Article Notes
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Local COVID PPE guidelines were used: face-shield, goggles/glasses, mask, gown & gloves. ↩
- Chloroquine/hydroxychloroquine
- Azithromycin
- Kaletra (Lopinavir/ritonavir)
- Colchicine
- Ivermectin
- Tocilizumab
- Thaildomide
- Remdesivir
- Droplet & contact precaution PPE: surgical mask, gown, gloves.
- General airborne, droplet & contact PPE: addition of N95 respirator mask and eye protection.
- PPE for high-risk aerosol-generating medical procedures: addition of gown neck protection and double gloves.
- AAMI level-2 gown, incluidng neck protection, noting that the neck is a high-risk area for contamination in simulation studies.
- Double gloves that overlap the sleeve, noting that the gown-glove interface is a common PPE failure site, and that Verbeek's 2020 Cochrane review concluded that there was less contamination vs single gloving (RR 0.36).
- Only allow presence of essential staff in room during AGP.
- Provide access to shower resources for staff after high-risk AGP.
- Do not ‘‘MacGyver’’ homemade combinations of PPE.
- Doffing is a high-risk critical moment, that should not be rushed, distractions should be minimised, and use a doffing supervisor. Pay attention when donning to ease later doffing.
- Masks should be the last item removed.
Also relevant to read is Duggan's 2019 CJA editorial: The MacGyver bias and attraction of homemade devices in healthcare
Daniel Jolley
Leff & Finucane's (JAMA 2008) 'gizmo idolatry' commentary is also related, and well worth a read. The human love of bells and whistles...
Daniel Jolley
Why the interest?
The combination of a deadly contagion (COVID-19) and recognition that endotracheal intubation is a high risk procedure for the airway technician has lead to the development of novel medical equipment. One such innovation is the clear-perspex 'intubating box' designed to contain viral-aerosols released during intubation. There has been limited prior evaluation of the safety or efficacy of such devices, despite their promotion.
What did they do?
Begley et al. conducted 36 simulated intubations with twelve PPE-adorned1 anaesthetists, with and without intubating boxes. They primarily aimed to quantify the effect on time to intubation.
Investigators tested both a first-generation and newer generation device. Each of twelve senior anaesthesiologists performed three block-randomised intubations: no box, original, and latest-design box. The airway manikin tongue was inflated to simulate a grade 2A airway.
And they found...
Intubation time was significantly increased by both the older and newer box designs (x̄=48s and x̄=28s longer respectively, though with wide confidence intervals). More relevantly there were frequent prolonged-duration intubations with the box (58% >1 minute, 17% >2 min), but none without the box.
Most worrying, there were eight breaches of PPE caused by box use, seven occurring with the newer, more advanced design.
"PPE breaches often seemed to go unrecognised by participants, potentially increasing their risk further."
Reality check
Despite the superficial appeal of an intubation box, this simulation study warns that such devices fail both to support safe and timely intubation and to protect the clinician – the very arguments used to advocate for its use.
These failings occur before even considering the actual effectiveness in reducing viral exposure, the box's impact on emergent airway rescue, or the practicality of cleaning a reusable device now coated with viral particles.
The intubating aerosol box appears dead on arrival.
Bonus biases
Begley notes the appeal of such novel devices may be partly driven by 'gizmo idolatry' (Leff 2008) and 'MacGyver bias' (Duggan 2019), blinding clinicians to consider unknown consequences of box use and discounting resultant hazards.
Daniel Jolley
The main premise of Duggan's argument is that our MacGyver bias is grounded in an overweighting of the perceived benefits of MacGyvered 'workarounds' to medical problems, with discounting or even ignoring of unknowns, risks and newly introduced hazards.
This bias is rooted in the satisfaction and enjoyment of solving a problem, the chance to "showcase one's creativity" and to be solutions oriented.
"The danger is that a workaround is so culturally appealing that it circumvents the level of scientific scrutiny that we would expect from any other equipment that we use. Novelty, immediacy, ownership, and ease of use can increase our propensity to bias and wilful blindness." – Duggan et al.
