On-call Shifts Research Articles

Work satisfaction, quality of life, and leisure time of neonatology fellows and senior neonatologists in Israel

ObjectivesTo examine work satisfaction, quality of life, and leisure time of neonatology fellows and senior neonatologists in Israel.MethodsA validated questionnaire was delivered during the second half of 2008 to all the neonatology fellows and senior neonatologists in Israel. Descriptive analysis, parametric Student’s t-test, and aparametric Mann Whitney and χ2 tests were conducted.ResultsOf 114 practicing neonatologists in that period in Israel (including both seniors and fellows), 112 (98.25%) participated in the study. The majority of neonatologists were male (53.2%), married (91.7%), 40–60 years old (69.7%), and studied in Israeli medical schools (62.0%). Most did their pediatric residencies and fellowships in Israel (97.2% and 75.7%, respectively). The average number of night/on-call shifts of fellows and senior neonatologists was 8.8 per month (SD ± 3.425) and the number of active on-call shifts was 4.04 (SD ± 3.194). The satisfaction level of neonatologists in Israeli medical centers with patient care, self-reward, work relations, and quality of life was high, but their satisfaction level with workload, income and prestige, and leisure time was low. The general index of work satisfaction and the general index of indices were both high in relation to the mid-range values. The majority of neonatologists stated that they would choose to practice medicine again. Most of them would encourage medical students to choose the same specialty they had chosen. Only a few neonatologists were contemplating changing their choice of specialty. Most neonatologists want to continue practicing medicine; however, a significant number will not recommend that their children do so.ConclusionsThe satisfaction level of neonatologists in Israel is high, mainly due to satisfaction with their work. High satisfaction levels promise high quality patient care, as well as high satisfaction levels of patients and their families. However, satisfaction with leisure time was low and it will require greater attention and focused steps to correct this.

A goal programming model for scheduling residents in an anesthesia and reanimation department

Medicine residency is three to seven years of challenging graduate medical training that puts a lot of mental and physiological burden over the residents. Like other surgical branches, anesthesia and reanimation departments provide 24h continuous service and the residents are the main providers of this service. The residents are assigned for on-call shifts during their training, as well as working during the regular day shifts. These schedules must address several considerations like preferences of the residents and coverage requirements of two different locations: the intensive care unit (ICU) and the surgery room (SR). In this study we develop a goal programming (GP) model for scheduling the shifts of the residents in the Anesthesia and Reanimation Department of Bezmialem Vakif University Medical School (BUMS). The rules that must be strictly met, like the number of on-duty shifts or preventing block shifts, are formulated as hard constraints. The preferences of the residents like increasing the number of weekends without shifts and assigning duties on the same night to the same social groups are formulated as soft constraints. The penalties for the deviation from the soft constraints are determined by the analytical hierarchy process (AHP). We are able to solve problems of realistic size to optimality in a few seconds. We showed that the proposed formulation, which the department uses currently, has yielded substantial improvements and much better schedules are created with less effort.

Incidencia de punción accidental de duramadre en un hospital universitario. Estudio prospectivo observacional

ObjectiveAccidental dura mater puncture is a potential complication during epidural block, and may be associated with multiple factors. Our objective was to determine the prevalence and risk factors of accidental dural puncture in a university hospital, evaluating the differences in the number of complications during different working hours. Material and methodsA prospective observational study was conducted on all women who requested regional anaesthesia in the Epidural Analgesia Unit between 1 January 2009 and 1 January 2011, and who fulfilled the inclusion criteria. The technique employed to control labour pains was epidural analgesia. ResultsA total of 12,480 pregnant women were included. The prevalence of accidental dura mater puncture was 0.4% (50 patients). Of these, 28% were due to medical residents. More accidental dura mater punctures were observed during September and in the afternoon shift. ConclusionsThe prevalence of accidental dura mater puncture is similar to other patient series. In ours, tiredness or lack of sleep did not influence the incidence of complications in analgesia for labour pains in a 24 hour care unit. This may be due to the distribution of on-call shifts not exceeding more than 6hours.

