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QTc prolonged with ondansetron in the PICU

September 8, 2016

Short Attention Span Summary

Ondansetron and QTc in sick kids
Last month we looked at a study that showed no change in the QT interval in ED patients getting ondansetron.  This PICU-based study found ondansetron significantly affected the QT interval.  The QTc increased to 460-500 ms in 29% and >500 ms in 11%.  However, baseline QTc was already increased in these kids.  Kids with an increased QTc were more likely to have associated electrolyte abnormalities, coadministration of drugs that prolonged QT, or increased severity of illness.  The study was limited to kids over age 8 for some reason.

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In run-of-the-mill PED patients, ondansetron has no effect on the QTc, but in critically ill patients, especially those with electrolyte abnormalities and other QT-prolonging medications, it increases the QTc in about a third of children.


Pediatr Crit Care Med. 2016 Jul;17(7):e317-23. doi: 10.1097/PCC.0000000000000776.

Effect of Ondansetron on QT Interval in Patients Cared for in the PICU.

Trivedi S1, Schiltz B, Kanipakam R, Bos JM, Ackerman MJ, Ouellette Y.

Author information:

11Division of Pediatric Critical Care, Department of Pediatric and Adolescent Medicine, Mayo Clinic, Rochester, MN. 2Division of Pediatric Cardiology, Department of Pediatric and Adolescent Medicine, Mayo Clinic, Rochester, MN. 3Division of Cardiovascular Diseases, Department of Medicine, Mayo Clinic, Rochester, MN. 4Windland Smith Rice Sudden Death Genomics Laboratory, Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, Rochester, MN.



There is no evidence regarding the effect of ondansetron on the QT interval in pediatric patients in the ICU. This study aimed to describe the effect of ondansetron on the corrected QT interval in patients cared for in the PICU.


Retrospective cohort, consecutive enrollment study.


Single-center, tertiary-level, medical/surgical PICU.


All patients less than 8 years old who received ondansetron over an 11-month period were included. Exclusion criteria were atrial arrhythmia, bundle-branch block, known congenital long QT syndrome, and concomitant administration of proarrhythmic antiarrhythmic agents.




Overall, 210 doses of ondansetron were administered to 107 patients, with a mean age 10.5 ± 4.8 years; 49% were men. Corrected QT interval increased to 460-500 ms in 29% and to more than 500 ms in 11% of events of ondansetron administration. The mean baseline corrected QT interval even before ondansetron administration was higher for these groups (460-500 and > 500 ms; 457 ± 33 and 469 ± 45, respectively; p ≤ 0.05). In multivariate analysis, both groups were associated significantly with underlying electrolyte abnormalities (odds ratio, 2.2; 95% CI, 1.1-4.4 and odds ratio, 5.1; 95% CI, 1.8-15.7, respectively); the group with corrected QT interval more than 500 ms was also significantly associated with organ dysfunction (odds ratio, 3.2; 95% CI, 1.1-9.4). As the numbers of risk factors increased from only ondansetron to three additional QT aggravating factors (electrolyte abnormalities, administration of other QT-prolonging drugs, and organ dysfunction), the likelihood of being associated with corrected QT interval more than 500 ms increased.


Prolonged QT interval is observed commonly in PICUs following the administration of ondansetron. Underlying risk factors, such as electrolyte abnormalities and organ dysfunction, seem to pose the highest risk of prolongation of QT interval in these patients. The awareness of prevalent risk factors for increased corrected QT interval may help identify patients at high risk for arrhythmias.

PMID: 27387786 [PubMed – in process]

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