COVID, * is the blue book article transfusion implications in COVID-19 Flashcards
What proportion of pts w COVID-19 suffer ischaemic stroke?
5%
Do surgical face masks protect against aerosolised particles?
No, but they do protect against droplet transmission
What are recommendations for COVID GA/intubation?
Could consider MAC (protect staff w PPE) BUT if think ANY risk of conversion to GA, just do GA as emergent intubation more risk to personnel
Airborne precautions for all intubation:
- properly-fitted N95 or PAPR
- goggles
- face shield
- fluid impervious gown
- shoe covers
- double gloves
Should do the induction/intubation in -ve pressure airborne isolation room (care w haemodynamics during transport to OT, minimise delays)
Minimise personnel
Cogniscence that pts w COVID-19 may have associated myocardial injury, exposing them to greater risk of haemodynamic instability
Pre-O2 for 5 mins w meticulous seal, adequate relaxant dose & RSI w CMAC by most experienced operator. Can consider wet gauze over pts nose & mouth
AVOID LMA except in difficult airway rescue
HEPA filter placed directly on tracheal tube immediately after intubation & viral filters btwn exp limb & machine to prevent machine contamination. Carefully discard breathing circuits after every use.
Avoid disconnection of breathing circuits & changes of ventilators (eg may use the transport ventilator for procedure vs changing, would therefore need TIVA)
If do need to disconnect & change ventilator, ensure adequately NMB so no breaths during disconnection & clamp the tracheal tube before disconnection AND keep the HEPA filter connected to the TT during disconnection
Gas sampling tubing should be protected by a HEPA filter with gases exiting the gas analyser scavenged
Avoid nasal/oesophageal temp probes
Extubate in -ve pressure room (usually in ICU), w special attention to preventing cough
Pt should wear a surgical mask after extubation & receive low-flow O2 as needed
when leaving the room, the PPE that was used for airborne procedures must be doffed & shouldn’t be worn during transport
Along w standard considerations for choosing MAC over GA for clot retrieval, what are some other considerations/planning elements for MAC for clot retrieval in covid +ve or suspected?
Only consider MAC @ centres w high rate of MAC use for clot retrieval & low conversion rate from MAC to GA
Pt is to wear a surgical mask (on top of nasal prongs or under a face mask)
Keep O2 flow as low as possible to achieve SpO2 >94%, avoid O2 flow rates >5L/min to minimise aerosolisation. ideally aim for an O2 mask w exp viral filters
Use minimal necessary sedation to reduce need for oral/nasal airway or jaw thrust/chin lift, aim to limit risk of secretion pooling requiring suction
Be prepared for potential GA conversion
What are some infection control considerations when anaesthetising a patient with covid-19?
Prevention of transmission to staff involved in care, prevention of contamination of anaesthesia machine & equipment- SAME for suspected or confirmed COVID-19
- Patient care: Meticulous hand hygiene, contact (double glove), droplet (goggles or full face shield, water resistant gown, disposable caps/hood (ensure coverage of ears & neck) & optional shoe covers) and aerosol (N95, PAPR or elastomeric) precautions used.
- Donning/doffing should be protocolised & occur with a trained observer.
- Patient transport: they should wear a surgical mask, ideally straight to OR, ideally use a portable tent with HEPA filtration, if intubated use a HMEF between Ambu bag & pt at all times. Helper who hasn’t touched pt to touch lift buttons etc.
- Passive protective barriers (ie. those not using fans/air filters or other means to generate negative pressure) shouldn’t be used as they may increase exposure of HCW & pts to airborne particles & may make intubation more difficult/prolonged, safe removal/cleaning an issue.
- Protecting anaesthesia machine, gas analyser & subsequent patients from viral cross-contamination: filters x2 with the highest VFE, in adults, one at the airway & one @ the expiratory limb.
- Intubation & extubation both risks for transmission due to proximity/contact with airway secretions particularly if the patient coughs. Efforts to avoid or minimise coughing are warranted.
- Recovery in the OR or in a negative pressure isolation room.
- vacant rooms recently occupied by covid-positive pts should be left unoccupied as long as possible before cleaning to allow air turnover. Wipe down surfaces (cleaning & disinfection) with products approved to kill viral pathogens (eg. ethanol 62-71%). Additional measures such as germicidal UV light fixtures (risk of sunburn-like skin damage & eye damage + may generate ozone) or hydrogen peroxide vapour have been used in some settings.
