Journal of Clinical Monitoring and Computing 15: 549^552, 1999.ß 2000 KluwerAcademic Publishers. Printed in the Netherlands.

ClinicalMinitutorial

VIGILANCE, BOREDOM, AND SLEEPINESSMatthew B.Weinger, MD

From the Department of Anesthesiology, University of California,San Diego, U.S.A. and the San DiegoVA Health Care System.

Received Jul 22, 1999. Accepted for publication Jul 22, 1999.

Address correspondence to Matthew B. Weinger, MD, VA MedicalCenter (125), 3350 La Jolla Village Drive, San Diego, CA 92161-5085,U.S.A.E-mail: mweinger@ucsd.edu

Weinger MB.Vigilance, Boredom, and Sleepiness.J Clin Monit 1999; 15: 549^552

INTRODUCTION

The presence of ``vigilance'' in the o¤cial seal of theAmerican Society of Anesthesiologists underscores theperceived importance of careful attention to details anddetection of subtle clinical signs. Vigilance is ` a state ofreadiness to detect and respond to certain speci¢ed smallchanges occurring at random intervals in the environ-ment'' [1]. Vigilance research was initiated in responseto the errors of early radar operators. The anesthesiolo-gist must continuously evaluate the patient's medicalstatus while assessing the e¡ects of anesthesia and thesurgical intervention. Although monitoring duringquiescent periods of the maintenance phase of a routineanesthetic resembles classical vigilance tasks studied inthe laboratory, anesthesia practice also requires otherhigher-order cognitive processes such as pattern recog-nition, divided attention, task prioritization, ``situationawareness,'' and dynamic decision making.A large number of factors (called ``performance-

shaping factors'') can adversely a¡ect anesthetic vigilanceand other aspects of clinical performance. For example,people are more likely to commit errors when they aremismatched to the task or their equipment is not user-friendly. Factors that can in£uence clinical performanceinclude skill level, motivation, stress, inadequate super-vision, task complexity, and faulty system design. Thistutorial will focus on only two such performance-shap-ing factors, boredom and excessive work schedules,both of which can promote fatigue, inattention, andsleepiness.

BOREDOM AND INTRAOPERATIVE READING

Boredom typically results from the need to maintainattention in the absence of relevant task informationand is most likely to occur in semi-automatic tasks thatprevent wandering of the mind but are not fully men-tally absorbing. The maintenance phase of most routineanesthetics is a period of low workload and infrequenttask demands. Up to 90% of anesthesia providers in onesurvey admitted to at least occasional boredom whileadministering anesthesia. The presence of fatigue orsleep deprivation will compound the performance-shaping e¡ects of boredom. Boredom may be mini-mized by altering the sequence of tasks or by addingnew tasks to a monotonous job.

During times of low workload, many anesthesiaproviders add additional tasks to their routine. Thesesecondary tasks may include clinically relevant func-tions such as reorganizing the anesthesia workspace.Anesthesia providers also commonly read, listen tomusic, talk on the telephone, or converse with theircolleagues about matters not related to caring for thepatient. The choice of secondary tasks is probably lessimportant than how those tasks are integrated withprimary patient care tasks as well as how e¡ectively lessimportant tasks are ``shed'' (set aside) when clinicaldemands increase.Some have expressed concern that intraoperative

reading can decrease visual vigilance for detecting acutechanges of the vital signs in the anesthetized patient.Others have asserted that reading during low workloadperiods actually helps to prevent boredom, sleepiness,and impaired vigilance. In the modern anesthesia workenvironment, continuous visual vigilance may be lessimportant during routine monitoring due to the avail-ability of continuous auditory indicators of oxygenation(e.g., a pulse oximeter tone synchronized with heartrate and scaled proportional to actual oxygen satura-tion) and fully integrated auditory alarms. It is clear,however, that reading or any other non-patient care-related activity, will have an adverse impact on clinicalcare if it detracts from the anesthesiologist's ability toperform critical tasks, attend to the surgeon's needs, orto respond to new demands and emergencies. Intra-operative reading may ``look bad,'' giving the appear-ance of inattention and boredomwhen, in fact, it can beserving the opposite e¡ect.

SLEEP DEPRIVATION AND FATIGUE

Recent research suggests that American anesthesia resi-dents work an average of 73 � 12 hours per week(including night and weekend responsibilities) and maybe chronically sleep deprived [2, 3]. In a sleep labora-tory, undisturbed anesthesia residents, even if they hadnot been on-call for two full days, had daytime sleeplatencies comparable to those of narcoleptic patients.Furthermore, these residents often denied falling asleepduring the sleep tests, despite objective EEG evidenceto the contrary. Concern about decreased clinical per-formance as a result of fatigue and sleep deprivation hasled state legislatures and academic institutions to try toconstrain residents' work hours, although with limitedsuccess. Despite the fact that many fully trained Ameri-can anesthesiologists have similarly rigorous clinicalschedules, there are no mandatory restrictions on theirwork hours.

