Setting and organisation

This prospective observational cohort study was carried out in a medical ICU of an academic tertiary care hospital in Montpellier, France. This 12-bed medical ICU admitted an average of 270 patients per year. Critical care unit team included 6 attending intensivists, 4 residents (critical care or other speciality fellows), medical students, nurses, and respiratory therapists. Intensivists and residents staffed the ICU 24h per day and every day of the week. During open hours, 2 teams provided ICU medical coverage: each including a senior intensivist and a resident and taking care of 6 bed-patients. The nurse-to-patient ratio was maintained at 1:3 every time of any day. Imaging technical platform and surgical operating room were available on a 24-hour and 7-days basis. Admissions may occur at any time of the day and the night. This organisation was maintained all along the study period and was comparable to the other ICUs of our hospital.

We defined two periods of ICU admissions: on- and off-hours periods. On-hours or open-hours admissions included time period from Monday to Friday from 8:00 a.m. to 5:59 p.m. at the exception of holidays. During on-hours admissions, almost the entire Unit personnel members were present leading to the highest level of medical presence (at least 2 intensivists and 2 residents). Patients admitted during on-hours were considered as reference group. Off-hour admissions included night-time (6:00 p.m. to 7:59 a.m.), weekend (from Saturday 08:00 a.m. to Monday 7:59 a.m.) and holidays’ admissions. Holidays were those officially recognised by the French Republic. During off-hours, medical team was reduced and included one intensivist and one resident.