One hour after administering IV furosemide (Lasix) to a client with heart failure, a short burst of ventricular tachycardia appears on the cardiac monitor. Which of the following electrolyte imbalances should the nurse suspect?
A. Hypocalcemia
B. Hypermagnesemia
C. Hypokalemia
D. Hypernatremia
Correct Answer: C. Hypokalemia
Furosemide is a potassium-depleting diuretic that can cause hypokalemia. In turn, hypokalemia increases myocardial excitability, leading to ventricular tachycardia. Hypokalemia can result in a variety of cardiac dysrhythmias. Although cardiac dysrhythmias or ECG changes are more likely to be associated with moderate to severe hypokalemia, there is a high degree of individual variability and can occur with even mild decreases in serum levels.
Option A: An EKG should be obtained for all suspected cases of hypocalcemia to look for QTc prolongation which if present is a risk factor for Torsades de pointes. Patients with ECG changes need monitoring during calcium supplementation.
Option B: Hypomagnesemia often occurs with and may worsen hypokalemia especially in the presence of chronic diarrhea, alcoholism, genetic disorders, diuretic use and chemotherapy. Both promote the development of cardiac dysrhythmias. The combination of hypokalemia and hypomagnesemia are associated with an increased risk of torsades de pointes, particularly in individuals receiving QT-prolonging medications.
Option D: Orthostatic hypotension and tachycardia are usually present in hypovolemic hypernatremia. The patient may have increased tone with brisk reflexes and myoclonus. Sodium is important to maintain extracellular fluid (ECF) volume. Changes in the ECF volume provide feedback to maintain total sodium content by increasing or decreasing sodium excretion in the urine. Sodium excretion also involves regulatory mechanisms such as the renin-angiotensin-aldosterone systems.
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