SciELO - Scientific Electronic Library Online

vol.54 issue5Effects of general anesthesia in elderly patients’ memory and cognitionUnilateral spinal anesthesia with low 0.5% hyperbaric bupivacaine dose author indexsubject indexarticles search
Home Pagealphabetic serial listing  

Services on Demand




Related links


Revista Brasileira de Anestesiologia

Print version ISSN 0034-7094On-line version ISSN 1806-907X

Rev. Bras. Anestesiol. vol.54 no.5 Campinas Sept./Oct. 2004 



Short sleep latency in residents after a period on duty in anesthesia*


El plantón nocturno en anestesia reduce la latencia al sueño



Lígia Andrade da Silva Telles Mathias, TSA, M.D.I; Christina Morotomi Funatsu Coelho, M.D.II; Elizabeth Pricoli Vilela, TSA, M.D.III; Joaquim Edson Vieira, TSA, M.D.IV; Marcelo Lacava Pagnocca, TSA, M.D.V

IDiretora do Serviço e Disciplina de Anestesiologia, Irmandade Santa Casa de Misericórdia de São Paulo e Faculdade de Ciências Médicas da Santa Casa de São Paulo. Responsável pelo Centro de Ensino e Treinamento, CET-SBA, ISCMSP
IIMédica responsável pelo setor de Eletroencefalografia, Irmandade Santa Casa de Misericórdia de São Paulo
IIIMédica assistente do Serviço de Anestesia, Irmandade Santa Casa de Misericórdia de São Paulo
IVCoordenador do Centro para Desenvolvimento da Educação Médica - CEDEM da FMUSP
VSupervisor em Neuroanestesia do Hospital das Clínicas da FMUSP e da Irmandade Santa Casa de Misericórdia de São Paulo. Doutor em Medicina pela FMUSP; Co-responsável do CET-SBA do HCFMUSP





BACKGROUND AND OBJECTIVES: Physicians in general, and anesthesiologists in particular, have long working hours. Residents of Anesthesiology may present significant fatigue and stress. This study aimed at investigating first and second year residents’ sleep latency after a period on duty.
METHODS: Participated in this study 11 residents in different situations: at 7:00 am, after a normal night sleep (> 7 h), without on duty period in the last 3 days (M1); at 7:00 am, after 24h of night work, without on duty period in the last 3 days (M2); and at 1:00 pm after 30h of work without on duty period in the last 3 days (M3). Continuous EEG was performed for all situations in adequate room to record sleep signals. Sleep latency (SL) was evaluated.
RESULTS: There has been significant shorter SL among residents after 24 or 30 hours without sleep. From residents after a normal night sleep the day before the evaluation, 36.4% presented pathological SL levels.
CONCLUSIONS: Periods on duty for 24 or 30 hours lead to SL values below 5 minutes, which are considered pathologic and reflect extreme fatigue of residents of Anesthesiology. It might be important to standardize the number of resting hours after duty periods.



JUSTIFICATIVA Y OBJETIVOS: Los médicos en general, los anestesiologistas en particular, tienen jornadas de trabajo prolongadas. Los practicantes de Anestesiologia pueden presentar fatiga y estrés significativos. El objetivo de este trabajo fue verificar, en practicantes (estudiantes) de primero y segundo años la latencia del sueño en períodos después del plantón.
MÉTODO: Fueron evaluados 11 residentes en situaciones distintas: a las 7 horas de la mañana, después de una noche de sueño normal (> 7h), sin plantón en los 3 días anteriores (M1); a las 7 horas de la mañana, después 24 horas de trabajo, sin dormir, sin plantón en los 3 días anteriores (M2); a las 13 horas de la tarde, después de 30 horas de trabajo, sin dormir, sin plantón en los 3 días anteriores (M3). En todas esas situaciones fue realizado electroencefalograma (EEG) continuo, en sala apropiada para registro de los señales de sueño, evaluándose la latencia del sueño (LS).
RESULTADOS: Se Verificó reducción significativa de la LS entre los residentes, después de 24 ó 30 horas de plantón sin dormir. Entre los praticantes que tuvieron noche de sueño normal en la víspera del examen, 36,4% presentaron LS en nivel considerado patológico.
CONCLUSIONES: La jornada de plantón de 24 ó 30 horas lleva a valores de LS menores que 5 minutos, considerados patológicos, reflejando la fatiga extrema de residentes de Anestesiologia. Pode ser importante la reglamentación del número de horas de descanso pos-plantón.




