Fatigue in Anesthesia: Implications and Strategies for Patient and Provider Safety
Warltier, David C. M.D., Ph.D., Editor; Howard, Steven K. M.D.*; Rosekind, Mark R. Ph.D.†; Katz, Jonathan D. M.D.‡; Berry, Arnold J. M.D., M.P.H.§
HEALTHCARE delivery takes place 24 h a day, 7 days a week, and is colloquially termed a “24/7” operation. Anesthesia providers are required to deliver critical around-the-clock care to a variety of patients. This parallels the situation in many other domains that provide such services, e.g., transportation, law enforcement, communications, fire fighting, technology, manufacturing, and the military. Even “convenience” industries (e.g., gas stations and grocery stores) now provide uninterrupted access. These continuous operational demands present unique physiologic challenges to the humans who are called on to provide safe operations within these systems. Human physiologic design dictates circadian patterns of alertness and performance and includes a vital need for sleep. Human requirements for sleep and a stable circadian clock can be, and often are, in direct opposition to the societal demand for continuous operations.
Recently, patient safety has taken center stage in health care. The Institute of Medicine's report “To Err Is Human: Building a Safer Health System,” revealed that medical errors contribute to many hospital deaths and serious adverse events. 1
The response to this report was widespread and included the Quality Interagency Coordination Task Force's response to the President of the United States, “Doing What Counts for Patient Safety: Federal Actions to Reduce Medical Errors and Their Impact.”∥ 2
This report listed more than 100 action items to be undertaken by federal agencies to improve quality and reduce medical errors. One action promised by the Agency for Healthcare Research and Quality was “the development and dissemination of evidence-based, best safety practices to provider organizations.” In addition to the multiple recommendations to improve patient safety, the report from the Agency for Healthcare Research and Quality included a review chapter on sleep, fatigue, #
and medical errors. **
There is evidence that the issue of fatigue in health care is coming to prominence on a national level. In April 2001, Public Citizen (a consumer and health advocacy group) and a consortium of interested parties petitioned the Occupational Safety and Health Administration to implement new regulations on resident work hours (table 1
). The primary intent of the regulations is to provide more humane working conditions, which the petitioners declare will result in a better standard of care for all patients. Also, the Patient and Physician Safety and Protection Act of 2001, which would limit resident physician work hours, was introduced in Congress. Recently, the Accreditation Council on Graduate Medical Education, the accrediting organization for residency training programs in the United States, has approved common program requirements for resident duty and rest hours that will take effect in July 2003. ††
The potential impact of sleep loss and fatigue, specifically among anesthesiologists, has received only sporadic attention. 3,4
The cognitive demands of intraoperative patient care requires an iteration of data collection, evaluation of its relevance to patient status, development and implementation of plans to maintain the desired patient status, and monitoring the outcome of interventions. These complex tasks require sustained attention or “vigilance” and are particularly vulnerable to the effects of fatigue. 5–8
The purpose of this article is to review the physiology of prolonged work cycles and fatigue, to relate this to the work milieu of the practice of anesthesiology, and suggest economically feasible recommendations to mitigate the effects of fatigue.
The Risks: Safety, Performance, and Health
Sleep loss and disruption of circadian rhythm that result from arduous work schedules can lead to reduced safety, performance, and health. While some of these outcomes are well documented, much remains to be learned about the short- and long-term effects of sleep and circadian disruption. The following nonmedical examples of the safety, performance, and health risks associated with around-the-clock operations illustrate the increasing human and economic costs related to ignoring the effects of these physiologic disruptions.
There have been several high-profile accidents where fatigue was identified as either causal or contributory. For example, although alcohol is often cited as the central reason in the Exxon Valdez marine grounding, the National Transportation Safety Board investigation identified fatigue as one of the probable causes of the accident. 9
Similarly, circadian factors were identified as contributing to the errors that resulted in the nuclear accidents at Three Mile Island and Chernobyl. 10,11
Fatigue resulting from the work–rest patterns of managers was also acknowledged as an important component of the flawed decision-making that contributed to the space shuttle Challenger
Fatigue-related accidents have been identified in every mode of transportation and can be found in many around-the-clock operational settings. Clearly, there are a variety of adverse outcomes such as economic costs, disrupted service, injuries, and even fatalities that result from these accidents. For example, the Exxon Valdez grounding was associated with environmental cleanup operations and legal cases involving billions of dollars, and Space Shuttle operations were suspended for several years after the Challenger disaster.
Fatigue-related safety risks affect us at both individual and societal levels. A recent poll by the National Sleep Foundation indicated that one of two drivers reported having driven while drowsy in the past year, ‡‡
and one of five acknowledged having “nodded off” while driving. Fatigue contributes to 100,000 crashes annually that result in 76,000 injuries and 1,550 fatalities, according to estimates by the National Highway Traffic Safety Administration. 13
Recently, an international group of scientists estimated that fatigue is causal in 15–20% of all transportation accidents, that official statistics underestimate the scope of the problem, and that fatigue exceeds the combined contribution of alcohol and drugs in transportation accidents. 14
Fatigue caused by sleep loss and circadian disruption can degrade performance and reduce many aspects of human capability. 15
Known performance effects include reduced attention–vigilance, impaired memory and decision-making, prolonged reaction time, and disrupted communications. 16–20
These degraded performance outcomes create a situation where there is increased risk for the occurrence of errors, critical incidents, and accidents. 15
Fatigue also creates increased performance variability, with cyclic reductions in alertness and performance. 21
Fatigued workers have a tendency to slow down work processes to maintain accuracy, a classic effect known as the speed-accuracy trade-off. 22
It takes only a moment of reduced performance during a critical task to have a negative outcome. Even if a lapse in performance occurs during a noncritical task, the system vulnerability shifts to a less safe state.
Fatigue-related accidents are sometimes considered to be a result of falling asleep. Performance gaps can be the result of these “microsleeps,” which are brief, uncontrolled, and spontaneous episodes of physiologic sleep. 8
There can be significant performance reductions that are sufficient to create safety risks prior to and immediately after the occurrence of a microsleep. 23,24
Slowed cognitive throughput, reduced memory, slowed reaction time, lowered optimal responding, and attention lapses can create an increased opportunity for errors to occur. 25
Consider the circumstance where an anesthesiologist's response to an alarm is slowed and an inappropriate decision guides an incorrect action. The practitioner may have been “awake,” but fatigue-related performance decrements could be contributory to the occurrence of any error, incident, or accident that resulted from the action.
The decrement in psychomotor performance resulting from sleep deprivation have been correlated with those resulting from the impairments associated with ethanol ingestion. 26
Performance on a hand–eye tracking task declined such that the impairment was equivalent to a blood alcohol level of 0.05% after 17 h of wakefulness. At 24 h of sustained wakefulness, the impairment in psychomotor function was equivalent to a blood alcohol concentration of 0.1%, at or above the legal limit for driving in most states. These data could be useful to help quantify fatigue-related effects with a drug that the public and policy makers better understand.
Specific clinical skills of importance to the practice of anesthesiology deteriorate as a result of fatigue. On a simulated monitoring task where subjects were asked to monitor and record the time of significant deviation of clinical variables (e.g
., heart rate, blood pressure), Denisco et al
. reported lower “vigilance scores” in the group that had been on call. 27
The ability to interpret electrocardiographic changes and to do simple mathematical calculations is compromised among sleep-deprived house officers. 28
The speed and quality of intubation was diminished among emergency department physicians working the night shift as compared with their performance while working during the day. 29,30
Many of the fatigue-related decrements in performance identified in residents are potentially worse in older physicians. Aging is associated with a tendency toward early awakening, an exaggerated dip in arousal midafternoon, and a decreased tolerance of late-night and shift work. 31
The unique demands of night call on older anesthesiologists are more onerous than those found in other specialties. 32
Among recently retired anesthesiologists, night call was identified as the most stressful aspect of anesthetic practice and the most important reason for retirement. 33,34
Beyond the safety risks and performance decrements associated with sleep loss and circadian disruption, there are a variety of personal health concerns. Several studies have shown that long-term exposure to shift work represents an independent risk factor for the development of both gastrointestinal and cardiovascular diseases. 35–39
A recent study found that women working the night shift had a 60% greater risk for breast cancer compared with women who never worked the late shift. 40
There is evidence that some adverse pregnancy outcomes are related to working conditions. 41
A meta-analysis of 29 studies, including more than 160,000 women, evaluated the association of physically demanding work, prolonged standing, long work hours, and cumulative “fatigue score” with preterm delivery, pregnancy-induced hypertension, and small-for-gestational-age infants. There was a positive association between physically demanding work and preterm births, pregnancy-induced hypertension, and delivery of small-for-gestational-age infants. Shift work alone was found to increase the incidence of preterm births. 41
There is evidence that sleep restriction alters physiologic function. Significant detrimental effects on immune function can be found after a few days of total sleep deprivation or after several days of partial sleep loss. 42,43
Sleep restriction of 4 h per night for six nights is associated with harmful effects on carbohydrate metabolism and endocrine function. 44
This degree of sleep restriction resulted in abnormal glucose tolerance, decreased thyrotropin concentrations, increased evening cortisol concentrations, and increased sympathetic nervous system activity (as measured by heart rate variability). Sleep deprivation and circadian disruption affect cerebral metabolic and cognitive function. In a study of changes in regional cerebral glucose utilization (i.e
., positron emission tomography) during 85 h of consecutive sleep loss, decreases in cerebral metabolic rate were observed primarily in the thalamus and prefrontal and posterior parietal cortices. Alertness and cognitive performance declined in association with these brain deactivations. 45
A recent study of aircrew members suggests there may be a linkage between long-term exposure to time-zone changes (i.e
., circadian disruption), temporal lobe atrophy, and deficits in learning and memory. 46
Investigations using functional magnetic resonance imaging technology contradict some of the aformentioned findings and reveal compensatory changes of increased activation in the prefrontal cortex and parietal lobes during verbal learning after sleep deprivation. 47–50
Studies show altered mortality with sleep loss and circadian disruption. Circadian disruption in hamsters and Drosophila
reduce life span from 11 to 15%. 51,52
A prospective investigation of more than one million individuals conducted by the American Cancer Society found that men who reported “usual” daily sleep times of less than 4 h were 2.8 times more likely to have died within a 6-year follow-up as men who obtained 7.0–7.9 h of sleep. 53
The risk for women was increased by 48%. Conversely, men and women who reported sleeping 10 h or more per day had about 1.8 times the mortality rate of those who reported 7.0–7.9 h of sleep.
