Fatigue in Anesthesia

Received from the Anesthesia Service, VA Palo Alto Health Care System, Department of Anesthesia, Stanford University School of Medicine, Palo Alto, California; the Department of Anesthesiology, Yale University School of Medicine, New Haven, Connecticut; and the Department of Anesthesiology, Emory University School of Medicine, Atlanta, Georgia.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. 1The 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.”∥2This 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. 3,4The 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. 5–8The 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.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. 9Similarly, circadian factors were identified as contributing to the errors that resulted in the nuclear accidents at Three Mile Island and Chernobyl. 10,11Fatigue 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 accident. 12Fatigue-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. 13Recently, 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. 14Fatigue caused by sleep loss and circadian disruption can degrade performance and reduce many aspects of human capability. 15Known performance effects include reduced attention–vigilance, impaired memory and decision-making, prolonged reaction time, and disrupted communications. 16–20These degraded performance outcomes create a situation where there is increased risk for the occurrence of errors, critical incidents, and accidents. 15Fatigue also creates increased performance variability, with cyclic reductions in alertness and performance. 21Fatigued workers have a tendency to slow down work processes to maintain accuracy, a classic effect known as the speed-accuracy trade-off. 22It 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. 8There can be significant performance reductions that are sufficient to create safety risks prior to and immediately after the occurrence of a microsleep. 23,24Slowed cognitive throughput, reduced memory, slowed reaction time, lowered optimal responding, and attention lapses can create an increased opportunity for errors to occur. 25Consider 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. 26Performance 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. 27The ability to interpret electrocardiographic changes and to do simple mathematical calculations is compromised among sleep-deprived house officers. 28The 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. 29,30Many 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. 31The unique demands of night call on older anesthesiologists are more onerous than those found in other specialties. 32Among recently retired anesthesiologists, night call was identified as the most stressful aspect of anesthetic practice and the most important reason for retirement. 33,34Beyond 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. 35–39A 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. 40There is evidence that some adverse pregnancy outcomes are related to working conditions. 41A 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. 41There 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. 42,43Sleep restriction of 4 h per night for six nights is associated with harmful effects on carbohydrate metabolism and endocrine function. 44This 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. 45A 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. 46Investigations 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. 47–50Studies show altered mortality with sleep loss and circadian disruption. Circadian disruption in hamsters and Drosophila reduce life span from 11 to 15%. 51,52A 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. 53The 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.The two primary determinants that underlie fatigue and interact in a dynamic manner are sleep homeostasis and circadian rhythms. 54An 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. 55Factors other than fatigue, such as workload, environment, stress, boredom, motivation, and professionalism, also influence the ability to perform. 4In addition, there are large interindividual differences on the effects of fatigue. 56Sleep serves a vital physiologic need. 57Like 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. 58,59The 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. 60Estimates suggest that most American adults obtain about 1–1.5 h less sleep than needed. §§This lost sleep accumulates to produce a “sleep debt.”8,58For 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. 20Sleep debts are not repaid hour for hour, but instead through an increase in deep sleep or nonrapid eye movement stages 3 and 4. 20A 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. 61Nocturia 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. 62The 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. 63–65Often, 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. 66,67Consistent 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. 68Alcohol is the most widely used sleep aid, and its use is typically intended to provide relaxation or to promote sleep. 69However, alcohol is a potent suppressor of rapid-eye-movement sleep, especially in the first half of the night. 70As 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. 