Fatigue and Safety
Fatigue has played a causal or contributory role in some famous accidents.1 In 1986, the Presidential Commission found that faulty decision-making by sleep-deprived managers contributed to the untoward launch of the space shuttle Challenger. The nuclear accidents at Three Mile Island and Chernobyl both occurred during the early morning hours when our bodies are craving sleep. The grounding of the Exxon Valdez was a monumental environmental catastrophe. The National Transportation Safety Board found that the probable cause of this accident was the fatigue of the person sailing the ship. The National Highway Traffic Safety Administrations estimates that over 100,000 people are killed or injured each year in crashes attributed to drivers who fell asleep at the wheel or were impaired by severe drowsiness. These examples and many others reveal that fatigue is a problem that extends beyond health care and is deeply embedded within our society.
Studies have shown a correlation between the performance effects of sleep deprivation and ethanol intoxication.2 At 24 hours of continuous wakefulness, psychomotor function was equivalent to a blood alcohol concentration of 0.1%. This is at or above the legal limit for driving in most states. Think of the professional and personal liability of coming to work intoxicated!
Anesthesia providers, like all health care providers, are required to care for patients when they present for care—anytime of the day or night. This is often in opposition to what our physiology demands. An irrefutable fact is that fatigue and sleep deprivation negatively impact performance and mood (see Table 1). In fact, the anesthesiologist’s role of monitoring the patient in a vigilant manner may be particularly vulnerable to the effects of fatigue.3 Vigilance is defined as the act of being alertly watchful, especially to avoid danger. The word “vigilance” is at the center of the seal and is the motto of the American Society of Anesthesiologists. If we become disengaged from our environment (such as the “microsleeps” that happen when we are sleep-deprived), all vigilance is lost.
Fatigue and Health
People who work irregular overnight shifts are at increased health risks.4 Gastrointestinal and cardiovascular complaints increase, and there is some evidence to suggest that long, strenuous work is also associated with obstetric complications (e.g., preterm delivery, pregnancy-induced hypertension). Immune function, carbohydrate metabolism, and endocrine function are impaired to some degree. One study revealed an increased mortality with severe shortening of daily sleep—sleep of <4 hours increased likelihood of death by a factor of 2.8 in a 6-year follow-up period.5 The health effects of chronic sleep deprivation are insidious and their impact may not manifest fully for years.
Physiology of Fatigue
Sleep homeostasis can be thought of as sleep balance. Every adult has a genetically hard-wired sleep requirement that does not change with age and cannot be trained. The average sleep need for adults is over 8 hours per 24 hours, and most in our society do not achieve this requirement. In fact, surveys done by the National Sleep Foundation reveal that we are a society of chronic under sleepers by over an hour per night. Sleep is a physiologic drive state similar to hunger or thirst. When sleep requirements are not met a “sleep debt” ensues and sleepiness becomes manifest. The only way to pay off this sleep debt is by acquiring adequate sleep. Laboratory studies of chronic partial sleep deprivation provide important information to practicing clinicians.6 Research has shown that sleeping 6 hours or less per night over 2 weeks results in cognitive performance deficits equivalent to 2 nights of total sleep deprivation. Data on subjective sleepiness (how sleepy the subjects felt) suggest that subjects are largely unaware of their level of impairment; this may explain why the impact of this level of chronic sleep deprivation is assumed to be benign.
Many anesthesiologists and nurse anesthetists are chronically sleep-deprived at baseline and periodically push the envelope further by performing call duties, thus layering acute sleep deprivation on top of a significant sleep debt. When the clinician works on the day after a busy on call night, a potentially catastrophic situation can exist.
Normal aging affects sleep.7 Disruptions become more frequent, the amount of slow wave (restorative) sleep decreases, and sleep becomes less consolidated. Since sleep needs remain essentially unchanged, the result is daytime sleepiness. This can be countered by daytime naps, but few working people are able to take naps in our society.
