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Difficulty: Very hardPharmacological and Parenteral Therapies

A client is admitted to the intensive care unit with acute digoxin toxicity. Initial laboratory results reveal a serum digoxin level of 5.2 ng/mL5.2\text{ ng/mL} and a serum potassium level of 6.4 mEq/L6.4\text{ mEq/L}. The healthcare provider prescribes a continuous intravenous infusion of digoxin immune Fab. Which of the following assessment findings during the hours following administration requires the nurse's immediate intervention?

  1. The appearance of prominent U waves and flattened T waves on the continuous electrocardiogram.Answer
  2. B
    A subsequent laboratory report indicating a total serum digoxin level of 7.1 ng/mL7.1\text{ ng/mL}.
  3. C
    An increase in the client's ventricular heart rate from 6868 to 105105 beats per minute.
  4. D
    The presence of a first-degree atrioventricular block with a PR interval of 0.26 seconds0.26\text{ seconds} on the electrocardiogram.

Answer

The appearance of prominent U waves and flattened T waves on the continuous electrocardiogram.
The correct answer identifies the electrocardiogram signs of severe hypokalemia (prominent U waves and flattened T waves). In acute digoxin overdose, the Na+/K+ ATPase pump is paralyzed, resulting in extracellular potassium accumulation (hyperkalemia). When digoxin immune Fab is administered, the pump is rapidly reactivated, causing a massive and swift shift of potassium from the blood back into the cells. This can quickly precipitate severe, life-threatening hypokalemia. The nurse must immediately intervene by notifying the provider to initiate a potassium replacement protocol to prevent lethal ventricular dysrhythmias.

Step-by-Step Solution

1
Analyze the pathophysiology of severe acute digoxin toxicity.
Acute digoxin overdose heavily poisons the Na+/K+ ATPase pump, preventing potassium from entering cells and leading to systemic hyperkalemia (initial level 6.4 mEq/L6.4\text{ mEq/L}).
Understanding the patient's baseline physiological state is necessary to predict the metabolic effects of the reversal agent.
2
Determine the physiological effect of digoxin immune Fab administration.
The antidote effectively binds to digoxin, neutralizing it and immediately reactivating the previously paralyzed Na+/K+ ATPase cellular pumps.
Reactivation of the cellular pumps alters the concentration gradients of major electrolytes in the bloodstream.
3
Identify the critical consequence of pump reactivation and recognize its clinical signs.
Reactivation causes a massive and rapid shift of extracellular potassium back into the intracellular space. This sudden shift frequently precipitates severe hypokalemia, which manifests on an electrocardiogram as prominent U waves and flattened T waves.
Severe hypokalemia can cause lethal ventricular dysrhythmias and requires immediate potassium replacement, making it the highest clinical priority.

Key Concept

Digoxin immune Fab rapidly reactivates the Na+/K+ ATPase pump, causing a massive intracellular shift of potassium. The nurse must prioritize monitoring for life-threatening hypokalemia (evidenced by U waves on an ECG) during and after administration.
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Topics

Pharmacological and Parenteral Therapies

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