Paediatric units should move towards resident on-call shifts for consultants

Paediatric units should always have a consultant present in the hospital outside normal working hours, to improve quality of patients’ care around the clock, the Royal College of Paediatrics and Child Health has recommended. This model of consultant delivered care will also ensure good handovers and improve communication with patients and their families, the college adds, and will help hospitals deal with rota vacancies, reduce costs of locums, and ensure compliance with the European Working Time Directive. “Patients deserve to be treated with the same high standard of care whatever time of day or night they are admitted to hospital, whether that be at 11 am on Tuesday morning or …

On-Call Shifts during Neurology Residency in a Spanish Tertiary Academic Hospital: A Quantitative Analysis (P07.243)

Objective: We will communicate the personal experience about the on-call shifts during a neurology residency in a Spanish tertiary hospital. Background Specialized neurology 24-hour on-call shifts are considered a fundamental tool in residency training. In Spain, these shifts are mandatory and aimed to teach neurology residents how to manage urgent or unexpected neurological disease. In our center, residents start neurology shifts on the second semester of their first year, always under the supervision of an attending physician. Design/Methods: Prospective quantitative analysis of the number of patients attended and pathology encountered during the on-call shifts made by a neurology resident on his residency training, between the years 2007 and 2011. Results: Neurology 24 hrs on-call shifts: 147; Number of patients attended: 1767, shifts per month: 3.65 (3-6); average number of patients per shift: 12.02 (5-25). Reasons for consultation: cerebrovascular disease: 590 patients (33.38%); Seizures: 288 (16.29%); headache: 132 (7.47%); neuromuscular disorders: 120 (6.79%); neuro-ophthalmology: 112 (6.33%); cognitive disorders: 91 (5.14%); altered level of consciousness: 82 (4.60%); Demyelinating disease: 66 (3, 77%); gait disturbance: 53 (2.99%); movement disorders: 39 (2.20%); dizziness / vertigo: 39 (2.20%); other causes: 155 (8.7%). Conclusions: Through communicating the experience of a neurology resident in a hospital in Spain, we expect to be able to show an example of the high prevalence of neurological disorders in the emergency room. The increase in the number of neurological diseases which require immediate attention, and the difficulty in diagnosis these may sometimes entail, can make the presence of an on-call neurologist essential in determining the course and prognosis of these diseases in many of our patients. Disclosure: Dr. Cuello has nothing to disclose. Dr. Rodriguez Cruz has nothing to disclose. Dr. Perez Gonzalez de Apodaca has nothing to disclose. Dr. De Andres has nothing to disclose. Dr. Martinez Gines has nothing to disclose. Dr. Mateo Gonzalez has nothing to disclose. Dr. Ezpeleta has nothing to disclose.

Effects of On-Call Shifts on Physicians' Cognitive Performance, Level of Alertness, Mood, and Safety:

A hospital physician's work demands high cognitive performance, quick judgment, prompt and flawless decision making, a high concentration level, and fine motor skills. However, physicians frequently experience periods of acute sleep deprivation due to the extended on-call shift lengths. This may affect cognitive functions, alertness, and mood; therefore, the overall performance. This article will review the effects of long shifts (on-call hours) and the result of sleep deprivation on physician affecting their general performance and safety, as well as the implications of such effects on patient care. Recommendations and suggestions proposals will be presented for consideration by the training boards, the Saudi Commission for Health Specialties, to improve physicians' performance and assure patients' safety without jeopardizing the trainees' postgraduate education.

Effects of On-Call Shifts on Physicians' Cognitive Performance, Level of Alertness, Mood, and Safety:

A hospital physician's work demands high cognitive performance, quick judgment, prompt and flawless decision making, a high concentration level, and fine motor skills. However, physicians frequently experience periods of acute sleep deprivation due to the extended on-call shift lengths. This may affect cognitive functions, alertness, and mood; therefore, the overall performance. This article will review the effects of long shifts (on-call hours) and the result of sleep deprivation on physician affecting their general performance and safety, as well as the implications of such effects on patient care. Recommendations and suggestions proposals will be presented for consideration by the training boards, the Saudi Commission for Health Specialties, to improve physicians' performance and assure patients' safety without jeopardizing the trainees' postgraduate education.

