Understaffing, overcrowding, inappropriate nurse:ventilated patient ratio and nosocomial infections: which parameter is the best reflection of deficits?

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Summary

Background

In stressed and high-throughput systems, periodic overcrowding (high bed occupancy) and understaffing (low nurse:patient ratio) are widely described risk factors for nosocomial infections.

Aim

The impact of bed occupancy (patient:bed ratio), nurse:patient ratio and nurse:ventilated patient ratio on nosocomial bloodstream infections (BSI) and pneumonia were investigated in 182 intensive care units (ICU).

Methods

The ICUs reported monthly data on device use and nosocomial device-associated infections to the German hospital surveillance system for nosocomial infections in 2007. Information on the number of healthcare workers on the ward per 24 h in 2007 and structure parameters was obtained by questionnaires. The association between occupancy or staff parameters and the number of nosocomial infections per month was analysed using generalized estimating equation models.

Findings

In total, 1313 cases of pneumonia and 513 cases of BSI were reported from 182 ICUs with 1921 surveillance months and 563,177 patient-days. Fewer nosocomial infections were associated with a higher nurse:ventilated patient ratio [adjusted incidence rate ratio 0.42 (95% confidence interval 0.32–0.55) for months with nurse:ventilated patient ratios >75th percentile compared with ≤25th percentile]. Interestingly, the nurse:patient ratio was not a significant parameter with respect to the occurrence of BSI and pneumonia. High bed occupancy (>75th percentile) was associated with fewer nosocomial infections.

Conclusion

A staffing parameter that reflects the intensity of care, such as the nurse:ventilated patient ratio, may enable better evaluation of workload and resources, especially at a time when nursing resources are being reduced but nosocomial infections are increasing.

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.

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