Methodological approaches to anaesthetists’ workload in the operating theatre
2005; Elsevier BV; Volume: 94; Issue: 6 Linguagem: Inglês
10.1093/bja/aei131
ISSN1471-6771
Autores Tópico(s)Hospital Admissions and Outcomes
ResumoThis review examines the basic concepts of workload and methods of measuring them. The components of anaesthetists' operating room activities, and the factors contributing to workload, are analysed using an ergonomic-based model for technological environments. The available evidence on the relationship between workload and training and supervision is presented and the effect of workload on the quality and safety of anaesthetic care is reviewed. There is, as yet, only a small body of work examining workload and its effects in anaesthesia. While studies have identified the general pattern of workload in relation to the different stages of the perioperative period, measurement, particularly of overlapping tasks, is still evolving. It is clear, however, that induction and emergence are the most intense periods of both practical and 'non-technical' aspects of work. Allocation of attention to a range of tasks simultaneously is a key characteristic of anaesthetic practice. Experienced staff appear to show 'spare capacity' in performance during routine cases, which, we suggest, allows them an attentional 'safety margin' should adverse events occur. The effects of production pressure and mental 'overload' remain speculative and so practical recommendations for anaesthetic staffing, both in terms of numbers and matching skills to surgical demand, cannot be made. The potential for delegation of tasks, for instance to non-physician anaesthetists, can also not be made on evidence-based grounds. Strategies for active management of workload may be useful in practice. This review examines the basic concepts of workload and methods of measuring them. The components of anaesthetists' operating room activities, and the factors contributing to workload, are analysed using an ergonomic-based model for technological environments. The available evidence on the relationship between workload and training and supervision is presented and the effect of workload on the quality and safety of anaesthetic care is reviewed. There is, as yet, only a small body of work examining workload and its effects in anaesthesia. While studies have identified the general pattern of workload in relation to the different stages of the perioperative period, measurement, particularly of overlapping tasks, is still evolving. It is clear, however, that induction and emergence are the most intense periods of both practical and 'non-technical' aspects of work. Allocation of attention to a range of tasks simultaneously is a key characteristic of anaesthetic practice. Experienced staff appear to show 'spare capacity' in performance during routine cases, which, we suggest, allows them an attentional 'safety margin' should adverse events occur. The effects of production pressure and mental 'overload' remain speculative and so practical recommendations for anaesthetic staffing, both in terms of numbers and matching skills to surgical demand, cannot be made. The potential for delegation of tasks, for instance to non-physician anaesthetists, can also not be made on evidence-based grounds. Strategies for active management of workload may be useful in practice. The work of anaesthetists includes many different duties. Their clinical work may be in the operating theatre, where, depending on country and context of practice, they may be providing anaesthesia themselves or supervising others, or in the intensive care unit, labour ward, or pain clinic. In addition, most anaesthetists have significant other responsibilities in administration, teaching, and research. However, the work of providing anaesthesia for surgery has specific characteristics, which has been described as 'managing a single highly interactive system composed of the patient, clinical equipment, surgeons, and other operating room (OR) personnel, and the broader OR environment'.34Weinger MB Slagle J Human factors research in anesthesia patient safety. Techniques to elucidate factors affecting clinical task performance and decision making.J Am Med Inform Assoc. 2002; 9: S58-S63Crossref Google Scholar Given these characteristics, the practice of anaesthesia presents many challenges in the field of ergonomics and it is this aspect of anaesthetists' work that this review will focus on, bringing together basic ergonomic concepts and published work applied to the practice of anaesthesia. We collected material from standard textbooks, from searches of the electronic databases Medline and Embase and from reference lists of cited papers. While we have concentrated on presenting the methodological aspects of the subject, we have also attempted to address the following questions: What does the intra-operative work of the anaesthetist consist of? How does workload change with experience, supervision, teaching or delegation? Is there a relationship between workload and safety or quality of anaesthetic care? Definitions of workload are rarely short and simple. Workload may be described best as a dynamic balance between the challenge of a task and an individual's response to that task. Annett has proposed a model reflecting this interaction (Fig. 1), which we will adopt in this review.2Annett J Subjective rating scales: science or art?.Ergonomics. 