- after the pt leaves OT, leave room closed until enough air exchanges to remove aerosolised pathogens (institution-dependent). Deep terminal cleaning.
- disposables (incl anaesthesia breathing circuit, reservoir bag, mask, FAWB should be bagged for disposal as contaminated waste)
What level of aerosol generation occurs with mask ventilation, intubation/extubation & SGA insertion/removal?
similar to tidal breathing & substantially less than from a cough. Total number of particles generated over 5 minutes during extubation is similar to the number from a single volitional cough.
What are different types of respirators available for PPE?
N95
Powered air-purifying respirator (PAPR)- highest level of protection, don’t require fit testing, can be repeatedly disinfected & reused BUT costly & require maintenance
Elastomeric respirators: reusable, high efficiency filters (similar protection to PAPRs)- quieter & don’t limit vision as do PAPRs BUT they require strict cleaning & make verbal communication difficult
What are different types of respirators available for PPE?
N95
Powered air-purifying respirator (PAPR)- highest level of protection, don’t require fit testing, can be repeatedly disinfected & reused BUT costly & require maintenance
Elastomeric respirators: reusable, high efficiency filters (similar protection to PAPRs)- quieter & don’t limit vision as do PAPRs BUT they require strict cleaning & make verbal communication difficult
What are different types of respirators available for PPE?
N95
Powered air-purifying respirator (PAPR)- highest level of protection, don’t require fit testing, can be repeatedly disinfected & reused BUT costly & require maintenance
Elastomeric respirators: reusable, high efficiency filters (similar protection to PAPRs)- quieter & don’t limit vision as do PAPRs BUT they require strict cleaning & make verbal communication difficult
What type of filters should be placed in adults with TV >300mL? and adults/kids with TV >30mL? Neonates with TV <30mL?
Pleated mechanical filter at the expiratory limb & another @ the airway, with gas analysis sampled from the machine side of the airway filter.
For adults/kids with TV >30mL (or kids <20kg), electrostatic filter (+/- HME component) can be substituted at the airway to decrease the dead space added by a mechanical filter (& this is better for long-term ventilation since mechanical pleated filters can become obstructed when placed @ the airway).
For neonates with TV <30mL, replace the airway filter with a mechanical filter at the inspiratory limb, keep a HME at the airway. The gas analyser is only protected by filters at the water trap OR a separate 0.2micron filter should be added to the gas analyser sampling line.
What are the pros & cons of pleated mechanical filters? and electrostatic?
Best filtration (VFE >99.99%) & their VFE isn't degraded by exposure to humidity, & they may provide some heat &moisture exchange when placed @ the airway. Cons: they have a large internal volume (approx 80mL) & squire a minimum TV of 300mL because of headspace ventilation. They are easily obstructed by secretions & condensed humidity. may also be less available during viral pandemics. Electrostatic filters have lower viral filtration efficacy & this gets worse as they get wet from humidified patient gases. They are, however, less prone to obstruction, are more available & can be made with a smaller internal volume.
Describe a pleated mechanical filter
contains a sheet of thick hydrophobic material that is pleated to increase the surface area & decrease resistance to flow
have small channels that trap particles, VFR >99.99%
VFE isn’t degraded by exposure to humidity
provide some HME when placed in the airway
most have an internal volume of approx 80mL & minimum TV requirement of 300mL due to dead space ventilation
Describe electrostatic filters
contain a thinner sheet of filter material that’s not so tightly woven
Less resistance to flow for a given surface area
have an electrostatic charge helping to attract & trap particles
VFE is generally <= 99.99% & this declines as the filter becomes wet (eg. high humidity)
Describe HMEFs
HMEFs combine heat & humidity exchange & a filter (typically electrostatic-type) in one unit. Ideal for use in the breathing circuit after the Y-connector to provide both filtration & heat & humidity conservation. If a HMEF is not coupled with a viral filter, they don’t remove viral particles or protect the anaesthesia machine.
Describe the membrane filters & how they may be relevant to COVID-19?
hydrophilic membrane filters usually used to filter liquids (eg. epidural infusions), sieve filters typically with a 0.20-0.22 micron pore size, not permitting any particle larger than the rated size to pass.
Hydrophobic membrane filters are in most gas analyser water traps to prevent liquid & particles from entering the gas analyser chamber. May trap viruses as filters are more efficient @ trapping particles in a gas medium vs a liquid medium.
Can add a 0.2-0.22 micron epidural filter to the gas analyser sampling line for additional filtration.