A nurse is administering haloperidol (Haldol) via IV push to a delirious patient. What is most important for the nurse to monitor?

• A. Heart rate
• B. PR interval
• C. QT interval
• D. Respiratory rate

Answer: (C)

The key issue here is the risk of QT interval prolongation with haloperidol when given intravenously. Haloperidol can affect cardiac repolarization by blocking potassium channels, which lengthens the QT interval on an ECG. A prolonged QT increases the risk of torsades de pointes, a potentially fatal ventricular arrhythmia. Because of this, ECG monitoring to assess the QT interval before and during IV haloperidol administration is essential. Correct any electrolyte disturbances (potassium, magnesium), avoid other QT-prolonging drugs, and consider giving the medication slowly to minimize risk. If the QT interval becomes markedly prolonged, the medication should be reassessed and, if needed, withheld.

While other vital signs like heart rate, PR interval, or respiratory rate are important for overall patient safety and assessment, they do not address the specific, potentially life-threatening cardiac risk associated with haloperidol’s effect on myocardial repolarization as directly as monitoring the QT interval.