gasexchange

We are now two and a half years into the COVID pandemic, and just beginning to see yet another case surge with the arrival of the BA.5 Omicron sub-variant. The good news just keeps coming! 😉

Along with new variants, 30 months has also given us a lot of research and data. Metajournal alone has indexed almost 39,000 COVID-related publications relevant to anaesthesia, pain, critical care and emergency medicine.

Of course that's a crazy volume of research to manage, with a pretty low signal-to-noise ratio. Sifting through that for quality and relevant studies is exactly what metajournal was designed for.

Here's a quick round-up of interesting COVID-related research...

RAT tests & infectiousness

As good quality, locally validated RAT tests become increasingly available, we are also collecting more data showing they are a good indicator of individual infectiousness at the moment in time the test is performed.

The article collection 'Does a COVID RAT-negative result mean non-infectious?' explores several of these studies, suggesting that a negative RAT is likely a reliable indicator of being non-infectious.

The bottom line...

A correctly-performed adequately-validated RAT, is likely a sensitive indictor of individual infectiousness at that specific moment in time. The reliability of a negative RAT will be improved if using the same manufacturer and technique as a previously positive test, and more so if there are several subsequent negative RATs.

Return to exercise after COVID?

A recent J Sci Med Sport editorial (Hughes 2022) from Australian elite sport, exercise medicine and sports cardiology experts, provides reassuring encouragement when returning to exercise after COVID recovery.

Read on for more on exercise after COVID...

GA caesarean section & post-partum depression

This large study (Guglielminotti 2020) of 428,204 New York caesarean section records (2006-2013), including 34,356 general anaesthetics (8%), investigated the association between mode of anaesthesia and post-partum depression (PPD). Other studies have shown an association between caesarean section (emergency > elective) and PPD. (Sun 2021, Xu 2017, and others), though this is the first to look specifically at general anaesthesia as a PPD risk factor.

Guglielminotti and Li found that general anaesthesia increased the odds of severe PPD by 54% (aOR 1.54, 1.21-1.95), and suicidal ideation by a massive 91% (aOR 1.91, 1.12-3.25), though not a significant increase in anxiety or PTSD.

The researchers discuss many potential causative factors, particularly known associations between GA CS & poor pain control, and subsequent pain & PPD – while also acknowledging the obvious potential for confounders. Of note patients receiving GA were older, more often non-Caucasian, had more co-morbidities, neonatal complexity, and lower socio-economic levels – also all independently associated with PPD risk.

In order to quantify the potential confounding contribution of emergency vs elective status, the researchers employed the novel E value:

To assess the impact of emergent cesarean delivery on our results, we calculated the E value associated with the aOR for the risk of PPD and suicidality. This relatively new metric takes into consideration 2 associations: (1) that between the confounder (emergent cesarean delivery) and the outcome (PPD); and (2) the association between the confounder (emergent cesarean delivery) and the exposure (general anesthesia).

An E value of 1.7 for the unmeasured confounder emergent cesarean delivery indicates that to explain away the association between general anesthesia and depression, either: (1) emergent cesarean delivery increases the risk of depression by at least 70%; or (2) emergent cesarean delivery is at least 70% more prevalent among general anesthesia than among neuraxial anesthesia. Either association is clinically plausible.

Keep it in perspective...

We already know that general anaesthesia for CS is suboptimal: it compromises both maternal experience and safety, but it should (hopefully) only ever be a chosen mode of anaesthesia when there is a true contraindication to regional anaesthesia – even at the modestly-high 8% GA rate among this New York cohort.

Looking at it from the other end, bear in mind that the modestly-faster time-to-incision for GA over regional is also of questionable neonatal benefit.

The take-home:

Just another reason to avoid GA CS when possible – but you already knew that, right?

"...general anesthesia is a potentially modifiable risk factor for PPD. This finding provides further supporting evidence favoring neuraxial over general anesthesia in cesarean delivery whenever possible."

Supraglottic airway training and manikins

Interesting prospective simulation & equipment study by way of the University of Freiburg. Schmutz et al. investigated how effective five different second generation supraglottic airway devices (SADs) performed in two common airway manikins: the TruCorp AirSim® and the crowd favourite, Laerdal's Resusci Anne® Airway Trainer™.

While ventilation was achieved in all SAD-manikin combinations, the Resusci Anne® Airway Trainer™ was associated with better and more consistent performance for SAD position, participant subjective assessment and ease of gastric tube insertion for most of the SADs. The TruCorp AirSim® did however achieve better leak pressures across most of the SADs (LMA® Supreme™, Ambu® AuraGain™, i-gel®, KOO™-SGA & LTS-D™).

But then, what are the implications for airway simulation training? The researchers correctly note that:

The most important quality of a manikin is the ability to simulate the real-world conditions and thus to give the trainee an authentic feedback.

The bottom line for SAD manikins?

While considering how manikin choice and SAD availability match with your aims for simulation training, the bigger picture is that the primary goal of any manikin-SAD coupling is real-life fidelity – and for that reason, participant subjective assessment is king. And so in this study at least, the Resusci Anne® Airway Trainer™ wins.

Read on for head rotation with LMAs & COVID vaccine persistence...

