To estimate the daily cost of intensive care unit (ICU) stays via micro-costing.

A multicentre, prospective, observational, cost analysis study was carried out among 21 out of 23 French ICUs randomly selected from French National Hospitals. Each ICU randomly enrolled 5 admitted adult patients with a simplified acute physiology II score ≥ 15 and with at least one major intensive care medical procedure. All health-care human resources used by each patient over a 24-hour period were recorded, as well as all medications, laboratory analyses, investigations, tests, consumables and administrative expenses. All resource costs were estimated from the hospital's perspective (reference year 2009) based on unitary cost data.

One hundred and four patients were included (mean age: 62.3±14.9 years, mean SAPS II: 51.5±16.1, mean SOFA on the study day: 6.9±4.3). Over 24hours, 29 to 186 interventions per patient were performed by different caregivers, leading to a mean total time spent for patient care of 13:32±05:00h. The total daily cost per patient was €1425±€520 (95% CI=€1323 to €1526). ICU human resources represented 43% of total daily cost. Patient-dependent expenses (€842±€521) represented 59% of the total daily cost. The total daily cost was correlated with the daily SOFA score (r=0.271, P=0.006) and the bedside-time given by caregivers (r=0.716, P<0.0001).

The average cost of one day of ICU care in French National Hospitals is strongly correlated with the duration of bedside-care carried out by human resources.