Objective: Hospital mortality increases if acutely ill patients are admitted to hospitals on weekends as compared with weekdays. Night discharges may increase mortality in intensive care unit (ICU) patients but the effect of ICU admission time on mortality is not known. We studied the effects of ICU admission and discharge times on mortality and the time of death in critically ill patients.
Design: Cohort study using a national ICU database.
Setting: Eighteen ICUs in university and central hospitals in Finland.
Patients: Consecutive series of all 23,134 emergency admissions in January 1998-June 2001.
Interventions: None.
Measurements and main results: We defined weekend (as opposed to weekday) from 1600 hours Friday to 2400 hours Sunday and "out-of-office" hours (as opposed to "office hours") from 1600 hours to 0800 hours. Mortality was adjusted for disease severity, intensity of care, and whether restrictions for future care were set. ICU-mortality was 10.9% and hospital mortality 20.7%. Adjusted ICU-mortality was higher for weekend as compared with weekday admissions [odds ratio (OR 1.20) 95% CI 1.01-1.43], but similar for "out-of-office" and "office hour" admissions (OR 0.98, 0.85-1.13). Adjusted risk of ICU death was higher during "out-of-office" hours as compared with office hours (OR 6.89, 5.96-7.96). The time of discharge from ICU to wards was not associated with further hospital mortality.
Conclusions: Weekend ICU admissions are associated with increased mortality, and patients in the ICU are at increased risk of dying in evenings and during nighttime. Our findings may have important implications for organization of ICU services.