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Summary

  1. Top of page
  2. Summary
  3. Methods
  4. Results
  5. Discussion
  6. Competing interests
  7. References

In aviation, the sterile cockpit rule prohibits non-essential activities during critical phases of flight, takeoff and landing, phases analogous to induction of, and emergence from, anaesthesia. We studied distraction during 30 anaesthetic inductions, maintenances and emergences. Mean (SD) noise during emergence (58.3 (6.2) dB) was higher than during induction (46.4 (4.3) dB) and maintenance (52 (4.5) dB; p < 0.001). Sudden loud noises, greater than 70 dB, occurred more frequently at emergence (occurring 34 times) than at induction (occurring nine times) or maintenance (occurring 13 times). The median (IQR [range]) of staff entrances or exits were 0 (0–2 [0–7]), 6 (3–10 [1–18]) and 10 (5–12 [1–20]) for induction, maintenance and emergence, respectively (p < 0.001). Conversations unrelated to the procedure occurred in 28/30 (93%) emergences. These data demonstrate increased distraction during emergence compared with other phases of anaesthesia. Recognising and minimising distraction should improve patient safety. Applying aviation’s sterile cockpit rule may be a useful addition to our clinical practice.

In 1981, analysis of a number of aviation accidents identified the fact that they were caused by distraction of flight crews from their duties at critical times. Consequently, the Federal Aviation Administration in the US introduced the sterile cockpit rule [1]. This requires pilots to refrain from all non-essential conversation and activity during critical phases of flight, normally below 10 000 feet, effectively, takeoff and landing. Concentration is thus focused on the task in hand.

Takeoff and landing can be regarded as analogous to critical phases of anaesthesia, induction and emergence. Induction of anaesthesia tends to be a calm, quiet and focused time, with the use of anaesthetic rooms providing a physical barrier to noise, interruption and distraction, but emergence in the operating theatre often seems a busier and noisier period. At the end of an operation, the task is to awaken the patient safely. Any non-essential activities could contribute to adverse events through distraction or confusion [2–4]. The aim of this study was to qualify and quantify commonly occurring distractions and non-essential activities during the different phases of anaesthesia.

Methods

  1. Top of page
  2. Summary
  3. Methods
  4. Results
  5. Discussion
  6. Competing interests
  7. References

Approval for the study was gained from the West of Scotland Research Ethics Service. Without revealing the nature of our study, we sought permission from the anaesthetist in charge of each theatre to record data. Data were collected for 30 inductions (from first administration of oxygen or medication until leaving the anaesthetic room), 30 maintenance phases (from commencement of surgical preparation until final wound closure) and 30 emergences (from wound closure completion until the patient left the operating theatre), selected at random, though not by randomisation, and representing all specialties operating within our elective theatres. We recorded the nature and frequency of potential distractions: noise levels; sudden loud noises; number of alarms sounding; whether music was playing; staff numbers present; their movements during each phase of anaesthesia; and the number of conversations unrelated to the task in hand.

Data was recorded during 5-min periods. A decibel reading was taken at time zero and then subsequently at 30-s intervals during each 5-min period. A precision sound-level meter (Bruël and Kjær Model 2215, Copenhagen, Denmark) was used, set for A-weighting [5], which takes account of the frequency sensitivities of the human ear. This meter had been calibrated before commencing data collection. The number of staff present at time zero was noted. Tallies were taken for sounding alarms, conversations and movements. A note was made of any sounds greater than 70 dB and their cause.

One person collected the data. He positioned himself in each theatre so that he was as close as possible to the anaesthetist (so as to represent the anaesthetist’s perspective most accurately) without causing any obstruction or interfering with the working environment. Due to the diversity of theatre layouts, it was not possible to standardise a single spot from which to collect data in all theatres. The sound-level data were analysed using ANOVA with a post-hoc Scheffé test. The ‘total number’ datasets were analysed using Kruskall–Wallis tests, each followed by three separate Mann–Whitney tests to act as post-hoc, with a Bonferroni correction applied. The ‘number of phases’ datasets were analysed using chi-squared tests. All tests were conducted using Predictive Analytics Software Statistics 16 (SPSS Inc, Chicago, IL, USA).