2002; 45: 966-987Crossref PubMed Scopus (187) Google Scholar A similar, but more inclusive definition comes from Hart and Staveland:18Hart SG Staveland LE Development of the NASA-TLX (Task Load Index): results of empirical and theoretical research.in: Hancock PA Meshkati N Human Mental Workload. Elsevier, Amsterdam1988: 139-183Crossref Scopus (7160) Google Scholar 'Workload is not an inherent property, but rather emerges from the interaction between the requirements of a task, the circumstances under which it is performed, and the skills, behaviours, and perceptions of the operator'. Farmer and Brownson10Farmer E Brownson A Review of Workload Measurement, Analysis and Interpretation Methods. Report for Eurocontrol Integra programme. European Organisation for the Safety of Air Navigation (Eurocontrol), EATMP document, Brussels2003Google Scholar identify three key aspects of workload. Task demands. Although objective and replicable for study purposes, task demands do not necessarily equate with workload because of varying skills and experience among those performing the task. Effort. This is described as 'the conscious allocation of mental processing resources'.10Farmer E Brownson A Review of Workload Measurement, Analysis and Interpretation Methods. Report for Eurocontrol Integra programme. European Organisation for the Safety of Air Navigation (Eurocontrol), EATMP document, Brussels2003Google Scholar Effort may not reflect workload, for example, where workload increases but there is resistance on the part of the subject to increase effort. Performance. Workload is particularly concerned with meeting set demands: performance is the way this is achieved and the effectiveness with which it is achieved. Performance is also important in evaluating effort needed, as a measure of primary and secondary task achievement and can indicate spare capacity. A further component of workload is attention. This is regarded as a key demand of the anaesthetist's work, especially during the maintenance stage of anaesthesia. A useful concept here is the multichannel theory of attention, which is based on the notion that humans process information in different modes. Through practice, certain tasks can be carried out with less direct attention, which allows their performance while maintaining spare capacity for other tasks.1Allport DA Antonis B Reynolds P On the division of attention: a disproof of the single channel hypothesis.Q J Exp Psychol. 1972; 24: 225-235Crossref PubMed Scopus (418) Google Scholar Workload is, in part, influenced by the nature of the task in question. This section briefly discusses task analysis and task, or action, density before reviewing what are specifically regarded as workload measures. The methods reviewed are illustrated by applications to anaesthesia where these exist. Weinger and Slagle suggest that 'Because workload is a multidimensional construct, different measures of clinical workload may reveal different aspects of clinical care'.34Weinger MB Slagle J Human factors research in anesthesia patient safety. Techniques to elucidate factors affecting clinical task performance and decision making.J Am Med Inform Assoc. 2002; 9: S58-S63Crossref Google Scholar Studies often make use of multiple methods and while this allows investigation of different perspectives, it is important to bear in mind the levels of agreement between different types of measurement.2Annett J Subjective rating scales: science or art?.Ergonomics. 2002; 45: 966-987Crossref PubMed Scopus (187) Google Scholar5Brookhuis KA De Waard D On the assessment of mental workload and other subjective qualifications.Ergonomics. 2002; 45: 1026-1030Crossref PubMed Scopus (26) Google Scholar33Weinger MB Reddy SB Slagle J Multiple measures of anesthesia workload during teaching and nonteaching cases.Anesth Analg. 2004; 98: 1419-1425Crossref PubMed Scopus (95) Google Scholar Task analysis involves 'an ordered sequence of tasks and subtasks, which identifies the performer or user; the action, activities or operations; the environment; the starting state, the goal state; the requirements to complete the task such as hardware, software or information.'29Snyder KM A Guide to Software Usability. IBM Internal Publication, Armonk, NY1991Google Scholar Task analysis and measurement of workload are not necessarily carried out together or for the same purpose but task analysis may facilitate workload measurement by identifying the individual work components or subtasks to be measured.26Slagle J Weinger MB Dinh My-Than T Brumer VV Williams K Assessment of the intrarater and interrater reliability of an established clinical task analysis methodology.Anesthesiology. 