Better-Rested Interns Make Fewer Serious Medical Errors in the Intensive Care Unit
Sleep deprivation has been shown to impair work performance. Research has estimated that a single night of continuous sleep deprivation causes decrements in performance comparable to those induced by a blood alcohol level of .10 percent. In hospitals, however, the effect of sleep deprivation on quality of clinical care has not been well studied. This may be due to a reluctance on the part of researchers to disrupt the workflow at hospitals, as well as the difficulty of measuring errors objectively in this setting.
It is concerning, though, that within hospitals, interns (doctors haning graduated from medical school within the past year) typically work the greatest number of hours per week—often over eighty hours. Three decades ago, researchers found that interns were almost twice as likely to misread an electrocardiogram after a shift of 24 hours or more than after a night of sleep. Since then, further evidence that lack of sleep leads to medical errors has amassed. For example, in a survey of resident doctors, 41% reported fatigue as the cause of their most serious mistake, 31% of these mistakes reportedly resulted in fatalities, and most of the mistakes were made while they were interns.
In the October 28, 2004 issue of the New England Journal of Medicine , researchers from Harvard reported a 36% increased risk of serious medical errors by interns on a traditional work schedule as compared to these same interns when switched to a schedule that promoted more regular sleep.
About the Study
The Intern Sleep and Patient Safety Study was conducted from July 2002 to June 2003 in the medical intensive care unit (MICU) and coronary care unit (CCU) of Brigham and Women’s Hospital, a large, Harvard-affiliated hospital in Boston. The researchers chose these settings because intern rotations in these units typically require the longest work hours and critical care settings also tend to have higher rates of clinical errors than other settings.
Study investigators worked with the hospital’s residency program and unit directors to design a new work schedule. The goal was to maximize opportunities for sleep while minimizing errors due to the resulting requirement for more frequent handoff of patients from one intern to the next.
Interns were assigned to work either the new intervention schedule in the CCU and the traditional schedule in the MICU or vise versa. On the traditional schedule, interns worked an average of 79 hours per week, with up to 34 continuous hours of scheduled work. On the intervention schedule, the goal was for interns to work a maximum of 63 hours per week and only up to 16 hours in a row.
A group of physicians and nurses measured medical errors by directly and continuously observing intern performance. In addition, the researchers collected voluntary reports from clinical staff and a data generated by a computerized event-detection monitor.
Two physician researchers, blinded as to which work schedule the error occurred under, rated each reported error on the following characteristics:
- Preventable or not
- Serious or not
- Intercepted or not
- Type of error: medication, procedural, or diagnostic
- Resulted in an adverse injury (either preventable or not)
The researchers also collected data on the errors of the unit as a whole, including those made by physicians and other clinical staff, in order to assess the potential impact of interns’ work performance on the whole team.
All interns kept careful sleep logs during both rotations in order to document whether the intervention schedule truly afforded them more sleep time, and if so, how much.
The study tracked interns over 1,294 patient-days during the traditional schedule and 909 patient-days during the intervention schedule (2,203 patient-days total), representing 634 total patient admissions.
Compared to the intervention schedule, interns working on the traditional schedule made:
- 36% more serious errors
- 28% more intercepted errors and 57% more non-intercepted errors
- 21% more medication errors
- 5.6 times as many serious diagnostic errors
On the traditional work schedule, unit-wide errors were 22% higher.
There was no significant difference in the amount of procedural errors made or in rates of preventable adverse events. And while the study was not large enough to determine the overall amount of adverse patient outcomes resulting from interns’ medical errors, patients’ lengths of stay and mortality rates did not differ between the two work schedules. The majority of serious errors were identified and addressed promptly by medical staff, or did not lead to clinically detectable harm.
The intervention schedule was not able to successfully lower intern work hours to the extent of its original goals, but it did manage to eliminate shifts over 24 hours, reduce weekly work hours by about 20, and increase average daily sleep duration by nearly an hour. Interns on the intervention schedule slept an average of approximately 7.5 hours per night as compared to 6.5 hours per night on the traditional schedule.
How Does This Affect You?
This study may have serious consequences for public health policy that could affect more than 100,000 medical trainees in U.S. hospitals today. Having demonstrated that intern errors can be significantly reduced by eliminating excessively long work shifts and increasing nightly sleep even by one hour, this study is likely to receive some attention from medical educators.
Historically, one of the great concerns of schedule reformers has been whether decreasing interns hours would result in disrupted patient care due to “cross-coverage.” Interns working shorter shifts are unable to provide as continuous care for the patients they admit, since they must more frequently hand over their patients to another intern’s watch. The current study demonstrated that this increased patient handoff did not disrupt care enough to offset the reduction in errors.
Nonetheless, critics of the intervention schedule cited much room for improvement in the system used for patient transfer between interns. With more frequent changeovers, there’s a greater need for a sense of team versus individual responsibility for each patient. And before an intervention schedule such as the one in this study could be initiated on a widespread basis, a more formal and comprehensive intern sign out process needs to be developed and tested, ensuring that all team members are sufficiently knowledgeable about each patient. As one physician editorialist put it, “We must be more than awake—we need to be awake and informed.”
To address broader patient safety issues, the researchers contend, “future studies should seek to improve and measure objectively the sleep and performance of all clinical unit personnel, since team performance may critically affect patients’ safety… and because it is unlikely that interns are uniquely susceptible to the adverse effects of sleep deprivation."
Accreditation Council for Graduate Medical Education (ACGME)
Drazen JM. Awake and Informed. New England Journal of Medicine . 2004; 351(18): 1884.
Landrigan CP, Rothschild JM, Cronin JW, Kaushal R, Burdick E, Katz JT, et al. Effect of Reducing Interns’ Work Hours on Serious Medical Errors in Intensive Care Units. New England Journal of Medicine . 2004; 351(18): 1838-1848.
Lockley SW, Cronin JW, Evans EE, Cade BE, Clark JL, Landrigan CP, et al. Effect of Reducing Interns’ Weekly Work Hours on Sleep and Attentional Failures. New England Journal of Medicine. 2004; 351(18): 1829-1837.
Last reviewed Oct 29, 2004 by
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