Physiologic Factors that Underlie Fatigue
The two primary determinants that underlie fatigue and interact in a dynamic manner are sleep homeostasis and circadian rhythms. 54
An individual's level of alertness (e.g
., on the job) or potential for sleep (e.g
., during a rest period) will be determined by a complex interaction of these factors. Performance and alertness decrements may occur when either of these elements is disrupted. 55
Factors other than fatigue, such as workload, environment, stress, boredom, motivation, and professionalism, also influence the ability to perform. 4
In addition, there are large interindividual differences on the effects of fatigue. 56
The Sleep Factor.
Sleep serves a vital physiologic need. 57
Like other basic physiologic requirements such as food and water, sleep plays a fundamental role in survival. Sleep homeostasis is the balance between sleep need and quality and quantity of sleep obtained by an individual. On average, the adult human requirement for sleep appears to be greater than 8 h (8 h:14 min) per 24-h period. 58,59
The range of sleep need varies from 6 to 10 h, and this requirement is probably genetically determined and cannot be “trained” to a different sleep need. 60
Estimates suggest that most American adults obtain about 1–1.5 h less sleep than needed. §§
This lost sleep accumulates to produce a “sleep debt.”8,58
For example, an individual who obtains 1.5 h less sleep per night over a 5-day work week will begin the weekend with 7.5 h of sleep debt. This deficit is roughly equivalent to the loss of a full night of sleep and requires about two nights of at least 8 h of sleep for recovery. 20
Sleep debts are not repaid hour for hour, but instead through an increase in deep sleep or nonrapid eye movement stages 3 and 4. 20
A variety of factors can affect sleep quantity and quality. Perhaps some of the most dramatic changes in sleep occur as a normal function of aging. Approaching age 50 and beyond, sleep becomes more disrupted with frequent awakenings. There are reduced amounts of deep sleep, and sleep becomes less consolidated. 61
Nocturia in men and menopausal symptoms in women are likely to contribute to sleep disturbances in older individuals. There are also age-related increases in complaints of insomnia and depression that negatively impact sleep. Sleep need does not necessarily decrease with age, and increased daytime sleepiness can be the consequence of reduced sleep quantity and quality. There have been no formal studies assessing whether these changes in sleep quantity and quality affect the performance of older anesthesia providers.
There are approximately 90 known sleep disorders that have been described and classified in a diagnostic nosology. 62
The causes for these disorders range from physiologic to psychological to environmental. Some sleep disorders are relatively prevalent in the population and have well-documented negative effects on waking alertness and performance. 63–65
Often, the affected individual is unaware of their disorder, and the bed partner may be the first to identify the problem. Obstructive sleep apnea is a common example of a sleep disorder that has implications in operational settings. There are many health consequences associated with sleep apnea, but, in addition, it has been shown to be associated with a twofold to sevenfold increase in risk for automobile accidents. 66,67
Consistent with this, Powell et al
. demonstrated that individuals with mild to moderate sleep apnea had a decrement in performance equivalent to that of an individual with a blood alcohol concentration of 0.05–0.08 g/dl. 68
Alcohol is the most widely used sleep aid, and its use is typically intended to provide relaxation or to promote sleep. 69
However, alcohol is a potent suppressor of rapid-eye-movement sleep, especially in the first half of the night. 70
As the blood alcohol concentration declines, there is a rapid-eye-movement rebound in the second half of the night, producing more rapid-eye-movement sleep with increased awakenings and a reduction in total sleep time. Therefore, although alcohol may be consumed as an aid to promote sleep, it actually has the potential to significantly disrupt it.
Sleep can be measured both subjectively, using a variety of questionnaires, and objectively, using standardized physiologic measures. Generally, humans are inaccurate subjective reporters of alertness. 71,72
Individuals can report being awake and alert, when physiologically they could be asleep in minutes. This discrepancy between self or subjective reports and physiologic levels of alertness can have significant operational implications. First, it indicates that verbal reports of subjective alertness are generally unreliable sources to determine an individual's fitness for duty. Second, an individual with the subjective experience and report of being alert might be less likely to engage an alertness strategy (e.g
., strategic caffeine or nap opportunity, as discussed in the section on alertness strategies) that could address the underlying disturbed physiologic state. It is important to note that when an individual reports a subjective experience at either end of the continuum (e.g
., extreme fatigue or sleepiness), it is more likely to reflect the actual physiologic status. 71
The Circadian Factor.
The human circadian (circa
= around, dies
=a day) timekeeper is located in the suprachiasmatic nucleus (SCN) of the hypothalamus and is an active pacemaker for internal 24-h rhythms. 73
The most powerful and well-studied synchronizer of the SCN is light, while melatonin, a complementary synchronizer of the SCN, is secreted by the pineal gland at night and is suppressed by light. 74
A retino-hypothalamic pathway to the SCN provides direct access for light and dark exposure to affect the circadian clock. The daily light–dark cycle entrains the SCN to its 24-h pattern. The natural tendency of the circadian clock is to run slightly slower (24.18 h) than our 24-h day, 75
which is the physiologic rationale to phase delay rather than phase advance work–rest cycles. In other words, rotation of shift assignments going from days to evenings to nights has a circadian physiologic justification, but this has not been a major solution to the problems of shift work. 76
The SCN controls a broad range of physiologic, behavioral, and mood functions. For example, it drives the 24-h sleep–wake pattern, daily digestive activity, hormone secretions, and mood, as well as alertness and performance levels. 55
The underlying mechanisms regulating the cellular neurobiology of sleep are important and complex but are beyond the scope of this article and are reviewed elsewhere. 77,78
Humans are programmed for increased sleepiness at two approximate times each day: 3–7 am and 1–4 pm 55,79
The circadian nadir, associated with the lowest levels of activity, alertness, and performance and greatest vulnerability to errors, incidents, and accidents, occurs at about 3–7 am. As an example, it has been well established that a peak in fatigue-related single car accidents, without alcohol involvement, occurs roughly between 3 and 5 am. 80–83
The complementary periods of maximal alertness occur at approximately 9–11 am and 9–11 pm.
Rotating to a different work schedule such as the night shift or crossing time zones disrupts the entrained circadian pattern. Jet lag will occur for days as the SCN synchronizes to the new local environmental cues (e.g
., the light–dark cycle) after traveling through several time zones. Night work creates a different challenge by its disruption of the circadian pattern. When individuals are working at night, circadian programming drives sleep, and when they attempt to sleep during the day, the circadian clock is programmed for wakefulness. Generally, studies have shown that “adaptation” does not occur despite prolonged exposure to night work. 84
After an all-night shift, the individual returns home and is exposed to daytime light cues that maintain SCN programming for a day–active, night–sleep pattern. Social factors such as interacting with family and performing duties that can only be done during daytime hours also play a major role in the inability to readily alter the endogenous rhythm to night work. 85
A study of unintentional dural puncture during epidural anesthesia has provided further support for a circadian difference in clinical performance among anesthesiologists. 86
The risk of dural puncture was greater at night (midnight to 8:00 am) and among inexperienced practitioners. Although this investigation is supportive of a negative circadian effect on performance, it was limited by the low frequency of unintentional dural punctures as well as by not including important covariants such as patient body habitus and physician workload.
Risks to Patients and Healthcare Providers
Subjective data from surveys of anesthesiologists 87–89
and other healthcare personnel 90,91
reveal that fatigue is perceived by practitioners as creating a significant risk for patients. In two studies of anesthesia caregivers, more than 50% reported having committed an error in medical judgment that they attributed to fatigue. 88,89
Cooper et al
., using the critical incident method of evaluating anesthetic errors, estimated that human error played a role in more than 80% of anesthetic mishaps and that fatigue was an associated factor in 6% of reported critical incidents. 92
In a survey of New Zealand anesthesiologists, 58% reported that they exceeded their self-defined limit for safe continuous administration of anesthesia, and 86% reported having committed a fatigue-related error. 87
Data from 5,600 reports of critical incidents to the Australian Incident Monitoring Study from 1987 to 1997 revealed that fatigue was listed as a contributing factor in 152 reports (3%). 93
These data suggest that there is a specific association between fatigue and medication errors (syringe swaps) occurring at circadian low points (2–4 am). The conclusions from these studies are limited since they are based on retrospective, self-report data, but the majority of respondents consistently indicate that quality of care is compromised and that some errors are attributed to working while fatigued.
