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Journal: Anaesthesia

149

Cognition may decline after surgery. Postoperative delirium, especially when hyperactive, may be easily recognised, whereas cognitive dysfunction is subtle and can only be detected using neuropsychological tests. The causes for these two conditions are largely unknown, although they share risk factors, the predominant one being age. Ignorance of the causes for postoperative cognitive dysfunction contributes to the difficulty of conducting interventional studies. Postoperative cognitive disorders are associated with increased mortality and permanent disability. Peri-operative interventions can reduce the rate of delirium in the elderly, but in spite of promising findings in animal experiments, no intervention reduces postoperative cognitive dysfunction in humans.

Concepts: Neurocognitive, Intervention

117

Awake tracheal intubation has a high success rate and a favourable safety profile but is underused in cases of anticipated difficult airway management. These guidelines are a comprehensive document to support decision making, preparation and practical performance of awake tracheal intubation. We performed a systematic review of the literature seeking all of the available evidence for each element of awake tracheal intubation in order to make recommendations. In the absence of high-quality evidence, expert consensus and a Delphi study were used to formulate recommendations. We highlight key areas of awake tracheal intubation in which specific recommendations were made, which included: indications; procedural setup; checklists; oxygenation; airway topicalisation; sedation; verification of tracheal tube position; complications; management of unsuccessful awake tracheal intubation; post-tracheal intubation management; consent; and training. We recognise that there are a range of techniques and regimens that may be effective and one such example technique is included. Breaking down the key practical elements of awake tracheal intubation into sedation, topicalisation, oxygenation and performance might help practitioners to plan, perform and address complications. These guidelines aim to support clinical practice and help lower the threshold for performing awake tracheal intubation when indicated.

106

Healthcare workers involved in aerosol-generating procedures, such as tracheal intubation, may be at elevated risk of acquiring COVID-19. However, the magnitude of this risk is unknown. We conducted a prospective international multicentre cohort study recruiting healthcare workers participating in tracheal intubation of patients with suspected or confirmed COVID-19. Information on tracheal intubation episodes, personal protective equipment use, and subsequent provider health status was collected via self-reporting. The primary endpoint was the incidence of laboratory-confirmed COVID-19 diagnosis or new symptoms requiring self-isolation or hospitalisation after a tracheal intubation episode. Cox regression analysis examined associations between the primary endpoint and healthcare worker characteristics, procedure-related factors, and personal protective equipment use. Between 23 March and 2 June 2020, 1718 healthcare workers from 503 hospitals in 17 countries reported 5148 tracheal intubation episodes. The overall incidence of the primary endpoint was 10.7% over a median (IQR [range]) follow-up of 32 (18-48 [0-116]) days. The cumulative incidence within 7, 14 and 21 days of the first tracheal intubation episode was 3.6%, 6.1%, and 8.5%, respectively. The risk of the primary endpoint varied by country and was higher in females, but was not associated with other factors. Around 1 in 10 healthcare workers involved in tracheal intubation of patients with suspected or confirmed COVID-19 subsequently reported a COVID-19 outcome. This has human resource implications for institutional capacity to deliver essential healthcare services, and wider societal implications for COVID-19 transmission.

65

Observational studies have highlighted the detrimental health effects of shift work. The mechanisms through which acute sleep deprivation may lead to chronic disease have not been elucidated, but it is thought that increased DNA damage or decreased repair can lead to disease. The objective of this study was to examine the effects of acute sleep deprivation on DNA damage. This was a cross-sectional observational study on 49 healthy, full-time doctors. Baseline blood was sampled from each participant after three consecutive days of adequate sleep. Participants (n = 24) who were required to work overnight on-site had additional blood sampled on a morning after acute sleep deprivation. DNA damage and expression of DNA repair genes were quantified. Information on health, working patterns and sleep diaries were collected. Independent t-tests were used to compare differences between groups and standardised mean differences expressed as Cohen’s d. Overnight on-site call participants had lower baseline DNA repair gene expression and more DNA breaks than participants who did not work overnight (d = 1.47, p = 0.0001; and 1.48, p = 0.0001, respectively). In overnight on-site call participants, after acute sleep deprivation, DNA repair gene expression was decreased (d = 0.90, p = 0.0001) and DNA breaks were increased (d = 0.87, p = 0.0018). Sleep deprivation in shift workers is associated with adverse health consequences. Increased DNA damage has been linked to the development of chronic disease. This study demonstrates that disrupted sleep is associated with DNA damage. Furthermore, larger prospective studies looking at relationships between DNA damage and chronic disease development are warranted, and methods to relieve, or repair, DNA damage linked to sleep deprivation should be investigated.

