PurposeWe aimed to analyze the changes in the disease spectrum data of a pediatric intensive care unit (PICU) in Nanjing, China, during the COVID-19 outbreak and explore a feasible plan for the treatment of critically ill children.MethodsThis retrospective study used data from our PICU from 1 January 2018 to 31 December 2020. Patient demographics, distribution of disease spectrum, results of etiological examinations, and the PICU length of stay (LOS) were compared during the COVID-19 period (2020) and the previous years (2018 and 2019).ResultsIn 2020, the number of PICU admissions was 46.8 and 47.8% lower than that in 2018 and 2019, respectively. There were significant differences in the number of patients in PICU among different age groups, and these differences were mainly found in children aged <4 years and older than 14 years. The percentage of the number of patients in PICU with respiratory diseases decreased significantly, while those with hematological diseases, poisoning, and rare diseases increased significantly. Moreover, the number of patients with rare diseases increased significantly, while the number of patients with mitochondrial diseases exceeded that of those with autoimmune encephalitis. The PICU LOS in 2020 was higher than that observed in 2018 and 2019, indicating that the changes in the PICU disease spectrum did not directly affect the PICU LOS. Etiological examinations revealed that during the COVID-19 period, the number of patients in PICU with bacterial infections increased, and those with viral infections decreased, although not statistically significant.ConclusionsA striking decrease in the number of PICU admissions was observed during the COVID-19 outbreak, which caused a significant change in the PICU disease spectrum. Changes in the number and characteristics of patients admitted to PICUs should be considered for facilitating the effective working of PICUs during the COVID-19 pandemic.