Association between ICU admission during off-hours and in-hospital mortality: a multicenter registry in Japan

BACKGROUND: The effect of ICU admission time on patient outcomes has been shown to be controversial in several studies from a number of countries. The imbalance between ICU staffing and medical resources during off-hours possibly influences the outcome for critically ill or injured patients. Here, we aimed to evaluate the association between ICU admission during off-hours and in-hospital mortality in Japan. METHODS: This study was an observational study using a multicenter registry (Japanese Intensive care PAtient Database). From the registry, we enrolled adult patients admitted to ICUs from April 2015 to March 2019. Patients with elective surgery, readmission to ICUs, or ICU admissions only for medical procedures were excluded. We compared in-hospital mortalities between ICU patients admitted during off-hours and office-hours, using a multilevel logistic regression model which allows for the random effect of each hospital. RESULTS: A total of 28,200 patients were enrolled with a median age of 71 years (interquartile range [IQR], 59 to 80). The median APACHE II score was 18 (IQR, 13 to 24) with no significant difference between patients admitted during off-hours and those admitted during office-hours. The in-hospital mortality was 3399/20,403 (16.7%) when admitted during off-hours and 1604/7797 (20.6%) when admitted during office-hours. Thus, off-hours ICU admission was associated with lower in-hospital mortality (adjusted odds ratio 0.91, [95% confidence interval, 0.84–0.99]). CONCLUSIONS: ICU admissions during off-hours were associated with lower in-hospital mortality in Japan. These results were against our expectations and raised some concerns for a possible imbalance between ICU staffing and workload during office-hours. Further studies with a sufficient dataset required for comparing with other countries are warranted in the future.