The corridor of uncertainty

Clinical decision-making is a strong theme throughout this month’s Anaesthesia. Using the example of cricket (more about the reason for this later!) ‘the corridor of uncertainty’ is an area a bowler aims to pitch their delivery so as to induce uncertainty in the batsman’s decision to play or leave, move forward or back, and defend or attack. Whether or not the correct decision was made soon becomes clear, particularly if a wrong shot, a late movement, hesitation or indecision result in a dismissal. The clinical corridor of uncertainty is arguably no different. We are pitched complex clinical problems and our job is to use knowledge, experience and ‘heuristics’ (more about that here) to make the best decisions for our patients. In anaesthesia and critical care, we soon find out whether or not we made the right choice too! This month’s edition is packed full of clinical content to help reduce uncertainty, guide decision-making and improve care for patients.

First up is a randomised controlled trial from Chambers et al. comparing leak, tidal volume and complications for cuffed vs. uncuffed tracheal tubes in children. They conclude cuffed tubes provide better ventilation and control of respiratory mechanics, are associated with less corrective measures following intubation and result in lower rates of adverse events (Table 1). Craig Bailey argues there is good evidence cuffed tubes enable accurate end tidal measurements, reduce theatre pollution, provide more reliable control of ventilation, are less likely to be exchanged for another sized tube and reduce the incidence of postoperative sore throat and pulmonary aspiration. Of course, such recommendations challenge the accepted wisdom of the last 50 years and we would very much like to know what you think. Will your practice change? Tell us!


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Table 1 Peri-operative and postoperative respiratory complications for all patients by cuffed/ uncuffed groups. Values number (proportion). TT, tracheal tube


The 2017 Australian flu season was the worst seen for many years and so-called ‘Aussie flu’ (H3N2) is now here in the UK. The spread of influenza along with other respiratory viruses seems to be putting considerable pressure on UK hospitals, intensive care units and severe respiratory failure centres (SRFCs). For patients with severe respiratory failure, care can be escalated through referral, acceptance and transfer to a SRFC for the consideration of veno-venous extracorporeal membrane oxygenation (VV-ECMO). Gillon et al. report the results of their retrospective analysis of SRFC referrals to Guy’s and St. Thomas’ in central London. Six-month survival was 72.8% for those accepted to the service and 72.1% for those retrieved with VV-ECMO, which is higher than previously reported. Their results appear to support decision making and clinical practice at the study site and cast doubt on the use of scoring systems as compared with experienced clinical judgment. In their editorial, Charlesworth et al. distil the decision-making process for SRFC referrals into seven themes and conclude expert collaborative clinical assessment is, at present, an acceptable way to manage such referrals. If you are working in an intensive care unit this winter, there is a good chance you will care for patients with severe respiratory failure, so make sure you read these papers!

In their review article, van de Donk et al. discuss the pharmacokinetics and pharmacodynamics of sufentanil and examine its use for acute postoperative pain. They argue the sufentanil sublingual tablet system (SSTS) is effective and may even provide a future alternative to an intravenous morphine PCA system. Bantel and Laycock discuss and critique this evidence in the context of the tactics used by the pharmaceutical industry to promote gabapentin in the 1990s. They find many problems, including the publication of more reviews than original articles, ethical approvals granted by commercial review boards, methodological deficiencies and the use of ghost-writers for two manuscripts. They ask therefore, are SSTSs being promoted with the same marketing tools as used for gabapentin in the 1990s?

We often see discussions on Twitter with regards the documentation of laryngeal view as a means of recording the difficulty of intubation. In his editorial, Brian Jenkins discusses the documentation of ‘the view from the top’ in relation to an article by O’Loughlin et al., in which the accuracy and reliability of three scoring systems for reporting the glottic view at videolaryngoscopy are compared. He argues it is important to contextualise the grade recorded by documenting, as a minimum, equipment, technique, adjuncts and difficulties with obtaining a good laryngeal view. He also suggests the resultant record is an invaluable source of information for to the next operator and the recording of inaccurate or unreliable data should be regarded by all as potentially dangerous.

