Ondansetron: Has it reduced need for IV rehydration in vomiting kids?

A 3-year-old male presents to the emergency department (ED) complaining of vomiting and diarrhea that has been occurring for 2 days. The mother states that the child has had fewer wet diapers today but has made tears when crying. On physical examination you note no rebound or guarding of the abdomen and determine that the child is moderately dehydrated. Your initial plan is to administer ondansetron and rehydrate the child orally. This is what you have been taught but is it actually efficacious? A just published 2014 JAMA Pediatrics article attempted to answer this question.

Background

Acute gastroenteritis (AGE) is one of the most common pediatric chief complaints in the ED. Ideally, children are rehydrated utilizing an oral rehydration route (ORT) preferentially over use of IV fluids. Unfortunately, in spite of the literature demonstrating the efficacy of oral rehydration, a 2007 study reported that 45% of providers preferred IV rehydration (1) in children with moderate dehydration. The largest barrier to ORT use is the inability to tolerate oral fluids because of vomiting in AGE. This suggests the potential utility of antiemetics. The efficacy of ondansetron has been established as an adjunct to facilitate ORT. However due to unfounded concerns regarding ED revisits, the masking of serious disease, and cost, it has not been recommended for routine care, and it has not been recommended by the American Academy of Pediatrics.

Article Citation

Freedman SB, Hall M, Shah SS, et al. Impact of increasing ondansetron use on clinical outcomes in children with gastroenteritis. JAMA Pediatr. 2014 Apr 1;168(4):321-9. PMID: 24566613.

Study Objectives

Determine whether increasing ondansetron administration to children with AGE is associated with a decrease in IV rehydration

Study Methods

• Multicenter retrospective cohort study utilizing the Pediatric Health Information System Participating hospital database
• Patients
  • <18 years old
  • Diagnosed with AGE or dehydration + AGE
• Excluded
  • Transfers and chronic co-morbidity
• Primary Outcome
  • % of children administered IV rehydration
• Secondary Outcomes
  • Hospitalization rate
  • 3-day ED revisit
  • Children with a significant alternative diagnosis within 3 days
  • Changes in cost over time

Results

• 18 hospitals accounted for 804,000 patient visits during 2002-11
• Ondansetron usage
  • 2002: 0.11% (Low usage)
  • 2011: 42.2% (High usage)
• IV rehydration rate
  • Low usage: 18.7%
  • High usage: 17.8%
    • 13.5% of those receiving IV hydration also received oral ondansetron
    • 54.1% received IV ondansetron
• Cost
  • High usage > low usage
• 3 day ED revisit rate
  • High usage associated with a decreased ED revisit rate
• Significant alternative diagnosis rate
  • 0.1%

Analysis

This is a retrospective database study and must be interpreted within the appropriate context of what such a study design is actually capable of finding. Retrospective studies, such as this, are able to discern associations that may or may not hold true in reality, divorced from the originating dataset. At best, the associations discovered retrospectively are good at generating hypothesis to be tested by prospective study deigns in order to discern actual causality that a retrospective study is not equipped to discover. All too often the literature is replete with erroneous interpretations of retrospective studies– particularly the assigning of causation to the findings where only associations exist.

This study did not find an association between the high usage of ondansetron with a concomitant decrease in IV rehydration. Interestingly however, very few patients who actually received IV rehydration (13.5%) actually received the study medication making it difficult to determine if this was actually due to medication failure or provider bias (i.e. “that kid looks too sick for PO medication.”) A large majority of patients (54.1%) received ondansetron in the IV form which would indicate that the decision to IV rehydrate these individuals was made prior to the administration of antiemetics. This study thus cannot conclude whether or not ondansetron is truly efficacious in AGE or whether the increasing usage of ondansetron was associated with lower IV rehydration rates given the overall low usage of the oral formulation.

An interesting hypothesis to take from the dataset is to consider that there is a bias in particular providers given specific clinical presentation to utilize IV rehydration without first attempting ORT. A further important finding is that the administration of ondansetron was not associated with significant alternative diagnosis, providing more data to dispel this erroneous and pervasive myth.

Practical Take Home Points

1. Consider trying ORT for patients with AGE before going to IV fluids with the assistance of oral ondansetron
2. Do not be afraid of giving ondansetron for fear of masking an alternative diagnosis.

Future Directions

It would be important to know the clinical parameters and provider-specific practice patterns that lead to increased IV usage in children. Further, this study was not able to assess the actual efficacy of ondansetron as an antiemetic in AGE given the study methodology. A future prospective study to assess both of these parameters would help determine the most efficacious and cost effective way to manage this cohort.

References

1. Bender BJ, Ozuah PO, Crain EF. Oral rehydration therapy: is anyone drinking? Pediatr Emerg Care. 2007 Sep;23(9):624-6. PMID: 17876250.

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