2002; 96: 1129-1139Crossref PubMed Scopus (52) Google Scholar Identifying tasks refines the measurement of workload associated with those tasks and facilitates consistent study design and comparison. Similarly, task analysis facilitates time and motion studies by identifying tasks and subtasks for time measurement. Manser and Wehner21Manser T Wehner T Analysing action sequences: variations in action density in the administration of anaesthesia.Cogn Tech Work. 2002; 4: 71-81Crossref Google Scholar draw on the activity theory to relate tasks to the motives, goals, and conditions of anaesthesia. Task analysis may seem straightforward but tasks may overlap and may not be independent of each other.30Weinger MB Englund CE Ergonomic and human factors affecting anesthetic vigilance and monitoring performance in the operating room environment.Anesthesiology. 1990; 73: 995-1021Crossref PubMed Google Scholar The issue of intra- and inter-rater agreement in analysis needs to be addressed26Slagle J Weinger MB Dinh My-Than T Brumer VV Williams K Assessment of the intrarater and interrater reliability of an established clinical task analysis methodology.Anesthesiology. 2002; 96: 1129-1139Crossref PubMed Scopus (52) Google Scholar and subjective judgements may be required in deciding which task is dominant if more than one takes place simultaneously. Manser and Wehner have addressed this through the development of a method, which measures 'action density'. This involves a trained observer observing in the anaesthetic room and operating theatre using a computer-based recording method called 'Flexible Interface Technique' (FIT-System).21Manser T Wehner T Analysing action sequences: variations in action density in the administration of anaesthesia.Cogn Tech Work. 2002; 4: 71-81Crossref Google Scholar Annett notes that although objective measurement of performance in ergonomics is generally preferable, subjective evaluation by experts has become common practice.2Annett J Subjective rating scales: science or art?.Ergonomics. 2002; 45: 966-987Crossref PubMed Scopus (187) Google Scholar Typically, studies designed to measure performance often include a secondary task, which subjects are asked to complete as and when they have the time while giving priority to a primary task. Performance on the secondary task is used as an indicator of spare capacity, from which workload is inferred. Measurement of performance on the main task aims to give an indication of workload, but it is not possible to assume that as workload increases, performance deteriorates. Variables for a proposed index of task difficulty include familiarity of stimuli, number of concurrent tasks, task difficulty (as a component measure), and competition for limited mental resources. The component task difficulty measure is based on the number of items to be remembered for the task including possible demands on short-term memory.16Gawron VJ. Guide to measuring workload and situational awareness. Human Factors and Ergonomics Society 44th Annual Meeting, San Diego, CA, USA, 2000Google Scholar We identified a number of examples of performance measurement in anaesthesia. Byrne and Jones6Byrne AJ Jones JG Errors on anaesthetic record charts as a measure of anaesthetic performance during simulated critical incidents.Br J Anaesth. 1998; 80: 58-62Crossref PubMed Scopus (39) Google Scholar asked trainee anaesthetists to keep 'an accurate, contemporaneous anaesthetic record' during simulated critical incidents. This record-keeping was used as a secondary task but, for the purposes of the study, the trainees were not made aware of this. As expected, competence in carrying out the secondary task was impaired as workload in the primary task increased. Gaba and Lee14Gaba DM Lee T Measuring the workload of the anesthesiologist.Anesth Analg. 1990; 71: 354-361Crossref PubMed Scopus (68) Google Scholar introduced mental arithmetic questions as a secondary task in real anaesthesia cases. They observed 'skipped problems' and a high response time in carrying out the secondary task, particularly while undertaking manual tasks and, less predictably, while there was conversation between staff. Weinger and colleagues have used the response time to a so-called 'vigilance light' illuminated intermittently during anaesthesia cases.32Weinger MB Herndon OW Zornow MH Paulus MP Gaba DM Dallen LT An objective methodology for task analysis and workload assessment in anesthesia providers.Anesthesiology. 1994; 80: 77-92Crossref PubMed Scopus (135) Google Scholar33Weinger MB Reddy SB Slagle J Multiple measures of anesthesia workload during teaching and nonteaching cases.Anesth Analg. 