Early Caloric Adequacy and Hospital Length of Stay in Children Younger than Two Years Hospitalized with Bronchiolitis.

Background/Objectives: Feeding difficulties are common during bronchiolitis hospitalization and may lead to reduced caloric intake. Evidence evaluating the relationship between caloric adequacy and hospital length of stay (LOS) remains limited. We aimed to characterize daily caloric adequacy during bronchiolitis hospitalization and evaluate its relationship with LOS. Methods: An ambispective cohort study included children younger than 2 years hospitalized with bronchiolitis between 2013 and 2023 at a tertiary hospital in Valencia, Spain. Caloric adequacy was calculated as the percentage of WHO/FAO estimated caloric requirements achieved, including all nutritional and intravenous caloric sources. Associations with LOS were evaluated using correlation and multivariable regression analyses. Results: A total of 613 patients were included, with caloric intake data available for 607. Median LOS was 5 days (IQR 3-7). Lower caloric adequacy during the first days of hospitalization was associated with longer LOS. Hospitalization day 2 showed the strongest early association with LOS (ρ = -0.230; p <0.001). After multivariable adjustment, each 10-percentage-point increase in day-2 caloric adequacy was associated with a 3.32% shorter LOS (95% CI, 1.74-4.87%; p < 0.001); subgroup associations were mainly observed in children younger than 12 months and were strongest in those with moderate acute malnutrition. Patients with longer LOS showed delayed achievement of ≥80% caloric adequacy, particularly those with LOS ≥ 9 days (day 6). Conclusions: Early caloric adequacy was associated with LOS in children hospitalized with bronchiolitis. Failure to achieve ≥80% within the first 48 h may serve as an early marker of a slower clinical course.