Understaffing, overcrowding, inappropriate nurse:ventilated patient ratio and nosocomial infections: which parameter is the best reflection of deficits?
Introduction
The structure of hospitals is changing, especially in high-income countries, because of a drive towards increased efficiency and economic rationalization (i.e. re-organization to improve cost-efficiency). In Germany, the healthcare system has been characterized by a 26% decrease in hospital beds per head, a 42% decrease in the mean length of stay, and a 17% increase in the overall number of patients treated between 1991 and 2008. In stressed and high-throughput systems, periodic overcrowding (high bed occupancy) and understaffing (low nurse:patient ratio) are inevitable because the system has limited capacity to scale available resources, such as the number of healthcare workers to patient admissions, as appropriate.1, 2, 3
Many studies have reported that a imbalance between workload and resources affects patient outcome. Transmission of meticillin-resistant Staphylococcus aureus (MRSA) has been shown to be greater during periods of understaffing, defined by a low healthcare worker:patient ratio, or by an excess in bed occupancy rate.4, 5, 6, 7 Hugonnet et al. investigated the influence of the nurse:patient ratio on the development of bloodstream infections (BSI) in an ICU over a four-year period. They estimated that more than one-quarter of nosocomial infections could be avoided if the nurse:patient ratio was kept above 2.2 in ICUs.8
However, there are few multi-centre data regarding whether the nurse:patient ratio or bed occupancy generally influences the occurrence of nosocomial infections, or whether there are better key determinants. To answer this question, this study investigated the impact of well-known parameters (nurse:patient ratio and bed occupancy rate) and a new parameter (nurse:ventilated patient ratio) on nosocomial BSI and pneumonia, and compared these three parameters in a network of 182 ICUs.
Section snippets
Surveillance method
Since 1997, ICUs have reported monthly data on device use and nosocomial device-associated infections to the German hospital surveillance system for nosocomial infections (KISS). KISS analyses the data in accordance with the National Nosocomial Infection Surveillance System/National Healthcare Safety Network method.9 Percentages of patient-days with intubation or central venous catheters (CVC), and device-associated infection rates (number of ventilator- or CVC-associated infections per 1000
Results
One hundred and eighty-two ICUs provided data on all parameters. In total, 1921 months (10.6 months per ICU) were included in the analysis, covering 159,400 patients corresponding to 563,177 patient-days. In total, 1313 cases of pneumonia (1064 were ventilator-associated) and 513 cases of BSI (491 were CVC-associated) were reported.
Of the ICUs, 45.6% were interdisciplinary, 21.4% were medical, 23.6% were surgical and 9.3% were categorized as ‘other specific ICU’. Almost half of the ICUs were
Discussion
The three main findings were: (1) the nurse:ventilated patient ratio was linearly and significantly associated with the occurrence of nosocomial infections (BSI and pneumonia); (2) a high bed occupancy rate (>75th percentile of all analysed months) was unexpectedly associated with fewer nosocomial infections; and (3) the nurse:patient ratio showed no significant association with nosocomial infections in the multi-variate analysis.
Several studies have evaluated the effect of nursing or physician
Acknowledgements
The authors thank the healthcare staff and the infection control personnel of all ICU-KISS ICUs for their participation and support of this surveillance project. This study was presented, in part, at the European Congress of Clinical Microbiology and Infectious Diseases in Milan, 7–10 May 2011. The authors also thank Ryan Plocher for his help in preparing the manuscript.
References (16)
- et al.
Overcrowding and understaffing in modern health-care systems: key determinants in meticillin-resistant Staphylococcus aureus transmission
Lancet Infect Dis
(2008) - et al.
Spread of methicillin-resistant Staphylococcus aureus in a neonatal intensive unit associated with understaffing, overcrowding and mixing of patients
J Hosp Infect
(2002) Bed occupancy and overcrowding as determinant factors in the incidence of MRSA infections within general ward settings
J Hosp Infect
(2003)- et al.
Five years working with the German nosocomial infection surveillance system (Krankenhaus Infektions Surveillance System)
Am J Infect Cont
(2003) - et al.
Epidemiology meets econometrics: using time-series analysis to observe the impact of bed occupancy rates on the spread of multidrug-resistant bacteria
J Hosp Infect
(2010) - et al.
The association of registered nurse staffing levels and patient outcomes: systematic review and meta-analysis
Med Care
(2007) - et al.
Nurse-staffing levels and the quality of care in hospitals
N Engl J Med
(2002) - et al.
Time-series analysis of the impact of bed occupancy rates on the incidence of methicillin-resistant Staphylococcus aureus infection in overcrowded general wards
Infect Control Hosp Epidemiol
(2008)