2004; 98: 1419-1425Crossref PubMed Scopus (95) Google Scholar The advantage of performance-based measurement lies in giving a measure of ability for the main task of interest and, where a secondary task is introduced, as a measure of spare capacity. This latter aspect is useful in the case of unexpected events in the workplace. The disadvantage of performance measures is that they may not be sensitive to an increase or decrease in workload if the subject compensates through increased, or reduced, effort respectively. The recording of concurrent or overlapping tasks is also subject to variation in observer interpretation.21Manser T Wehner T Analysing action sequences: variations in action density in the administration of anaesthesia.Cogn Tech Work. 2002; 4: 71-81Crossref Google Scholar26Slagle J Weinger MB Dinh My-Than T Brumer VV Williams K Assessment of the intrarater and interrater reliability of an established clinical task analysis methodology.Anesthesiology. 2002; 96: 1129-1139Crossref PubMed Scopus (52) Google Scholar Other possible limitations relate to the multi-channel theory of attention. The secondary task, if included in the study, may interfere with the primary task or may not depend on the performance of the primary task.4Bridger RS Introduction to Ergonomics. 2nd Edn. Taylor and Francis, London2003Google Scholar10Farmer E Brownson A Review of Workload Measurement, Analysis and Interpretation Methods. Report for Eurocontrol Integra programme. European Organisation for the Safety of Air Navigation (Eurocontrol), EATMP document, Brussels2003Google Scholar Overall performance is difficult to measure in anaesthesia because of the range of factors affecting outcome and the low proportion of adverse outcomes.13Gaba DM Human work environment and simulators.in: Miller RD Anesthesia. 5th Edn. Churchill Livingstone, Philadelphia2000: 2613-2668Google Scholar Subjective or psychological workload is a well-established but much-debated measure. Typically, study subjects are asked to complete questionnaires. A range of factors can contribute to subjective workload and be used for rating. 'Usability' is typically an audit of workplace features using checklists and report forms but may be used in subjective ratings, for example the Software Usability Measurement Inventory or System Usability Scale and questionnaires/interviews. Other scales include: presence or 'being there' (applied to the design of simulators and other virtual environments), comfort/annoyance, and perceived urgency of auditory warning signals.2Annett J Subjective rating scales: science or art?.Ergonomics. 2002; 45: 966-987Crossref PubMed Scopus (187) Google Scholar A key factor is the degree of shared meaning or 'inter-subjectivity' among raters.2Annett J Subjective rating scales: science or art?.Ergonomics. 2002; 45: 966-987Crossref PubMed Scopus (187) Google Scholar O'Donnell and Eggemeier,24O'Donnell RD Eggemeier FT Boff KR Kaufman L Thomas JP Handbook of Perception and Human Performance. Volume II: Cognitive Processes and Performance. John Wiley and Sons, New York1986: 42Google Scholar Wickens,35Wickens CD Engineering Psychology and Human Performance. 2nd Edn. Harper Collins, New York1992Google Scholar Annett2Annett J Subjective rating scales: science or art?.Ergonomics. 2002; 45: 966-987Crossref PubMed Scopus (187) Google Scholar and Farmer and Brownson10Farmer E Brownson A Review of Workload Measurement, Analysis and Interpretation Methods. Report for Eurocontrol Integra programme. European Organisation for the Safety of Air Navigation (Eurocontrol), EATMP document, Brussels2003Google Scholar review a number of scales. These include the Cooper–Harper Scale, which was originally developed as a checklist for use by pilots to assess handling characteristics of aircraft. The questionnaire is in the form of a decision tree. Two scales that concern the response of the user specifically to the demands of the task are the Subjective Workload Assessment Technique (SWAT) and the NASA Task Load Index (NASA-TLX). SWAT includes scales for time load, mental effort load, and psychological stress load each with three levels. NASA-TLX includes six workload categories presented as questions with visual analogue scales to which subjects respond (Table 1).Table 1The NASA Task Load Index rating scales35Wickens CD Engineering Psychology and Human Performance. 2nd Edn. Harper Collins, New York1992Google ScholarTitleEndpointsDescriptionsMental demandLow/highHow much mental and perceptual activity was required (e.g. thinking, deciding, calculating, remembering, looking, searching, etc.)? Was the task easy or demanding, simple or complex, exacting or forgiving?Physical demandLow/highHow much physical activity was required (e.g., pushing, pulling, turning, controlling, activating, etc.)