A recently litigated case clearly demonstrates the effect of fatigue in the operating room. An anesthesiologist was accused of literally falling asleep while his patient, an 8-yr-old child, died. 94
During the litigation, testimony was given that the defendant had been repeatedly warned by supervisors about falling asleep during operations. He was convicted of criminal medical negligence and acquitted of felony counts of reckless manslaughter and criminally negligent homicide. The conviction was later overturned on a technicality as the statute of limitations on the misdemeanor charge had expired. Interestingly, using NTSB methods of accident analysis (table 2
), the majority of errors and accidents that occur in the healthcare environment are likely to have fatigue as a contributing factor based on work schedules alone. 95
There is a well-documented association between long work hours or late work and an increased potential for injury from industrial accidents. The risk of an accident increases exponentially with each hour after the ninth consecutive hour of work. 96
This effect is exaggerated when extended work hours occur on a late shift. Needle stick injuries, among the most frequent of the occupational injuries suffered by anesthesia providers, are usually self-inflicted, occur during disposal or recapping of sharp devices, and are associated with carelessness from fatigue. Among residents and medical students, there is a 50% greater risk of sustaining a bloodborne pathogen exposure during night work than during days. 97
Studies have extended the previously described risks associated with drowsy driving to physicians. 98–100
Fatigued physicians are at risk for accident and injury as they drive home after completing their duty cycle. In a study of an academic pediatrics department, 49% of residents (averaging 2.7 h of sleep while on call) reported falling asleep at the wheel compared with 13% of faculty members. These residents had almost twice as many traffic citations for moving violations than did the better-rested faculty members. 98
Residents in pediatrics and emergency medicine have been reported to suffer twice the expected number of accidents, in many cases while driving home after being on call. 98–100
In a more recent retrospective study of driving-accident risk among anesthesia trainees, only eight accidents were reported, which did not differ from the control. 101
The authors attributed this finding to the “protective” circadian alerting effect during the drive home (8–10 am).
The effect of work hours on pregnancy outcomes in female resident physicians has been evaluated. These data reveal that there is an increased incidence of pregnancy-induced hypertension, 102
preterm labor, 103
and small-for-gestational-age infants. 104
Another study documented an association between preterm delivery and residents who worked more than 100 h per week. 105
The Death of Libby Zion and Work Hours Regulations
As in other “24/7” settings, health care has experienced some high-visibility tragedies where fatigue was identified as causal or contributory. 94,106–110
The most often referenced example is the death of Libby Zion, which focused attention on work hours and supervision of resident physicians. Although there has been much debate 106–110
as to whether her death was related to the fatigued healthcare providers who cared for her, a high-profile commission was formed in 1987 that issued recommendations to limit house staff work hours and to increase their supervision. These recommendations became part of the revised Section 405 of the New York State Health Code (table 3
The Accreditation Council on Graduate Medical Education and its Residency Review Committees developed institutional and program requirements for resident supervision, duty hours, and work environment. ∥∥
Institutions were required to ensure that each training program established formal policies for resident duty hours that fostered education and facilitated care of patients. The Residency Review Committee for Anesthesiology specifies that in-house duty hours should not be excessive and suggested that, on average, residents should have “at least 1 day out of 7 free of routine responsibilities and be on call in the hospital no more often than every third night.” Finally, if these policies are followed, residents are prohibited from “administering anesthesia on the day after in-house overnight call.”
Subsequent evaluation suggests that the regulation of resident duty hours may not be the panacea that alone improves patient outcome. Data collected before and after implementation of the New York regulations found that there were no differences in in-hospital mortality rates, rate of patient transfer to intensive care units, or length of stay, and that there were more patients having at least one complication. 112
Petersen et al
. demonstrated that preventable adverse events were more common when cross-covering house staff were caring for patients compared with times when a resident knowing the patient was involved with the care. 113
A follow-up study revealed that improving the quality of communication during patient sign-outs improved the quality of care. 114
This suggests that during some circumstances, use of cross-covering residents to relieve tired house staff may introduce the possibility of more medical errors, but that these errors might be mitigated in other ways.
Research Related to Fatigue in Health Care
There is little consensus among studies on the effects of fatigue on the performance of healthcare personnel. 3,4,115–119
Previous authors have detailed the methodologic problems inherent in most of the studies (table 4
It is not surprising that the interpretation of this body of data are contradictory given these methodologic problems.
There is a tremendous inconsistency across studies in the definitions used for fatigue or sleep loss. Although studies of partial sleep deprivation consistently reveal that measurable performance decrements occur if sleep is restricted by as little as 1 h, 120
Bartle et al
. used 4 h of sleep on the night prior to performance testing to distinguish between fatigued and rested subjects. 121
There is no scientific basis for the assumption that sleep times of greater than 4 h should be considered as “rested.” Many other investigations use similarly arbitrary study conditions. 27,122–130
An additional source of inconsistency in previous studies is the lack of a standardized instrument to test performance. A wide range of measures such as simple psychomotor tests and written standardized tests have been used. 131,132
Only a few studies have used face-valid, healthcare-related tasks such as monitoring tasks 27
or tracheal intubation. 30
Also, measurement of “on the job” work is complicated by a paucity of tested metrics to adequately judge the components of satisfactory performance. This lack of standardization limits the ability to quantify the impact of fatigue in healthcare settings. A “lack of significant” findings in a study may be interpreted as a demonstration that fatigue does not represent a performance or safety risk, but the findings may be due to methodologic flaws or the use of inappropriate measures rather than a valid assessment of the effects of fatigue.
There are a growing number of well-controlled, scientifically sound investigations of healthcare personnel that test for performance impairment secondary to fatigue. Results obtained with virtual-reality simulators have shown significant reductions in the performance of sleep-deprived surgeons. 133,134
In two studies of surgical dexterity, sleep-deprived surgeons (defined as zero 134
or < 3 h of sleep 133
) made more errors and operated more slowly than they did in the rested condition. Both speed and accuracy were negatively affected by sleep deprivation.
In a recent study of anesthesia trainees designed to mitigate the core methodologic flaws found in many previous studies, 72
residents were tested in each of three experimental conditions in the sleep laboratory (a within-subjects design). In the baseline condition, residents were assigned to a typical general operating room rotation without any on-call period in the previous 48 h. In the postcall condition, subjects were studied after a 24-h in-hospital call period while rotating on a clinically busy service such as obstetric anesthesia or the intensive care unit. The third condition, termed sleep extended
, attempted to produce a truly rested control condition by permitting four consecutive nights of increased sleep. Subjective measures and a standard physiologic measure of daytime sleepiness, the Multiple Sleep Latency Test, were used to quantify differences among the three conditions. 135,136
There were three major findings of this study. First, there were no significant differences found in physiologic sleepiness between the baseline and postcall conditions. This was interpreted to demonstrate that the residents were chronically sleep-deprived to the extent that their baseline condition was equivalent to a postcall level of sleepiness. Second, in the extended condition, alertness levels were significantly increased compared with the baseline and postcall conditions. The subjects went from a level of sleepiness associated with severe sleep loss and sleep disorders (i.e
., sleep apnea and narcolepsy) to a normal range of alertness after four consecutive nights of increased sleep. These observations cast doubt on prior studies that demonstrated no significant differences comparing a “baseline” condition to a “postcall” condition. Such findings more likely indicate that the “control” condition does not accurately reflect the rested state. Third, there was a significant discrepancy between subjective reports of fatigue and alertness and objective measures of physiologic status. Subjects were asked to provide a subjective rating of sleepiness for comparison to their physiologic measure as determined by their Multiple Sleep Latency Test score. On more than half of the occasions, when subjects reported they had been awake, they were actually asleep. This was a simple and straightforward demonstration that increased sleep is the most direct intervention that can improve waking levels of alertness.
Consistent Findings in the Literature of Healthcare Personnel
Survey Data on Work Hours and Fatigue-related Error.
Several surveys have been performed evaluating work hours of anesthesia caregivers, including nurse anesthetists, residents, and practitioner anesthesiologists. 87,89,137,138
Residents work longer hours (60–70 h/week) than their nursing and physician specialist counterparts (47.5– 52 h/week). This is in marked contrast to the surgical subspecialties that commonly report 80–100 h work weeks while caring for patients. 90,139–141
There are consistent findings that report impairment of mood as work is extended or done at night. 14,28–30,121–124,128,130,142–151
Mood is typically measured using various subjective scales anchored at either end with descriptive words. In these studies, as time awake increases, levels of anger, confusion, anxiety, depression, and fatigue increase while positive emotions such as happiness and vigor decrease. The effects of negative moods on patient care have not been measured directly.
Results from a Meta-analysis.
Pilcher and Huffcutt performed a meta-analysis using data from 19 of 56 published studies that met their acceptance criteria. 14
The studies, assessing the effects of sleep deprivation on performance, included both medical and nonmedical participants (1,932 total sample size). Short-term total sleep deprivation was defined as less than or equal to 45 h; long-term total sleep deprivation, more than 45 h; and partial sleep deprivation, a sleep period of less than 5 h in a 24-h period. When all sleep deprivation categories were combined, the sleep-deprived subjects performed at a level 1.37 SDs lower than rested subjects, and the greatest impact was on mood and cognitive measures, with little change in motor performance. Compared with short- or long-term sleep deprivation, partial sleep deprivation had the greatest affect on mood and cognitive performance. Performance on complex and long tasks was reduced more by short-term sleep deprivation than performance on simple, short tasks.