Results

  1. Top of page
  2. Summary
  3. Methods
  4. Results
  5. Discussion
  6. Competing interests
  7. References

Data collected were representative of all surgical specialties in our hospital’s operating theatres. The 90 datasets recorded comprised 27 orthopaedic, 15 general, 15 ear, nose and throat, 12 urology, 11 ophthalmology and 10 vascular cases. Although we had planned to make 900 measurements (30 cases with 10 measurements each in the three phases), in total 841 sound level measurements were made, as some induction and emergence phases were completed before a full set was taken. There were at least four measurements in every case, and a complete set of 10 measurements was made in 72 of 90 cases. The mean (SD) time that data were recorded during each of the phases, in minutes and seconds, was 4 min 42 s (35 s) for induction, 5 min (0 s) for maintenance and 4 min (53 s) during emergence.

Auditory distractions increased significantly as phases of anaesthesia progressed. Sound levels were significantly greater during emergence than during other phases. All three phases differed significantly from each other, with induction being the quietest phase. As well as having the highest sound level, emergence also showed the greatest variation in levels, with the highest standard deviation of the three phases. Sudden loud sounds, above 70 dB, were also more frequent during emergence (occurring 34 times) than other phases (occurring nine and 13 times, respectively). Common sources of such noises included slamming doors or bins, loud conversation, singing and dropped equipment. Significantly greater alarm noise was also noted at emergence versus induction. In addition, we found that the number of unrelated conversations varied significantly with phase. More conversations occurred during emergence and there was also a greater likelihood of multiple simultaneous conversations during this phase. Finally, music was significantly more likely to be playing during emergence and maintenance than induction (Table 1).

Table 1.   Auditory distractions during three phases of anaesthesia. Values are mean (SD), median (IQR [range]) or number (proportion).
 Induction (n = 30)Maintenance (n = 30)Emergence (n = 30)p value
Sound level; dB46.4 (4.3)52.0 (4.5)58.3 (6.2)< 0.001
Total number of alarms1 (0–1 [0–4])0 (0–0 [0–7])1 (0–2 [0–7])0.003
Phases with conversations12 (40%)22 (73%)28 (93%)0.001
Phases with ≥ 2 simultaneous conversations1 (3%)6 (20%)13 (43%)0.001
Phases with music playing09 (30%)11 (37%)0.001

Physical distractions followed a similar trend to auditory distractions. Significantly fewer staff members were present at induction than during the other phases of anaesthesia. Two inductions occurred in theatre and had nine staff members present on each occasion. We found that the number of room entrances and exits by staff varied with phase, with induction having significantly fewer movements than other phases. Nineteen inductions (63%) had zero entrances or exits during data recording. One case during emergence had 20 entrances/exits recorded over a 5-min period (Table 2).

Table 2.   Physical distractions during phases of anaesthesia. Values are median (IQR [range]) or number (proportion).
 Induction (n = 30)Maintenance (n = 30)Emergence (n = 30)p value
  1. *Induction differed significantly from the other phases but maintenance and emergence did not differ significantly from one another.

Total number of staff present3 (3–4 [2–9])8 (6–10 [4–10])7 (6–8 [3–12])< 0.001*
Total number of staff entrances or exits0 (0–2 [0–7])6 (3–10 [1–18])10 (5–12 [1–20])< 0.001*
Number of phases with ≥ 10 entrances or exits08 (27%)17 (57%)< 0.001

Discussion

  1. Top of page
  2. Summary
  3. Methods
  4. Results
  5. Discussion
  6. Competing interests
  7. References

These data suggest that there is substantial noise and a potential for auditory and physical distraction during every phase of anaesthesia but that the noise levels and distractions are least during induction and greatest during emergence. Emergences occurred in the presence of more staff, making more noise and with greatly increased staff movement when compared with induction. All the authors have worked in several UK hospitals and feel that practice in our current hospital is representative.

Excessive noise has several potentially detrimental physiological and psychological effects [2]. Operating theatre noise has been shown to reduce anaesthetic residents’ mental efficiency and short-term memory [3]. It is recognised that excessive noise interferes with performance during any task reliant on auditory signals and that unpredictable noises cause greater distraction [4]. We found that noise levels were significantly higher during emergence compared with other phases and that the difference between mean noise levels during induction and emergence was 12 dB. This is at least a doubling of subjective loudness.

