Association between nursing workload and mortality of intensive care unit patients.

PURPOSE: To investigate differences in mortality of intensive care unit (ICU) patients according to the ratio between total patient care demands and nurse staffing.
DESIGN: Observational, prospective study. Patients consecutively admitted in the medical-surgical ICU of a Greek hospital over a 1-year period were enrolled.
METHODS: The Therapeutic Intervention Scoring System (TISS)-28 was used for measuring patient care demands. Daily sum of TISS-28 of patients and daily number of nurses were considered for estimating median and peak patient exposure to nursing workload. According to the values of median and peak patient exposure to nursing workload, patients were divided into three groups (low, medium, and high). Logistic regression was used for evaluating the associations between mortality during ICU length of stay and median or peak patient exposure to nursing workload, after adjusting for patient clinical severity.
FINDINGS: 396 patients were included and 102 died. Differences in ICU mortality between high and low groups of median and peak patient exposure to nursing workload, although not statistically significant, were clinically remarkable, both when all patients were studied and when medical and surgical patients were separately studied.
CONCLUSIONS: Consideration of individual differences in patient acuity might add sensitivity to the detection of associations between nurse understaffing and ICU mortality. CLINICAL RELEVANCE: The findings indicate that not only differences among nurse characteristics, but also differences in patient care demands, are important when investigating the effect of nurse understaffing on mortality of ICU patients. Proper nurse staffing levels should be based on the estimation of total patient acuity, rather than on the absolute number of patients.