Consecutive Hours of Wakefulness
As hours since the last sleep episode accrue, the physiologic pressure to acquire sleep increases. Extending work shifts past 17 consecutive hours increases the likelihood of errors in laboratory6 and clinical settings.8 In a recent study reported in the New England Journal of Medicine, interns rotating in the intensive care unit were evaluated on two different schedules.9 The traditional schedule allowed for work of up to 30 consecutive hours, while the intervention schedule limited the number of consecutive hours to <17. In this well designed study, residents on the reduced schedule obtained more sleep and made 36% fewer errors. The intervention group also showed fewer “attentional failures,” which were actual electroencephalographic (EEG) episodes of sleepiness during patient care.8 These findings match those of many laboratory studies: wakefulness for periods of over 16 hours predicts performance lapses.6
Humans have a circadian timer that regulates many body processes such as temperature and hormone secretion, but for this discussion the 24-hr sleep-wake cycle is of importance. The circadian clock is located in the suprachiasmatic nucleus of the hypothalamus. The daily light/dark variation entrains this clock to the 24-hour day. We are programmed for 2 periods of decreased alertness every 24 hours: between 3-7 AM and 1-4 PM. The lowest point in this cycle occurs during the early morning one, making it the period of greatest vulnerability to fatigue-related performance impairment.10
As we know from shift work and transmeridian air travel, the circadian pacemaker is resistant to change. This is the primary reason for the inability of humans to readily adapt to shift work and why jet lag occurs. For example, workers on the night shift attempt to function when their clocks are primed for sleep. When they attempt to sleep during the day, their clock is programmed for wakefulness. Opposing this normal rhythmic pattern of day-awake and night-asleep is made more difficult because our society’s activities are strongly linked to this pattern. Some errands and family responsibilities can only be performed during the day, making adaptation to shift work difficult.
Over 80 sleep disorders have been described. Common complaints include insomnia, excessive daytime sleepiness, and abnormal movements or breathing during sleep. Some of these disorders are relatively common and have documented negative effects on wake performance. The most common sleep disorders are obstructive sleep apnea (OSA), insomnia, and periodic limb movements. Shift work sleep disorder has gained attention recently and has an approximate incidence of 10% in night and rotating shift work populations.11
OSA is of special significance because it is prevalent in the population (at least 3-5%), but still underdiagnosed. It is associated with the risk factors of obesity (BMI >27), habitual snoring, and large neck circumference, and is most commonly found in middle-aged males. Excessive daytime sleepiness is a common complaint of patients with OSA and occurs because of the cyclical awakenings caused by airway obstruction during sleep. People with OSA have great difficulty getting restorative sleep because it is like having a pager go off 100 times during each night. The incidence of automobile accidents increases in people with OSA, and experiments reveal impairments that are equivalent to ethanol intoxication.
Other Factors That Affect Waking Function
Depressant and stimulant drugs, whether prescription drugs or substances of abuse, have obvious effects on alertness and performance. In low to moderate doses, caffeine can transiently improve alertness and performance. Social interaction, rest breaks, and exercise can all improve subjective alertness and performance. These factors have no effect on the underlying physiologic level of sleepiness. Other performance shaping factors include chronic or acute illness, boredom, noise, extremes of temperature, and lack of environmental stimuli.
There have been many studies on the effect of sleep deprivation and fatigue on the mood and performance of health care personnel. Extensive reviews on this topic have been published in the last 5 years and the following highlight the important findings.12,13
Anesthesia personnel report working long hours, often without taking breaks. In these surveys, over half the respondents reported having committed an error in judgment due to fatigue and feel that fatigue impairs patient safety.
Mood is found to be consistently worse as work hours are extended and with work done at night. Levels of anger, hostility, tension, bewilderment, confusion, fatigue, anxiety, and depression increase while measures such as vigor and happiness decrease. No studies have been done to evaluate how these mood shifts impact patient care, but they likely play a role in decreased job satisfaction and the occurrence of burnout.
Meta-analyses have been performed concerning the effects of sleep loss on performance.14 These analyses suggest that sleep deprivation impairs cognitive performance and mood with less effect on motor performance. Known performance effects include reduced vigilance, impaired memory, prolonged reaction time, and poor communication. Performance also becomes more variable—one moment performance is adequate, followed by perceptual disengagement from the environment at sleep onset. Performance is zero upon drifting into sleep.