Major characteristic of anesthesiologists’ life is continuous vigilance and the state of readiness allowing them to promptly react during critical situations. Cognitive demands of patients care during anesthetic-surgical procedures require fast access to a large volume of information, evaluating such information in terms of its relevance for patients status, development and implementation of plans to maintain desired physical status and monitoring the result of such interventions. Such complex tasks require continuous vigilance and are particularly vulnerable to the effects of fatigue and other not totally explained factors 1-4.

Fatigue and sleep deprivation, although being different processes, interact to degrade working, learning and reasoning ability, in addition to changing mood, memory and impairing interpersonal relationships. Cognitive impairment precedes physical impairment. Several studies on individuals submitted to work overload have shown that anesthesiologists in this condition tend to be less careful and more prone to miss morbid events, in addition to being unable to effectively respond to them 4,5.

Results of non-medical professions surveys have indicated that sleep deprivation leads to poorer performance 6,7. This connection, however, has not been fully determined in Medicine, and especially in Anesthesiology, although it is unquestionable that physicians in general, and Anesthesiologist in particular, may have long working hours 2,8. Resident physicians, more than other physicians, may present significant fatigue and stress after on duty periods, especially if they are not followed by adequate rest periods, or if they are associated to long daily journeys with work overload and sleep deprivation 9-13.

This study aimed at evaluating, in first and second year residents of Anesthesiology, sleep latency after a normal night sleep as compared to sleep deprivation situations, such as on duty periods.



After the Ethics Committee approval and their informed consent, participated in this study 15 first and second year resident physicians of the Medical Residence of Anesthesiology, Faculdade de Ciências Médicas, Santa Casa de São Paulo. Exclusion criteria were: presence of any associated disease, previous diagnosis of sleep disorders, use of illicit drugs and/or medications, including ethylic alcohol. Volunteer residents were included in the groups when the below-mentioned conditions were met. Residents were evaluated in three different moments for a period of 8 weeks, with a minimum interval of one week between evaluations:

M1 - EEG at 7:00 am, after a normal night sleep, defined as equal to or above 7 hours, without night duty periods in the last 3 days;

M2 - EEG at 7:00 am, after 12 hours of routine work the day before and night duty period, having worked the whole night (24 hours of work without sleep), with no duty period in the last 3 days;

M3 - EEG at 1:00 pm after 12 hours of routine work the day before and nigh duty period, having worked the whole night plus 6 hours of morning routine activities (30 hours of work without sleep), with no duty period in the last 3 days.

In all cases, residents were referred to the EEG Sector and, after being placed in the supine position, EEG electrodes were installed. Then, after orientation to relax and try to sleep, they were kept alone in a dark room and continuous EEG was started. When EEG readings showed signs of sleepiness, the exam was interrupted and the resident was awakened. EEG exam parameters were: a) paper rate of 3 centimeters per second; b) amplitude gauging 5 mm/50 µv; and c) monopolar and bipolar assemblies, all with occipital electrodes.

Waves were considered according to their frequency, in cycles per second or Hertz (Hz) and periods considered in this study were 20 seconds (60 centimeters) each. So, wakefulness was considered when it was possible to observe alpha rhythm in occipital areas (8 to 13 Hz), associated or not to slow eye movements, in amount above 50% of period (above 10 seconds or 30 centimeters).

Sleep stage I was considered when alpha rhythm could be observed in occipital areas (8 to 13 Hz), in amount below 50% of period (below 10 seconds or 30 centimeters), intermingled with the presence of theta frequency rhythms in amounts below 20% of period, lower amplitude (maximum 75 µV) and acute vortex waves (approximately 200 µV) 14,15.

Stage II was considered when spindles (oscillations of 12 to 14 Hz lasting 0.5 to 1.5 seconds), K complexes (high amplitude two-phase waves lasting 0.5 second) and slow theta and delta waves in amounts varying 20% and 50% of period could be observed.

For EEG tracing evaluation, time interval to reach sleep pattern, called sleep latency (SL), was considered. Results were submitted to Analysis of Variance (ANOVA) for repeated measures with multiple comparisons by Tukey’s test, considering significant p < 0.05. Sigma Stat (Sigma Stat for Windows 2.03) was used for statistical analysis.



Among 15 volunteer residents, two have reported sleeping while on duty in 2 subsequent duties; one has not completed 7 hours of sleep in the group of normal sleep in two consecutive days; one went to sleep before EEG at 1:00 pm. So, these four residents were excluded from the study.