Effects of the Restriction of Working Time for Residents: A Dutch Perspective

A main objective of restricting working time for residents, whether it is the Accreditation Council for Graduate Medical Education (ACGME) regulation or the European Working Time Directive (EWTD), is to protect patients from exhausted doctors. However, in the Netherlands, legislation enacted in 1993 to reduce working hours for junior doctors, as residents are termed, and midwives was prompted by trainees in a teaching hospital who complained to members of parliament about long working hours and miserable personal lives. At the time, public working hours were mandated to no more than 38 h/wk. An arbitrary 10 hours was added for education and training: thus, trainees were allowed to work 48 hours a week. In the first years, the Dutch Department of Labor took a more or less lenient position but, in 1997, started to enforce the law. Site visits to hospitals are made routinely, resident schedules are inspected, and hospitals are fined if they do not comply with the rules. Initially the surgical community fiercely opposed the new regulation and argued that a work week of 48 hours would not suffice to adequately train young surgeons. However, their plea for a 60-hour work week was politically unacceptable to the Dutch government, which had already accepted the limits of the European Working Time Directive. In 1995, the yearly survey of the Dutch Association of Surgical Trainees reported a work week of 57 hours. This number decreased to 55 hours in 2005 and has remained unchanged since.1

Public health on-call in Scotland: how much experience is sufficient?

ObjectivesTo quantify the out-of-hours experience obtained by public health trainees in Scotland and to assess whether this is sufficient to meet the Faculty of Public Health guidelines.Study designProspective survey.MethodsAll public...

Use of Mannequin-Based Simulators in Anesthesiology

he field of anesthesiology is one of the first medical specialties to use igh-fidelity simulation in a quest to improve patient safety and reduce uman errors. Medical mistakes have been shown to result in significant orbidity and mortality, including preventable adverse anesthetic vents. “See one, do one, teach one” may be inadequate to educate rainees on complex procedures and skills, let alone communication and eadership required during critical situations. Traditionally, long hours of he working day and on-call shifts provided the crude exposure to these xperiences, but restrictions and streamlining of the time spent in the ospital reduce the exposure to various situations. Simulators may rovide training on less common, but critical, events, while standardizing he residents’ approach to these situations. Furthermore, simulations equire the ability to physically put into practice knowledge, and solidify earning by creating an emotional attachment through the juxtaposition of aking a decision and realizing the consequences. The limitations of adequately preparing for uncommon or dangerous vents can limit the ability to adequately manage such events. Throughout istory, humankind has been confronted with numerous situations for hich he has been unable to anticipate or master. Historically, the ability o fully prepare for battle was restricted because of safety concerns for oth the trainee and the trainer. The Roman soldiers developed fighting imulators, or “quintains,” to replicate the actions that would be dangerus to practice. This ability to practice individual skills is similar to odern task trainers, while more advanced computerized simulators now llow for replication of an entire environment, from flight simulators to ull multinational war games. The military, aircraft, medical, and nuclear ower industries are just a few notable employers of modern simulators. y training and evaluating personnel through simulators, a variety of

Oxidative Stress Increased in Healthcare Workers Working 24-Hour On-Call Shifts

IntroductionLong work hours, night shifts, stressful situations and insufficient social support increase levels of anxiety and depression and decrease motivation to perform among healthcare professionals. In this study, we evaluated oxidative stress levels in medical residents working 24-hour on-call shifts, and in nurses, relative to non-healthcare hospital staff in sedentary positions. We also measured serum prolidase activity, a measure of collagen turnover, as an objective proxy for level of physical activity. MethodsFifty-five male and 15 female medical residents on 24-hour, in-house, on-call duty, and 45 nurses and 30 (15male/15 female) non-healthcare staff working 8-hour shifts were recruited. All were healthy nonsmokers. Parameters of oxidative stress and serum prolidase activity were measured twice for each subject, upon arising at 8 am after an overnight fast; and then again near the end of the work shift, or after 16hours of consecutive work (at 12 pm) for residents. ResultsAfter hours of continuous work, serum total oxidative status and the oxidative stress index increased significantly, whereas total antioxidant status decreased (all P < 0.0001) in healthcare staff (nurses, male and female residents). All these variables remained virtually unchanged in non-healthcare staff. Similarly, serum prolidase activity increased in healthcare staff (P < 0.0001), but failed to increase statistically in non-healthcare staff. ConclusionsHealthcare workers suffer increased oxidative stress after prolonged work hours, especially while still on duty. Possible mechanisms for this include increased workload and, perhaps, psychological stress as well. However, long-term studies are needed to clarify the effects of sustained exposure to oxidative stress.