Managing Alertness in Health Care: A Proposed Solution
The two principal barriers to change in the healthcare work environment include its history and its complex economics. Tradition, or “that's the way its always been done,” is a position that has impeded change. Economic and workforce limitations affect all aspects of the healthcare system and must be directly addressed if any potential change is to be accomplished. Reduction of fatigue-related risks and enhancement of patient and provider safety poses complicated challenges. There are diverse operational requirements (e.g
., job tasks, shift schedules), individual differences (e.g
., age, experience), and complexity of the physiologic factors that preclude any simple or single solution. Given the complexity of the challenges, a comprehensive approach to managing alertness offers the greatest opportunity for change. A comprehensive approach involves at least the following four components: education, alertness strategies, scheduling policies, and healthy sleep. 152
The foundation for any change in fatigue-related risks begins with education. Basic knowledge of sleep medicine is critical to understanding the physiologic factors that underlie fatigue and the risks of performing in suboptimal conditions and for addressing widely held misconceptions about sleep. During 8 yr or more of medical school and residency, it is not uncommon for trainees to receive little or no information regarding sleep, sleep disorders, and related topics. 153
Lacking this knowledge, physicians are unlikely to appreciate the need for change. Successful educational modules have been developed for other high-risk domains that could be used as models for health care. 154 ##
There are a variety of strategies that have been empirically validated to improve alertness and performance. Three examples include planned naps, strategic caffeine use, and good sleep habits.
Laboratory investigations have demonstrated that planned naps can improve subsequent alertness and performance. 155,156
A NASA field study evaluated the benefit of naps in the cockpit. 157
In this study, a 40-min nap increased performance by 34% and physiologic alertness by 54% compared with a no-nap condition. Table 5
shows straightforward alertness guidelines for napping. Planned naps provide one of the most direct and basic interventions for sleep deprivation and do not require training or technology for effective use.
Caffeine is the most widely used stimulant to maintain wakefulness. The strategic use of caffeine involves ingestion at times that will promote alertness and performance during periods of vulnerability. Generally, the pharmacologic onset of caffeine occurs about 15–30 min after ingestion and its effect lasts about 3–4 h, although tolerance may reduce its alerting effects. A significant performance and alertness boost can be obtained from 200 mg of caffeine, with positive effects at doses ranging from 100 to 600 mg. Caffeine has a variety of adverse actions, such as tremors and heart palpitations, that are dose-related and may limit its usefulness in higher concentrations. A recent report from the Institute of Medicine ***
provides guidelines on the operational use of caffeine.
Good Sleep Habits.
There are a variety of good sleep habits that can promote sleep quality and quantity at home or in the hospital. Examples of good sleep habits are listed in table 6
Other Drugs and Light Therapy.
Other alertness-enhancing drugs have been studied, especially by the military (e.g
., d-amphetamine, pemoline, modafinil). Modafinil is a schedule IV, nonamphetamine, alertness-enhancing drug used in the treatment of narcolepsy. Off-label studies of the drug are underway among military personnel and shift workers (including physicians) to determine its effectiveness in the maintenance of alertness and performance. 158
Thus far, modafinil has been found to have significant alertness-promoting properties with fewer side effects and little effect on recovery sleep when compared with the amphetamine class of drugs. 159
The abuse potential for modafinil appears low, but it is unclear whether this drug would or should be accepted for use by medical professionals.
Melatonin, a hormone produced by the pineal gland, has been claimed by some as a panacea for jet lag and for the problems associated with shift work. It has sleep-promoting effects if given in doses of 0.3–80 mg throughout the biologic day. Daytime sleep latencies are shortened, and self-rated sleepiness increases. When melatonin is administered close to the habitual nocturnal sleep episode (when endogenous melatonin increases), its effects on sleep latency and subjective sleepiness have yielded inconsistent results. 74
Melatonin also has circadian phase-shifting effects with the direction of the phase shift dependent on the timing of its administration. This action can be masked by exposure to light, which exerts a much stronger influence on the human circadian pacemaker. 74
Studies evaluating the efficacy of melatonin in shift workers have yielded mixed results. 38,160
Since melatonin is considered a food supplement and not a drug by the US Food and Drug Administration, its purity and dose in commercial preparations are often unknown, and it has not undergone rigorous safety testing.
Light therapy is also being studied as a fatigue countermeasure for shift workers. 161–164
The implementation and timing of light therapy is complex and has to be correctly applied to have the desired effects. Whether use of light will become a viable countermeasure remains to be seen.
Individuals need to be educated about effective alertness strategies and should have an appropriate skepticism for unproven, anecdotal techniques. Policies should be developed to support the use of strategies (e.g., a hospital policy that permits appropriate napping) and explicit organizational assistance where needed (e.g., appropriate nap facility).Organized policies regarding alertness strategies have traditionally not been provided for healthcare personnel. For example, napping during work hours often carries a negative connotation, is often interpreted as a sign of laziness and may be prohibited in the workplace.
Issues related to scheduling are the most complex and contentious areas to be addressed in an alertness management program. Scheduling issues touch on resources, economics, lifestyle, and a range of other factors in addition to fatigue. Some of the specific physiologic issues that need to be taken into account in scheduling proposals include duty or shift length, off-duty or minimum rest opportunities, effects of cumulative fatigue due to consecutive duties or reduced rest opportunities, recovery periods, direction of shift rotation, start and end times of shifts, and circadian effects. Alteration of scheduling policies will require a complete and thoughtful assessment of all of the above factors, and this has not been done for any medical specialty.
Some industries have specific regulations or policies that dictate the details of these scheduling factors. Table 7
provides an example of the complicated scheduling practices of different industries. Even though regulated, it is important to note that there are large differences in the number of work hours that can accumulate per unit time across these transportation modes. Legislation and regulation have not played a role in healthcare work practices, with the notable exceptions of Section 405 of the New York State Health Code, which only limits work hours of resident physicians. In an attempt to track compliance with the New York regulations, a survey, based on unannounced inspections, revealed significant violations as 37% of all residents exceeded 85 h per week. Surgical residents grossly exceeded the work hour limit, as 60% worked 95 h or more per week. 165
Ironically, part of the State's response to these findings was to increase fines and to provide financial support for greater enforcement of the limitations rather than allocating more funds to increase hospital resources such as to provide for extra staffing. Section 405 has not been uniformly effective at reducing resident work hours, which demonstrates the need for a comprehensive approach to fatigue management.
Implementing work limitations will not be sufficient alone to effectively manage fatigue. Two examples from attempted scheduling strategies in health care illustrate these challenges. In the first investigation, a cross-cover float system was instituted to provide a protected block of sleep time during the night for on-call residents in an attempt to minimize sleep loss. 166
However, the on-call residents did not significantly increase their sleep time because they chose to use the time to catch up on paperwork and other tasks. In another intervention study, participants were provided a variety of strategies and information to improve alertness and performance during night shifts in the emergency department. 29
Following the intervention period, the participants did not significantly change their amount of sleep despite the opportunities provided by scheduling changes. Although by limiting work hours they were given the opportunity to increase their sleep, participants were just as sleep-deprived during the intervention phase as during the baseline condition. This suggests that there is no guarantee that individuals will benefit from interventions intended to increase the amount of sleep.
Given the current state of knowledge and the potential safety risks associated with sleep disorders, a comprehensive fatigue management program should include activities related to healthy sleep. These activities could take a variety of forms: (1) provide information on sleep disorders and resources for diagnosis and treatment; (2) provide tools to individuals that would promote their seeking evaluation where appropriate; or (3) identify individuals at risk in a more formal process (e.g., sleep apnea screening). When addressing healthy sleep, it is critical to include family outreach, as this resource may be essential in the ultimate identification and treatment of an individual at risk.
Potential for a Long-term Plan.
Sufficient scientific data and operational experience exist to recommend changes designed to reduce fatigue-related safety risks in anesthesiology. In addition, there is also a clear need to develop a broad, comprehensive, long-term plan to address fatigue in all healthcare settings. Anesthesiology could be on the cutting edge of such reform. Anesthesiologists have already provided leadership in the advancement of patient safety activities. 1,167
Inherent cultural attitudes and practices are the most challenging impediments to reforming the medical community's management of fatigue. A significant paradigm shift is necessary for universal recognition of fatigue-related risks and acceptance of scientifically validated approaches to improve safety and performance.
There are three steps that could be taken immediately. First, implement an education program regarding fatigue risks, physiologic factors, and effective countermeasures required for individuals throughout the healthcare system. Second, fully support the implementation of effective alertness strategies through education and appropriate institutional policies. Third, develop recommendations for work–rest schedules in health care similar to those that have been promulgated in aviation. 168
An outline of relevant scientific principles can be translated into recommendations that provide a structure that has appropriate flexibility to address unforeseen circumstances. Recommendations for work–rest schedules will have pertinence to the practice of anesthesiology just as they have in the high-hazard industry of aviation. Other safety-sensitive, high-performance industries have already established standards for their workers. For example, each of the transportation modes under the Department of Transportation have federally established hours-of-service regulations that limit a variety of relevant scheduling factors. There are few, if any, such restrictions placed on the work hours of physicians. The practice of anesthesiology and patient safety would benefit from similar strategies intended to reduce fatigue and promote safety in these demanding work environments. Because implementation of specific work limits would likely have significant economic and workforce implications on the practice of anesthesia in many settings, limits should not be arbitrarily promulgated without supporting data.
Experimental and survey data from medical and nonmedical settings demonstrate the impact that fatigue has on mood as well as psychomotor and cognitive performance. Recent work suggests that residents may be functioning in a baseline state of long-term sleep deprivation. 72
Disruption of the circadian clock during nightshift work is associated with decrements in performance of psychomotor tasks and with adverse health effects for personnel. The participants in most studies have been residents rather than older practitioners, and, therefore, the interaction between fatigue and aging remains unknown and must be elucidated.
