Article Notes
- 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.
- The significance of airborne transmission, in particular the infectivity of airborne viral particles beyond 1 meter, is uncertain.
- PPE should be seen as an important and essential part of a larger safety system.
- Intubation is a high-risk procedure for aerosol generation. A ventilated negative pressure room and airborne-precaution PPE is recommended. Ventilation (frequency of air-exchange) is likely more important than negative pressure.1 Chinese evidence suggests COVID transmission at intubation is low with appropriate PPE, although there is wide variability in extremes of PPE used along with post-exposure disinfection (eg. showering).
- High-flow nasal oxygen and supraglottic airway (eg. LMA) placement may also be aerosol generating.
- Most risk of transmission from sneezing and coughing is probably droplet and contact, rather than airborne, although the science behind these questions are complex and uncertain. Evidence attempting to answer these questions is often from non-clinical settings.
- Fluid-resistant surgical masks when worn by staff may reduce transmission by at least 80%. Superiority of respirator masks (eg. P2,P3,N95) is not yet reliably supported by evidence.
- Cook highlights two main PPE problems: 1. PPE supply; 2. Inappropriate use of PPE (using higher level than required).
- PPE should be simple to remove (doff) after use, to reduce contamination risk. Cook notes that Canada's SARS experience highlighted increased risk of self contamination with more complex PPE.
- Contact precautions (gloves & gown) are recommended when in vicinity of COVID positive patient but not within 2 meters.
- Droplet precautions (+ mask & eye protecting) are recommended within 2 meters of patients.
- Airborne precautions (+ FFP3 respirator mask) are only recommended for aerosol generating procedures (AGP). However classification of procedures as AGP or not is only loosely evidence based.
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It's worth highlighting that negative pressure confers no protection on those in the room, it's purpose is to prevent escape of contagion to areas outside the room. ↩
- Hospitals are frequent sources of outbreaks, among both staff, patients and the wider community.
- The quality of PPE evidence is low. Most evidence must be contextualised in consideration of expert opinion, and of the similarities between SARS-CoV-2 and SARS (SARS-CoV-1), MERS and influenza.
- Droplet-vs-airborne spread is a conceptual simplification and not a simple dichotomy. It is best understood as a spectrum of transmission risk.
- Time-exposed may be a more important consideration, especially in indoor, poorly ventilated spaces.
- PPE supply is globally limited, and so a pragmatic approach must be taken to its use, considering individual risk scenarios.
- Training, simulation and fit testing are critical for effective use of PPE.
- There are specific steps in the PPE donning & doffing workflow that are frequently associated with breaches exposing HCWs to infection. These require extra attention.
- Beyond cost, increasingly complex PPE (eg. PAPR, hoods, intubation boxes etc.) also increase the opportunity for PPE failure and exposure if users have not had adequate training in their use, and some PPE has been demonstrated to make intubation more difficult.
- The superiority of N95/P2 respirator masks over standard surgical masks for personal protection is unclear and unproven.
- N95 mask fit-testing and fit-checking; notably shaving facial hair to ensure a face-mask interface seal.
- Use of extended-cuff gloves with gown cuff tucked securely into glove.
- Time management: PPE donning should never be rushed, even in critical medical emergencies.
- Glove removal is a high-risk step. When removing the second, inner glove, ensure as little contact as possible with the glove sleeve by the ungloved hand.
- Gown removal is the next highest risk step. Do not touch the front of the gown, especially with ungloved hands.
- Mask removal avoid touching front of mask; avoid any snapping of straps.
- Perform alcohol-based hand-hygiene after each article is removed.
- Powered air-purifying respirator (PAPR) with coverall may be more protective than N95 masks and gown (RR 0.27), but create unique donning challenges.
- Long-gowns may be better than a coverall, but are also more difficult to doff. Gowns are better than aprons. Better sealing, fitting, and one-piece removal at gown-glove interfaces and closer fit around the neck may reduce exposure.
- Double-gloving may reduce exposure.
- Better training, computer simulation, video lectures, following CDC protocols, and spoken instruction may improve donning and doffing compliance.
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.
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
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:
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.
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.
Why do we need another PPE review?
This review contextualises the PPE issues with their (relatively low quality) evidence base, focusing particularly on anaesthesia given that this is a high-risk occupational group. Coming from both a UK expert and journal, the recommendations should be carefully considered in terms of the UK's severe COVID outbreak and PPE supply issues.
Important takeaways?
On specific levels of PPE
"Public Health England recommends airborne precautions are used in ‘hot spots’ where aerosol generating procedure are regularly performed, if any suspected COVID-19 patients are present – these include intensive care unit, operating theatre, emergency department resuscitation bays and labour wards where mothers are in stage 2 or 3 of labour"
(Interesting that two recent meta-analyses found no evidence of benefit of N95 masks vs surgical masks for healthcare workers: Bartoszko 2020 & Long 2020.)
Hang on...
The elephant in the room is that the lack of PPE supply appears to be the main driver of the rapidly-changing PPE recommendations.
PPE choices need to be made in consideration of the spectrum of risk, hazard and cost, acknowledging different risk profiles depending on location, procedure and individual clinicians.
This growing collection of articles focuses on the evidence and expert guidance relating to the use of personal protective equipment (PPE) and the SARS-CoV-2 / COVID pandemic, with specific focus on PPE use by anaesthesiologists and anaesthetists.
More articles can found found via the PPE topic index.
What we know:
Toronto anaesthesiologists Muñoz-Leyva & Niazi share observations from PPE training simulations, identifying the 'high risk' moments where frequent exposures and PPE failures are seen.
Why is this important?
For all the understandable concern over adequate access to PPE and discussion of appropriate levels of protection, HCW safety is entirely dependent on the effective use of this protective equipment.
Identifying common areas of 'biosafety breach' allows both clinicians and PPE supervisors to apply added attention to these steps. These areas can be conceptualised as offering a disproportionate safety benefit for the time and resources deployed in ensuring compliance at these moments.
Which areas did they identify as most important?
Donning
Doffing
This relatively small study (N=19) randomised emergency resident trainees (14) and first responders (5) to cadaveric intubation with and without 'Level C PPE':
Level C PPE typically includes a full face mask with air respirator, a hooded chemical resistant clothing, inner and outer gloves and chemical resistant boots with covers.
First-pass intubation success was significant lower (58% vs 96%) while wearing PPE than without. Subjects identified the visibility impact of wearing protective hoods as the most common impediment to intubation.
This is the second update to Verbeek et al.'s 2016 Cochrane Review of personal protective equipment (PPE) for preventing infections in healthcare workers (HCW). The prior update was in July 2019.
What's worth knowing?
Overall most studies of PPE efficacy are of low quality and offer a low certainty of conclusions. Caveat emptor...