Resident Workload, Pager Communications, and Quality of Care

With the recent regulations limiting resident work hours, it has become more important to understand how residents spend their time. The volume and content of the pages they receive provide a valuable source of information that give insight into their workload and help identify inefficiencies in hospital communication. We hypothesized that above a certain workload threshold, paging data would suggest breakdowns in communication and implications for quality of care. All pages sent to six general surgery interns at the University of Michigan over the course of one academic year (7/1/2008-6/30/2009) were retrospectively categorized by sender type, message type, message modifier, and message quality. Census, discharge, and admission information for each intern service were also collected, and intern duties were further analyzed with respect to schedule. "On-call" days were defined as days on which the intern bore responsibility for care of all admitted floor patients. The interns received a total of 9,843 pages during the study period. During on-call shifts, each intern was paged an average of 57±3 times, and those on non-call shifts received an average of 12±3 pages. Floor/intensive care unit (ICU) nurses represented 32% of the page volume received by interns. Interestingly, as patient volume increased, there was a decrease in the number of pages received per patient. By contrast, at higher patient volumes, there was a trend toward an increasing percentage of urgent pages per patient. At high intern workloads, our data suggest no major communication breakdowns but reveal the potential for inferior quality of care.

Atención continuada, ¿un factor de riesgo cardiovascular más a considerar?

Objective To assess blood pressure (BP) in Primary Care (PC) professionals while working extra shifts and its relationship with the professional role, anxiety level and social support. Method Descriptive,, cross-sectional, multicentre and prospective study. Population: PC health workers from Toledo Health Area who work on-call shifts. Exclusion criteria: diagnosed hypertension, African origin, cardiovascular disease or chronic treatment. Voluntary sampling. Variables: sociodemographic, occupational and STAI questionnaire (anxiety state/feature); ISTAS21 questionnaire (psychosocial risks at work), and Ambulatory BP Monitoring with a Holter for two days, 48 h: one of them during the shift and the other one during a day without being on-call. Results The BP monitor showed significant differences in daytime systolic BP: rest day115.9±8,3 mmHg/ Shift mean: 120.2±8,1 ( t=4.319; P<0.001); daytime diastolic: rest day 73.3±5.9 mmHg/Shift 77.9±6.1 ( t=6.555; P<0.001); night systolic: rest day 106.8±8.3 mmHg/shift 111.6±9.5 ( t=3.4; P<0.001); night diastolic: rest day 65.1±5.6 mmHg/Shift 69.1±6.9 ( t=4.14; P<0.0001). We found no relationship between variations in the BP, the category or role. The ISTAS dimensions (health situation status) and the anxiety level (average of 5/10 during the shift) are not related with the BP either. Conclusions There are significant changes in the BP of the professional during the extra shifts, independently of professional role, anxiety level or psychosocial risk. Studies need to be conducted on the demonstrated variation in BP working extra shifts to assess its impact on health.

Prospective Observational Study of Clinical Activities, Education and Sleep During Paediatric Resident On-Call Shifts

Prospective Observational Study of Clinical Activities, Education and Sleep During Paediatric Resident On-Call Shifts

Forecasting and Perception of Average and Latest Hours Worked by On-Call Anesthesiologists

We studied the value of providing information to anesthesia providers about the length of time typically worked during on-call shifts. The mean time at which a shift ends can be used for purposes of trades, payments, or reverse auctions, because the mean is proportional to the total time. The 80th percentile (with a suitable upper confidence limit for uncertainty due to limited sample sizes) can be used for judging the earliest time by which after-work activities reasonably can be planned. (A) Three years of operating room (OR) information system data were analyzed. Dependent variables were the earliest times when the numbers of ORs running were always <or=6 ORs, <or=4 ORs, and <or=2 ORs. We progressively built linear regression models for each of the three dependent variables using day of the week, scheduled number of cases, scheduled hours of cases (including turnovers), and linear time trend. Calculations were repeated after excluding residuals. Calculations were repeated using regression trees. (B) Anesthesiologists were surveyed about their perceptions of the mean and 80th percentiles. (A) For the three thresholds and two end points (mean and 80th percentile), differences among days of the week were as large as 45 min. Differences between end points for the same weekdays were as large as 245 min. Comparatively, additional knowledge about the number or hours of cases provided in the late afternoon on the working day before surgery reduced the mean absolute error by only 4.1-6.0 min. Results were insensitive to a variety of analytic methods. Information available more days before the day of surgery (e.g., 1 wk) would have had even less incremental predictive value. (B) The mean absolute error of anesthesiologists' estimates for 80th percentiles was 60 min, principally because of underestimation of the 80th percentiles. More than half (69%, P = 0.0003) of anesthesiologists' estimates for 80th percentiles had error >30 min, whereas errors of this magnitude were less for the mean (44%, P = 0.0004). Historical data from OR or anesthesia information management systems, or from anesthesia billing systems, can be used months before staff scheduling to provide insight to anesthesia providers on respective calls. The data are useful because experience provides limited intuition. Updates on scheduled workload available closer to the day of surgery provided only marginal increases in knowledge over the use of historical data.

