QT prolonging effects of intravenous haloperidol: does every patient need electrocardiogram monitoring?

Purpose: Recent warnings of QT prolongation and torsades de pointes with intravenous (IV) haloperidol suggest electrocardiogram (ECG) monitoring; however, it is debatable if necessary in every patient. The purpose was to evaluate patients who received IV haloperidol to determine the mean increase in QT interval from baseline and whether a dose correlation was present.

Methods: An analysis of prospectively collected data was conducted on all patients who received IV haloperidol at our institution during four consecutive months. Patients were further included if continuous ECG monitoring occurred.  The ECG recorded before the first dose of haloperidol represented the patient’s baseline QT interval; subsequent results were obtained from daily rhythm strips and other ECGs during haloperidol administration. A QT interval greater than 470 ms was defined as prolonged.  

Results: A total of 64 patients were included (age 71.5 ± 18.6 years) who received haloperidol for a median of 2 (1-3) days. Overall, the average QT interval increased from 464 ms to 488 ms after haloperidol initiation (P<0.0001). Of patients with a normal baseline QT interval, 55.3% developed a prolonged QT interval after haloperidol administration. The following risk factors did not demonstrate a significant effect on prolonging the QT interval: gender, age, hypothyroidism, diabetes, hypertension, history of heart block, hypokalemia, hypomagnesemia, and bradycardia. Patients with a history of heart disease (P=0.041), history of arrhythmia (P=0.015), and use of concomitant QT prolonging medications (P=0.024) were more likely to develop QT prolongation. A prolonged QT interval was more common in patients who received a cumulative haloperidol dose greater than 5 mg compared to lower dosages (76.7% vs. 52.9%, P=0.048).

Conclusion: At our institution, intravenous haloperidol administration was related to an increase in the QT interval. Patients who received a cumulative dose greater than 5 mg were more likely to develop a prolonged QT interval.