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.
does the gas sampling line and water trap need to be replaced between COVID-19 +ve pts?
yes for sampling line, no for water trap if HMEFs were used
does the CO2 absorber need to be changed btwn COVID-19 +ve pts?
no, as it’s protected by filters in the breathing circuit & it’s highly alkaline & likely viricidal
What are some considerations for pre-operative evaluation during the pandemic?
COVID-19 screening or testing
Symptoms: sore throat, loss of taste/smell, cough, shortness of breath, muscle aches, fevers, fatigue within the prior 2/52
History regarding recent COVID-19 infection & symptom status (international cohort study published in Anaesthesia March 2021 suggests should delay elective surgery until >=7/52 following SARS-CoV-2 infection & longer if the patient remains symptomatic or required ICU admission for their infection, surgery should ideally be delayed until the patient has recovered to baseline cardiopulmonary status & is no longer infectious.
Risk assessment for peri-operative morbidity & mortality & risk of spread of the virus to care providers & other patients
Decision to perform surgery in patients who are symptomatic with COVID-19, suspected of having COVID-19 or are likely to still be infective after having COVID-19 needs to be balanced against the risk of delaying surgery given that there’s increased perioperative morbidity & mortality in pts with COVID-19 (COVIDSurg Collaborative). Elective surgery shouldn’t be performed on any of these 3 groups of pts.
C-19 may have long-term deleterious effects on myocardial anatomy & function so preop evaluation should give special attention to the cardiopulmonary system in those who’ve recovered from C-19.
Residual symptoms include fatigue, dyspnoea & chest pain & may be present for >60/7 after Dx.
What were the findings from the international cohort study by the COVIDSurg Collaborative published in Lancet may 2020?
international multicentre cohort study, patients undergoing surgery who had a SARS-CoV-2 infection confirmed within 7 days before or 30 days after surgery.
1128 patients.
Outcomes/results:
30-day mortality was 23.8%
Pulmonary complications (pneumonia, ARDS, unexpected postoperative ventilation) occurred in 51.2% of pts & 30-day mortality in those patients was 38% (these pts accounted for 81.7% of deaths)
30-day mortality was associated with male sex, age >=70, ASA 3-5, malignant diagnoses, Emerg vs elective & major vs minor surgery.
What were the findings from the international cohort study by the COVIDSurg Collaborative published in Lancet may 2020?
international multicentre cohort study, patients undergoing surgery who had a SARS-CoV-2 infection confirmed within 7 days before or 30 days after surgery.
1128 patients.
Outcomes/results:
30-day mortality was 23.8%
Pulmonary complications (pneumonia, ARDS, unexpected postoperative ventilation) occurred in 51.2% of pts & 30-day mortality in those patients was 38% (these pts accounted for 81.7% of deaths)
30-day mortality was associated with male sex, age >=70, ASA 3-5, malignant diagnoses, Emerg vs elective & major vs minor surgery.
Aside from the COVIDSurg Collaborative study, what’s some other evidence regarding outcomes with perioperative COVID-19 diagnoses?
international prospective cohort study from Oct 2020 (published in Anaesthesia March 2021), among 140,000 patients who underwent surgery, 3100 had a pre-op COVID-19 diagnosis. Surgery within 7/52 of C-19 Dx was associated with increased odds of 30-day post-op mortality as follows:
- If the pt had been symptomatic but the symptoms resolved, odds of 30-day mortality at 0-2, 2-4 & 5-6/52 after Dx were: 6.93, 6.32 & 5.82
- if the pt had been asymptomatic, odds of 30-day mortality after surgery performed within 7/52 of the Dx were also increased, but to a lesser extent than if the pt had been symptomatic. 3.94, 3.57, 3.26 ORs, respectively.
For pts who had been asymptomatic or whose symptoms had resolved @ the time of surgery, post-op mortality was similar to baseline (adjusted 30-day mortality 1.5%) for surgery performed >=7/52 after diagnosis.
Pts who were symptomatic at the time of surgery had higher 30-day mortality rates at all time periods, including after a >= 7/52 delay.
Study limited by lack of surgery-specific data & data on anaesthesia management.
What’s the take-home message regarding timing of surgery following SARS-CoV-2 infection? Overall current stance?
Where possible, surgery should be delayed for @ least 7/52 following SARS-CoV 2 infection- if ongoing symptoms >=7/52 from diagnosis, there may be benefit from further delay.
Overall timelines aren’t definitive, each pts preoperative risk Ax should be individualised, factoring in comorbidities (eg, DM), surgical intensity, risk/benefit of delaying surgery.
What determines when a patient confirmed to have COVID-19 is no longer infectious? ie. when can transmission-based precautions be discontinued? Should a patient be re-tested?
In patients with mild-moderate C-19, repeat RT-PCR testing may detect SARS-CoV-2 RNA for a prolonged period after symptoms first appear, but replication-competent virus hasn’t been recovered after 10/7 has elapsed following symptom onset.
So, a time & symptom-based strategy should be used to decide when C-19 pts are no longer infectious.
For pts with C-19 who aren’t severely immunocompromised & have mild-moderate symptoms, can discontinue precautions if at least 10/7 have passed since first symptoms, at least 24hrs have passed since last fever without the use of fever-reducing medications & symptoms have improved.
