Article Text

Quantitative study—other
Higher nurse staffing levels associated with reductions in unplanned readmissions to intensive care or operating theatre, and in postoperative in-hospital mortality in heart surgery patients
  1. Steven A Frost1,2,
  2. Evan Alexandrou1,2
  1. 1School of Nursing and Midwifery, University of Western Sydney, Penrith, New South Wales, Australia
  2. 2Department of Intensive Care, Intensive Care, Liverpool Hospital, Liverpool, New South Wales, Australia
  1. Correspondence to:Steven A Frost
    University of Western Sydney, Campbelltown Campus, Bld 7 locked bag 1797, Penrith, NSW 2751, Australia; S.Frost{at}

Statistics from

Commentary on: Diya L, Van den Heede K, Sermeus W, Lesaffre E. The relationship between in-hospital mortality, readmission into the intensive care nursing unit and/or operating theatre and nurse staffing levels. J Adv Nurs 2012;68:1073–81.

Implications for practice and research

  • Higher nurse staffing levels for postoperative care of cardiac surgery patients reduces the risk of unplanned re-admission to the intensive care or operating theatre and in-hospital mortality.

  • Larger international studies are needed to assess the effect of nurse staffing levels and risk of hospital-wide adverse events.


The effect of nurse staffing levels associated with adverse events in the hospital setting has been an important area of patient safety research. Market forces, in particular in North America, have resulted in efforts to reduce costs in all sectors of the healthcare setting.1 Throughout the world, nurse staffing levels have been shown to be associated with adverse events in the hospital setting.1– ,3

The rate of unplanned re-admission to the intensive care unit (ICU) has been widely used as an indicator of the quality of care of patients in the hospital setting.4 In particular, patients readmitted to the ICU have been observed to have significantly higher in-hospital mortality.4 ,5 Other markers of the quality of care being regularly reported have included hospital mortality and unplanned return to the operating theatre (in surgical patients). In particular, this study by Diya and colleagues has used Belgian hospital data to assess the relationship between nurse staffing variables and unplanned readmission to ICU, or return to the operating theatre, and in-hospital mortality in elective cardiac surgery patients.6


Data from two routinely collected administrative databases: the Belgian Nursing Minimum Dataset and the Belgian Hospital Discharge Dataset, for 2003 provided the patient cohort for the study. The sample consisted of 9054 patients, aged between 20 and 85 years, undergoing elective coronary artery bypass or heart valve surgery, in 28 Belgian acute care hospitals. The data collected were at the patient level (age, sex, diagnostic category, severity of illness and risk of mortality), nursing care unit level (nursing staff levels, educational level of nurses and intensity of nursing care) and hospital level (yearly volume of cardiac procedures, the average intensive care staffing levels, the average general nursing unit staffing levels and the average percentage of nurses with a bachelor degree within intensive care and general care units). The outcomes of interest were unplanned re-admission to the ICU and or operating theatre, and in-hospital mortality. Due to the multilevel nature of the data, Bayesian random-effects models were used to assess the relationship between nurse staffing variables and the outcomes of interest, while adjusting for potential confounders.


In this study of elective cardiac surgery patients, an association was observed between increasing nurse staffing levels and reduction risk of unplanned readmission to ICU/OT and in-hospital morality. In particular, the protective effect of higher nurse staffing levels was modified by the volume of cardiac procedures a hospital undertook, in that higher nurse staffing levels in higher-volume hospitals resulted in lower in-hospital mortality. Additionally, in the general postoperative nursing care unit setting, the protective effect of higher nurse staffing levels was greater among cardiac surgery patients with lower severity of illness.


The results of this study highlight the important role nursing staff play in ensuring patients safety in the hospital setting. Despite being limited to patients undergoing elective cardiac surgery, the results add to the increasing body of evidence which shows that nurse staffing levels play an important role in reducing adverse events in the hospital setting. Future research should assess the benefit of higher nurse staffing levels throughout the hospital setting, incorporating various patient populations.

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  • Competing interests None.

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