title: Nurse staffing, medical staffing and mortality in Intensive Care: An observational study.
abstract: OBJECTIVE
  To investigate whether the size of the workforce (nurses, doctors and support staff) has an impact on the survival chances of critically ill patients both in the intensive care unit (ICU) and in the hospital.
  
  
  BACKGROUND
  Investigations of intensive care outcomes suggest that some of the variation in patient survival rates might be related to staffing levels and workload, but the evidence is still equivocal.
  
  
  METHODS
  Information about patients, including the outcome of care (whether the patient lived or died) came from the Intensive Care National Audit & Research Centre (ICNARC) Case Mix Programme. An Audit Commission survey of ICUs conducted in 1998 gave information about staffing levels. The merged dataset had information on 65 ICUs and 38,168 patients. This is currently the best available dataset for testing the relationship between staffing and outcomes in UK ICUs.
  
  
  METHODS
  A cross-sectional, retrospective, risk adjusted observational study.
  
  
  METHODS
  Multivariable, multilevel logistic regression.
  
  
  METHODS
  ICU and in-hospital mortality.
  
  
  RESULTS
  After controlling for patient characteristics and workload we found that higher numbers of nurses per bed (odds ratio: 0.90, 95% confidence interval: [0.83, 0.97]) and higher numbers of consultants (0.85, [0.76, 0.95]) were associated with higher survival rates. Further exploration revealed that the number of nurses had the greatest impact on patients at high risk of death (0.98, [0.96, 0.99]) whereas the effect of medical staffing was unchanged across the range of patient acuity (1.00, [0.97, 1.03]). No relationship between patient outcomes and the number of support staff (administrative, clerical, technical and scientific staff) was found. Distinguishing between direct care and supernumerary nurses and restricting the analysis to patients who had been in the unit for more than 8h made little difference to the results. Separate analysis of in-unit and in-hospital survival showed that the clinical workforce in intensive care had a greater impact on ICU mortality than on hospital mortality which gives the study additional credibility.
  
  
  CONCLUSIONS
  This study supports claims that the availability of medical and nursing staff is associated with the survival of critically ill patients and suggests that future studies should focus on the resources of the health care team. The results emphasise the urgent need for a prospective study of staffing levels and the organisation of care in ICUs.
authors.affiliation: Faculty of Education and Health, University of Greenwich, United Kingdom. Electronic address: e.west@gre.ac.uk.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: West
authors.affiliation: Saïd Business School and Jesus College, University of Oxford, United Kingdom.
authors.forename: David N
authors.initials: DN
authors.lastname: Barron
authors.affiliation: Intensive Care National Audit and Research Centre, United Kingdom.
authors.forename: David
authors.initials: D
authors.lastname: Harrison
authors.affiliation: Kings College, London, United Kingdom.
authors.forename: Anne Marie
authors.initials: AM
authors.lastname: Rafferty
authors.affiliation: Intensive Care National Audit and Research Centre, United Kingdom.
authors.forename: Kathy
authors.initials: K
authors.lastname: Rowan
authors.affiliation: London School of Hygiene and Tropical Medicine, United Kingdom.
authors.forename: Colin
authors.initials: C
authors.lastname: Sanderson
mesh_terms: D003422:Critical Care; D003430:Cross-Sectional Studies; D017052:Hospital Mortality; D006801:Humans; D015999:Multivariate Analysis; D009741:Nursing Staff, Hospital / Q000600:supply & distribution*; D010561:Personnel Staffing and Scheduling; D012189:Retrospective Studies; D006113:United Kingdom / Q000453:epidemiology
keywords: Intensive care units; Medical staffing; Mortality; Multilevel modelling; Nurse staffing; Observational studies