Public debate on work hours for medical personnel has focused on trainees, and the New York State Health Code and Accreditation Council for Graduate Medical Education regulations are the only policies that have been implemented to limit work hours for healthcare practitioners. The current paradigm of work scheduling for nonresident anesthesiologists has generally remained unchanged, although the healthcare environment has undergone radical alterations over the past decade. As the public and federal agencies advocate practices to make health care safer, we should no longer ignore the accumulating body of data regarding the effects of fatigue and sleep deprivation on performance.
The “24/7” work demands for medical care impose a continuing challenge to all anesthesia providers. Fatigue has become a ubiquitous fact of our professional lives. Only by applying findings from scientific study and focused advocacy can we maintain a practice that is safe for the health of our patients and ourselves.
∥QuIC report to the President on Medical Errors available at: http://www.quic.gov/report
. Accessed July 1, 2002. Cited Here...
#In this manuscript, the word fatigue
is used as the summary or synthesis descriptor for the varied effects and labels used to describe the cognitive, behavioral, and physiologic outcomes of sleep loss and circadian disruption. The term sleepiness
as used in this manuscript describes the changes in physiologic alertness measured by standardized, objective sleep laboratory methodology. Cited Here...
**Jha AK, Duncan BW, Bates DW: Chapter 46. Fatigue, sleepiness and medical errors, Making Health Care Safer: A critical analysis of patient safety practices. Edited by Shojania KG, Duncan BW, McDonald KM, Wachter RM. Agency for Healthcare Research and Quality Evidence Report/Technology Assessment, No 43. Available at: http://www.ahrq.gov/clinic/ptsafety/chap46a.htm
. Accessed July 1, 2002. Cited Here...
††ACGME Work Group on Resident Duty Hours. Proposed common requirements for resident duty hours. Available at: http://www.acgme.org/index2.htm
. Accessed July 1, 2002. Cited Here...
‡‡National Sleep Foundation Web site. Summary of 2001 Sleep in America Poll. Available at: http://www.sleepfoundation.org/publications/2001poll.html
. Accessed July 1, 2002. Cited Here...
§§National Sleep Foundation Web site. Summary of 2001 Sleep in America Poll. Available at: http://www.sleepfoundation.org/publications/2001poll.html
. Accessed July 1, 2002. Cited Here...
∥∥ACGME common program requirements. Available at: http://www.acgme.org/index2.htm
. Accessed July 1, 2002. Cited Here...
##In 1998, the Committee on Patient Safety and Risk Management of the American Society of Anesthesiologists sponsored the production of an educational video entitled, “Fatigue: Implications for the Anesthesiologist.” The video provides basic information on the physiologic determinants of fatigue, describes some alertness strategies, and portrays some real-world scenarios demonstrating their application. The free video download is available at: http://gasnet.med.yale/videos/index.php
. Accessed July 1, 2002. Cited Here...
***Vanderveen JE (Chair), Committee on Military Nutrition Research: Caffeine for the sustainment of mental task performance: Formulations for military operations. Summary from the Institute of Medicine. Available at: http://www.iom.edu/iom/iomhome.nsf
./ Accessed July 1, 2002. Cited Here...
1. Kohn LT, Corrigan JM, Donaldson MS: To Err Is Human: Building a Safer Health System. Washington, DC, National Academy Press, 1999, pp 1–223
2. Eisenberg JM, Foster NE, Meyer G, Holland H: Federal efforts to improve quality of care: The Quality Interagency Coordination Task Force (QuIC). Jt Comm J Qual Improv 2001; 27: 93–100
3. Parker JB: The effects of fatigue on physician performance: An underestimated cause of physician impairment and increased patient risk. Can J Anaesth 1987; 34: 489–95
4. Weinger MB, Englund CE: Ergonomic and human factors affecting anesthetic vigilance and monitoring performance in the operating room environment. A nesthesiology 1990; 73: 995–1021
5. Paget NS, Lambert TF, Sridhar K: Factors affecting an anaesthetist's work: Some findings on vigilance and performance. Anaesth Intensive Care 1981; 9: 359–65
6. Krueger GP: Sustained work, fatigue, sleep loss and performance: A review of the issues. Work Stress 1989; 3: 129–41
7. Brendel DH, Reynolds CF3rd, Jennings JR, Hoch CC, Monk TH, Berman SR, Hall FT, Buysse DJ, Kupfer DJ: Sleep stage physiology, mood, and vigilance responses to total sleep deprivation in healthy 80-year-olds and 20-year-olds. Psychophysiology 1990; 27: 677–85
8. Dinges DF, Pack F, Williams K, Gillen KA, Powell JW, Ott GE, Aptowicz C, Pack AI: Cumulative sleepiness, mood disturbance, and psychomotor vigilance performance decrements during a week of sleep restricted to 4–5 hours per night. Sleep 1997; 20: 267–7
9. National Transportation Safety Board: Grounding of US Tankship Exxon Valdez on Bligh Reef, Prince William Sound Near Valdez, AK, March 24, 1989. Washington, DC, National Transportation Safety Board, 1990
10. Moss TH, Sills DL: The Three Mile Island Nuclear Accident: Lessons and Implications. New York, New York Academy of Sciences, 1981, pp 341
11. Report on the Accident at the Chernobyl Nuclear Power Station. Washington, DC, US Government Printing Office, 1987
12. Report of the Presidential Commission on the Space Shuttle Challenger Accident. Washington, DC, US Government Printing Office, 1986
13. Stutts JC, Wilkins JW, Vaughn BV: Why Do People Have Drowsy Driving Crashes? Input from Drivers who Just Did. Washington, DC, AAA Foundation for Traffic Safety, 1999
14. Akerstedt T: Consensus statement: Fatigue and accidents in transport operations. J Sleep Res 2000; 9: 395
15. Mitler MM, Dement WC, Dinges DF: Sleep medicine, public policy, and public health, Principles and Practice of Sleep Medicine, 3rd edition. Edited by Kryger MH, Roth T, Dement WC. Philadelphia, Saunders, 2000, pp 580–8
16. Dinges DF, Kribbs NB: Performing while sleepy: Effects of expermientally-induced sleepiness, Sleep, Sleepiness, and Performance. Edited by Monk TH. Chichester, Wiley, 1991, pp 97–128
17. Dinges DF: Probing the limits of functional capability: The effects of sleep loss on short-duration tasks, Sleep, Arousal, and Performance. Edited by Broughton R, Ogilvie R. Boston, Birkhauser, 1992, pp 177–88
18. Pilcher JJ, Huffcutt AI: Effects of sleep deprivation on performance: A meta-analysis. Sleep 1996; 19: 318–26
19. Dement WC, Vaughn C: The Promise of Sleep. New York, Delacorte Press, Random House, 1999, pp 1–542
20. Bonnet MH: Sleep deprivation, Principles and Practice of Sleep Medicine, 3rd edition. Edited by Kryger MH, Roth T, Dement WC. Philadelphia, Saunders, 2000, pp 53–71
21. Doran SM, Van Dongen HP, Dinges DF: Sustained attention performance during sleep deprivation: Evidence of state instability. Arch Ital Biol 2001; 139: 253–67
22. Craig A, Condon R: Speed-accuracy trade-off and time of day. Acta Psychol (Amst) 1985; 58: 115–22
23. Roth B, Nevsimalova S, Sagova V, Paroubkova D, Horakova A: Neurological, psychological and polygraphic findings in sleep drunkenness. Schweiz Arch Neurol Neurochir Psychiatr 1981; 129: 209–22
24. Valley V, Broughton R: The physiological (EEG) nature of drowsiness and its relation to performance deficits in narcoleptics. Electroencephalogr Clin Neurophysiol 1983; 55: 243–51
25. Dinges DF: An overview of sleepiness and accidents. J Sleep Res 1995; 4: 4–14
26. Dawson D, Reid K: Fatigue, alcohol and performance impairment (scientific correspondence). Nature 1997; 388: 235
27. Denisco RA, Drummond JN, Gravenstein JS: The effect of fatigue on the performance of a simulated anesthetic monitoring task. J Clin Monit 1987; 3: 22–4
28. Friedman RC, Bigger JT, Kornfeld DS: The intern and sleep loss. N Engl J Med 1971; 285: 201–3
29. Smith-Coggins R, Rosekind MR, Buccino KR, Dinges DF, Moser RP: Rotating shiftwork schedules: Can we enhance physician adaptation to night shifts? Acad Emerg Med 1997; 4: 951–61
30. Smith-Coggins R, Rosekind MR, Hurd S, Buccino KR: Relationship of day versus night sleep to physician performance and mood. Ann Emerg Med 1994; 24: 928–34
31. Reilly T, Waterhouse J, Atkinson G: Aging, rhythms of physical performance, and adjustment to changes in the sleep-activity cycle. Occup Environ Med 1997; 54: 812–6
32. Chevalley CT, Perneger T, Garnerin P, Forster A: Consequence of aging on medical activity: Does anesthesiology differ from other specialties? (abtract). A nesthesiology 2000; 93: A1205