71,72Individuals can report being awake and alert, when physiologically they could be asleep in minutes. This discrepancy between self or subjective and physiologic of alertness can have significant operational it that verbal of subjective alertness are to an individual's for an individual with the subjective and report of being be less likely to an alertness (e.g ., or as in the on alertness that could the physiologic is important to that when an individual a subjective at either of the (e.g ., fatigue or it is more likely to the physiologic human circadian is in the of the and is an for 24-h rhythms. most and of the is while a of the is by the at night and is by to the direct for and exposure to affect the circadian The daily the to its 24-h The tendency of the circadian clock is to than 24-h day, is the physiologic to than work–rest In other of shift from days to to nights has a circadian physiologic but this has not been a to the of shift work. a range of and For example, it the 24-h daily and as well as alertness and performance levels. the of sleep are important and complex but are the scope of this article and are are for increased sleepiness at two times and circadian associated with the of and performance and vulnerability to errors, incidents, and accidents, occurs at about an example, it has been well that a in fatigue-related accidents, alcohol occurs roughly between 3 and of alertness occur at approximately and to a different work such as the night shift or time the circadian will occur for days as the to the new environmental (e.g ., the after through several time work creates a different by its disruption of the circadian individuals are working at night, circadian sleep, and when they to sleep during the day, the circadian clock is for wakefulness. Generally, studies have shown that does not occur prolonged exposure to night work. an the individual and is to daytime that maintain for a factors such as with and that can only be during daytime hours also a role in the to the rhythm to night work. study of during anesthesia has for a circadian in clinical performance among risk of was greater at night to and among this investigation is of a negative circadian effect on performance, it was by the of as well as by not including important such as patient and physician data from of anesthesiologists other that fatigue is by as a significant risk for patients. In two studies of anesthesia more than reported having an in medical that they to fatigue. et al ., using the critical of anesthetic errors, estimated that human a role in more than of anesthetic and that fatigue was an associated factor in of reported critical a of New anesthesiologists, reported that they their limit for safe continuous of and reported having a fatigue-related from of critical to the from to revealed that fatigue was listed as a contributing factor in data suggest that there is a association between fatigue and errors at circadian The from these studies are they are on but the of that quality of care is compromised and that some errors are to working while recently the effect of fatigue in the was of falling asleep while an the was that the had been by about falling asleep during was of medical and of of and The was on a as the of on the had using of accident (table the of errors and accidents that occur in the are likely to have fatigue as a contributing factor on work schedules is a well-documented association between long work hours or late work and an increased potential for from accidents. The risk of an accident increases with hour after the consecutive hour of work. effect is exaggerated when work hours occur on a late shift. injuries, among the most frequent of the injuries by anesthesia are occur during or of and are associated with from fatigue. residents and medical there is a greater risk of a exposure during night work than during have the described risks associated with drowsy driving to physicians. physicians are at risk for accident and as they after their duty In a study of an of residents h of sleep while on reported falling asleep at the compared with of These residents had as many for than the in and emergency have been reported to the of accidents, in many cases while driving after being on call. a more recent study of risk among anesthesia only accidents were which not from the this to the circadian effect during the effect of work hours on pregnancy outcomes in resident physicians has been These data reveal that there is an increased incidence of pregnancy-induced hypertension, small-for-gestational-age infants. study an association between preterm delivery and residents who worked more than 100 h per in other “24/7” health care has some where fatigue was identified as causal or contributory. most often example is the of which attention on work hours and of resident physicians. there has been much to whether was related to the providers who for a high-profile was in that recommendations to limit house work hours and to increase their These recommendations of the of the New Health (table Accreditation Council on Graduate Medical and its and program requirements for resident duty hours, and work were required to that training program formal for resident duty hours that and care of patients. The for that duty hours not be and on average, residents have least day of 7 of and be on call in the hospital no more often than every if these are residents are from anesthesia on the day after evaluation suggests that the of resident duty hours may not be the that alone patient outcome. and after implementation of the New regulations found that there were no differences in mortality rate of patient to care or of and that there were more having at least one et al . demonstrated that adverse were more common when house were for compared with times when a resident the patient was with the care. follow-up study revealed that the quality of during patient the quality of care. suggests that during some use of residents to house may the of more medical errors, but that these errors be in other is among studies on the effects of fatigue on the performance of have the in most of the studies (table is not that the of this of data are these is a studies in the used for fatigue or sleep loss. studies of partial sleep deprivation reveal that performance decrements occur if sleep is by as as h, et al . used 4 h of sleep on the night prior to performance to between and is no for the that sleep times of greater than 4 h be considered as other use study conditions. of in studies is the of a standardized to performance. A