Perceived sleepiness in Canadian anesthesia residents: a national survey

To compare the self-perceived sleepiness of Canadian anesthesia residents providing modified on-call duties (12-16 h) vs. traditional on-call duties (24 h). A 25-item online survey was distributed to all Canadian anesthesia residents who, at that time, were on anesthesia rotations. The survey assessed resident demographics, perceived work patterns, and sleepiness, as well as their opinions on resident work hour reform. Self-perceived sleepiness was quantified using the validated Epworth sleepiness scale (ESS). Three hundred eight of 400 (77%) eligible Canadian anesthesia residents completed the survey. Forty-three percent of residents who worked traditional on-call (duration 24.1 +/- 0.5 h) shifts and 48% of residents who worked modified on-call (duration 15.5 +/- 1.8 h) shifts met ESS criteria for excessive daytime sleepiness. Overall mean ESS scores did not differ significantly between the traditional (9.1 +/- 4.9) and the modified call groups (9.5 +/- 4.8). Residents with an on-call frequency of >or=1:4 days or those who slept <or=2 h while on call perceived themselves as significantly more sleepy (P = 0.045 and P = 0.008, respectively). Six percent of residents admitted to taking "something other than caffeine" to stay awake on call. Many anesthesia residents do exhibit excessive daytime sleepiness, with a similar incidence for those working within either modified or traditional call systems. Our study suggests that sleepiness may be reduced by scheduling on-call duties no more frequently than one in every five nights and by ensuring that residents sleep more than 2 h while on call.

Society of Obstetricians and Gynaecologists of Canada Junior Member Committee Survey: Future Career Plans of Canadian Obstetrics and Gynaecology Residents

ObjectiveAlthough the SOGC Strategic Directions 2006–2011 includes a commitment to the development of a human resource strategy for obstetrical and gynaecological care, little is known about the career plans of Canadian obstetrics and gynaecology residents. If we are to determine the needs of our profession, we must be aware of the expected practice patterns of future women’s health care providers. The primary objective of this study was to evaluate the future career plans of Canadian obstetrics and gynaecology residents. MethodsThe SOGC Junior Member Committee administered two career surveys to Canadian obstetrics and gynaecology residents. The first was directly distributed to all Canadian residents and collected by local representatives of the SOGC Junior Member Committee in November 2002. The second was electronically administered from November 2005 to January 2006. The data collected from the surveys were collated and analyzed using statistical analysis software. ResultsThe first survey, in 2002, was completed by 236 obstetrics and gynaecology residents (68% response rate) and the second, in 2006, by 246 (65% response rate). In both surveys, respondents were evenly distributed over all five years of residency training and all residency training programs. In 2002, 63 residents (30%) were considering additional postgraduate fellowship training following completion of residency compared with 130 residents (53%) in 2006 (P < 0.001). In both surveys, senior residents (postgraduate years IV and V) were significantly less likely to consider further postgraduate training than residents in their first three years (2002: 17% vs. 38%; 2006: 42% vs. 58%). Of total respondents to the 2002 and 2006 surveys, 87% planned to practice obstetrics upon graduation. The 2006 survey also found that the majority of residents desired to work in call groups of 6 to 10 physicians, work three to five on-call shifts per month, and work a 40- to 60-hour week; 44% of residents planned work as locums after graduation. ConclusionRecognition of the planned practice patterns of our current residents may assist in the development of an appropriate human resource strategy for future obstetrical and gynaecological care in Canada.