33. Travis KW, Mihevc NT, Orkin FK, Zeitlin GL: Age and anesthetic practice: A regional perspective. J Clin Anesth 1999; 11: 175–86
34. Katz JD: Issues of concern for the aging anesthesiologist. Anesth Analg 2001; 92: 1487–92
35. Vener KJ, Szabo S, Moore JG: The effect of shift work on gastrointestinal (GI) function: A review. Chronobiologia 1989; 16: 421–39
36. Costa G: The impact of shift and night work on health. Appl Ergonomics 1996; 27: 9–16
37. Costa G: The problem: Shiftwork. Chronobiol Int 1997; 14: 89–98
38. Richardson G, Tate B: Hormonal and pharmacological manipulation of the circadian clock: Recent developments and future strategies. Sleep 2000; 23(suppl 3): S77–85
39. Knutsson A, Boggild H: Shiftwork and cardiovascular disease: Review of disease mechanisms. Rev Environ Health 2000; 15: 359–72
40. Davis S, Mirick DK, Stevens RG: Night shift work, light at night, and risk of breast cancer. J Natl Cancer Inst 2001; 93: 1557–62
41. Mozurkewich EL, Luke B, Avni M, Wolf FM: Working conditions and adverse pregnancy outcome: A meta-analysis. Obstet Gynecol 2000; 95: 623–35
42. Dinges DF, Douglas SD, Hamarman S, Zaugg L, Kapoor S: Sleep deprivation and human immune function. Adv Neuroimmunol 1995; 5: 97–110
43. Rogers NL, Szuba MP, Staab JP, Evans DL, Dinges DF: Neuroimmunologic aspects of sleep and sleep loss. Semin Clin Neuropsychiatry 2001; 6: 295–307
44. Spiegel K, Leproult R, Van Cauter E: Impact of sleep debt on metabolic and endocrine function. Lancet 1999; 354: 1435–9
45. Thomas M, Sing H, Belenky G, Holcomb H, Mayberg H, Dannals R, Wagner H, Thorne D, Popp K, Rowland L, Welsh A, Balwinski S, Redmond D: Neural basis of alertness and cognitive performance impairments during sleepiness. I. Effects of 24 h of sleep deprivation on waking human regional brain activity. J Sleep Res 2000; 9: 335–52
46. Cho K: Chronic ‘jet lag’ produces temporal lobe atrophy and spatial cognitive deficits. Nat Neurosci 2001; 4: 567–8
47. Drummond SP, Gillin JC, Brown GG: Increased cerebral response during a divided attention task following sleep deprivation. J Sleep Res 2001; 10: 85–92
48. Drummond SP, Brown GG, Stricker JL, Buxton RB, Wong EC, Gillin JC: Sleep deprivation-induced reduction in cortical functional response to serial subtraction. Neuroreport 1999; 10: 3745–8
49. Drummond SP, Brown GG, Gillin JC, Stricker JL, Wong EC, Buxton RB: Altered brain response to verbal learning following sleep deprivation. Nature 2000; 403: 655–7
50. Drummond SP, Brown GG: The effects of total sleep deprivation on cerebral responses to cognitive performance. Neuropsychopharm 2001; 25: S68–73
51. Penev PD, Kolker DE, Zee PC, Turek FW: Chronic circadian desynchronization decreases the survival of animals with cardiomyopathic heart disease. Am J Physiol 1998; 275: H2334–7
52. Klarsfeld A, Rouyer F: Effects of circadian mutations and LD periodicity on the life span of Drosophila melanogaster. J Biol Rhythms 1998; 13: 471–8
53. Kripke DF, Simons RN, Garfinkel L, Hammond EC: Short and long sleep and sleeping pills: Is increased mortality associated? Arch Gen Psychiatry 1979; 36: 103–16
54. Edgar DM, Dement WC, Fuller CA: Effect of SCN lesions on sleep in squirrel monkeys: Evidence for opponent processes in sleep-wake regulation. J Neurosci 1993; 13: 1065–79
55. Van Dongen HP, Dinges DF: Circadian rhythms in fatigue, alertness, and performance, Principles and Practice of Sleep Medicine, 3rd edition. Edited by Kryger MH, Roth T, Dement WC. Philadelphia, Saunders, 2000, pp 391–9
56. Harma M: Sleepiness and shiftwork: Individual differences. J Sleep Res 1995; 4: 57–61
57. Rechtschaffen A, Bergmann BM: Sleep deprivation in the rat: An update of the 1989 paper. Sleep 2002; 25: 18–24
58. Carskadon MA, Dement WC: Nocturnal determinants of daytime sleepiness. Sleep 1982; 5(suppl 2): S73–81
59. Wehr TA, Moul DE, Barbato G, Giesen HA, Seidel JA, Barker C, Bender C: Conservation of photoperiod-responsive mechanisms in humans. Am J Physiol 1993; 265: R846–57
60. Toh KL, Jones CR, He Y, Eide EJ, Hinz WA, Virshup DM, Ptacek LJ, Fu YH: An hPer2 phosphorylation site mutation in familial advanced sleep phase syndrome. Science 2001; 291: 1040–3
61. Bliwise DL: Normal aging, Principles and Practice of Sleep Medicine, 3rd edition. Edited by Kryger MH, Roth T, Dement WC. Philadelphia, Saunders, 2000, pp 26–42
62. Diagnostic Classification Steering Committee: The International Classification of Sleep Disorders: Diagnostic and Coding Manual. Edited by Thorpy MJ. Rochester, American Sleep Disorders Association, 1990, pp 1–396
63. Aldrich MS: Cardinal manifestations of sleep disorders, Principles and Practice of Sleep Medicine, 3rd edition. Edited by Kryger MH, Roth T, Dement WC. Philadelphia, Saunders, 2000, pp 526–33
64. Thorpy MJ: Classification of sleep disorders, Principles and Practice of Sleep Medicine, 3rd edition. Edited by Kryger MH, Roth T, Dement WC. Philadelphia, Saunders, 2000, pp 547–57
65. Partinen M, Hublin C: Epidemiology of sleep disorders, Principles and Practice of Sleep Medicine, 3rd edition. Edited by Kryger MH, Roth T, Dement WC. Philadelphia, Saunders, 2000, pp 558–79
66. George CF, Smiley A: Sleep apnea & automobile crashes. Sleep 1999; 22: 790–5
67. Masa JF, Rubio M, Findley LJ: Habitually sleepy drivers have a high frequency of automobile crashes associated with respiratory disorders during sleep. Am J Respir Crit Care Med 2000; 162: 1407–12
68. Powell NB, Riley RW, Schechtman KB, Blumen MB, Dinges DF, Guilleminault C: A comparative model: Reaction time performance in sleep-disordered breathing versus alcohol-impaired controls. Laryngoscope 1999; 109: 1648–54
69. Zarcone VP: Alcoholism and sleep, Pharmacology of the State of Alertness. Edited by Passonant P, Oswald I. Oxford, Pergamon Press, 1979, pp 9–38
70. Zarcone VP: Sleep hygiene, Principles and Practice of Sleep Medicine, 3rd edition. Edited by Kryger MH, Roth T, Dement WC. Philadelphia, Saunders, 2000, pp 657–61
71. Sasaki M, Kurosaki Y, Mori A, Endo S: Patterns of sleep-wakefulness before and after transmeridian flight in commercial airline pilots, Crew Factors in Flight Operations: IV. Sleep and Wakefulness in International Aircrews. Edited by Graeber RC. NASA Ames Research Center, Moffett Field, CA, National Aeronautics and Space Administration, 1986
72. Howard SK, Gaba DM, Rosekind MR, Zarcone VP: The risks and implications of excessive daytime sleepiness in resident physicians. Acad Med 2002; 77: 1019–25
73. Lydic R, Schoene WC, Czeisler CA, Moore-Ede MC: Suprachiasmatic region of the human hypothalamus: Homolog to the primate circadian pacemaker? Sleep 1980; 2: 355–61
74. Czeisler CA, Cajochen C, Turek FW: Melatonin in the regulation of sleep and circadian rhythms, Principles and Practice of Sleep Medicine, 3rd edition. Edited by Kryger MH, Roth T, Dement WC. Philadelphia, Saunders, 2000, pp 400–6
75. Czeisler CA, Duffy JF, Shanahan TL, Brown EN, Mitchell JF, Rimmer DW, Ronda JM, Silva EJ, Allan JS, Emens JS, Dijk DJ, Kronauer RE: Stability, precision, and near-24-hour period of the human circadian pacemaker. Science 1999; 284: 2177–81
76. Czeisler CA, Moore-Ede MC, Coleman RH: Rotating shift work schedules that disrupt sleep are improved by applying circadian principles. Science 1982; 217: 460–3
77. Siegel JM: Brainstem mechanisms generating REM sleep, Principles and Practice of Sleep Medicine, 3rd edition. Edited by Kryger MH, Roth T, Dement WC. Philadelphia, Saunders, 2000, pp 112–33
78. Jones BE: Basic mechanisms of sleep-wake states, Principles and Practice of Sleep Medicine, 3rd edition. Edited by Kryger MH, Roth T, Dement WC. Philadelphia, Saunders, 2000, pp 134–54
79. Czeisler CA, Khalsa SB: The human circadian timing system and sleep-wake regulation, Principles and Practice of Sleep Medicine, 3rd edition. Edited by Kryger MH, Roth T, Dement WC. Philadelphia, Saunders, 2000, pp 353–75
80. Mitler MM: Sleepiness and human behavior. Curr Opin Pulm Med 1996; 2: 488–91
81. Philip P, Mitler M: Sleepiness at the wheel: Symptom or behavior? Sleep 2000; 23(suppl 4): S119–21
82. Akerstedt T, Kecklund G: Age, gender and early morning highway accidents. J Sleep Res 2001; 10: 105–10
83. Akerstedt T, Kecklund G, Horte LG: Night driving, season, and the risk of highway accidents. Sleep 2001; 24: 401–6
84. Gander PH, Gregory KB, Connell LJ, Graeber RC, Miller DL, Rosekind MR: Flight crew fatigue IV: Overnight cargo operations. Aviat Space Environ Med 1998; 69: B26–36
