UMEM Educational Pearls

Title: Effect of QTc-prolonging agents in emergent dialysis patients with baseline QTc prolongation

Category: Pharmacology & Therapeutics

Keywords: QTc prolongation, torsades, antiemetics, antihistamines (PubMed Search)

Posted: 10/1/2016 by Michelle Hines, PharmD
Click here to contact Michelle Hines, PharmD

What they did:

End stage renal disease (ESRD) patients presenting to the ED for emergent hemodialysis (HD) with baseline QTc prolongation (>450 msec in men and >470 msec in women) were given antiemetics or antihistamines for symptomatic relief of nausea and pruritis. A repeat ECG was obtained 2 hours after medications were given.
Most patients received oral or intravenous promethazine 25 mg, ondansetron 4-8 mg, or diphenhydramine 25-50 mg.

What they found:

44 patients had a mean initial QTc of 483.7 msec (SD 18.4). Two hours after medication administration, the mean QTc was 483.8 msec (SD 20.0).
Among 13 patients with initial QTc intervals >500 msec, 9 had an increased QTc interval after medication administration (average increase 11.8 msec, SD 6.7 msec).
8 patients with baseline QTc <500 msec had QTc >500 msec after medication administration.
No patients experienced dysrhythmias, death, or were admitted for dysrhythmia or syncope 1 week after medication administration.

Application to clinical practice:

While the mean QTc did not change, the proportion of individuals who experienced an increase in QTc interval is not reported.
Although greatly limited by a small sample size, this study suggests that usual doses of promethazine, ondansetron, or diphenhydramine in patients presenting for emergent HD with baseline QTc prolongation may be safe.
Additional studies, especially in patients with QTc prolongation >500 msec, are warranted.

References

Burdette S, Roppolo LP, Green W, et al. The effect of antiemetics and antihistamines on the QTc interval in emergent dialysis patients with baseline QTc prolongation. J Emerg Med 2016; 51:99-105. (PMID 27614302)

Follow me on Twitter @mEDPharmD