Continuing with the cricket theme (there was a reason we chose it!), Tavare and Pandit present their much anticipated statistically speaking article, ‘When rain stops play: a ‘Duckworth-Lewis method’ for surgical operating list productivity?’ Is it possible to compare the productivity of, for example, a cardiac theatre with two scheduled cases and a urology theatre undertaking ten operations in the same time period? It turns out we can use a well-known statistical method whose usual function is to calculate the target score for a team batting second in a limited overs match that is interrupted, typically by rain (Figure 1). In fact, the curves for operating theatre productivity are similar to the Duckworth-Lewis cricket model and the same principles seem to apply. Is working in the NHS the same as batting in the rain? The answer is educational, philosophical and entertaining, as is the article as a whole. We really enjoyed reading this one!

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Figure 1 Duckworth–Lewis performance curve relating resources (%, y-axis) to overs remaining (x-axis), as a function of wickets (isopleths). The resource % is then used to calculate the target score for the second team after an interruption.


Elsewhere this month we have a randomised controlled trial comparing high-flow nasal oxygen with standard management for conscious sedation during bronchoscopy, a description of real-time continuous monitoring of injection pressure at the needle tip for peripheral nerve blocks and a review of 21 years of litigation for pain during caesarean section. Finally, if you have exams on the horizon, need a paper for a journal club or simply want to become a statistics expert, we have completely re-organised and updated our special collections. Topics include cardiothoracics, guidelines, hip fractures, obstetrics, paediatrics, regional, research misconduct, statistics, reviews, training and education, and ultrasound. We hope you enjoy this month’s issue as much as we did and we look forward to discussing the articles with our followers on Twitter (each article we tweet is made #FOAMed for that day) in the next few weeks!

Mike Charlesworth, Editor Fellow


Andrew Klein, Editor-in-Chief


Complications of Anaesthesia

The start of a new year isn’t usually much fun. Short days, long nights, back to work and a guilt-driven desire to visit a gym and eat salad. On the other hand, it’s nearly time for the AAGBI Winter Scientific Meeting, and we recently published our free to access supplement issue, ‘Complications’! Our Friday morning session (12th January) is all about the complications of anaesthesia and it is no coincidence the two are related. First up is Dr Alastair Glossop from Sheffield discussing respiratory complications followed by Dr Guillermo Martinez from Cambridge, who will give a much-anticipated talk about cardiovascular complications. Finally, we are delighted to have Dr Heidi Doughty, a consultant in Transfusion Medicine from the NHS Blood & Transplant service, present the complications of blood transfusion. If you are registered for #WSMLondon18 please do come along and engage with us either in person or on Twitter. If you aren’t yet registered, here is the link.

If you simply cannot wait to hear from our speakers, you’re in luck, as our 2018 supplement issue is simply everything you need to know about the complications of anaesthesia. Our special issues are growing in popularity, with each allowing for a particular topic to be set out in extraordinary depth. They are an excellent educational resource that we hope contribute in some way to enhancing the care we provide for our patients. In 2017, we published ‘Monitoring in the peri-operative period’ preceded by ‘Peri-operative medicine’ in 2016 and ‘Transfusion, Thrombosis and Bleeding Management’ in 2015. ‘Complications’ is already having an impact and we hope to see lots of discussions about the articles as we tweet each one over the coming week or so.

Valchanov and Sturgess set the scene (and issue an apology to Atul Gwande!) with their editorial ‘Complications: an anaesthetist’s rather than a surgeon’s notes’. They argue the complications issue is a timely publication, as demands on anaesthetists are increasing, the population is aging, we are seeing more patients with complex comorbid conditions and therefore complications are no-doubt increasing. The culture of complications is changing too, as it is becoming more acceptable to report critical incidents and learn from these reports in an open, no-blame and shared manner.

