Curarisation compared with other methods of securing relaxation in anaesthesia

We begin 2021, the year of our 75th anniversary, with a special commentary on our first ever original article, which was published in 1946 and was all about initial experiences with curare. This is the first in a new limited monthly series of articles we have called ‘Contemporary Classics’, and each looks at a popular paper from a subsequent decade. This month’s offering reminds us of three important areas for future research: studying the effects of deep intra‐operative neuromuscular blockade on patient‐centred outcomes; the implementation of quantitative neuromuscular blocking monitoring into widespread clinical practice; and the need for an ideal neuromuscular blocking drug that can be readily switched on and off. Next month, we tackle the subject of deaths associated with anaesthesia, and the index paper from the 1950s shows just how far clinical governance and audit have come in 60 or so years. We hope you enjoy these articles and all that the Association of Anaesthetists have planned to celebrate the occasion throughout the year.

Resternotomy following cardiac surgery has always been suspected to be associated with poor outcomes, and this new national audit from Agarwal et al. seems to confirm these suspicions. They were able to pool data from 23 UK centres and found that the mortality in these patients was 15%, with ~90% requiring transfusion of red cells and ~23% requiring renal replacement therapy (Fig. 1). Kendall and O’Keeffe list strategies that may one day enable us to eradicate resternotomy from clinical practice, and provide a discussion of the associated historical context. In October 2020, the PREVENTT trial of pre-operative intravenous iron to treat anaemia before major abdominal surgery was published in The LancetA summary of the methods, results and clinical implications is provided this month by Lachlan Miles, who suggests we should now all re-evaluate our practice but also that the story of intravenous iron in the pre-operative period is by no means over. In their editorial, Sharma et al. discuss the role of routine postoperative troponin measurement in the diagnosis and management of myocardial injury after non-cardiac surgery. They argue there should now be a shift to the use of pre-operative biochemical marker measurements instead of tools such as the modified revised cardiac risk index to risk stratify patients before surgery. 

Figure 1 Time from arrival in ICU to resternotomy in those who did and did not require renal replacement therapy. The (median (IQR [range]) of those who required renal replacement therapy 960 (293–3805 [5–44,640]) min vs. those who did not 420 (180–1046 [0–60,500]) min. *, p < 0.001.

Last year, Khan et al. published their secondary analysis showing that fluid optimisation before induction of general anaesthesia did not significantly affect the occurrence or degree of haemodynamic instability during induction. This month, Wong and Irwin discuss the implications, including the limitations of the study by Khan et al., and conclude it is not possible to determine from the available data whether modest fluid administration, presumably to compensate for fasting, can indisputably prevent post‐induction hypotension. Do you agree? Send us a letter and there is a good chance we will publish it! There is reasonable evidence to suggest there is an increase in positive airway pressure in spontaneously breathing patients receiving high-flow nasal oxygen, but what about when it is used for apnoeic oxygenation? This new randomised controlled trial from Riva et al.finds that high flow nasal oxygen generates positive airway pressures during apnoea when the mouth is closed. The airway pressures depend on flow rate, but remained < 10 cmH2O despite flow rates of up to 80 l.min−1. They conclude that maintenance of high oxygen concentration appears to be of greater importance than flow rate and airway pressure (Fig. 2).

Figure 2 Fitted mean trajectories of airway pressure with 95%CIs for combined closed and open mouth based on linear mixed models with different assumptions for the effect of flow rate (as indicated right).

The environmental impact of our work has been in the spotlight again recently, and this new cohort study from Zucco et al. suggests that desflurane is not associated with reduced risk of postoperative respiratory complications as compared with sevoflurane. This new piece of evidence might help organisations make decisions about the use of desflurane in their operating theatres. A more surprising result was reported in this randomised controlled trial from Albrecht et al. on the impact of short-acting vs. standard anaesthetic agents on obstructive sleep apnoea. They found that agents such as desflurane and remifentanil did not reduce obstructive sleep apnoea on postoperative nights one and three compared with standard agents (Fig. 3).

Figure 3 Change in the apnoea‐hypopnoea index (AHI) in the supine position over time (values are shown as mean with 95%CI). PreOP, pre‐operative; PON1, postoperative night 1; PON3, postoperative night 3. Blue line, standard agents; red line, short‐acting agents

An accurate, non‐invasive and economical method of pre‐operative anaemia screening would help with early diagnosis and hence expedite further investigations into its aetiology. This new study by Ke et al. finds that the Rad‐67 Rainbow was found to be inadequate for estimating actual haemoglobin levels and insensitive for detecting pre‐operative anaemia. Elsewhere, we have: a review of fit testing N95, FFP2 and FFP3 masksa review of apnoeic oxygenation in paediatric anaesthesiaa randomised controlled trial of trimodal prehabilitation in patients undergoing colorectal surgerya comparison of cardiopulmonary exercise testing in severe osteoarthritis; and a population based study of gestational anaemia and severe acute maternal morbidity. Finally, will this new systematic review, meta-analysis and trial sequential analysis by Desai et al. finally settle the question of epidural vs. transversus abdominis plane (TAP) block for abdominal surgery? They find that epidural analgesia was statistically superior to TAP block in the postoperative pain score at rest at 12 h and the need for intravenous morphine‐equivalent consumption at the 0–24 h interval, but these differences were not clinically important. They suggest clinicians should balance the risks against the benefits for individual patients and decide on that basis.

We hope you enjoyed our first live broadcast all about a new paper on COVID-19 vaccines by Professor Sir Jeremy Farrar and Professor Tim Cook, which has now been viewed > 10k times! We are planning a special live Twitter broadcast on the 11th of January to launch our new 2020 regional anaesthesia supplement with our editors, authors and you! Chairing the sessions will be Kariem El-Boghdadly, Ed Mariano, Ki Jinn Chin and Laura Duggan.

See you there!

Mike Charlesworth and Andrew Klein

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