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...

A very interesting study in JAMA Surgery from Wallis et al. received a lot of press coverage. The research team showed that female patients treated by male surgeons not only more commonly experienced post-operative complications, but also suffered a higher mortality, than when treated by female surgeons.

What did they do?

This big-data study covered 12 years of the 20-most-common surgical procedures performed in Ontario, Canada. Wallis and team investigated how patient-surgeon sex discordance correlated to a composite for adverse postoperative outcomes. (A deeper investigation of the earlier Wallis 2017 study).

And they found?

While ~15% of all patients experienced an adverse post-operative outcome, female patients treated by a male surgeon experienced significantly higher odds of a composite of adverse events (OR 1.15 [1.10-1.20]), 30-day complications (OR 1.16 [1.11-1.22]), readmissions (OR 1.11 [1.04-1.19]), and death (OR 1.32 [1.14-1.54]) compared to when treated by female surgeons.

Yet male patients treated by female surgeons experienced either lower odds (death 0.87 [0.78-0.97]) or statistically-similar odds of complications (composite end-point, readmission or post-op complications).

The hot-take

Women once again receive the metaphorical short-end of the medical-stick. Whether societal or elsewhere in the health industry value-chain, long established gender inequity reveals itself in worse surgical outcomes for female patients.

Hang on a sec…

But this cannot just be written off as a consequence of existing social gender inequity, but rather a disquieting causal loop between this as a cause and the result then perpetuating further inequity.

If some part of a surgeon’s ’professional success’ is wrapped-up in the ability to achieve positive outcomes for patients while minimising the adverse, then male surgeons are failing their female patients when compared to either female surgeons, or to the care they provide their male patients.

And yet the same discordance cost is not true for female surgeons.

Read on for the take-home & more medical-gender influences...

In anaesthesia, sitting at the point where the ideal meets reality, is compromise.

Compromise is the practical, real-world necessity that allows a health system to function in the face of competing demands. Every point of care in a hospital is a balance of compromises, frequently between safety and the many other flavours of medical quality.

For anaesthesiology the most common compromise is balancing safety with the quality of the patient experience: pain, distress, cost, delays, efficiency, levels of intervention, seniority of care… (Though let’s acknowledge, suffering injury because of a safety compromise is also a pretty poor patient experience.)

In a dynamic world of external stressors (<cough>pandemic<cough>) compromise becomes both more important and more fraught. How do we balance conflict between the needs and priorities of care? Compromises are then a pragmatic necessity, recognising the fractal complexity of patients and hospitals that the inherently reductive nature of best practice and theory struggles to accomodate.

A great example of this is found within the Zero Harm safety movement, aspiring to the worthy (though naive) goal of reducing healthcare staff & patient injury to zero. Zero Harm’s mistake is to build an entire ideology upon an unachievable goal, for as Thomas points out in 'The harms of promoting Zero Harm':

“...some harms are inevitable and impossible to eliminate.”
– Thomas (2020)

Zero Harm is itself a compromise, deprioritising other components of care in service to absolute safety. Only by recognising the natural compromises at every level of the health system can we make informed decisions about the risk-price we are willing to pay for compromise.

Many years ago as a junior resident, a senior colleague dropped some wisdom about compromise that sticks with me today. He made the observation in the setting of one of the commonest and discrete medical interventions: intravenous cannulation. Sometimes you have a cannula that is smaller or not flowing as well as you would prefer. Depending on the circumstance, this is often tolerable and we grudgingly accept it.

"But beware”, he said, “never allow more than one compromise.”

Although imperfect intravenous access may be a small compromise, it represents an increased-risk point of failure. Perhaps you now feel compelled to accept a ‘minor’ airway compromise (LMA over an ETT?), or a fasting compromise, or location, or the presence (or not) of a parent at induction? While each step may be justifiable, stacking compromises increases points of failure and risk in a non-linear way.

Stacked compromises increase risk geometrically.

Stacked compromises are fragile.

While there may be no true hard rules in anaesthesia, we need to appreciate that risk exists on a dynamic spectrum. The adolescent ideology of Zero Harm may have near Zero Place in anaesthesia, yet the primacy of risk management and harm minimisation always requires considering how our compromises interact and compound to alter the risk profile of the care we provide. Our goal in managing risk in complex systems should be to reduce risk where we can, and build resilience where we cannot.

You may still feel it necessary to stack your compromises, but by the Gods of Anaesthesia, if you do then you better make sure you know the price being paid – and who is ultimately paying it.

• Explore more in the metajournal knowledge collection: Reducing health-system harm: Safety I vs Safety II.

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...