Anaesthesia
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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?
- 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.
On specific levels of 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.
"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.
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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. ↩
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In December 2019, a cluster of atypical pneumonia cases were reported in Wuhan, China, and a novel coronavirus elucidated as the aetiologic agent. Although most initial cases occurred in China, the disease, termed coronavirus disease 2019, has become a pandemic and continues to spread rapidly with human-to-human transmission in many countries. This is the third novel coronavirus outbreak in the last two decades and presents an ensuing healthcare resource burden that threatens to overwhelm available healthcare resources. ⋯ Based on the Chinese experience, some 19% of coronavirus disease 2019 cases develop severe or critical disease. This results in a need for adequate preparation and mobilisation of critical care resources to anticipate and adapt to a surge in coronavirus disease 2019 case-load in order to mitigate morbidity and mortality. In this article, we discuss some of the peri-operative and critical care resource planning considerations and management strategies employed in a tertiary academic medical centre in Singapore in response to the coronavirus disease 2019 outbreak.
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Observational Study
Clinician perception of long-term survival at the point of critical care discharge: a prospective cohort study.
Critical care survivors suffer persistent morbidity and increased risk of mortality as compared with the general population. Nevertheless, there are no standardised tools to identify at-risk patients. Our aim was to establish whether the Sabadell score, a simple tool applied by the treating clinician upon critical care discharge, was independently associated with 5-year mortality through a prospective observational cohort study of adults admitted to a general critical care unit. ⋯ Sabadell 2 patients had 71.0%, 52.7%, 44.8% and 23.7% 5-year mortality for these same age categories. The Sabadell score was independently associated with 5-year survival after critical care discharge. These findings can be used to guide provision of increased support for patients after critical care discharge and/or informed discussions with patients and relatives about dying to ascertain their future wishes.
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The global COVID-19 pandemic has led to a worldwide shortage of ventilators. This shortage has initiated discussions on how to support multiple patients with a single ventilator (ventilator splitting). Ventilator splitting is incompletely tested, experimental and the effects have not been fully characterised. ⋯ The restriction apparatus successfully modified the inspiratory pressure, minute ventilation and volume delivered to the high compliance test lungs in both pressure control (27.3-17.8 cmH2 O, 15.2-8.0 l.min-1 and 980-499 ml, respectively) and volume control (21.0-16.7 cmH2 O, 10.7-7.9 l.min-1 and 659-498 ml, respectively) ventilation modes. Ventilator splitting is not condoned by the authors. However, these experiments demonstrate the capacity to simultaneously ventilate two test lungs of different compliances, and using only standard hospital equipment, modify the delivered pressure, flow and volume in each test lung.