60

The COVID-19 pandemic has led to the production of novel devices intended to protect airway managers during the aerosol-generating procedure of tracheal intubation. Using an in-situ simulation model, we evaluated laryngoscopist exposure of airborne particles sized 0.3 - 5.0 microns using five aerosol containment devices (aerosol box; sealed box with and without suction; vertical drape; and horizontal drape) compared with no aerosol containment device. Nebulised saline was used as the aerosol-generating model for 300 seconds, at which point, the devices were removed to assess particle spread. Primary outcome was the quantity and size of airborne particles measured at the level of the laryngoscopist’s head at 30, 60, 120, and 300 seconds, as well as 360 seconds (60 seconds after device removal). Airborne particles sizes of 0.3, 0.5, 1.0, 2.5 and 5.0 microns were quantified using an electronic airborne particle counter. Compared with no device use, the sealed intubation box with suction resulted in a decrease in 0.3, 0.5, 1.0 and 2.5 micron, but not 5.0 micron, particle exposure over all time-periods (p = 0.003 for all time periods). Compared with no device use, the aerosol box showed an increase in 1.0, 2.5 and 5.0 micron airborne particle exposure at 300 seconds (p = 0.002, 0.008, 0.002, respectively). Compared with no device use, neither horizontal nor vertical drapes showed any difference in any particle size exposure at any time. Finally, when the patient coughed, use of the aerosol box resulted in a marked increase in airborne particle exposure compared with other devices or no device use. In conclusion, novel devices intended to protect the laryngoscopist require objective testing to ensure they are fit for purpose and do not result in increased airborne particle exposure.

57

Despite being infrequent, complications of airway management remain an important contributor to morbidity and mortality during anaesthesia and care of the critically ill. Developments in the last three decades have made anaesthesia safer, and this has been mirrored in the equipment and techniques available for airway management. Modern technology including novel oxygenation modalities, widespread availability of capnography, second-generation supraglottic airway devices and videolaryngoscopy provide the tools to make airway management safer still. However, technology will only take safety so far, and non-technical aspects of airway management are critically important for communication and decision making during airway crises, acknowledging a ‘cannot intubate, cannot oxygenate’ situation and transitioning to emergency front of neck airway. Randomised controlled trials provide little useful information about safety in this setting, and data from registries and databases are likely to be of more value. This narrative review focuses on recent evidence in this area.

Concepts: Critical thinking, The Canon of Medicine, Randomized controlled trial, Decision theory, Anesthesia, Endotracheal tube, Pulse oximetry, Character

49

Randomised, controlled trials have been retracted after publication because of data fabrication and inadequate ethical approval. Fabricated data have included baseline variables, for instance, age, height or weight. Statistical tests can determine the probability of the distribution of means, given their standard deviation and the number of participants in each group. Randomised, controlled trials have been retracted after the data distributions have been calculated as improbable. Most retracted trials have been written by anaesthetists and published by specialist anaesthetic journals. I wanted to explore whether the distribution of baseline data in trials was consistent with the expected distribution. I wanted to determine whether trials retracted after publication had distributions different to trials that have not been retracted. I wanted to determine whether data distributions in trials published in specialist anaesthetic journals have been different to distributions in non-specialist medical journals. I analysed the distribution of 72,261 means of 29,789 variables in 5087 randomised, controlled trials published in eight journals between January 2000 and December 2015: Anaesthesia (399); Anesthesia and Analgesia (1288); Anesthesiology (541); British Journal of Anaesthesia (618); Canadian Journal of Anesthesia (384); European Journal of Anaesthesiology (404); Journal of the American Medical Association (518) and New England Journal of Medicine (935). I chose these journals as I had electronic access to the full text. Trial p values were distorted by an excess of baseline means that were similar and an excess that were dissimilar: 763/5015 (15.2%) trials that had not been retracted from publication had p values that were within 0.05 of 0 or 1 (expected 10%), that is, a 5.2% excess, p = 1.2 × 10(-7) . The p values of 31/72 (43%) trials that had been retracted after publication were within 0.05 of 0 or 1, a rate different to that for unretracted trials, p = 1.03 × 10(-10) . The difference between the distributions of these two subgroups was confirmed by comparison of their overall distributions, p = 5.3 × 10(-15) . Each journal exhibited the same abnormal distribution of baseline means. There was no difference in distributions of baseline means for 1453 trials in non-anaesthetic journals and 3634 trials in anaesthetic journals, p = 0.30. The rate of retractions from JAMA and NEJM, 6/1453 or 1 in 242, was one-quarter the rate from the six anaesthetic journals, 66/3634 or 1 in 55, relative risk (99%CI) 0.23 (0.08-0.68), p = 0.00022. A probability threshold of 1 in 10,000 identified 8/72 (11%) retracted trials (7 by Fujii et al.) and 82/5015 (1.6%) unretracted trials. Some p values were so extreme that the baseline data could not be correct: for instance, for 43/5015 unretracted trials the probability was less than 1 in 10(15) (equivalent to one drop of water in 20,000 Olympic-sized swimming pools). A probability threshold of 1 in 100 for two or more trials by the same author identified three authors of retracted trials (Boldt, Fujii and Reuben) and 21 first or corresponding authors of 65 unretracted trials. Fraud, unintentional error, correlation, stratified allocation and poor methodology might have contributed to the excess of randomised, controlled trials with similar or dissimilar means, a pattern that was common to all the surveyed journals. It is likely that this work will lead to the identification, correction and retraction of hitherto unretracted randomised, controlled trials.

