Adverse events drop as RN use rises, study shows

Proper mix of staff still is an issue

Hard data are finally starting to prove what nurses and nurse managers have been saying for years: Patients treated by registered nurses have fewer adverse events that those treated by unlicensed personnel.

Anecdotal evidence has existed for some time, but data are finally being released that confirm the supposition. According to the second half of a two-part study, hospitals with high proportions of care delivered by RNs have lower rates of medication errors, patient falls, and other adverse patient outcomes. (For the role played by the American Association of Critical-Care Nurses, see March 1998 Critical Care Management, pp. 25-28.)

The data were compiled by Mary Blegen, PhD, professor and associate dean at the University of Iowa College of Nursing. She led two studies on the relationship between the use of registered nurses and adverse events affecting patients. The most recent incorporated data from 39 inpatient nursing units in 11 hospitals in Iowa. The data are expected to be published in a future edition of the journal Nursing Economics.

The finding is important because managed care and increased competition have prompted many hospitals to substitute unlicensed caregivers for registered nurses, decreasing the overall proportion of patient care delivered by RNs in these settings. At the same time, Blegen says, shorter hospital stays mean hospitalized patients generally are more acutely ill and in greater need of skilled care.

Despite these trends, Blegen says, the question of what level and mix of staffing are appropriate for different types of inpatient units remains unanswered. "Part of the reason we did these studies is that there is very little research to guide nursing administrators in determining how to staff their units," Blegen says.

"Currently, hospital restructuring responding to managed care is driving staff cuts at many hospitals," she added. "But the level of staff needed to deliver the best patient care should also be a factor, and that ís what this research is about."

Both studies used data commonly reported by hospitals for quality control and accreditation reviews. Investigators gathered information on adverse patient occurrences in each unit as well as the number of patient days of care delivered. To determine the staff mix of each unit, they looked at the total hours of care by staff and what proportion of those hours was delivered by registered nurses.

The two studies found a direct relationship between the proportion of care by RNs and the number of certain adverse occurrences per thousand patient days or, in the case of some units, the number of medication errors per 10,000 doses. As the proportion of professional nurses increased, the adverse occurrences decreased.

One surprising exception to this finding was that medication errors decreased as RN care increased to 87.5% of total care hours, but increased when the RN mix rose above that level. Blegen and Thomas Vaughn, an assistant professor of hospital and health administration at the university who co-authored the second study with her, suggest possible explanations for this phenomenon but wrote that additional research is needed to find out why an RN mix above 87.5% would be associated with increased medication errors.

The first study, published in January in the journal Nursing Research, used data from 42 inpatient nursing units at the University of Iowa Hospitals and Clinics, an 880-bed teaching hospital. It found a clear statistical correlation between nursing staff mix and rates of medication errors, patient complaints, and bedsores (technically known as decubitus ulcers or decubiti). Less clear was the relationship between nursing skill mix and patient falls, hospital-acquired infections and deaths.

The second study, using data from 11 Iowa hospitals ranging in size from fewer than 100 beds to more than 300 beds, also looked at the rates of cardiac arrest in the 39 patient units but found no clear correlation with nursing staff mix.