Effects of the Accreditation Council for Graduate Medical Education Duty Hour Limits on Sleep, Work Hours, and Safety

To mitigate the risks of fatigue-related medical errors, the Accreditation Council for Graduate Medical Education introduced work hour limits for resident physicians in 2003. Our goal was to determine whether work hours, sleep, and safety changed after implementation of the Accreditation Council for Graduate Medical Education standards. We conducted a prospective cohort study in which residents from 3 large pediatric training programs provided daily reports of work hours and sleep. In addition, they completed reports of near-miss and actual motor vehicle crashes, occupational exposures, self-reported medical errors, and ratings of educational experience. They were screened for depression and burnout. Concurrently, at 2 of the centers, data on medication errors were collected prospectively by using an established active surveillance method. A total of 220 residents provided 6007 daily reports of their work hours and sleep, and 16 158 medication orders were reviewed. Although scheduling changes were made in each program to accommodate the standards, 24- to 30-hour shifts remained common, and the frequency of residents' call remained largely unchanged. There was no change in residents' measured total work hours or sleep hours. There was no change in the overall rate of medication errors, and there was a borderline increase in the rate of resident physician ordering errors, from 1.06 to 1.38 errors per 100 patient-days. Rates of motor vehicle crashes, occupational exposures, depression, and self-reported medical errors and overall ratings of work and educational experiences did not change. The mean length of extended-duration (on-call) shifts decreased 2.7% to 28.5 hours, and rates of resident burnout decreased significantly (from 75.4% to 57.0%). Total hours of work and sleep did not change after implementation of the duty hour standards. Although fewer residents were burned out, rates of medication errors, resident depression, and resident injuries and educational ratings did not improve.

Learning in patient-based education sessions: A prospective evaluation*

The educational impact of on-call scheduling for physicians in training is not well understood. The benefit of patient-based educational sessions during postcall periods may be enhanced by the greater patient familiarity associated with long on-call shifts, or it may be attenuated by fatigue. The objective was to evaluate the impact of in-house call on cognitive attention, learning, and recall of critical care medicine trainees, before and after a reduction in call period. A prospective before and after survey during 8 wks in 2004. Two critical care units at the Hospital for Sick Children, Toronto. Trainees in a university-affiliated critical care medicine program at the Hospital for Sick Children. Duty hour reduction from 26.5-hr to 18-hr on-call shifts. Likert scales were completed after morning educational seminars self-reporting alertness, concentration, how well discussions were followed, and the acquisition of new or practice changing knowledge. Respondents were classified according to how recently they had been on call. Eleven trainees completed 231 questionnaires (80% response rate). Fellows with more recent on-call periods had reduced concentration (p = .002), alertness (p < .0001), and recall of the previous session (p = .009) and followed discussions less well (p = .019). Eighteen-hour shifts were associated with increased postcall alertness (p = .002), concentration (p = .03), and assimilation of discussions (p = .045). However, neither the duration of call nor the length of time since being on call was associated with differences in the acquisition of new theoretical or practice-changing knowledge. Reduced mental attention after being on call is more pronounced after longer shifts. Learning was not affected by shift duration or by how recently trainees were on call. Increased patient familiarity does not augment learning in patient-based medical education.

Effects of Health Care Provider Work Hours and Sleep Deprivation on Safety and Performance

There has been increasing interest in the impact of resident-physician and nurse work hours on patient safety. The evidence demonstrates that work schedules have a profound effect on providers' sleep and performance, as well as on their safety and that of their patients. Nurses working shifts greater than 12.5 hours are at significantly increased risk of experiencing decreased vigilance on the job, suffering an occupational injury, or making a medical error. Physicians-in-training working traditional > 24-hour on-call shifts are at greatly increased risk of experiencing an occupational sharps injury or a motor vehicle crash on the drive home from work and of making a serious or even fatal medical error. As compared to when working 16-hours shifts, on-call residents have twice as many attentional failures when working overnight and commit 36% more serious medical errors. They also report making 300% more fatigue-related medical errors that lead to a patient's death. The weight of evidence strongly suggests that extended-duration work shifts significantly increase fatigue and impair performance and safety. From the standpoint of both providers and patients, the hours routinely worked by health care providers in the United States are unsafe. To reduce the unacceptably high rate of preventable fatigue-related medical error and injuries among health care workers, the United States must establish and enforce safe work-hour limits.