Merry and Mitchell provide an overview of complications in anaesthesia and question whether or not there is an easy way in which they can be defined or attributed to anaesthesia. Such questions seem trivial enough, but there are no easy answers. From the perspective of human error, which is statistically inevitable, they argue the occurrence of a complication or adverse event does not always equate with a failure in care standards. Nevertheless, every effort should be made to prevent such errors from precipitating these events. This leads nicely to the systematic review from Jones et al. where the role of human factors in preventing anaesthetic complications is examined (methodologically, this is a very difficult literature search/synthesis and the authors must be congratulated!). They included 74 studies and highlight the way in which human factors have become embedded into clinical practice in anaesthesia (Figure 1 and 2). Though the relationship between human factors and anaesthesia is emphasised with the example of complex trauma in the emergency department and operating theatre, the principles are transferrable to all manner of scenarios.

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Figure 1 Human factors recognised by NAP4

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Figure 2 Human factors recognised by NAP5


The respiratory and cardiovascular complications of anaesthesia are core topics for all and the articles by Mills and Sellers et al. are therefore essential reading. Professor Mills sets out the evidence-base for postoperative pulmonary complications and underlines the need for more research to establish the role of postoperative CPAP, non-invasive ventilation and high-flow nasal oxygen. Although the optimum level of intraoperative PEEP is uncertain, the use of lung-protective ventilation during anaesthesia likely reduces the incidence of postoperative pulmonary complications and there is therefore scope for us all to improve patient outcomes. Cardiac complications following major non-cardiac surgery are common and Sellers et al. argue patients should be better triaged to more advanced postoperative care environments based on their preoperative risk. Myocardial injury after non-cardiac surgery is a spectrum (Figure 3) and the use of postoperative troponin assays merits attention through further research. Overall therefore, there seems to be more questions than answers, but there are several measures we can take to prevent respiratory and cardiovascular complications.

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Figure 3 The spectrum of myocardial injury and troponin rise after non-cardiac surgery


There are a range of different topics covered in this issue such as, for example, spinal cord and peripheral nerve injury following anaesthesia, peri-operative neurological complications associated with cardiac surgery and adverse drug reactions. Obstetric anaesthesia is an area with high patient expectation in combination with the need for time-critical high stakes anaesthetic intervention. It is of little surprise there are several commonly occurring obstetric complications together with a small number of rare yet potentially catastrophic complications. The narrative review from Maronge and Bogod discusses their pathophysiology, prevention and management in detail and is therefore a ‘must read’ for all those practicing obstetric anaesthesia. They argue women should be believed when describing symptoms consistent with an iatrogenic injury and that steps should be taken to ensure complications are identified early and treated appropriately.

Though the pathophysiology of perioperative acute kidney injury (AKI) is complex, the article from McKinlay et al. offers an excellent summary of the relationship between contributory surgical, anaesthetic and haemodynamic factors (Figure 4). It is somewhat alarming that, despite easily identifiable risk factors, perioperative AKI accounts for 30-40% of all in-hospital AKI cases and is associated with significant morbidity and mortality, even for seemingly trivial postoperative creatinine rises. Detailed recommendations are provided for preoperative, intraoperative and postoperative strategies to prevent renal complications and the authors call for more consistency in the diagnosis and reporting of postoperative AKI.

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Figure 4 Schematic representation of the potential pathophysiology of perioperative AKI.


Finally, what should we do when complications occur? There are obvious consequences for patients but the impact on healthcare workers must also be considered. Cruikshanks and Bryden argue it is important to put matters right (if possible), apologise and explain the implications of complications when events don’t take their intended course. They list recommendations from the Francis report into the Mid-Staffordshire NHS Trust and argue poor handling of complications will likely lead to complaints and litigation through attempts by patients to receive explanations and support which should have been provided initially.

That’s all for now, but planning for the 2019 supplement ‘Pre-operative optimisation of the surgical patient’ is already well underway. We do hope you enjoy the 2018 complications supplement and that it provides ample education and stimulation whilst retaining clinical relevance to all. Please discuss and engage with the articles either through twitter or formally through our correspondence site as we are always interested to hear what you think. See you in London next week!


Mike Charlesworth                                                               Andrew Klein

Editor Fellow                                                                          Editor-in-Chief