level of your PT/INR, the clot will begin to dissolve.": This response is misleading, as heparin's effect is not primarily monitored by PT/INR; rather, heparin is monitored by activated partial thromboplastin time (aPTT). Moreover, heparin does not directly dissolve clots; it prevents further clot formation.
B. "After the first dose, the clot will begin to dissolve.": This statement inaccurately suggests that heparin has an immediate effect on dissolving existing clots. While heparin acts quickly to inhibit further clotting, it does not lead to the dissolution of clots after the first dose.
C. "It usually takes heparin at least 2 to 3 days to reach a therapeutic blood level.": This is not accurate for heparin, which has an immediate effect on coagulation. While the therapeutic effects can be optimized over several days, heparin begins to work right away to prevent further clotting.
D. "Heparin does not dissolve clots. It stops new clots from forming.": This response accurately describes the mechanism of action of heparin. Heparin prevents the extension of existing clots and the formation of new clots, but it does not actively dissolve clots. This clarification is essential for the client’s understanding of their treatment and expectations regarding DVT management.
Correct Answer is A
Explanation
A) Hypokalemia: Hypokalemia, or low potassium levels, significantly increases the risk of digoxin toxicity. Since digoxin competes with potassium for binding at the sodium-potassium ATPase site in the heart, low potassium levels can lead to increased digoxin effects and toxicity. Therefore, it is crucial to monitor potassium levels and correct any deficiencies before administering digoxin.
B) Hyperkalemia: While hyperkalemia is a serious concern and can also affect digoxin therapy, it usually results in decreased effectiveness of digoxin rather than increasing toxicity. Elevated potassium levels can diminish the drug's positive inotropic effect.
C) Hypocalcemia: Although calcium levels can influence cardiac function, hypocalcemia is not directly related to digoxin toxicity. Monitoring calcium is important for overall cardiac health, but it is not the primary focus when assessing the risk for digoxin toxicity.
D) Hypernatremia: Elevated sodium levels do not have a direct impact on the efficacy or toxicity of digoxin. While sodium levels are essential to monitor for overall health, they are not critical in the context of digoxin administration and toxicity risk.