Daniel Jolley
Human Love of Bells and Whistles
"Increasing the technological complexity of treatment appears to increase the significance of an illness and the appeal of an intervention. Furthermore, if hospitalization is required, additional distinction may be conferred. For instance, good evidence demonstrates that oral rehydration during acute diarrheal illness is at least as good as intravenous therapy. For most patients, metered-dose inhalers are as effective as nebulized bronchodilators, but inhalers are generally regarded as lesser treatments. The gadgetry of gizmos somehow provides cachet, and electrified intravenous pumps and nebulizer machines seem more substantive."
– Leff & Finucane, 2008
Daniel Jolley
Wong briefly summarises COVID pharmaceutical therapies that are currently in trial, and importantly have received media attention.
Highlighting that off-label use of these drugs may be important causes of future toxicological presentations to emergency departments, especially for those widely used in the community for other indications (eg. Plaquenil, Kaletra, colchicine...).
Briefly discussed are:
Daniel Jolley
Why is this review important?
Although the importance of managing spinal anaesthesia-associated hypotension during caesarean section is well appreciated, there continues to be some debate over relative efficacy of interventions, whether vasopressors or fluid-loading.
Fitzgerald at al.'s review and network meta-analysis quantitatively compares a complete range of interventions across 109 studies.
What did they show?
Vasopressors were more effective at preventing intra-operative hypotension than fluid infusion techniques alone. Although there was no statistically significant difference in the incidence of hypotension among metaraminol, phenylephrine or noradrenaline/norepinephrine, metaraminol appeared the most effective (OR 0.04-0.26) and ephedrine the least (0.09-0.85). [vs Norepinephrine (OR 0.06-0.28), Phenylephrine (OR 0.11-0.29)]
Similarly, nausea and vomiting incidence was lower with vasopressors than other interventions. Phenylephrine more commonly caused bradycardia than other pressors, and ephedrine more commonly tachycardia. There was no significant difference in reactive hypertension.
The bottom-line...
The most effective way of preventing and managing maternal intraoperative hypotension is, as international guidelines already assert, alpha-agonist vasopressors. Using more complex protocols, such as phenylephrine or norepinephrine infusions, does not appear to offer benefit over metaraminol. Fluid infusions are at best a secondary intervention.
Daniel Jolley
Lockhart et al. provide a considered exploration of COVID-19 infection-control issues specific to anaesthesiologists, proposing an additional third category of personal protective equipment (PPE).
Give it to me in point form!
They propose three PPE types:
Why should I take notice?
The Canadian view on PPE is tempered by both their current significant COVID burden, and their experience of the 2003 SARS pandemic which infected 257 Canadians, 20% of whom were healthcare workers. Much of our PPE evidence is based upon SARS. This article emphasises the importance of PPE for anaesthesiologists and their airway assistants.
On airborne spread?
Unfortunately much of what we did not know about respiratory spread and SARS in 2005 persists today:
Although this observation [about lack of knowledge of SARS infectious droplets] was made 15 years ago, basic questions regarding nosocomial spread during the SARS epidemic, and now the COVID-19 pandemic, have yet to be answered.
Absence of evidence however, should not imply evidence of absent airborne spread.
The role of airborne particles in the spread of COVID-19 remains unclear, although Lockhart notes the infamous case of Hong Kong's Amoy Gardens housing complex in the 2003 SARS outbreak, resulting in 187 cases – likely via airborne spread.
Endotrachial intubation has been shown in several studies to be a high-risk procedure for healthcare worker infection. Considering this the authors reccomend a third level of PPE, adding:
Additionally:
Final word
Lockhart emphasises that there is no ideal PPE, but by focusing on consistent protection at known high-risk interactions (ie. intubation) safety improvements can be made.
Daniel Jolley
When considering whether COVID could have significant airborne transmission, note that during the SARS pandemic at least one large Hong Kong outbreak (187 cases) was very likely due to airborne infection: Yu 2004 (NEJM).
Daniel Jolley