Outcomes sensitive to critical care nurse staffing levels: A systematic review.

Objective: To determine associations between variations in registered nurse staffing levels in adult critical care units and outcomes such as patient, nurse, organisational and family outcomes.
Methods: We published and adhered to a protocol, stored in an open access repository and searched for quantitative studies written in the English language and held in CINAHL Plus, MEDLINE, PsycINFO, SCOPUS and NDLTD databases up to July 2020. Three authors independently extracted data and critically appraised papers meeting the inclusion criteria. Results are summarised in tables and discussed in terms of strength of internal validity. A detailed review of the two most commonly measured outcomes, patient mortality and nosocomial infection, is also presented.
Results: Our search returned 7960 titles after duplicates were removed; 55 studies met the inclusion criteria. Studies with strong internal validity report significant associations between lower levels of critical care nurse staffing and increased odds of both patient mortality (1.24-3.50 times greater) and nosocomial infection (3.28-3.60 times greater), increased hospital costs, lower nurse-perceived quality of care and lower family satisfaction. Meta-analysis was not feasible because of the wide variation in how both staffing and outcomes were measured.
Conclusions: A large number of studies including several with high internal validity provide evidence that higher levels of critical care nurse staffing are beneficial to patients, staff and health services. However, inconsistent approaches to measurement and aggregation of staffing levels reported makes it hard to translate findings into recommendation for safe staffing in critical care.
Competing Interests: Declaration of Competing Interest This paper presents independent research funded by the National Institute for Health Research (Programme Development Grants, Safe staffing in ICU: development and testing of a staffing model, NIHR200100). The views expressed in this publication are those of the author(s) and not necessarily those of the National Institute for Health Research or the Department of Health and Social Care, neither of whom have had involvement in any aspect of the design, data collection, synthesis, interpretation or writing of, this review.
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