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1/ Some thoughts on #PPE 😷 & #COVID for anaesthetists/ologists after sampling the evidence the past week(s).

TLDR: evidence is scant, but gives guidance; keep it simple; perfect vs pragmatic; consider supply limits!

Summarised article collection here:
2/ Because hospitals are a frequent outbreak source, #PPE is both important, but also EMOTIVE.

I saw a recent comment that for anaesthesia this is our first true 'pilot goes down with the plane' safety issue...🛩 we should stop and think on that...
3/ #PPE publications 📄 seem to mainly fall into three groups:

1. Non-clinical laboratory and simulation studies.
2. SARS experience studies.
3. Systematic reviews.

(Although there ARE two interesting influenza-N95 RCTs... ⇣😉)
4/ There are some good recent reviews: Cook (Anaesth 2020), Lockhart (CJA), Odor (BJA) that cover similar ground, though w/ slightly different takes. They need to be considered in context of the healthsystems that the authors inhabit. #SysRv

Collected: metajournal.com/collections/12…
5/ I do find there's a bit of a chiding tone around notion of "inappropriate use" of #PPE (a real issue to be sure!) but they stop short of admitting what we all know:

Guidelines are written in the context of globally limited N95/PPE supply.
😷🥽🧤👗
6/ So let me spell it out for you: global supply of respirator masks is INCREDIBLY limited.

We need to accept that while in a perfect world an N95 mask 😷 would be used for all contact with #COVID risk pt, this is not possible.

Perfect vs pragmatic. Wishful vs reality.
7/ In general I think these reviews try to justify the guidelines (contact, droplet, airborne) too much based on the (limited & over-simplified) science with not enough admission of risk-benefit pragmatism. ⚖️

But, potato pot-ah-oto...
8/ N95 mask consumption can be HUGE. @doctordanholmes tells me that during SARS one Canadian hospital went through 80,000 N95's PER DAY! One of our North Tas hospitals has been using 900/day during recent NW outbreak...
9/ The world is not binary, and neither is risk. When it comes to valuable, single-use (😱) safety equipment we must deploy it with consideration of a DYNAMIC risk-cost-benefit balance... which is really what the (various!) guidelines try to do.
10/ First, on droplet-vs-airborne spread: this is at best a (useful) conceptual simplification that I fear we over-fixate on. Wilson (Anaesth 2020) makes interesting argument that 'time exposed' may be more critical factor: metajournal.com/articles/97975… #SysRv
11/ Wilson et al's article is a MUST read, and is the best current exploration of the science of respiratory transmission. It challenges the simplistic droplet vs aerosol concept.
metajournal.com/articles/97975… #SysRv Image
12/ There ARE anecdotal examples of COVID transmission from aerosols, along with lab studies (of uncertain clinical significance) showing greater spread of #covid viral particles (Bahl 2020 J Inv Dis):
metajournal.com/articles/97975…
13/ There is also an example of a LARGE 2003 outbreak of SARS, very likely due to airborne viral spread throughout an apartment complex:
14/ But even considering that, we shouldn't fixate on what IS or IS NOT an aerosol generating procedure (AGP) as this is only a surrogate label for what really matters: risk of transmission. And we have SOME data on that already.
15/ Top of the list is intubation (OR 6.6), followed by NIV (OR 3.1), trache (4.2) and manual vent (2.8) – from a 2012 SARS meta-analysis (Tran 2012 PLOS ONE).
📄→ metajournal.com/articles/98118…
16/ If we then include Wilson's argument of 'time exposed' ⏰ (to aerosols) with consideration of small enclosed spaces 📦 & ventilation 🌬 we have a pretty good conceptualisation to use for assessing risk. (Arghh! Delivery rooms! 🤰)
17/ Which then brings us to #PPE itself... first let's touch on the evidence for N95+ respirator masks. Although the physical science says these are more protective than surgical masks 😷 the (limited) clinical evidence has NOT shown this 😬
18/ Two #metaanalyses looking at influenza RCTs in HCWs failed to show benefit of N95 over standard masks... plus there are many anecdotal stories of HCW unknowingly exposed to #covid successfully protected by surg masks.

📄 metajournal.com/articles/950884
📄 metajournal.com/articles/980798
19/ ...but these studies were not specifically looking at 1. Coronaviruses, 2. High-risk events like intubation. But they should nonetheless give us _some_ reassurance about safety of current #covid contact/droplet precautions.
20/ Specifically on intubation #PPE, although similar the guidelines do differ at points. Lockhart (CJA 2020) in particular proposes adding both DOUBLE GLOVES and NECK PROTECTION to N95-mask/eye/gown, noting that...
21/ ...sim and lab studies show neck and glove-gown interface is a common site of contamination. Verbeek's Cochrane 2020 update covers the research behind these recommendations:
📄 → metajournal.com/articles/97982…
22/ Other important #PPE points that appear REPEATEDLY but really deserve emphasis:
- PPE is not enough, must be part of a bigger safety system.
- Gotta get training in donning & doffing; practice; simulation; fit test.
- Time management: don't rush!
23/ The more complex the #PPE (eg. hoods, PARP) the greater the risk of self-contamination with doffing. Doing this well takes training and repetition.
(More on common PPE failures: metajournal.com/articles/97869…)
24/ More complex #PPE impedes other interventions, like INTUBATION 👄 [ metajournal.com/articles/78660… ] and CPR ❤️. Consider this!
25/ Conversely, even fit-tested N95 masks may not protect adequately DURING CPR!
26/ And finally, Lockhart (CJA 2020) strongly discourages MacGyvering homemade PPE combinations.

This also extends to the intubating boxes 📦 and other inventions that seem to be more of a target for latent anaesth anxiety than practical solutions.

Don't do this stuff!
27/ Aside, @drlauraduggan & @hypoxicchicken et al.'s 2019 editorial 'The MacGyver bias and attraction of homemade devices in healthcare' is a good and relevant read: metajournal.com/articles/88880…
28/ So, the various guidelines aren't trying to hide anything from anyone, they're trying to balance the limited supply of PPE and match to (somewhat) evidence-based need. If you have access to reusable PPE and processing (!!) then this might obviate some limits.
29/ The old anaesthetic adage "it's not what's in the syringe but who's behind it that matters" applies equally to #PPE - once you reach a suitable level of protection, fastidious conduct & use discipline is prob the most important factor.
30/ All these referenced articles, many with summaries, can be found collected here on metajournal: 👍 (disclaimer: I run MJ 😜)
📄→ metajournal.com/collections/12…
/end 😬
31/ Correction - as the good @doctordanholmes pointed out (thank you! 🙏), it was 18,000 N95 masks/day used by one Canadian hospital during 2003 SARS... 😬
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