Research shows that a single night of sleep loss cansigni¢cantly decrease performance, especially on skilledcognitive tasks, with signi¢cant decrements beginningby 18 hours after awakening. The magnitude of cogni-tive psychomotor impairment after remaining awakefor 24 hours appears equivalent to that produced byacute inebriation (Figure 1). One or more days withoutsleep consistently produce progressively impairedmemory and reaction time. Omission errors increaseand work rate is appreciably slowed, particularly whensubjects are required to make choices. Sleep-deprivedworkers fail appropriately to allocate attention, set taskpriorities, or evaluate potentially faulty information,skills that are essential to optimal anesthesia care.Concerns about the danger to patients of sleep de-

prived or fatigued physicians providing care have, how-ever, been di¤cult to substantiate in objective studies. Inan early study, sleep deprivation appreciably a¡ected theability of medical interns to detect cardiac arrhythmias.Post-call anesthesia residents have decreased performanceon laboratory psychomotor vigilance tests and this maycontribute to a higher incidence of automobile acci-dents post-call compared with the overall U.S. popula-tion [4, 5].The task performance and workload of anesthesia

residents doing actual OR cases was measured undertwo conditions: ^ once at night (average start timeabout 2 am) while fatigued and a second time during aregular work day (average start time 10:30 am) [6].Because the residents had awakened 18 � 1 hours priorto the start of night cases, they were likely both fatiguedand sleep deprived under this condition.The paired caseswere matched as closely as possible for case complexity,

Fig. 1. The e¡ects of sleep deprivation on psychomotor performancebecomes equivalent to the e¡ects of acute alcohol intoxication afternearly 24 hours without sleep. Redrawn with permission fromDawson and Reid: Nature 388: 235, 1997.

550 Journal of Clinical Monitoring and Computing Vol 15 Nos 7^8 December 1999

the patient's ASA status, and the type of anesthesia andsurgery. At night, the residents spent almost twice asmuch time observing the monitors and signi¢cantly lesstime doing manual tasks compared with day cases.Average workload was higher at night. These results,consistent with research in other ¢elds, suggest thatfatigued physicians may require additional cognitiveresources to perform routine clinical tasks leading todecreased task e¤ciency, load shedding, increasedworkload, and reduced ``spare capacity'' to deal withpotential crises.In a complementary study using a realistic patient

simulator, Stanford anesthesia residents performed twocomparable 4-hour simulated anesthetics for laparo-scopic surgery in a darkened operating room-like envi-ronment with trained actors playing the surgeon andnurses [7, 8]. The residents were studied on 2 separatedays under two conditions: 1) under the fatigued con-dition, after being kept awake for at least 25 hour beforethe study, simulating conditions at the end of a di¤cult24-hour call; 2) in a well-rested condition, where theyaveraged 2 extra hours of sleep for 4 consecutive nightsbefore the study. An observer, blinded to the subjects'condition, reviewed videotapes of all of the cases.There was strong behavioral evidence of signi¢cant

sleepiness under the fatigue condition. The appreciableintra- and inter-subject variability in the distribution oftask activities and workload was greater under thefatigued condition. However, in contrast to the OR¢ndings, fatigued subjects did not spend more time onprimary tasks. During these long boring simulatedanesthetics, subjects employed a variety of sleepiness-reducing strategies, including conversation and busywork (similar to the boredom-reducing activities de-scribed previously). Some subjects used these strategiesmore e¡ectively than others and, to the extent theywere successful, their use may have reduced any di¡er-ences which otherwise might have been observed in thissimulator study.In summary, fatigue and sleep deprivation a¡ect the

clinical performance of anesthesiologists although theirimpact may be more important during non-routinecognitively demanding situations. Other performanceshaping factors may interact to produce greater adversee¡ects. Work schedule can thus, under some circum-stances, be an important factor a¡ecting the occurrenceof and recovery from clinical error.

RELIEF BREAKS

Because anesthesia cases can be long, stressful, orboring, it is common to provide intermittent breaks.