A big PONV meta-analysis

Interesting Cochrane meta-analysis looking at PONV prophylaxis from German (Weibel et al. 2021) that included almost 100,000 study participants across 585 trials. Interesting not so much because it confirms much of what we already new (or assumed, based on our common PONV prophylaxis drug choices), but because it reassures us that side-effects from commonly used PONV drugs are low to non-existent.

PONV Takeaway:

Granisetron is probably the best single-agent or in combination with other agents because of it's efficacy (better than ondansetron), low-cost, long duration, and absent side-effects.

A cognitive aid to better manage perioperative bleeding

Although the benefits of cognitive aids to many areas of anaesthesia are well established, our resistance to using decision support tools persists. Whether due to misplaced perceptions of losing autonomy or Dunning Kruger-adjacent inflated belief in our ability to perform under pressure, is unclear.

In Anaesthesia, Kataife et al. (2021) describe a cognitive aid for better managing perioperative haemorrhage, the Haemostasis Traffic Light algorithm. Using a simulation-based RCT across two centres (University Hospital Zurich & The Italian Hospital of Buenos Aires, N=84), they showed that using the HTL improved case solutions (OR 7.23, 3.82-13.68), quickened therapeutic decisions, (HR 1.97, 1.18-3.29), improved therapeutic confidence, (OR 4.31, 1.67-11.11) and reduced workload perception.

The aim of the HTL is to improve both situational awareness and decision making, by integrating clinical judgement and point-of-care testing (ROTEM) within an accessible, structured algorithm.

Haemostasis Traffic Light takeaway:

Kataife's study again shows the benefit of cognitive aids, particularly in critical, time-sensitive situations. The anaesthesia and critical care community's historical resistance to decision-support tools requires challenge.

Read on for timing of surgery after COVID infection...

On a Monday morning in March, an anaesthetist stood outside his children's inner Sydney school as a solitary protestor, asking parents to keep their children home if they could.

In the heady early days of the coronavirus pandemic, alarm was raised by a disparate mix of professionals: virologists and epidemiologists, journalists and technologists, and a range of frontline and critical care medical specialists exposed to the first COVID patients.

But as concern spread from the earliest hit countries to those threatened by their own surge, one specialty group was over-represented in public calls for early action: anaesthesia.

In Australia, medical anaesthetists from all states and territories spoke-up, not for health authorities and legislators, but for their communities. For a specialty most comfortable when not spoken of, suddenly anaesthetists were appearing in national newspapers, on radio, television, and even (very small) picket lines.

In Victoria, Dr Pieter Peach was a prominent early voice pushing for cancellation of Melbourne's Grand Prix. The Australian Society of Anaesthetist's fearless president Dr Suzi Nou guided the society's careful campaigns to prepare for the pandemic, pause elective surgery and then cautiously restart. In NSW, Dr Tanya Selak's advocacy was celebrated on Telstra's #saythanks billboard, while Rob picketed outside his children's school.

Like a warning telegram from 1940s London, the message scrawled on Rob's chest captured the zeitgeist of our specialty at the time:

"Lives depend on it. Government too slow to act."

Read on for why…

The cries of 'over-reaction' are as predictable as they are simplistic. Epidemiologists and pubic health experts knew they were coming, because avoiding a disaster brings little thanks.

As Australia emerges unevenly from its soft lockdown, anxious and still responding to COVID flares, it is the envy of much of the world. Alongside success achieved in places as varied as New Zealand, Vietnam, Taiwan, South Korea, Iceland and even austerity-inflicted Greece – the contrast with those that have suffered disastrous outcomes is obvious.

And yet the naysayers still question the painful necessity of the lockdowns, even as study after study demonstrates how the measures have avoided or delayed hundreds of millions of infections.

The United Kingdom, uniquely and even justifiably proud of its National Health System, first chose instead to ignore expert advice and offer up its venerated NHS as a funeral-pyre sacrifice to COVID and the gods of conservatism. Today more than 43,000 British are dead. (You know what would help NHS healthcare workers more than clapping? Earlier border closure and adequate access to PPE!)

Sweden pursued a Claytons lockdown founded on an ideological mix of misplaced intellectual-exceptionalism and responsibility-abdicating libertarianism (my eyes are rolling...). It has not gone well.

Despite making up less than 40% of the Nordic population, Sweden now accounts for five out of of six Nordic COVID deaths. Sweden has twice the population of neighbouring Norway but twenty-times the COVID mortality.

And then there is the Land of the Free, the United States. The wealthiest country on the planet, now the epicentre of the pandemic with well over 2 million infected and 120,000 deaths. A disaster due to a failure to act either early or decisively, a dash of magical thinking and an embarrassing absence of leadership.

It is disappointing that the main contribution the United States is currently making to the global COVID response is to serve as a warning to other nations.

The common theme among these failures is the inability to develop a rational response guided by expert advice. A virus does not care for your wishful thinking. A virus does not care for your political posturing, your dog-whistling or your belief in national uniqueness. A virus is the honey-badger of microbiology.

Which leads us back to the braying calls of 'over-reaction'. Whether former politicians, conservative economists, or performance artists playing opinion writers, they are all making the same mistake: misattributing causality and misunderstanding the purpose of modelling.

Read more on the paradox of avoidance...