REDUCING INAPPROPRIATE USE OF QT PROLONGING MEDICATION IN HIGH RISK PATIENTS

Background: Drug-induced prolonged QT syndrome significantly increases the risk of fatal arrhythmias such as torsades de pointes.  Patients with baseline QTc prolongation are particularly vulnerable.  Limiting administration of QT-prolonging medications to high-risk individuals is important for patient safety.

Methods: Patients with a baseline QTc > 500 ms were defined as having a high risk for arrhythmia.  We compiled a list of 21 QT-prolonging medications commonly ordered in the inpatient setting, and reviewed the frequency with which they were administered to high-risk patients admitted to an academic medical center during a 1 month period.  Ondansetron was the medication most frequently administered to high-risk patients; it comprised 58% of all such orders.  Therefore, we modified the computerized order entry platform to present the ordering clinician with the patient’s most recent QTc value at the time of each ondansetron order. No additional instructions or decision support were included. To assess the impact of the intervention, we retrospectively reviewed ordering practices for ondansetron in at risk patients in the 5 months before and after the intervention.

Results:   We identified 7578 orders for ondansetron in a 1-month period prior to the intervention, and 8200 in a 1-month period subsequent to the programming change.  The baseline rate of administration of ondansetron to high-risk patients was 1.3%.  Following the intervention, the rate dropped to 0.8% [RRR 38%, p = 0.002].  Interestingly, ordering practices in patients with QTc values > 450 ms did not change (5.0% and 5.0%).

Conclusions: Presentation of the QTc interval at the time of order entry reduced the frequency of ondansetron use in patients at high risk for arrhythmias.  This data suggests that making key clinical information available at the point of care impacts ordering behavior.  Additional guidance at the time of order entry (e.g. more directive language suggesting a potential risk) may produce an even larger effect.  Further study is needed to determine if broader application of such an intervention could impact safer prescribing practices for all QT prolonging medications.