Ventilator-Associated Pneumonia Linked to ICU Nursing Shortages

GENEVA, Switzerland, July 19 -- The risk of late-onset ventilator-associated pneumonia in ICU patients rises as the nurse-to-patient ratio declines, reported investigators here.

Among critically ill patients on mechanical ventilation, the risk of late-onset pneumonia (occurring six days or more after intubation) was 58% lower when there were two or more nurses for each patient than when nurse:patient ratios were lower, reported Stephan Hugonnet, M.D., and colleagues, of the University of Geneva Hospitals.

Nurse staffing levels did not appear to affect the incidence of early-onset disease, however, the authors noted in the study, published online in Critical Care.

"At a time of universal cost containment policies, there is growing evidence that high workload or low staffing level increases the risk for negative patient outcomes, such as death and nosocomial infection," the investigators wrote.

The current study is just one in a long line suggesting that penny-wise hospital staffing practices may translate into pound-foolish increases in the human and financial costs of care related to poorer outcomes, including higher mortality rates.

For example, in 2003 investigators from the Oregon Health and Sciences University in Portland published a study indicating that lower nurse-to-patient ratios were associated with higher rates of nonfatal adverse outcomes at both the hospital and the nursing unit levels.

And in a 2002 paper published in the Journal of the American Medical Association, Linda H. Aiken, Ph.D., R.N., of the University of Pennsylvania, and colleagues reported that, after adjusting for patient and hospital characteristics, each additional patient per nurse was associated with a 7% increase in the likelihood of death within 30 days of admission and a 7% increase in the odds of failure-to-rescue.

Dr. Hugonnet and colleagues conducted a prospective, observational study of all patients who were at risk for ICU-acquired infection admitted from January 1999 through December 2002.

They looked at patient characteristics, admission diagnosis, Acute Physiology and Chronic Health Evaluation II (APACHE II) score, comorbidities, exposure to invasive devices, daily number of patients and nurses on duty, nurse training level and all-site ICU-acquired infections.

They found that of the 936 patients who were put on ventilators, 209 (22.3%) developed ventilator acquired pneumonia. The median time spent on the ventilator was three days (interquartile range two to six days) among patients who did not develop pneumonia, and 11 days (interquartile range six to 19 days) among patients who developed ventilator-associated pneumonia.

Nearly two-thirds of the pneumonia episodes (61%) were late onset. The rate of ventilator-associated pneumonia was 37.6 episodes per 1,000 days at risk (95% confidence interval 33.2 to 42.4 episodes).

During the study period, the median daily nurse-to-patient ratio was 1.9 (interquartile range 1.8 to 2.2).

When they created multivariate Cox regression models, the authors found that a high nurse-to-patient ratio was associated with a decreased risk for late-onset pneumonia (hazard ratio 0.42, 95% CI 0.18 to 0.99), but not early onset pneumonia.

"We hypothesize that increased workload results in noncompliance with basic hygiene measures and infection control recommendations," they wrote. "Time constraints can increase the probability of error by creating a busy, stressful environment with distractions and interruptions, leading to low compliance with hand hygiene recommendations and isolation procedures, or inadequate care for the ventilated patient."

Although the ICU ratio of two nurses to one patient described by the Swiss researchers may be one that few American hospitals want to pay for, the severity of illness seen among patients in major urban teaching hospitals warrants it, nursing advocates say.

"It's very clear, that never, ever should a nurse in an ICU have more than two patients," said David Schildmeier, a spokesman for the Massachusetts Nurses Association. "This has been known for years and there was great research done on this at Johns Hopkins, which showed that the costs of care go up dramatically when nurses have more than two patients."

The authors of the current study noted that ventilator-associated pneumonia alone prolongs length of stay by up to 50 days and generates ,000 to ,000 in extra costs per episode.

"We did a study of ICUs in Massachusetts, and found that in more than 35% of the cases, hospitals had assigned as many as three patients to a nurse, which is patently dangerous," noted Schildmeier. "All of the studies confirm that when you increase the patient to nurse ratio beyond two in the ICU and beyond four on medical/surgical floors, bad things start happening."

Last month, the association's members staged a two-hour demonstration outside a Boston teaching hospital to protest nursing staff shortages and working conditions in the emergency department, post-anesthesia care unit, and medical floors.

Dr. Hugonnet and colleagues noted that their study, and all similar studies, may be limited by the fact that all patients in the ICU at a given time are exposed to the same nurse-to-patient ratios, which could affect the results. Additionally, the authors determined staffing levels by reviewing schedules drawn up in advance for the days in question, which may not necessarily reflect what occurred during the actual shifts.