BOSTON - Hospitals that operate at or over their capacity may be at increased risk of adverse events that injure patients, according to a study led by investigators from Massachusetts General Hospital (MGH) and Brigham and Woman's Hospital (BWH). The report in the May issue of the journal Medical Care suggests that efforts to meet two primary challenges facing hospitals today - reducing costs and improving patient safety - may work against each other.

"While financial and political pressures to make health care more efficient are leading to increased hospital occupancy and greater patient turnover, patients and policymakers are quite rightly demanding that health delivery systems be made safer," says Joel Weissman, PhD, of the MGH Institute of Health Policy, the report's lead author. "Our study suggests that pushing efficiency efforts to their limits could be a double-edged sword that may jeopardize patient safety."

In order to examine their hypothesis that increased workload could raise the likelihood of adverse events, the investigators examined data from four hospitals in two states - two large urban teaching hospitals and two suburban teaching hospitals - over the 12 months from October 2000 through September 2001. To compile patient care information they reviewed patient charts and billing records on almost 25,000 patients, selecting 6,841 for comprehensive review, and analyzed that data against information on hospital workloads and staffing patterns, with a focus on variations within each hospital.

From the nearly 7,000 records receiving detailed review, 1,530 adverse events - defined as preventable injuries not resulting from patients' underlying medical condition - were identified. The most common such events were wound infections and adverse drug events. At three of the four hospitals, the rate of adverse events did not appear to increase at times of peak workload. But at the fourth - a major urban teaching hospital with consistently high occupancy rates, exceeding 100 percent for more than three months - workload increases and higher patient-to-nurse ratios were associated with more adverse events.

"While we looked at only four hospitals, which limits the ability to generalize these findings, the hospital where we found a relationship between working conditions and adverse events was disproportionately crowded for much of the study period," says study co-author Eran Bendavid, MD. "That suggests hospitals operating at the high end of their capacity may need to examine safety systems with an eye towards coping with periods of high stress." Formerly with the MGH Institute of Health Policy, Bendavid is now at the Center for Health Policy at Stanford University.

"This study helps quantify the impression that many clinicians have and confirms that systems perform poorly when they are overloaded," says study co-author David Bates, MD, MSc, of the BWH Division of General Medicine and Primary Care.  "Future research should address approaches for distributing workload and examine the effectiveness of strategies to improve safety in high-workload situations."

Additional co-authors of the Medical Care report are Jeffrey Rothschild, MD, MPH, and Francis Cook, PhD, BWH; Peter Sprivulis, MBBS, PhD, University of Western Australia; Scott Evans, PhD, Peter Haug, MD, and Jim Lloyd, University of Utah; Yevgenia Kaganova, PhD, Melissa Bender, MD, and JoAnn David-Kasdan, RN, MS, MGH Institute of Health Policy; Leslie Selbovitz, MD, Newton-Wellesley Hospital; and Harvey Murff, MD, MPH, Vanderbilt University Medical Center. The study was supported by grants from the Agency for Healthcare Research and Quality, U.S. Department of Health and Human Services.