gasexchange

Posts written by Daniel Jolley.
Daniel Jolley

About the author

Daniel Jolley is an anesthesiologist, and founder of metajournal, providing personalized medical research recommendations to fellow doctors.

Read more from Daniel or follow on twitter.

Old, new and current trends in obstetric anaesthesia

Some interesting research on common and not-so-common obstetric anaesthesia topics: both new trends and continuing trends, as well as a cautionary medicolegal reminder.

Supraglottic airways for GA Caesarean?

Metodiev & Mushambi's editorial looks at the attitude shift among obstetric anaesthesiologists to more favourably consider the LMA or SGA for Caesarean section under GA.

They review the evidence for aspiration risk, particularly noting what we learned from NAP4 (2011) but contrast this with many studies showing safety of SGAs for GA CS (over 8,000 patients in total, with Halaseah 2010 investigating 3,000 alone!). Interesting, but before we get too excited keep in mind that the populations studied are likely very different from parturients you may typically look after.

They conclude:

"...there is insufficient evidence to recommend universal or selective replacement of tracheal tubes with SGA devices during general anaesthesia for Caesarean delivery. Aspiration remains the main concern." – Metodiev & Mushambi (2020)

Cautionary reminders of neuraxial injury

McCombe & Bogod reviewed 21 years of obstetric anaesthetic medicolegal claims, noting common themes around consent, types of nerve injury, and recognition and management failures.

Not only is neurological injury the second most common reason for obstetric anaesthetic claims (behind inadequately managed pain during Caesarean section), it carries the highest average claim cost.

The review is full of many useful observations, but Reynold's 2000 advice regarding interspace level choice for spinal access is by far the most important: always access the intrathecal space at the lowest possible level, and "...the L2/3 interspace should not be an option."

McCombe & Bogod spend some time exploring the variability of cord termination level, individual variability of the intercristal line, and the inaccuracy of anaesthetist interspace level estimation. Well worth reading the whole review.

Read on for CS vasopressor choices & heavy bupivacaine alternatives...

All Things Endotracheal

There have been some interesting papers recently exploring all-things endotracheal, relevant to anaesthesiologists, intensivists and emergency physicians alike.

Some challenge long-accepted dogma (ETT size), others confirm natural trends (cuffed paediatric tubes), or delve into ventilation physiology long forgotten by some of us (the ventral shift...).

Here's a brief stroll through five articles that may challenge your practice.

Choose smaller...

First, Karmali & Rose challenge the dogma surrounding endotracheal tube sizing in adult anaesthesia. They explore both the functional consequences of ETT size, good and bad, as well as the implications for airway trauma.

They describe how a modern ETT ≥ 6.0mm ID will accomodate most intraluminal devices, and in fact smaller sizes might even facilitate some airway procedures. Similarly, inspiratory and expiratory flow dynamics of smaller ETTs are inconsequential for most fit and healthy patients.

Noting that there is wide individual variation in tracheal dimensions, such that some patients are poorly served by a traditional ETT-size choice, they highlight the correlation between ETT size and airway trauma, hoarseness and sore throat, noting that for many patients a 'large' ETT offers little practical benefit.

"Instead of opting for ‘the largest tube that the larynx will comfortably accommodate’, we perhaps should consider using the smallest tube which permits the safe conduct of anaesthesia."

For routine anaesthesia of ASA 1 & 2 patients, an ETT sized 6.0-7.0 mm is probably the best balance between ventilation needs and airway trauma.

Don't cough

Yang et al.'s high quality meta-analysis explores the use of intravenous lidocaine/lignocaine to reduce a common, but potentially significant post-operative problem: coughing on extubation. Both coughing (reported incidence 15-94%) and post-operative sore throat (21-72%) are common among surgical patients.

This meta-analysis of 16 trials (though only 1,516 total subjects) showed a significant reduction in cough RR 0.64 (0.48-0.86 & NNT=5), and post-operative sore throat RR 0.46 (0.32-0.67), though no difference in laryngospasm, adverse events or time to extubation when using modern volatile agents.

However, they could make no clear recommendation of optimal timing or dose of lidocaine – although past reviews had found suggestion of a dose-effect, settling on 1.5 mg/kg as the best choice (Clivio et al. 2019).

Regardless, a simple intervention with peri-operative IV lidocaine reduces coughing on extubation and reduces post-operative sore throat, without any apparent increase in adverse events.

Read on for more ETT tidbits...

Thoughts on PPE

Amidst the medical anxiety surrounding COVID-19, no issue appears more emotive than the use and access to personal protective equipment (PPE).

Whether anaesthesia, intensive care or those poor bastards on the front-line in emergency departments and ambulances, adequate PPE has never been simultaneously so important across the entire planet. To outsiders the emotion and fear may seem excessive, but for healthcare workers fear is protective.

It was recently said that for anaesthesia this is our first modern "pilot goes down with the plane" safety issue. While we might be stretching that metaphor too far, it does help to frame our collective anxiety. It reveals both the shared hazard of a contagion, and also the foundation for the anxiety many feel.

Read more on PPE and COVID...

Peer-reviewed COVID-19 articles on metajournal

Metajournal now has a dedicated index of peer-reviewed COVID-19 articles published in critical care, anesthesia, emergency medicine and resuscitation journals, along with relevant coronavirus articles from major general medical publications, including Lancet, BMJ, NEJM, JAMA, MJA & CMAJplus specialist articles from infectious disease, epidemiology and immunology journals.

metajournal.com/covid

This shows the latest covid and pandemic articles as they are indexed, or click on the 'Best' tab to see the highest quality and most important articles – many of which have metajournal summaries.

If you want to stay up to date with the latest COVID-19 articles, make sure to follow the relevant coronavirus topics by clicking on the red topic tags at the top of the page. Relevant articles will then be included in your weekly metajournal email if you are a metajournal subscriber.

There are already over 1,000 peer-reviewed covid articles indexed.

If you are looking specifically for articles covering Personal Protective Equipment (PPE) in the time of covid, the PPE article index along with the "Anaesthesiology, Personal Protective Equipment (PPE) and COVID" collection, has you covered. 😷

Biased thinking in a time of COVID

The 2020 coronavirus pandemic for all it's horror and challenge, has highlighted certain uncomfortable truths about the human condition. One of these has been the impact of our cognitive short-comings: our difficulty understanding the non-linear and non-binary, and our susceptibility to cognitive biases.

Many of these problems led to missteps at the beginning of the pandemic response, and now early in the fight continue to impede our decisions. By better understanding these cognitive traps we can at least be more alert to our blind spots and alter our actions in response.

As early data seeped out of China in January, quickly followed by cases appearing in global travel hubs, many national governments along with their populations refused to acknowledge the pandemic threat. Even as Northern Italy's health system first bent then broke, surpassing China's own COVID death count a mere 47 days after Italy's first confirmed case, world governments continued to water-down the threat.

Read on about exponential growth and biased thinking...

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