A patient, 3 days after an anterior wall MI, is in the critical care unit.
She is currently receiving oxygen at 4 L/min by nasal cannula; nitroglycerin paste, 1 inch qh; and the beta-blocker Lopressor 25 mg PO qh.
The monitor shows that she begins to have PVCs.
Over the course of the next several hours, the PVCs increase in frequency to more than 15 per minute, with occasional runs of multifocal bigeminal PVCs.
The patient's vital signs are heart rate, 84 beats/min, sinus rhythm, with described PVCs; blood pressure, 124/68 mm Hg; respirations, 20 breaths/min; SpO2, 92 Laboratory values are blood pH, 7.44; potassium, 4.4 mEq/L; and magnesium, 0.2 mEq/L. Which of the following, if ordered, would be inappropriate for this patient.
Magnesium sulfate 2 g IV piggyback over a 2-hour period.
Increase oxygen to 6 L/min by nasal cannula.
Potassium chloride 40 mEq in 250 ml 0.9
Lidocaine 100 mg IV push.
The Correct Answer is C
Choice A rationale
Magnesium sulfate administration is scientifically indicated because the patient's magnesium level is 0.2 mEq/L, which is significantly lower than the normal range of 1.5 to 2.5 mEq/L. Hypomagnesemia increases myocardial irritability and can directly precipitate premature ventricular contractions or torsades de pointes. Providing 2 grams intravenously helps stabilize the cardiac membrane potential by restoring the necessary cofactor for the sodium potassium adenosine triphosphatase pump, which maintains the appropriate intracellular and extracellular electrolyte gradients.
Choice B rationale
Increasing oxygen to 6 L/min is appropriate because the patient's SpO2 is currently 92 percent, which is at the lower limit of acceptable for a patient three days post anterior wall myocardial infarction. Normal SpO2 should ideally be ≥ 94 percent in cardiac patients to ensure adequate myocardial oxygenation. Increasing the fraction of inspired oxygen helps reduce the workload of the heart and may decrease the frequency of ectopy caused by localized areas of myocardial hypoxia.
Choice C rationale
Administering 40 mEq of potassium chloride is inappropriate for this specific patient because her potassium level is 4.4 mEq/L, which falls perfectly within the normal physiological range of 3.5 to 5.0 mEq/L. Over-supplementing potassium when the serum level is already optimal carries a significant risk of inducing hyperkalemia. Excessive potassium can lead to lethal arrhythmias, such as ventricular fibrillation or asystole, by disrupting the resting membrane potential and interfering with cardiac repolarization.
Choice D rationale
Lidocaine 100 mg IV push is a standard pharmacological intervention for a patient experiencing frequent or multifocal premature ventricular contractions following an acute myocardial infarction. Lidocaine is a Class IB antiarrhythmic that works by blocking fast voltage-gated sodium channels, particularly in ischemic tissues. This action shortens the action potential duration and raises the fibrillation threshold, thereby suppressing ventricular ectopy and preventing the progression to more dangerous rhythms like ventricular tachycardia or ventricular fibrillation.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is A
Explanation
Choice A rationale
The patient is currently hemodynamically stable with a blood pressure of 102/68, which is within an acceptable range for an adult. A racing heart and nervousness can stem from numerous non-cardiac causes such as caffeine intake, anxiety, electrolyte imbalances, or fever. Obtaining further information allows the nurse to identify potential triggers or underlying conditions before initiating invasive or pharmacological interventions that could potentially harm the patient if the cause is benign.
Choice B rationale
Administering a beta-blocker is a significant pharmacological intervention used to decrease the heart rate and myocardial oxygen demand. However, medications should not be administered until the underlying rhythm is clearly identified and the cause of the tachycardia is understood. Giving a beta-blocker to a patient who might have a compensatory tachycardia due to an underlying issue like dehydration or pulmonary embolism could lead to severe hypotension or clinical deterioration in the emergency department.
Choice C rationale
Electrical cardioversion is a highly invasive procedure reserved for patients who are hemodynamically unstable, showing signs of poor perfusion, or experiencing life-threatening tachyarrhythmias. Since this patient has a stable blood pressure of 102/68 and is only reporting nervousness and a racing heart, cardioversion is not indicated as the next step. Performing this procedure unnecessarily exposes the patient to risks associated with sedation and electrical discharge without a clear clinical justification based on stability.
Choice D rationale
The Valsalva maneuver is a vagal maneuver used specifically to terminate supraventricular tachycardia by increasing intrathoracic pressure and stimulating the vagus nerve. While it is a non-invasive option, the nurse must first determine the exact heart rhythm from the ECG tracing before attempting any maneuver to alter it. Performing a Valsalva maneuver on a rhythm that is not a vagal-responsive supraventricular tachycardia would be inappropriate and potentially delay the correct diagnostic workup.
Correct Answer is A
Explanation
Choice A rationale
The 42-year-old client exhibits signs of a potential tension pneumothorax or flail chest, evidenced by dyspnea and chest asymmetry. In trauma triage, airway and breathing take absolute precedence over other injuries. Chest asymmetry suggests a major mechanical disruption of ventilation that can quickly lead to respiratory arrest or obstructive shock. This client requires immediate assessment and intervention, such as chest tube insertion or needle decompression, to stabilize their breathing and ensure adequate systemic oxygenation.
Choice B rationale
Facial lacerations in a 4-year-old are distressing but usually do not represent an immediate threat to life unless the airway is obstructed by blood or edema. If the child is crying and breathing, the airway is currently patent. While pediatric patients are often prioritized due to their physiological vulnerability, the mechanical respiratory distress seen in the adult client with chest asymmetry is a more urgent clinical priority. Lacerations can be managed after the primary survey and stabilization of breathing.
Choice C rationale
Blunt abdominal trauma in a 30-year-old carries a risk for internal hemorrhage and organ rupture. This client requires close monitoring of vital signs and possibly an ultrasound or CT scan. While potentially life-threatening if the client enters hemorrhagic shock, the immediate airway and breathing compromise in the client with chest asymmetry is a higher priority. In the ABCDE triage sequence, breathing issues are addressed before circulatory issues like potential abdominal bleeding are fully managed.
Choice D rationale
A fractured arm in a 17-year-old is generally considered a non-urgent or "green tag" injury in a mass casualty or trauma triage setting, provided there is no massive external hemorrhage. Although the client is in pain and requires splinting and imaging, this musculoskeletal injury does not compromise the airway, breathing, or overall hemodynamic stability. This client can wait for treatment while more critically injured individuals with respiratory or circulatory distress are stabilized by the medical team.
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