? Was the task easy or demanding, slow or brisk, slack or strenuous, restful or laborious?Temporal demandLow/highHow much time pressure did you feel due to the rate or pace at which the tasks or task elements occurred? Was the pace slow and leisurely or rapid and frantic?EffortLow/highHow hard did you have to work (mentally and physically) to accomplish your level of performance?PerformanceGood/poorHow successful do you think you were in accomplishing the goals of the task set by the experimenter (or yourself)? How satisfied were you with your performance in accomplishing these goals?Frustration levelLow/highHow insecure, discouraged, irritated, stressed and annoyed vs secure, gratified, content, relaxed, and complacent did you feel during the task? Open table in a new tab Subjective measures of effort and fatigue include the Rating of Perceived Exertion (RPE and CR10 scales) produced by Borg and the Swedish Occupational Fatigue Inventory (Table 2).3Borg GAV Psychophysical bases of perceived exertion.Med Sci Sports Exerc. 1982; 14: 377-381Crossref PubMed Scopus (10867) Google Scholar The scale of 6 to 20 corresponds to a heart rate of 60–200 beats min−1. Subjects' ratings on the scale usually correlate closely with actual heart rates.4Bridger RS Introduction to Ergonomics. 2nd Edn. Taylor and Francis, London2003Google Scholar This was used by Weinger and colleagues to measure subjective workload as part of a broader range of measurements of task analysis and workload in anaesthesia.32Weinger MB Herndon OW Zornow MH Paulus MP Gaba DM Dallen LT An objective methodology for task analysis and workload assessment in anesthesia providers.Anesthesiology. 1994; 80: 77-92Crossref PubMed Scopus (135) Google Scholar33Weinger MB Reddy SB Slagle J Multiple measures of anesthesia workload during teaching and nonteaching cases.Anesth Analg. 2004; 98: 1419-1425Crossref PubMed Scopus (95) Google ScholarTable 2Borg's RPE scale3Borg GAV Psychophysical bases of perceived exertion.Med Sci Sports Exerc. 1982; 14: 377-381Crossref PubMed Scopus (10867) Google ScholarRatingDescription of rating6:No exertion at all7:8:Extremely light9:Very light10:11:Light12:13:Somewhat hard14:15:Hard16:17:Very hard18:19:Extremely hard20:Maximal exertion Open table in a new tab The advantages of subjective workload measurement are its high 'face' validity and the apparent ease with which operators apply the ratings.10Farmer E Brownson A Review of Workload Measurement, Analysis and Interpretation Methods. Report for Eurocontrol Integra programme. European Organisation for the Safety of Air Navigation (Eurocontrol), EATMP document, Brussels2003Google Scholar It is particularly appropriate for complex workload situations with multiple demands. The Borg scale has the advantage of being a global measure, unlike some subjective scales which do not take account of all demands.4Bridger RS Introduction to Ergonomics. 2nd Edn. Taylor and Francis, London2003Google Scholar There are also a number of disadvantages of subjective measures: the difficulty of comparing qualitatively different tasks; the lack of agreement on components of workload and therefore the scales to be used;10Farmer E Brownson A Review of Workload Measurement, Analysis and Interpretation Methods. Report for Eurocontrol Integra programme. European Organisation for the Safety of Air Navigation (Eurocontrol), EATMP document, Brussels2003Google Scholar and some evidence to suggest that the more experience the subjects have, the more likely they are to under-estimate workload in demanding, experimental tasks.4Bridger RS Introduction to Ergonomics. 2nd Edn. Taylor and Francis, London2003Google Scholar Although included in some subjective evaluations of workload as seen above, physiological measures are usually regarded as a distinct category of workload measures. Their relevance is based on the premise that changes in workload cause changes to the body. Although there are a number of possible physiological measures of effort, heart rate has been most commonly used in studies of workload in anaesthesia. The advantages are that objective measurement is possible and it can be carried out unobtrusively. The disadvantages are that physiological effects do not necessarily correlate with performance and a large quantity of data is produced requiring analysis and time-matching with tasks.10Farmer E Brownson A Review of Workload Measurement, Analysis and Interpretation Methods. Report for Eurocontrol Integra programme. European Organisation for the Safety of Air Navigation (Eurocontrol), EATMP document, Brussels2003Google Scholar Use of heart rate as a measure of physiological workload can be refined by taking account of varying levels of oxygen consumption between individuals4Bridger RS Introduction to Ergonomics. 2nd Edn. Taylor and Francis, London2003Google Scholar but this has not so far been applied to studies in anaesthesia. Heart rate and heart rate variability have been used among a number of measures of workload of anaesthetists.33Weinger MB Reddy SB Slagle J Multiple measures of anesthesia workload during teaching and nonteaching cases.Anesth Analg. 