For patients who aren’t severely immunocompromised & who’ve been asymptomatic throughout infection, precautions can discontinue when @ least 10/7 has passed since date of first +ve viral Dx test.
If severe to critical illness or if a pt is severely immunocompromised, discontinue precautions when 10-20/7 have passed since symptoms first appeared, at least 24hrs have passed since the last fever without fever-reducing medications & symptoms have improved. Should consult with ID prior to discontinuing precautions for these patients.
Asymptomatic patients shouldn’t be retested within 90/7 of symptom onset; after 90/7 they can have one pre-op PCR ideally <=3/7 preop. If they present with symptom recurrence within 90/7 they could have re-testing & ID consultation.
What’s considered mild COVID-19 illness?
S&S of C-19 (eg. fever, cough, sore throat, malaise, headache, muscle pain) without shortness of breath, dyspnoea or abnormal chest imaging
What’s considered moderate C-19 illness?
Evidence of lower respiratory disease by clinical Ax or imaging & SpO2 >=94% on RA
What’s considered severe C-19 illness?
RR >30/min
SpO2 <94% on RA (or for pts w chronic hypoxaemia, a decrease from baseline of >3%)
PaO2/FiO2 <300mmHg
or
lung infiltrates involving >50% of the lung fields
What’s considered critical C-19 illness?
respiratory failure
septic shock
+/- multi-organ dysfunction
What are the aims of securing the airway for a C-19 pt? extubating?
Full PPE
Minimal staff in OT
most experienced operator to intubate
plans (& contingencies, aim= secure airway rapidly, on 1st attempt, reducing or eliminating aerosolisation of respiratory secretions), assistant, monitoring, equipment & drugs all ready
double glove & remove outer glove immediately after laryngoscopy
preset ventilator
pts surg mask/O2 prongs into clinical waste
pre-O2 FiO2 100% for 5 mins with vice grip & tight-fitting mask
modified RSI
paralyse well, no cricoid (unless concern re: aspiration) & don’t place bougie too far (aim to limit coughing)
No BMV (if hypoxic, low pressures & low volume)
reduce flows when circuit open (drugs Dr)
1st line videolaryngoscope (use whichever scope clinician is most comfortable with; video may increase likelihood of 1st pass success & allows clinician to be further from oropharynx)
cuff up, connect up THEN CO2
clean equip to R) & dirty to L) (place used airway equipment into double zip-locked plastic bag for removal & decontamination)
airway person is the only one touching the airway
plastic sheet over prepared for extubation
other personnel can return to OT after the institution-specified time interval (may be based on the frequency of air exchanges if re-entering a positive-pressure OR)
If require disconnects, keep filter in place, if not spont venting turn ventilator off & clamp ETT prior to disconnect
Extubate with minimal staff in OT
under plastic sheet (could also put a surgical mask over pts nose/mouth or wet gauze over nose/mouth- whatever use, it needs to be treated as a biohazard)
Pt on ward bed
Staff positioned behind pt
suction deep (use closed tracheal/oropharyngeal suction system)
sitting up spont breathing, TOFR >0.9
aim for minimal coughing (can give IV, topical or cuff lignocaine, low-dose opioids or dexmed) & minimal time that the airway open
transfer EtCO2 onto a mask with filter
disconnect proximal to filter & put circuit on mask
remove tube with sheet, mask with filter straight on
once pt not coughing, put on surgical mask & O2 (if facemask, that goes over the surgical mask. nasal prongs under the surgical mask)
recover pt in the C-19 theatre
What are some considerations for the choice of anaesthetic technique for a C-19 patient?
Neuraxial/regional vs GA:
- preference for avoiding airway instrumentation but many C-19 patients are anti-coagulated
- pts not receiving GA should wear a surgical mask @ all times, any supplemental O2 placed under the mask, if O2 is needed the lowest flows possible for maintenance of oxygenation should be used
For GA:
- RSI often appropriate (if mask ventilation is essential, use low pressure small volume breaths with tight mask seal)
- should use video laryngoscope (aim=secure airway rapidly on 1st attempt)
- aim to avoid coughing
- avoid AFOI wherever possible; if essential, meticulous topicalisation with LA. Avoid nebulised LA & transtracheal injection of LA. use sedation sparingly.
- ETT should be used (more effective seal of the airway)
- consider preloading with fluid/vasopressors in anticipation of induction, consider ketamine or a combo of ketamine & propofol for induction
- anticipate that critically ill C-19 pts may become even more hypoxaemic & hypotensive after induction
*What are the features of the COVID-19 coagulation profile?
Lower antithrombin levels & prothrombin time
Higher D-dimer, fibrin/FDPs & fibrinogen
*Which features of COVID-19 coagulation profile are associated with poorer prognosis & increased mortality?
Higher D-dimer & FDP values & shorter thrombin times
*Are anaemia & thrombocytopenia common in COVID-19 pts?
No, but if present, are associated with worse outcomes
*What’s the rate of thrombotic complications in severe COVID-19?
9.5%
*Is there an association between blood group & SARS-CoV-2 infection?
Yes- group O may be associated with lower risk of SARS-CoV-2 & group A may be associated with higher risk of infection & severe disease
