Month: December 2021

Understanding unrecognised oesophageal intubation

Last week, we brought you a live broadcast all about the new editorial from Pandit, Young and Davies, which is available now on early view. We received some excellent commentary on Twitter, none more so than this thread from Tanya Selak. This month, Professor Pandit also argues that ‘no trace, wrong place’ does not mean ‘positive trace, right place’. It seems that a better way of thinking is that absent traces justify tube removal, and abnormal or attenuated waveforms warrant investigation to re-confirm tracheal tube position, with further management guided by the balance of risks (Fig. 1). There is much here in these contributions to think about for all those with an interest in airway management.

Figure 1 Examples of ETCO2 waveforms with suggested courses of actions for each. From left to right: normal trace; flat trace, as might arise with oesophageal intubation (notwithstanding other causes in blue section of Fig. 1a); attenuated trace (here, a maximum value < 0.2 kPa is shown; it may be higher), as might arise with CPR (pink section of Fig. 1a). This scheme applies primarily to attempted tracheal intubation during CPR but also has relevance for all other situations. With an attenuated trace, ETCO2 may be optimised by more effective CPR. So long as the trace remains attenuated, these measures may need to be repeated. FOB, fibreoptic bronchoscopy (ultrasound may also be used); ABG, arterial blood gas analysis.

Patients generate aerosols, not procedures – say scientists. But most local and national infection control policies in the UK still refer to precautions required around certain procedures, even in low risk isolated test-negative patients. The new paper from the AERATOR study group is all about manual facemask ventilation, and the results will come as no surprise to many. They found that tidal breathing and a volitional cough generate many-fold more aerosol than facemask ventilation. Another so called aerosol generating procedure is the use of nasal high flow oxygen, which is becoming increasingly important in peri-operative practice. Lyons et al. report that pre-oxygenation with high-flow nasal oxygen in combination with oxygen via a mouthpiece causes higher arterial oxygen partial pressures and lengthens the time-to-desaturation after the onset of apnoea when compared with facemask pre-oxygenation. However, Thiruvenkatarajan et al. find that in high-risk patients undergoing ERCP within the context of target-controlled infusion based propofol administration, oxygen delivery using high-flow nasal oxygen did not reduce the rate of hypoxaemia, hypercarbia and the need for major and minor airway interventions, compared with low-flow nasal plus mouthguard oxygen. In the associated editorial, Patel and El-Boghdadly discuss the case for switching to high-flow nasal oxygen in all circumstances. It seems that only when we can seamlessly transition between oxygen delivery systems, without the risk of barotrauma and with optimal monitoring, will this switch be embraced. Until then, high-flow nasal oxygen has a specifically defined role for certain indications only. 

Figure 2 Aerosol concentration measured during the experimental protocol. This shows the concentration of particles detected during baseline respiratory manoeuvres (tidal breathing and voluntary coughs), background monitoring, facemask ventilation with no leak and facemask ventilation with a leak.

In August, we were delighted to publish the COVIDSurg/GlobalSurg collaborative work on SARS-CoV-2 infection and venous thromboembolism (VTE) after surgery. They found that SARS-CoV-2 infection was independently associated with an increased incidence of postoperative VTE in patients with peri-operative and recent SARS-CoV-2 infection. Marshall and Duggan in their editorial discuss various aspects of the study as well as the effect of VTE on surgical patients, prophylaxis protocols, and how this all fits in with contemporary peri-operative risk management. 

Which size tracheal tube best facilitates general anaesthesia in adults? This new RCT from Cho et al. stimulated a lot of discussion on social media, with the main finding that sore throat and hoarse voice 1 and 24 h after surgery were less frequent and less severe after intubation with smaller tubes. Ventilatory mechanics were unaffected. Another controversy is the management of haematoma after thyroid surgery, but this new guideline aims to change that as the first to report the multidisciplinary management of haematoma following thyroid surgery, either in the anaesthetic or in the surgical literature. A final area of controversy is how best to define the ‘decision-to-delivery’ interval for a non-elective caesarean section. In particular, there is a wide variation as to the interpretation of when the ‘decision’ occurs, ranging from the time that the obstetrician in attendance documents the decision, to when the whole team is alerted, or to when the patient is prepared for the operating theatre. May et al. review all the relevant literature and provide a useful definition that can be used for audits, research and clinical practice.

Elsewhere we have: an observational study of surgery and general anaesthesia on sleep-wake timing; an observational study of the right supraclavicular fossa ultrasound view for correct catheter tip positioning in right subclavian vein catheterisation; a non-inferiority trial of supraclavicular versus infraclavicular approach for ultrasound-guided right subclavian venous catheterisation; and a discussion of best practice for subclavian central venous access. 

Finally, we are looking forward to releasing our 2022 supplement in early January, which is all about the brain and implications for peri-operative practice. We will also be relaunching our popular ‘how to publish a paper’ workshop at the Winter Scientific Meeting on the 14th of January. It is free for all delegates. See you there!

Mike Charlesworth and Andrew Klein