85. Monk TH: Shift work, Priniciples and Practice of Sleep Medicine, 3rd edition. Edited by Kryger MH, Roth T, Dement WC. Philadelphia, Saunders, 2000, pp 600–5
86. Aya AG, Mangin R, Robert C, Ferrer JM, Eledjam JJ: Increased risk of unintentional dural puncture in night-time obstetric epidural anesthesia. Can J Anaesth 1999; 46: 665–9
87. Gander PH, Merry A, Millar MM, Weller J: Hours of work and fatigue-related error: A survey of New Zealand anaesthetists. Anaesth Intensive Care 2000; 28: 178–83
88. Gaba DM, Howard SK, Jump B: Production pressure in the work environment: California anesthesiologists’ attitudes and experiences. A nesthesiology 1994; 81: 488–500
89. Gravenstein JS, Cooper JB, Orkin FK: Work and rest cycles in anesthesia practice. A nesthesiology 1990; 72: 737–42
90. Defoe DM, Power ML, Holzman GB, Carpentieri A, Schulkin J: Long hours and little sleep: Work schedules of residents in obstetrics and gynecology. Obstet Gynecol 2001; 97: 1015–8
91. Wu AW, Folkman S, McPhee SJ, Lo B: Do house officers learn from their mistakes? JAMA 1991; 265: 2089–94
92. Cooper JB, Newbower RS, Long CD, McPeek B: Preventable anesthesia mishaps: A study of human factors. A nesthesiology 1978; 49: 399–406
93. Morris GP, Morris RW: Anaesthesia and fatigue: An analysis of the first 10 years of the Australian Incident Monitoring Study 1987–1997. Anaesth Intensive Care 2000; 28: 300–4
94. Pankratz H: Witness: Doctor Dozed. Denver, Denver Post, September 15, 1995, pp 1A
95. Rosekind MR, Gregory KB, Miller DL, Co EL, Lebacqz JV: Aircraft Accident Report: Uncontrolled Collision with Terrain, American International Airways Flight 808, Douglas DC-8, N814CK, U.S. Naval Air Station, Guantanamo Bay, Cuba, August 18, 1993, Report #NTSB/AAR-94/04. Washington, DC, National Transportation Safety Board, 1994
96. Hanecke K, Tiedemann S, Nachreiner F, Grzech-Sukalo H: Accident risk as a function of hour at work and time of day as determined from accident data and exposure models for the German working population. Scand J Work Environ Health 1998; 24(suppl 3): 43–8
97. Parks DK, Yetman RJ, McNeese MC, Burau K, Smolensky MH: Day-night pattern in accidental exposures to blood-borne pathogens among medical students and residents. Chronobiol Int 2000; 17: 61–70
98. Marcus CL, Loughlin GM: Effect of sleep deprivation on driving safety in housestaff. Sleep 1996; 19: 763–6
99. Steele MT, Ma OJ, Watson WA, Thomas HA, Jr, Muelleman RL: The occupational risk of motor vehicle collisions for emergency medicine residents. Acad Emerg Med 1999; 6: 1050–3
100. Kowalenko T, Kowalenko J, Gryzbowski M, Rabinovich A: Emergency medicine resident related auto accidents: Is sleep deprivation a risk factor? Acad Emerg Med 2000; 7: 1171
101. Dixon JM, Doyle PW: Are anaesthetic trainees a high-risk group for road accidents? Anaesthesia 1999; 54: 1232–3
102. Phelan ST: Pregnancy during residency: II. Obstetric complications. Obstet Gynecol 1988; 72: 431–6
103. Miller NH, Katz VL, Cefalo RC: Pregnancies among physicians: A historical cohort study. J Reprod Med 1989; 34: 790–6
104. Grunebaum A, Minkoff H, Blake D: Pregnancy among obstetricians: A comparison of births before, during, and after residency. Am J Obstet Gynecol 1987; 157: 79–83
105. Klebanoff MA, Shiono PH, Rhoads GG: Outcomes of pregnancy in a national sample of resident physicians. N Engl J Med 1990; 323: 1040–5
106. Asch DA, Parker RM: The Libby Zion case: One step forward or two steps backward? N Engl J Med 1988; 318: 771–5
107. McCall TB: The impact of long working hours on resident physicians. N Engl J Med 1988; 318: 775–8
108. Glickman RM: House-staff training: The need for careful reform. N Engl J Med 1988; 318: 780–2
109. Condon RE: Resident hours. Only work? Arch Surg 1989; 124: 1121–2
110. Condon RE: Sleep deprivation and resident call schedules. Curr Surg 1989; 46: 361–4
111. New York Ad Hoc Committee on Emergency Services: Final Report. Albany, New York State Department of Health, 1987
112. Laine C, Goldman L, Soukup JR, Hayes JG: The impact of a regulation restricting medical house staff working hours on the quality of patient care. JAMA 1993; 269: 374–8
113. Petersen LA, Brennan TA, O'Neil AC, Cook EF, Lee TH: Does housestaff discontinuity of care increase the risk for preventable adverse events? Ann Intern Med 1994; 121: 866–72
114. Petersen LA, Orav EJ, Teich JM, O'Neil AC, Brennan TA: Using a computerized sign-out program to improve continuity of inpatient care and prevent adverse events. Jt Comm J Qual Improv 1998; 24: 77–87
115. Asken MJ, Raham DC: Resident performance and sleep deprivation: a review. J Med Educ 1983; 58: 382–8
116. Samkoff JS, Jacques CH: A review of studies concerning effects of sleep deprivation and fatigue on residents’ performance. Acad Med 1991; 66: 687–93
117. Leung L, Becker CE: Sleep deprivation and house staff performance. Update 1984–1991. J Occup Med 1992; 34: 1153–60
118. Owens JA: Sleep loss and fatigue in medical training. Curr Opin Pulm Med 2001; 7: 411–8
119. Weinger MB, Ancoli-Israel S: Sleep deprivation and clinical performance. JAMA 2002; 287: 955–7
120. Tilley AJ, Wilkinson RT: The effects of a restricted sleep regime on the composition of sleep and on performance. Psychophysiology 1984; 21: 406–12
121. Bartle EJ, Sun JH, Thompson L, Light AI, McCool C, Heaton S: The effects of acute sleep deprivation during residency training. Surgery 1988; 104: 311–6
122. Hawkins MR, Vichick DA, Silsby HD, Kruzich DJ, Butler R: Sleep and nutritional deprivation and performance of house officers. J Med Educ 1985; 60: 530–5
123. Hart RP, Buchsbaum DG, Wade JB, Hamer RM, Kwentus JA: Effect of sleep deprivation on first-year residents’ response times, memory, and mood. J Med Educ 1987; 62: 940–2
124. Rubin R, Orris P, Lau SL, Hryhorczuk DO, Furner S, Letz R: Neurobehavioral effects of the on-call experience in housestaff physicians. J Occup Med 1991; 33: 13–8
125. Engel W, Seime R, Powell V, D'Alessandri R: Clinical performance of interns after being on call. South Med J 1987; 80: 761–3
126. Reznick RK, Folse JR: Effect of sleep deprivation on the performance of surgical residents. Am J Surg 1987; 154: 520–5
127. Deaconson TF, O'Hair DP, Levy MF, Lee MB, Schueneman AL, Codon RE: Sleep deprivation and resident performance. JAMA 1988; 260: 1721–7
128. Light AI, Sun JH, McCool C, Thompson L, Heaton S, Bartle EJ: The effects of acute sleep deprivation on level of resident training. Curr Surg 1989; 46: 29–30
129. Storer JS, Floyd HH, Gill WL, Giusti CW, Ginsberg H: Effects of sleep deprivation on cognitive ability and skills of pediatrics residents. Acad Med 1989; 64: 29–32
130. Ford CV, Wentz DK: The internship year: A study of sleep, mood states, and psychophysiologic parameters. South Med J 1984; 77: 1435–42
131. Godellas CV, Huang R: Factors affecting performance on the American Board of Surgery in-training examination. Am J Surg 2001; 181: 294–6
132. Stone MD, Doyle J, Bosch RJ, Bothe A, Jr, Steele G Jr: Effect of resident call status on ABSITE performance. American Board of Surgery In-Training Examination Surgery 2000; 128: 465–71
133. Grantcharov TP, Bardram L, Funch-Jensen P, Rosenberg J: Laparoscopic performance after one night on call in a surgical department: Prospective study. BMJ 2001; 323: 1222–3
134. Taffinder NJ, McManus IC, Gul Y, Russell RC, Darzi A: Effect of sleep deprivation on surgeons’ dexterity on laparoscopy simulator (research letter). Lancet 1998; 352: 1191
135. Richardson GS, Carskadon MA, Flagg W, Van den Hoed J, Dement WC, Mitler MM: Excessive daytime sleepiness in man: Multiple sleep latency measurement in narcoleptic and control subjects. Electroencephalogr Clin Neurophysiol 1978; 45: 621–7
136. Carskadon MA, Dement WC, Mitler MM, Roth T, Westbrook PR, Keenan S: Guidelines for the multiple sleep latency test (MSLT): A standard measure of sleepiness. Sleep 1986; 9: 519–24
137. Berry AJ, Hall JR: Work hours of residents in seven anesthesiology training programs. Anesth Analg 1993; 76: 96–101
138. Dercq JP, Smets D, Somer A, Desantoine D: A survey of Belgian anesthesiologists. Acta Anaesthesiol Belg 1998; 49: 193–204
139. Schwartz RJ, Dubrow TJ, Rosso RF, Williams RA, Butler JA, Wilson SE: Guidelines for surgical residents’ working hours: Intent vs reality. Arch Surg 1992; 127: 778–82; discussion 782–3
140. Daugherty SR, Baldwin DC: Sleep deprivation in senior medical students and first-year residents. Acad Med 1996; 71: S93–5