Sleep During Patient Care
Ambulatory EEG and videotape of clinicians have been used to quantify sleep in field and simulator studies. “Attentional failures” are greater in interns working 30-hour duty periods when compared to shorter work shifts.8 Studies of anesthesiologists providing care to a simulated patient reveal similar data.15 Based on detailed videotape analysis of “sleepy behaviors” (eyes closing, head nodding, and actual sleep), the most impaired anesthesiologist in this study had these behaviors for over 30% of a 4-hour case! These studies support what is commonly seen in the operating room, the classroom, and in conference rooms in hospitals around the world. People manifest severe levels of sleepiness at critical time periods.
A growing number of studies describe an increased risk of drowsy driving in health care providers. A recent study from the New England Journal of Medicine found that interns were 2.3 times as likely to report a crash after working an extended shift.16 They calculated that for every extended work shift scheduled in a month, the risk of a motor vehicle crash increased by 9.1%. This is compelling real-world evidence of how lack of sleep leads to decreased alertness and impacts our abilities to perform.
To summarize, we face many challenges in our current health care environment. As you will read in the accompanying articles in this special issue of the APSF Newsletter, finding solutions to the issues that revolve around fatigued health care personnel are not simple and clear-cut. We owe it to our patients and ourselves to come to work optimally prepared. We can lead the way for all of health care by helping to solve the problem.
- Mitler MM, Dement WC, Dinges DF. Sleep medicine, public policy, and public health. In: Kryger MH, et al., eds. Principles and Practice of Sleep Medicine, 3rd ed. Philadelphia: W.B. Saunders Company, 2000: 580-8.
- Dawson D, Reid K. Fatigue, alcohol and performance impairment [Scientific Correspondence]. Nature 1997;388:235.
- Weinger MB, Englund CE. Ergonomic and human factors affecting anesthetic vigilance and monitoring performance in the operating room environment. Anesthesiology 1990; 73:995-1021.
Costa G. Shift work and occupational medicine: an overview. Occup Med (Lond.) 2003;53:83-8.
- 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.
- Van Dongen HP, Maislin G, Mullington JM, Dinges DF. The cumulative cost of additional wakefulness: dose-response effects on neurobehavioral functions and sleep physiology from chronic sleep restriction and total sleep deprivation. Sleep 2003;26:117-26.
- Bliwise DL. Normal aging. In: Kryger MH, et al., eds. Principles and Practice of Sleep Medicine, 3rd ed. Philadelphia: W.B. Saunders, Co., 2000: 26-42.
- Lockley SW, Cronin JW, Evans EE, et al. Effect of reducing interns' weekly work hours on sleep and attentional failures. N Engl J Med 2004;351:1829-37.
- Landrigan CP, Rothschild JM, Cronin JW, et al. Effect of reducing interns' work hours on serious medical errors in intensive care units. N Engl J Med 2004;351:1838-48.
- Van Dongen HP, Dinges DF. Circadian rhythms in fatigue, alertness, and performance. In: Kryger MH, et al., eds. Principles and Practice of Sleep Medicine, 3rd ed. Philadelphia: W.B. Saunders, Co., 2000: 391-9.
- Drake CL, Roehrs T, Richardson G, et al. Shift work sleep disorder: prevalence and consequences beyond that of symptomatic day workers. Sleep 2004;27:1453-62.
- Weinger MB, Ancoli-Israel S. Sleep deprivation and clinical performance. JAMA 2002;287:955-7.
- Owens JA. Sleep loss and fatigue in medical training. Curr Opin Pulm Med 2001;7:411-8.
- Pilcher JJ, Huffcutt AI. Effects of sleep deprivation on performance: a meta-analysis. Sleep 1996;19:318-26.
- Howard SK, Gaba DM, Smith BE, et al. Simulation study of rested versus sleep-deprived anesthesiologists. Anesthesiology 2003;98:1345-55; discussion 5A.
- Barger LK, Cade BE, Ayas NT, et al. Extended work shifts and the risk of motor vehicle crashes among interns. N Engl J Med 2005;352:125-34.