Nurse Staffing Influences Infection Rates in Elderly

Abstract & Commentary

By Leslie A. Hoffman, PhD, RN, Department of Acute/Tertiary Care, School of Nursing, University of Pittsburgh. Dr. Hoffman reports no financial relationship to this field of study.

This article originally appeared in the September 2007 issue of Critical Care Alert. It was edited by David J. Pierson, MD, and peer reviewed by William Thompson, MD. Dr. Pierson is Professor, Pulmonary and Critical Care Medicine, Harborview Medical Center, University of Washington, and Dr. Thompson is Staff Pulmonologist, VA Medical Center; Associate Professor of Medicine, University of Washington. Drs. Pierson and Thompson report no financial relationships relevant to this field of study.

Synopsis: In this study of 51 adult ICUs, units with higher nurse staffing had a lower incidence of central line-associated bloodstream infections, ventilator-associated pneumonia, and decubiti.

Source: Stone PW, et al. Nurse working conditions and patient safety outcomes. Med Care. 2007;45:571-578.

The sample for this study comprised 15,846 patients admitted to 51 adult ICUs in 31 hospitals participating in the Centers for Disease Control and Prevention's Nosocomial Infection Surveillance system. All Medicare patients in these institutions who experienced central line-associated bloodstream infections, ventilator-associated pneumonia (VAP), and catheter-associated urinary tract infections were identified using standard protocols. Medicare files and discharge codes were used to identify 30-day mortality and decubiti. Nurse staffing, overtime, and wages were determined using administrative databases. In addition, ICU nurses were surveyed using the Perceptions of Nurse Work Environment scale. A total of 1095 RNs responded, for an average response rate of 60% (range 44% to 100% per ICU).

Patients admitted to an ICU with more RN hours per patient day had a significantly lower incidence of central line-associated bloodstream infections, VAP, 30-day mortality, and decubiti (P < 05). Patients admitted to ICUs in which the nurses perceived a more positive organizational climate had a slightly higher odds of developing a central line-associated bloodstream infection (adjusted OR 1.19; 95% CI, 1.05-1.36), but were 39% less likely to develop a catheter-related urinary tract infection (adjusted OR 0.61; 95% CI, 0.44-0.83). When nurses worked less overtime, patients experienced fewer central line-associated bloodstream infections (adjusted OR 0.33; 95% CI, 0.15-0.72). Conversely, when nurses worked more overtime, patients had increased odds of acquiring catheter-associated urinary tract infection (P < .0001) and higher rates of decubiti (adjusted OR 1.91; 95% CI, 1.17-3.11). Nurses' wages were not associated with any of the patient safety outcomes. Also, magnet accreditation was not related to any of the patient safety outcomes measured.


This study adds to the mounting body of evidence that supports an association between adverse patient safety outcomes and insufficient RN staffing. In this study, 3 of 4 patient safety indicators examined, eg, central line- associated bloodstream infections, VAP, 30-day mortality, and decubiti, occurred less frequently when patients were admitted to an ICU with more RN hours per patient day. Each year, an estimated 250,000 cases of central line-associated bloodstream infections occur in hospitals in the United States, with an estimated attributable mortality of 12%-25% for each infection. The marginal cost to the health-care system is approximately $25,000 per episode. Thus, strategies that reduce the incidence of such complications can be highly cost-effective. Similarly, VAP and decubiti represent very costly complications.

While it may appear cost-effective to reduce nursing hours, the net result may be an increase in costly complications. Of interest, the study also found an association between the number of overtime hours and patient safety outcomes. Increased overtime was associated with a higher number of catheter-related urinary tract infections and decubiti, suggesting that longer work hours can impact the incidence of some infection-related complications. Less overtime was associated with fewer central line infections. The explanation for this finding is less obvious. Potentially, the need for less overtime resulted in more meticulous catheter care. There has also been an emphasis on improving workplace culture as a means of improving patient outcomes. Results here were mixed.

Findings of this study were presented as a pooled analysis of data from the 51 hospitals and 31 ICUs participating in the study. Likely, it would be necessary to examine data at the unit (ICU) level to interpret how (or if) nurse perceptions of their work environment influenced risk for these complications. In good and adverse work environments, nurses are confronted with the challenge of providing a safe environment where patients can trust caregivers who attempt to deliver care despite a multitude of interfering forces that include personnel shortages, increased work hours, new therapies and technology, reimbursement structures, and the ever-changing transformation of systems and processes. These results suggest that improving nurse conditions by providing adequate staffing can improve patient safety.