For example, nurse anesthetists often receive one 15-minute break every 2 hours and a meal break every4 hours. But how safe is it to allow another anesthesiaprovider, unfamiliar with the course of an on-goinganesthetic, to assume care, albeit transiently? Cooperet al. [9, 10] studied critical incidents associated withintraoperative exchanges of anesthesia personnel. Of the90 incidents that occurred during a break, 28 weredeemed favorable (i.e., the relieving anesthesiologistdiscovered and corrected a potentially dangerous pre-existing situation) while only 10 incidents were con-sidered unfavorable (i.e., the relieving anesthesiologist` caused'' the critical incident). In a few incidents, theproblem was perpetuated by the relieving anesthesiolo-gist. Out of over 1000 critical incidents studied, not onerelief-related incident could be identi¢ed that resultedin signi¢cant morbidity or mortality. Unfortunately,because of the limitations of this technique (includingselection and hindsight bias), the relative frequencywith which relief results in favorable versus unfavorableoutcomes can not be accurately determined. What isclear, however, is that breaks are essential, especially atnight, and the successful detection of problems during abreak may depend on a systematic and comprehensivereview of the anesthetic course by the relieving anesthesiaprovider.

REFERENCES

1. Mackworth NH. Some factors a¡ecting vigilance. Ad-vancement of Science 1957; 53: 389^393

2. Howard SK, Gaba DM, Rosekind MR. Subjectiveassessment of sleepiness and sleep onset perception inresident anesthesiologists (Abstract). Anesthesiology1995; 83: A1009

3. Howard SK, Healzer JM, Gaba DM. Sleep and workschedules of anesthesia residents: A national survey (Ab-stract). Anesthesiology 1997; 87: A932

4. Geer RT, Jobes DR, Gilfor J, Traber K, Dinges D.Reduced psychomotor vigilance in anesthesia residentsafter on-call duty cycles (Abstract). Anesthesiology 1997;87: A938

5. Geer RT, Jobes DR, Tew Jr JD, Stepsis LH. Incidence ofautomobile accidents involving anesthesia residents afteron-call duty cycles (Abstract). Anesthesiology 1997; 87:A938

6. Weinger MB, Vora S, Herndon OW, Mazzei WJ.Changes in task patterns, workload, and mood offatigues resident physicians performing night-time anes-thesia cases (Abstract). Proc Human Factors Ergo SocAnnMtg 1998; 42: 1622

7. Howard SK, Keshavacharya S, Smith BE, RosekindMR, Weinger M, Gaba DM. Behavioral evidence offatigue during a simulator experiment (Abstract). Anes-thesiology 1998; 89: A126

Clinical Minitutorial: Weinger: Vigilance, Boredom, and Sleepiness 551

8. Herndon CN, Weinger MB, Smith BE, Howard SK,Rosekin MR, Gaba DM. Use of task analysis to evaluatethe e¡ects of fatigue on performance during simulatedanesthesia cases (Abstract). Anesthesiology 1998; 89: A1180

9. Cooper JB, Long CD, Newbower RS, Philip JH. Criticalincidents associated with intraoperative exchanges ofanesthesia personnel. Anesthesiology 1982; 56: 456^461

10. Cooper JB. Do short breaks increase or decrease anes-thetic risk? J Clin Anesth 1989; 1: 228^231

SUGGESTED READING LIST

Dawson D, Reid K. Fatigue, alcohol and performance im-pairment. Nature 1997; 388: 235

Deaconson TF, O'Hair DP, Levy MF, Lee MBF, SchuenemanAL, E. CR: Sleep deprivation and resident performance.JAMA1988; 260: 1721^1727

Gaba D, Howard SK, Jump B. Production pressure in thework environment: California anesthesiologists' attitudesand experiences. Anesthesiology 1994; 81: 488^500

Gaba DM, Howard SK, Small SD. Situation awareness inanesthesiology. Human Factors 1995; 37: 20^31

Weinger M, Englund C. Ergonomic and human factorsa¡ecting anesthetic vigilance and monitoring performancein the operating room environment. Anesthesiology 1990;73: 995^1021

Weinger MB, Smith NT. Vigilance, alarms, and integratedmonitoring systems. In: Ehrenwerth J, Eisenkraft JB,eds. Anesthesia Equipment: Principles and Applications.Malvern, PA: MosbyYear Book, 1993: 350^384

Weinger MB, Herndon OW, Gaba DM. The e¡ect of elec-tronic record keeping and transesophageal echocardiogra-phy on task distribution, workload, and vigilance duringcardiac anesthesia. Anesthesiology 1997; 87: 144^155

Weinger MB. Lack of outcome data makes reading a personaldecision. J Clin Monit 1996; 12: 1^2

552 Journal of Clinical Monitoring and Computing Vol 15 Nos 7^8 December 1999