This way, actively participated in the study 11 residents, being 6 males and 5 females, mean age of 24 years (23 - 26). Mean sleep latency (SL) results in the three experiment moments for 10-second intervals (p < 0.001, ANOVA repeated measures) are shown in Table I. Mean sleep latency for the group with 7 hours of sleep was 420.9 seconds and was significantly higher as compared to residents awaken for 24 hours (267.3 seconds) (p = 0.025) or awaken for 30 hours (81.4 seconds) (p < 0.001). Among residents remaining awaken at night, SL for those on duty for 24 hours was significantly different as compared to those working for 30 hours (p = 0.007) (Figure 1).



Our study could show that residents of Anesthesiology with regular sleep deprived by professional activities had shorter sleep latency. The longest the awaken period, the shortest the latency.

Anesthesia morbidity/mortality has decreased in recent years, but human errors as still pointed as determining perioperative and very often preventable accidents 15-19. Errors are normal components of human cognitive function and play an important role in learning 18,20. Anesthesiologists’ errors may have catastrophic consequences if not promptly corrected. Human factors, such as sleep deprivation, fatigue or stress may not only increase error potential but also prevent effective recovery 4.

Experimental techniques aiming at evaluating the importance of sleepiness in other similar professions, such as aviation, have been currently applied to Medicine, especially to Anesthesiology 2,21.

Among several available tests, MLST (multiple latency of sleep test), performed in conditions similar to this study, evaluates sleep latency (SL) through EEG tracings. Sleep latency is the time between beginning of test and the moment in which the first sleep sign is detected by EEG 22. Normal SL values are above 10 minutes, abnormal or limitrophe are between 5 and 10 minutes, and pathological when below 5 minutes.

It was observed in our study that after a normal night sleep (M1), 36.4% (4/11) residents had pathological SL (below 5 minutes). Howard has found mean SL of 6.6 ± 5.3 minutes in a similar study with residents of Anesthesiology with no duty period in the last 48 hours 3. These results suggest that residents of Anesthesiology have a chronic insomnia, probably due to excess work and studying hours, fact confirmed by Geer et al. who have evidenced a higher number of car accidents with residents of Anesthesiology as compared to general population 23.

Results after 24 hours on duty (M2), with mean SL of 4 minutes and 27 seconds, were significantly lower as compared to the group sleeping the whole night (7 minutes) and below normal MLST values. Even so, mean SL for the group after 30 hours on duty (M3), was 1 minute and 21 seconds, an even lower result. These values show increased risk for decreased attention of residents of Anesthesiology acting in operating rooms after 24 hours on duty. It is known that in many places it is possible to find residents after duty working until 1:00 pm.

This period totalizes 30 hours on duty. Results of our study have shown that SL at this time is very low, reflecting extreme fatigue and the risk of maintaining residents performing anesthetic acts and acting as co-responsible for patients’ safety.

It is important to stress that in the beginning of anesthesia, be it regional or general, residents perform activities stimulating attention and, even tired, they may not sleep. However, when anesthesia stabilizes and residents have to be vigilant and observe patients and monitors, is when they run the highest risk for sleeping. As shown in this study, few minutes of quietness, even in the operating room, are enough for residents to have progressive vigilance decrease until they sleep. This may be a critical moment for anesthetic accidents.

In 1984, an 18 years old female patient died in a hospital of New York, USA, while being cared by resident physicians with work overload and without sleep for a long time 24. This fact has led to changes in 1989 on the rules of that State with regard to residents’ workload 2. In 2002, the American Council of Graduate Medical Education Accreditation (ACGME) has limited to 80 weekly hours the number of residents working hours and rest time after duty was established as a minimum of 10 hours 2,25.

Although the Brazilian National Committee of Medical Residence and the Brazilian Society of Anesthesiology have already established a limit of 60 weekly work hours, there is no consideration about post-duty rest. Our results have clearly shown the need to regulate the number of rest hours after duty of residents of Anesthesiology. This may be an additional factor for the safety and wellbeing of patients and physicians involved with a specialty prioritizing safety.



01. Kestin IG, Miller BR, Lockhart CH - Auditory alarms during anesthesia monitoring. Anesthesiology, 1988;69:106-109.        [ Links ]

02. Howard SK, Rosekind MR, Katz JD et al - Fatigue in anesthesia: implications and strategies for patient and provides safety. Anesthesiology, 2002;97:1281-1294.        [ Links ]

03. Howard SK - The anesthesiologist and fatigue. Am Soc Anesth Newsletter, 2001;65:1-4.        [ Links ]

04. Weinger MB, Englund CE - Ergonomic and human factors affecting anesthetic vigilance and monitoring performance in the operating room environment. Anesthesiology, 1990;73:995-1021.        [ Links ]