2004; 98: 1419-1425Crossref PubMed Scopus (95) Google Scholar34Weinger MB Slagle J Human factors research in anesthesia patient safety. Techniques to elucidate factors affecting clinical task performance and decision making.J Am Med Inform Assoc. 2002; 9: S58-S63Crossref Google Scholar One recent study used multiple measures to evaluate workload through the period from arrival of the patient for anaesthesia to departure of the patient from the theatre. The mean heart rate for all subject groups was highest at intubation, and displayed a secondary peak at extubation. Heart rate was positively correlated with workload density, observer workload rating, and subjective workload rating for non-teaching cases but not for teaching cases.33Weinger MB Reddy SB Slagle J Multiple measures of anesthesia workload during teaching and nonteaching cases.Anesth Analg. 2004; 98: 1419-1425Crossref PubMed Scopus (95) Google Scholar This question can be addressed on three levels. First, what factors contribute to workload and work intensity in general? Secondly, what are the mental and physical tasks, which the anaesthetist must perform? Thirdly, how are these tasks distributed'that is, how do anaesthetists spend their intra-operative time? Edwards' ergonomic-based model for technological environments identifies four components,9Edwards E Introductory overview.in: Wiener EL Nagel DC Human Factors in Aviation. Academic Press, San Diego, CA1988Crossref Google Scholar which we have drawn on to classify the human and physical factors involved in anaesthesia (Table 3). 'Software' is not restricted to the definition used in computing but includes aspects such as regulations and operating procedures. The 'liveware' element is the most complex, concerning as it does the actions of humans, as individuals and in teams. One specific aspect, noted by Galea and colleagues, is that mental 'underload' can be as stressful as mental overload and is potentially harder to detect.15Galea M Tooze A Smith AF Anaesthetic risk: analysis and reassurance.Clin Risk. 2004; 10: 92-96Crossref Scopus (4) Google ScholarTable 3Factors contributing to workload based on Edwards' typology9Edwards E Introductory overview.in: Wiener EL Nagel DC Human Factors in Aviation. Academic Press, San Diego, CA1988Crossref Google ScholarSoftwareHardwareEnvironmentLivewareList schedulingClarity and intelligibility of monitorsLightingIndividual:Production pressureRange and accuracy of alarmsNoise FatigueMatching workload and work intensity to the availability and capabilities of anaesthetic staffAvailability and reliability of equipmentTemperature and humidity Sleep deprivationDegree of automationLayout of theatres and anaesthetic rooms Boredom Knowledge, skills, experience Attitudes to risk, stress and unanticipated events. Familiarity with equipmentTeam: Communication Lines of authority Training within theatre Open table in a new tab Edwards' classification is useful but the categories are not mutually exclusive. Thus, liveware and hardware elements may interact as in Weinger and colleagues' study, where the use of transoesophageal echocardiography increased workload and decreased vigilance. A further finding was that electronic record-keeping allowed only a small reduction in the charting time but did not adversely affect workload or vigilance.31Weinger MB Herndon OW Gaba DM The effect of electronic record keeping and transesophageal echocardiography on task distribution, workload, and vigilance during cardiac anesthesia.Anesthesiology. 1997; 87: 144-155Crossref PubMed Scopus (122) Google Scholar Loeb found that vigilance levels were similar for anaesthesia residents undertaking manual record-keeping and anaesthesia residents who had assistants to keep records.20Loeb RG Manual record keeping is not necessary for anesthesia vigilance.J Clin Monit. 1995; 11: 5-8Crossref PubMed Scopus (24) Google Scholar The practical procedures of anaesthesia are common and visible but competent anaesthesia requires that appropriate mental tasks are carried out at the same time, in order to ensure patient safety.27Smith AF Goodwin D Mort M Pope C Expertise in practice: an ethnographic study exploring acquisition and use of knowledge in anaesthesia.Br J Anaesth. 2003; 91: 319-328Crossref PubMed Scopus (88) Google Scholar Weinger and colleagues noted that the practice of anaesthesia requires 'many skills, including sustained vigilance, parallel decision-making, and fine motor skills'.32Weinger MB Herndon OW Zornow MH Paulus MP Gaba DM Dallen LT An objective methodology for task analysis and workload assessment in anesthesia providers.Anesthesiology. 1994; 80: 77-92Crossref PubMed Scopus (135) Google Scholar Such skills are a product of sustained practice and experience and are guided in their use by a body of specialized knowledge. While the intra-operative period may have a lower physical task density than the induction and emergence periods, it involves '… querying many sources, which include the patient, the various electronic and manual d
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