Concepts: Surgery, Anesthesia, Anesthesiologist, Local anesthetic, Retraction, Journal of the American Medical Association, American Medical Association, Twilight anesthesia

39

The Obstetric Anaesthetists' Association and Difficult Airway Society have developed the first national obstetric guidelines for the safe management of difficult and failed tracheal intubation during general anaesthesia. They comprise four algorithms and two tables. A master algorithm provides an overview. Algorithm 1 gives a framework on how to optimise a safe general anaesthetic technique in the obstetric patient, and emphasises: planning and multidisciplinary communication; how to prevent the rapid oxygen desaturation seen in pregnant women by advocating nasal oxygenation and mask ventilation immediately after induction; limiting intubation attempts to two; and consideration of early release of cricoid pressure if difficulties are encountered. Algorithm 2 summarises the management after declaring failed tracheal intubation with clear decision points, and encourages early insertion of a (preferably second-generation) supraglottic airway device if appropriate. Algorithm 3 covers the management of the ‘can’t intubate, can’t oxygenate’ situation and emergency front-of-neck airway access, including the necessity for timely perimortem caesarean section if maternal oxygenation cannot be achieved. Table 1 gives a structure for assessing the individual factors relevant in the decision to awaken or proceed should intubation fail, which include: urgency related to maternal or fetal factors; seniority of the anaesthetist; obesity of the patient; surgical complexity; aspiration risk; potential difficulty with provision of alternative anaesthesia; and post-induction airway device and airway patency. This decision should be considered by the team in advance of performing a general anaesthetic to make a provisional plan should failed intubation occur. The table is also intended to be used as a teaching tool to facilitate discussion and learning regarding the complex nature of decision-making when faced with a failed intubation. Table 2 gives practical considerations of how to awaken or proceed with surgery. The background paper covers recommendations on drugs, new equipment, teaching and training.

Concepts: Pregnancy, Childbirth, Surgery, Obstetrics, Anesthesia, Endotracheal tube, Caesarean section, Pulmonary aspiration

38

The global COVID-19 pandemic has led to a worldwide shortage of ventilators. This shortage has initiated discussions of how to support multiple patients with a single ventilator (ventilator splitting). Ventilator splitting is incompletely tested, experimental and the effects have not been fully characterised. This study investigated the effect of ventilator splitting on system variables (inspiratory pressure, flow, and volume) and the possibility of different ventilation targets for each limb using only standard hospital equipment. Experiments were conducted on two test lungs with different compliances (0.02 and 0.04 l.cmH2 O-1 ). The ventilator was used in both pressure and volume control modes and was set to ventilate the low compliance lungs at end-tidal volumes of 500 ± 20 ml. A flow restrictor apparatus consisting of a Hoffman clamp and tracheal tube was connected in series to the inspiratory limb of the high compliance test lungs and the resistance modified to achieve end-tidal volumes of 500 ± 20 ml. The restriction apparatus successfully modified the inspiratory pressure, minute ventilation, and volume delivered to the high compliance test lungs in both pressure control (27.3-17.8 cm H2 O, 15.2-8.0 l.min-1 and 980-499 ml, respectively), and volume control (21.0-16.7 cm H2 O, 10.7-7.9 l.min-1 and 659-498 ml, respectively) ventilation modes. Ventilator splitting is not condoned by the authors. However, these experiments demonstrate the capacity to simultaneously ventilate two test lungs of different compliances, and using only standard hospital equipment, modify the delivered pressure, flow, and volume in each test lung.

38

We examined the prevalence of novel acronyms in the titles of anaesthetic and related studies and the response of anaesthetists to them. We separately analysed trainee-led research projects in the UK supported by the Research and Audit Federation of Trainees (RAFT), and a 10-year cohort of papers identified using the PubMed literature search tool. We also conducted a survey of 20 anaesthetists within our institution regarding the utility and impact of titles containing acronyms, and their recall of the associated topics. Finally, we developed a scoring system for acronym accuracy and complexity, the ORigin of AcroNym letterinG Used Term AppropriateNess (ORANGUTAN) score, and measured the progression of acronym usage over the 10-year period studied. Our results show that while acronyms themselves are sometimes considered memorable, they do not aid recall of topics and are, in general, not considered helpful. There has been an increase in the prevalence of acronymic titles over 10 years, and in the complexity of acronyms used, suggesting that there is currently a selective pressure favouring the use of acronyms even if they are of limited benefit.