05. Howard SK, Keshavacharya S, Brian ES et al - Behavioral evidence of fatigue during a simulator experiment. Anesthesiology, 1996;89:A1236.        [ Links ]

06. Lyznicki JM, Doege TC, Davis RM et al - Sleepiness, driving, and motor vehicle crashes. JAMA, 1998;279:1908-1913.        [ Links ]

07. Mitler MM, Carskadon MA, Czeisler CA et al - Catastrophes, sleep, and public policy: consensus report. Sleep, 1988;11: 100-109.        [ Links ]

08. Jha AK, Duncan BW, Bates DW - Fatigue - Sleepiness and Medical Errors. Chapter 46, em: Shojania KG, Duncan BW, McDonald KM et al - Making Health Care Safer: A Critical Analysis of Patient Safety Practices Agency for Healthcare Research and Quality Publication N° 01-E058 San Francisco, University of California - Stanford University Evidence-based Practice Center http// (access in: May 19th 2003).        [ Links ]

09. Lydic R - Fact and fantasy about sleep and Anesthesiology. Anesthesiology, 2002;97:1050-1051.        [ Links ]

10. Daugherty SR, Baldwin Jr DC, Rowley BD - Learning, satisfaction, and mistreatment during medical internship: a national survey of working conditions. JAMA, 1998;279:1194-1199.        [ Links ]

11. Williamson AM, Feyer AM - Moderate sleep deprivation produces impairments in cognitive and motor performance equivalent to legally prescribed levels of alcohol intoxication. Occup Environ Med, 2000;57:649-655.        [ Links ]

12. Parks DK, Yetman RJ, McNeese MC et al - Day-night pattern in accidental exposures to blood-borne pathogens among medical students and residents. Cronobiol Int, 2000;17:61-70.        [ Links ]

13. Marcus CL, Loughlin GM - Effect of sleep deprivation on driving safety in housestaff. Sleep, 1996;19:763-766.        [ Links ]

14. Berry RB - Sleep Medicine Pearls, 1st Ed, Philadelphia, Hanley & Belfus, Inc, 1999;1-6.        [ Links ]

15. Rechtschaffen A, Kates A - A Manual of Standardized Terminology, Techniques and Scoring System for Sleep Stages of Human Subjects - Principles and Practice of Sleep Medicine, 3rd Ed, Philadelphia, W. B. Saunders Company, 2000;93-111        [ Links ]

16. Keenan RL - Anesthesia disasters: incidence, causes, and preventability. Semin Anesth, 1986;5:175-179.        [ Links ]

17. Olsson GL, Hallen B - Cardiac arrest during anesthesia. A computer-aided study in 250,543 anaesthetics. Acta Anaesthesiol Scand, 1988;32:653-664.        [ Links ]

18. Cooper JB, Newbower RS, Kitz RJ - An analysis of major errors and equipment failures in anesthesia management: considerations for prevention and detection. Anesthesiology, 1984;60: 34-42.        [ Links ]

19. Craig J, Wilson ME - A survey of anaesthetic misadventures. Anaesthesia, 1981;36:933-936.        [ Links ]

20. Cooper JB, Newbower RS, Long CD et al - Preventable anesthesia mishaps: a study of human factors. Anesthesiology, 1978; 49:399-406.        [ Links ]

21. Taffinder NJ, McManus IC, Russell RC et al - Effect of sleep deprivation on surgeons’ dexterity on laparoscopy simulator. Lancet 1998;352:(9135):1191.        [ Links ]

22. Mitler MM, Miller J - Methods of testing for sleepliness. Behav Med, 1996;21:171-183.        [ Links ]

23. Geer RT, Jobes DR, Tew Jr JD et al - Incidence of automobile accidents involving anesthesia residents after on-call duty cycles. Anesthesiology, 1997;87:A938.        [ Links ]

24. Asch DA, Parker RM - The Libby Zion case. One step forward or two steps backward? N Engl J Med, 1988;318:771-775.        [ Links ]

25. Mhyre JH - New York limitations give residents a break. Am Soc Anesth Newsletter, 2002;66:31.        [ Links ]



Correspondence to
Dra. Ligia Andrade da Silva Telles Mathias
Alameda Campinas, 139/41
01404-000 São Paulo, Brazil

Submitted for publication September 9, 2003
Accepted for publication February 25, 2004



* Received from Centro de Ensino e Treinamento da Faculdade de Ciências Médicas da Santa Casa de São Paulo, SP

Creative Commons License All the contents of this journal, except where otherwise noted, is licensed under a Creative Commons Attribution License