IMPORTANCE: The emergency department (ED) is an important safety net for children experiencing mental and behavioral health crises and can serve as a navigational hub for families seeking support for these concerns. OBJECTIVES: To evaluate the outcomes of a novel mental health care bundle on child well-being, satisfaction with care, and health system metrics. DESIGN, SETTING, AND PARTICIPANTS: Nonrandomized trial of 2 pediatric EDs in Alberta, Canada. Children younger than 18 years with mental and behavioral health presentations were enrolled before implementation (preimplementation: January 2020 to January 2021), at implementation onset (run-in: February 2021 to June 2021), and during bundle delivery (implementation: July 2021 to June 2022). INTERVENTION: The bundle involved risk stratification, standardized mental health assessments, and provision of an urgent follow-up appointment after the visit, if required. MAIN OUTCOMES AND MEASURES: The primary outcome, child well-being 30 days after the ED visit, was assessed using the Stirling Children's Wellbeing Scale (children aged <
14 years) or Warwick-Edinburgh Mental Wellbeing Scale (children aged 14-17 years). Change in well-being between the preimplementation and implementation periods was examined using interrupted time-series analysis and multivariable modeling. Changes in health system metrics (hospitalization, ED length of stay [LOS], and revisits) and care satisfaction were also examined. RESULTS: A total of 1412 patients (median [IQR] age, 13 [11-15] years), with 715 enrolled preimplementation (390 [54.5%] female
55 [7.7%] First Nations, Inuit, or Métis
46 [6.4%] South, Southcentral, or Southeast Asian
and 501 [70.1%] White) and 697 enrolled at implementation (357 [51.2%] female
51 [7.3%] First Nations, Inuit, or Métis
39 [5.6%] South, Southcentral, or Southeast Asian
and 511 [73.3%] White) were included in the analysis. There were no differences between study periods in well-being. Reduced well-being z scores were associated with mood disorder diagnosis (standardized mean difference, -0.14
95% CI, -0.26 to -0.02) and nonbinary gender identity (standardized mean difference, -0.41
95% CI, -0.62 to -0.19). The implementation period involved fewer hospitalizations (difference in hospitalizations, -6.9
95% CI, -10.4 to -3.4) and longer ED LOS (1.1 hours
95% CI, 0.7 to 1.4 hours). There were no differences between study periods in ED revisits or care satisfaction. CONCLUSIONS AND RELEVANCE: In this study, the delivery of a care bundle was not associated with higher child well-being 30 days after an ED visit. Hospitalizations did decrease during bundle delivery, but ED LOS did not. These health system findings may have been affected by broader changes in patient volumes and flow processes that occurred during the COVID-19 pandemic, which took place as the study was conducted. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT04292379.