Patient Safety/Quality

Limiting medical interns' work to 16 consecutive hours can substantially reduce serious medical errors in ICUs

The rate of serious medical errors committed by first-year doctors in training (interns) in two intensive care units (ICUs) at a Boston hospital fell significantly when traditional extended work shifts (30 hours in a row) were eliminated and when interns' continuous work schedules were limited to 16 hours. These findings are from two complementary studies that were funded by the Agency for Healthcare Research and Quality (HS12032, K08 HS13333, and F32 HS14130) and the National Institute for Occupational Safety and Health within the Centers for Disease Control and Prevention.

Interns made 36 percent more serious medical errors, including five times as many serious diagnostic errors, on the traditional schedule than on an intervention schedule that limited scheduled work shifts to 16 hours and reduced scheduled weekly work from approximately 80 hours to 63. The rate of serious medication errors was 21 percent greater on the traditional schedule than on the new schedule.

In the first research of its kind on the impact of lack of sleep on the safety of hospital care, researchers at Brigham and Women's Hospital in Boston eliminated the traditional schedule that required interns to work "extended duration work shifts" of approximately 30 consecutive hours every other shift. Under the traditional schedule, interns in hospital ICUs were scheduled to work approximately 80 hours per week. Under the intervention schedule that was tested in the studies, the "extended duration work shift" was eliminated, and weekly scheduled work hours were decreased by approximately 20 hours. Interns also were encouraged to sleep on their time off and to take naps before night shifts.

In this study, Christopher P. Landrigan, M.D., M.P.H., Director of the Sleep and Patient Safety Program at Brigham and Women's Hospital, and his colleagues randomly assigned 24 interns to work either the traditional schedule in the cardiac care unit and the intervention schedule in the medical intensive care unit or the converse from July 2002 to June 2003. The study covered 624 ICU admissions totaling 2,203 patient days. Interns were directly observed by six physicians while they worked, and their charts were reviewed by two nurse chart reviewers.

The change in work schedule did not diminish interns' role in ICUs or shift the burden of work to more senior staff, according to the study authors. The number of medications ordered and tests interpreted by interns did not differ significantly. In addition, the error rates for more senior residents and other staff did not increase during the study.

The findings from this study suggest that limiting interns' scheduled shifts to 16 consecutive hours in intensive care settings could substantially improve patient safety. Most of the 100,000 doctors-in-training in the United States regularly work 30-hour shifts, which continue to be allowed under the scheduling reforms instituted last year by the Accreditation Council for Graduate Medical Education. Dr. Landrigan notes that further limitation of consecutive work hours could be an important means of preventing medical errors.

In the second study, researchers examined the impact of the new work schedule on interns' sleep patterns and "attentional failures," characterized by nodding off while on duty, even while providing care to patients. Steven W. Lockley, Ph.D., and his colleagues studied 20 interns each in two 3-week ICU rotations under both the traditional and intervention work schedules.

Interns worked an average of 84.9 hours per week on the traditional schedule and 65.4 hours per week on the new schedule. They completed daily sleep and work logs that were validated through observation by study staff. In addition, interns were monitored using polysomnography, in which a device is used to objectively document sleep and attentional failures.

Under the new schedule, the researchers found that interns worked 19.5 hours per week less, slept 5.8 hours per week more, and had typically slept more in the previous 24 hours when working. The percentage of work hours preceded by more than 8 hours of sleep in the traditional schedule was 17 percent, compared with 33 percent for the new schedule. Overall, the rate of attentional failures was twice as high at night on the traditional schedule than on the intervention schedule.

The study found that interns who worked the intervention schedule were less sleep-deprived at work and were able to sleep longer at home, which resulted in the interns having less cumulative and acute sleep deprivation. Interns on the new schedule were encouraged to take naps in the afternoon before overnight shifts to mitigate the effects of sleep deprivation on their ability to provide care. In conclusion, the researchers note that the findings of this study may apply beyond the ICU to those on other rotations and specialties as well as to more senior residents, attending physicians, nurses, and other hospital staff.

For more information, see "Effect of reducing interns' work hours on serious medical errors in intensive care units," by Dr. Landrigan, Jeffrey M. Rothschild, M.D., M.P.H., John W. Cronin, M.D., and others, in the October 28, 2004, New England Journal of Medicine 351(18), pp. 1838-1848; and "Effect of reducing interns' weekly work hours on sleep and attentional failures," by Dr. Lockley, John W. Cronin, M.D., Erin E. Evans, B.S., and others, in the same journal, pp. 1829-1837.

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