In particular, we demonstrate a large number of unpredictable loud noises during emergence and high levels of conversation unrelated to the anaesthetic procedure, often with multiple conversations occurring simultaneously. Previous work has shown that this sort of communication directed at anaesthetists can cause significantly greater distraction in the operating theatre than those directed at surgeons [6]. Music was found to be playing during over a third of emergences, but never during induction. Although there is some evidence that music can improve performance [7, 8], over a quarter of anaesthetists in one survey said that music reduces their vigilance and ability to communicate and over 50% felt that it would be distracting during a difficult anaesthetic. In addition, any beneficial effects may be dependent on whether the music is to the anaesthetist’s taste [9].

Perhaps the most notable differences, in the three phases of anaesthesia examined, were in staff movements, with emergence presenting the greatest problem. The entrances/exits of staff frequently caused sudden loud noises, with door slamming the commonest cause of sounds over 70 dB. The physical barrier provided by the anaesthetic room at induction presumably contributes to the lack of such distractions. Apart from direct distraction of the anaesthetist by excessive movements, a busy theatre may effect important non-verbal communication and also hamper the patient’s calm emergence from anaesthesia [10].

As many as 11% of hospital patients experience an adverse event, of which up to half may be preventable [11]. This study highlights the potential distraction of the anaesthetist as a safety issue and is timely, considering the safety initiatives coordinated by the National Patient Safety Agency [12]. A large body of work highlights the impact of human factors on the occurrence of adverse events and their role in improving safety in anaesthesia [13–19]. In particular, the failure of non-technical skills is frequently cited directly or by implication. The importance of non-technical skills for anaesthetists has been discussed previously [20] and it is recognised that effective communication underpins this. Situational awareness is a key non-technical skill [21] and the most basic level of competence in this demands ‘the perception of the elements in the environment within a volume of time and space’ [22]; in our case, the anaesthetised patient within the operating theatre environment [23, 24]. Previous work has studied noise in the operating theatre and concluded that excessive noise has caused difficulties in communication and concentration [25]. Distracting concentration will impact on anaesthetists’ situational awareness. Studies in aviation have shown a correlation between situational awareness and performance [26, 27]. Interruptions have been reported as a significant contributory cause in 7% of aviation incidents [28].

Without awareness of one’s environment or the ability of staff to communicate clearly, appropriate care of the patient may be absent, misinformed or misdirected and the opportunity for error increases. It is difficult to identify what absolute level of noise, distraction or interruption should be regarded as unacceptable. Common sense will inevitably be required, but we feel that our results warrant reflection at least, if not an actual change in theatre practice during emergence. A reminder to theatre staff towards the end of an operation to eliminate extraneous conversations and unnecessary movements until the patient has left theatre would be a simple intervention to make. Music could be turned off and staff not involved in emergence could leave theatre. This may cause a few minutes’ delay in case turnover but the effect would be minor when considered against a backdrop of improved patient safety during emergence from anaesthesia. Even if such changes could not be implemented, a simple increase in vigilance by the anaesthetist during emergence may help with patient safety. According to error modelling [29], any single distraction, of the sort that we have demonstrated, would be unlikely in itself to lead directly to a critical incident. It would, however, increase the adverse conditions of a system, thus increasing the opportunity for serious harm.

The concept of the sterile cockpit may well be a useful lesson from aviation [30]. Takeoff and landing can be regarded as analogous to induction and emergence from anaesthesia. There has been some interest in this concept in surgical specialties [31–33], whereas other studies have considered intra-operative distractions [2, 6, 25]. We are, however, unaware of any studies measuring anaesthetic distractions with particular emphasis on the critical phases of induction and emergence and reference to the sterile cockpit concept. Psychological factors such as distraction are difficult to measure and manage, but by identifying the organisational elements giving rise to these, it may be possible to reduce harm [34]. A systems-centred approach to safety, identifying latent risk within an environment, is an alternative to the more widely considered person-centred approach [35]. The idea of an anaesthetic sterile cockpit may well be a useful for improving patient safety and warrants further study.

Competing interests

  1. Top of page
  2. Summary
  3. Methods
  4. Results
  5. Discussion
  6. Competing interests
  7. References

No external funding and no competing interests declared.

References

  1. Top of page
  2. Summary
  3. Methods
  4. Results
  5. Discussion
  6. Competing interests
  7. References