Aerosol-generating patients, not procedures

Peri-operative literature exploded in early 2020 with much in the way of low-quality COVID-19 anecdotes, secondary analyses, reviews and reviews of reviews. Today, we are delighted to have published several excellent primary scientific experiments that challenge our now well-established and sometimes precautionary guidelines and protocols. The AERATOR study group have done it again with a paper grounded in aerosol science but with significant clinical implications for all. The message is that we should see the issue as one of ‘aerosol-generating patients’ rather than ‘aerosol-generating procedures’ (Fig. 1). However, we remain a long way from truly acknowledging test-positive awake COVID-19 patients as ‘riskier’ to care for than test-negative patients undergoing elective surgery. Thankfully, the AERATOR group have another paper coming soon to reinforce the message!

Figure 1 Aerosol measurements during supraglottic airway insertion and removal. (a) Time profile of aerosol generation from volitional coughs. Average time course of volitional coughs plotted (mean with 95%CI) showing a peak after 2 s and a rapid decay back to baseline. Individual recordings (n = 27) represented on heat map showing the total number particle concentration over time. (b) Size distribution of peak aerosol concentrations from volitional coughs (n = 27). (c) Time-course of aerosol during uneventful supraglottic airway insertions (n = 11, mean ± 95%CI); inset chart with altered y-axis to demonstrate very low concentration of particles sampled. (d) Aerosol detected during the eventful insertion showing the period of supraglottic airway removal and reinsertion; inset chart shows particle size distribution of the peak aerosol sample associated with the supraglottic airway removal, note the difference in size distribution compared with a volitional cough (b).

Obesity is increasingly prevalent in England and there is a suggestion that patients undergoing elective surgery are more likely to be obese than the general population. This new prospective observational study from Shaw et al. finds this to be the case for a population of patients in the London area, with obesity also associated with increased minor airway events. The most common of these was oxygen desaturation below 90% and the second was maintaining adequate ventilation using a supraglottic airway device. In the associated editorial, Duggan and El-Boghdadly set these results in their clinical context and remind us that data were collected before the COVID-19 pandemic. Much has since changed. They remind us of the power of observational studies in airway management: randomised trials are scarce; observational studies can change practice; and collaborative research is the future.

How best to study postoperative recovery after major surgery? There has been (rightly so!) a move away from mortality and complication rates and focus has instead shifted to functional recovery. This new multicentre prospective cohort study from Ladha et al. finds that more participants reported decline than improvement in at least one EQ-5D functional domain 30 days after surgery but not 1 y after surgery. Functional decline was associated with worse pre-operative fitness and moderate or severe postoperative complications. We have two further excellent peri-operative papers this month. First, Drake et al. report a before-and-after analysis of the introduction of a standardised maternity early warning system. They observed a significant and sustained reduction in severe maternal morbidity, and a non-significant reduction in cardiorespiratory arrest calls. Second, Awadalla et al. describe the impact of the Australian/New Zealand organisational position statement on extended-release opioid prescribing among surgical inpatients. They found it was associated with an overall decrease in opioid prescribing among surgical inpatients as well as a decrease in extended-release opioids among patients who received any opioid at two Australian hospitals (Fig. 2). In the associated editorial, Levy et al. list the problems with extended-release opioid preparations as well as strategies for their de-implementation.

Figure 2 Proportion of patients who were prescribed extended-release opioids among all surgical inpatients who received any opioid by month.

How can Never Event data be used to reflect or improve hospital safety performance? Olivarius-McAllister et al. compare annual rates of Never Events and finished consultant episodes from 2017 to 2020 by acute hospital Trust (Fig. 3). The absolute number of Never Events was correlated with workload (r2 = 0.51, p < 0.001), but the five Trusts above the upper 95% confidence limit did not have the highest number of Never Events. They argue we should focus now on reducing the mean national Never Event rate through an integrated safety strategy. In the associated editorial, Devlin and Smith describe the problems associated with Never Events, such as that they continue to happen with near certainty and can be well modelled. They argue we should try to improve by redesigning our systems to reinforce their components that create safety, rather than continuing to grant cultural and linguistic supremacy to negative and punitive approaches.

Figure 3 Correlation of 3 years’ cumulative events vs. episode in 151 Trusts (black circles). The solid red (jagged) line is the predicted number of events (rounded) from the overall mean. The dashed red lines are the 95%CIs. The grey line is the linear regression line (slope 1.6 events per 100,000 episodes; r2 0.510, p < 0.001).

Guidelines can sometimes present an editorial dilemma. This new document is an Association of Anaesthetists guideline and we are the journal of the Association. Yet, some might suggest this guideline and others are not scientific or clinical enough to warrant publication in the journal. Some initial feedback on Twitter seems to suggest we made the correct decision, as it turns out ergonomics as applied to peri-operative practice is an incredibly important topic to clinically practicing anaesthetists. For example, we received over 200 retweets and 198,532 Twitter impressions on the day of publication, which is great! The guideline is novel too, as there were, until now, no guidelines on ergonomics in the anaesthetic workplace. Much of the included evidence is from other industries which seems to suggest a need for more primary evidence in this area.

Elsewhere we have: a systematic review of intrathecal morphine for analgesia after lower joint arthroplasty; validation of the factors influencing family consent for organ donation in the UK; and editorials commenting on research in regional anaesthesia and organ donation.

Finally, this new statistics contribution describes some fundamental aspects of significance testing, which is the basis of most of what we need to know as clinicians. It is, therefore, essential reading for all, and probably one of the most useful statistics papers that we have read recently. From time-to-time, questions about shifts in practice come up. Should we scrap the p value? Should we use confidence intervals? Should we report the fragility index? Should we use a Bayesian approach? Perhaps rather than shaking up how we ‘do’ statistics, we should instead focus on better understanding. This paper helps greatly to achieve that goal for us all.

As we come towards the end of the year our focus now moves to our 2022 supplement, which will this time be all about the brain and anaesthesia! We will also be rekindling our popular ‘how to publish a paper’ workshop for the Winter Scientific Meeting 2022 which is free to all who register. We look forward to seeing you there.

Mike Charlesworth and Andrew Klein

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