141. Thorpe KE: House staff supervision and working hours: Implications of regulatory change in New York State. JAMA 1990; 263: 3177–81
142. Wesnes KA, Walker MB, Walker LG, Heys SD, White L, Warren R, Eremin O: Cognitive performance and mood after a weekend on call in a surgical unit. Br J Surg 1997; 84: 493–5
143. Leonard C, Fanning N, Attwood J, Buckley M: The effect of fatigue, sleep deprivation and onerous working hours on the physical and mental wellbeing of pre-registration house officers. Ir J Med Sci 1998; 167: 22–5
144. Lingenfelser T, Kaschel R, Weber A, Zaiser-Kaschel H, Jakober B, Kuper J: Young hospital doctors after night duty: Their task-specific cognitive status and emotional condition. Med Educ 1994; 28: 566–72
145. Orton DI, Gruzelier JH: Adverse changes in mood and cognitive performance of house officers after night duty. BMJ 1989; 298: 21–3
146. Baldwin PJ, Dodd M, Wrate RW: Young doctors’ health: I. How do working conditions affect attitudes, health and performance? Soc Sci Med 1997; 45: 35–40
147. Friedman RC, Kornfeld DS, Bigger TJ: Psychological problems associated with sleep deprivation in interns. J Med Educ 1973; 48: 436–41
148. Wilkinson RT, Tyler PD, Varey CA: Duty hours of young hospital doctors: Effects on the quality of work. J Occup Pscyhol 1975; 48: 219–29
149. McManus IC, Lockwood DN, Cruickshank JK: The preregistration year: Chaos by consensus. Lancet 1977; 1: 413–7
150. Browne BJ, Van Susteren T, Onsager DR, Simpson D, Salaymeh B, Condon RE: Influence of sleep deprivation on learning among surgical house staff and medical students. Surgery 1994; 115: 604–10
151. Deary IJ, Tait R: Effects of sleep disruption on cognitive performance and mood in medical house officers. BMJ (Clin Res Ed) 1987; 295: 1513–6
152. Rosekind MR, Gander PH, Gregory KB, Smith RM, Miller DL, Oyung R, Webbon LL, Johnson JM: Managing fatigue in operational settings 2: An integrated approach. Behav Med 1996; 21: 166–70
153. Rosen RC, Rosekind M, Rosevear C, Cole WE, Dement WC: Physician education in sleep and sleep disorders: A national survey of U.S. medical schools. Sleep 1993; 16: 249–54
154. Rosekind MR, Gander PH, Connell LJ, Co EL: Crew Factors in Flight Operations X: Alertness Management in Flight Operations. NASA Technical Memorandum #208780. Moffett Field, CA, NASA Ames Research Center, 1999
155. Dinges DF, Orne MT, Whitehouse WG, Orne EC: Temporal placement of a nap for alertness: Contributions of circadian phase and prior wakefulness. Sleep 1987; 10: 313–29
156. Dinges DF, Broughton RJ, eds: Sleep and Alertness: Chronobiological, Behavioral, and Medical Aspects of Napping. New York, Raven Press, 1989, pp 1–322
157. Rosekind MR, Graeber RC, Dinges DF, Connell LJ, Rountree MS, Spinweber CL, Gillin KA: Crew Factors in Flight Operations IX: Effects of Planned Cockpit Rest on Crew Performance and Alertness in Long-Haul Operations. NASA Technical Memorandum #108839. Moffett Field, CA, NASA Ames Research Center, 1994
158. Caldwell JA Jr, Caldwell JL, Smythe NK3rd, Hall KK: A double-blind, placebo-controlled investigation of the efficacy of modafinil for sustaining the alertness and performance of aviators: A helicopter simulator study. Psychopharmacology (Berl) 2000; 150: 272–82
159. Buguet A, Montmayeur A, Pigeau R, Naitoh P: Modafinil, d-amphetamine and placebo during 64 hours of sustained mental work: II. Effects on two nights of recovery sleep. J Sleep Res 1995; 4: 229–41
160. Sharkey KM, Fogg LF, Eastman CI: Effects of melatonin administration on daytime sleep after simulated night shift work. J Sleep Res 2001; 10: 181–92
161. Horowitz TS, Cade BE, Wolfe JM, Czeisler CA: Efficacy of bright light and sleep/darkness scheduling in alleviating circadian maladaptation to night work. Am J Physiol Endocrinol Metab 2001; 281: E384–91
162. Czeisler CA, Dijk DJ: Use of bright light to treat maladaptation to night shift work and circadian rhythm sleep disorders. J Sleep Res 1995; 4: 70–3
163. Eastman CI, Boulos Z, Terman M, Campbell SS, Dijk DJ, Lewy AJ: Light treatment for sleep disorders: Consensus report. VI. Shift work. J Biol Rhythms 1995; 10: 157–64
164. Eastman CI, Martin SK: How to use light and dark to produce circadian adaptation to night shift work. Ann Med 1999; 31: 87–98
165. Bell BM: How the New York state regulatory environment has failed to reduce errors in health care, Proceedings of Enhancing Patient Safety Reducing Errors in Health Care. Rancho Mirage, CA, National Patient Safety Foundation, 1999, pp 298–301
166. Richardson GS, Wyatt JK, Sullivan JP, Orav EJ, Ward AE, Wolf MA, Czeisler CA: Objective assessment of sleep and alertness in medical house staff and the impact of protected time for sleep. Sleep 1996; 19: 718–26
167. Keats AS, Siker ES: International Symposium on Preventable Anesthetic Morbidity and Mortality (meeting report). A nesthesiology 1985; 63: 349–50
168. Dinges DF, Graeber RC, Rosekind MR, Samel A, Wegmann HM: Principles and guidelines for duty and rest scheduling in commercial aviation (NASA Technical Memorandum TM110404). Moffett Field, CA, NASA Ames Research Center, 1996
This article has been cited 25 time(s).
Journal of Cardiothoracic and Vascular AnesthesiaClosed-loop control of consciousness during lung transplantation: An observational studyJournal of Cardiothoracic and Vascular Anesthesia
Journal De Chirurgie
Evidence based arguments regarding work hours, sleep, and safety
Journal De Chirurgie, 141(3):
Annales Francaises D Anesthesie Et De ReanimationPrevalence and risk factors for substance abuse and dependence among anaesthetists: a national surveyAnnales Francaises D Anesthesie Et De Reanimation
Anasthesiologie Intensivmedizin Notfallmedizin SchmerztherapieSimulation as strategy for risk minimizing in AnesthesiaAnasthesiologie Intensivmedizin Notfallmedizin Schmerztherapie
ErgonomicsProspective memory failures as an unexplored threat to patient safety: results from a pilot study using patient simulators to investigate the missed execution of intentionsErgonomics
Journal of Clinical AnesthesiaConflict and its resolution in the operating roomJournal of Clinical Anesthesia
Fatigue and doctors
Hospital Medicine, 66(3):
AnaesthesiaA simulation design for research evaluating safety innovations in anaesthesiaAnaesthesia
'Safety in sleep': anaesthetists, patients and the European Working Time Directive
Sleep deprivation and fatigue in residency training: Results of a national survey of first- and second-year residents
Work hours regulations for house staff in psychiatry: Bad or good for residency training?
Academic Psychiatry, 32(1):
Canadian Journal of Anaesthesia-Journal Canadien D AnesthesiePerceived sleepiness in Canadian anesthesia residents: a national surveyCanadian Journal of Anaesthesia-Journal Canadien D Anesthesie
Annales Francaises D Anesthesie Et De ReanimationRest of safety: which stakes?Annales Francaises D Anesthesie Et De Reanimation
Academic Emergency MedicineQuality of emergency care on the night shiftAcademic Emergency Medicine
Canadian Medical Association Journal
Preparing physicians for the real world - Dr. Howard responds
Canadian Medical Association Journal, 171(7):
Human FactorsDifferences in day and night shift clinical performance in anesthesiologyHuman Factors
Clinical Gastroenterology and HepatologyFewer Polyps Detected by Colonoscopy as the Day Progresses at a Veteran's Administration Teaching HospitalClinical Gastroenterology and Hepatology
International Journal of Oral and Maxillofacial SurgeryOut-of-hours maxillofacial trauma surgery: a risk factor for complications?International Journal of Oral and Maxillofacial Surgery
Annals of Thoracic MedicineEffect of on-call-related sleep deprivation on physicians' mood and alertnessAnnals of Thoracic Medicine
Gastrointestinal EndoscopyDiagnostic and therapeutic yield is not influenced by the timing of small-bowel enteroscopy: morning versus afternoonGastrointestinal Endoscopy
Academic MedicineIntern to Attending: Assessing Stress Among PhysiciansAcademic Medicine
European Journal of Anaesthesiology (EJA)The impact of a single 24 h working day on cognitive and psychomotor performance in staff anaesthesiologistsEuropean Journal of Anaesthesiology (EJA)
AnesthesiologyFact and Fantasy about Sleep and AnesthesiologyAnesthesiology
© 2002 American Society of Anesthesiologists, Inc.
Publication of an advertisement in Anesthesiology Online does not constitute endorsement by the American Society of Anesthesiologists, Inc. or Lippincott Williams & Wilkins, Inc. of the product or service being advertised.