COVID, * is the blue book article transfusion implications in COVID-19 Flashcards

1
Q

What proportion of pts w COVID-19 suffer ischaemic stroke?

A

5%

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2
Q

Do surgical face masks protect against aerosolised particles?

A

No, but they do protect against droplet transmission

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3
Q

What are recommendations for COVID GA/intubation?

A

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

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4
Q

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?

A

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

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5
Q

What are some infection control considerations when anaesthetising a patient with covid-19?

A

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)
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6
Q

What level of aerosol generation occurs with mask ventilation, intubation/extubation & SGA insertion/removal?

A

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.

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7
Q

What are different types of respirators available for PPE?

A

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

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8
Q

What are different types of respirators available for PPE?

A

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

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9
Q

What are different types of respirators available for PPE?

A

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

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10
Q

What type of filters should be placed in adults with TV >300mL? and adults/kids with TV >30mL? Neonates with TV <30mL?

A

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.

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11
Q

What are the pros & cons of pleated mechanical filters? and electrostatic?

A
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.
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12
Q

Describe a pleated mechanical filter

A

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

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13
Q

Describe electrostatic filters

A

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)

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14
Q

Describe HMEFs

A

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.

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15
Q

Describe the membrane filters & how they may be relevant to COVID-19?

A

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.

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16
Q

does the gas sampling line and water trap need to be replaced between COVID-19 +ve pts?

A

yes for sampling line, no for water trap if HMEFs were used

17
Q

does the CO2 absorber need to be changed btwn COVID-19 +ve pts?

A

no, as it’s protected by filters in the breathing circuit & it’s highly alkaline & likely viricidal

18
Q

What are some considerations for pre-operative evaluation during the pandemic?

A

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.

19
Q

What were the findings from the international cohort study by the COVIDSurg Collaborative published in Lancet may 2020?

A

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.

19
Q

What were the findings from the international cohort study by the COVIDSurg Collaborative published in Lancet may 2020?

A

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.

20
Q

Aside from the COVIDSurg Collaborative study, what’s some other evidence regarding outcomes with perioperative COVID-19 diagnoses?

A

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.

21
Q

What’s the take-home message regarding timing of surgery following SARS-CoV-2 infection? Overall current stance?

A

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.

22
Q

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?

A

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.

23
Q

What’s considered mild COVID-19 illness?

A

S&S of C-19 (eg. fever, cough, sore throat, malaise, headache, muscle pain) without shortness of breath, dyspnoea or abnormal chest imaging

24
Q

What’s considered moderate C-19 illness?

A

Evidence of lower respiratory disease by clinical Ax or imaging & SpO2 >=94% on RA

25
Q

What’s considered severe C-19 illness?

A

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

26
Q

What’s considered critical C-19 illness?

A

respiratory failure
septic shock
+/- multi-organ dysfunction

27
Q

What are the aims of securing the airway for a C-19 pt? extubating?

A

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

28
Q

What are some considerations for the choice of anaesthetic technique for a C-19 patient?

A

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
29
Q

*What are the features of the COVID-19 coagulation profile?

A

Lower antithrombin levels & prothrombin time

Higher D-dimer, fibrin/FDPs & fibrinogen

30
Q

*Which features of COVID-19 coagulation profile are associated with poorer prognosis & increased mortality?

A

Higher D-dimer & FDP values & shorter thrombin times

31
Q

*Are anaemia & thrombocytopenia common in COVID-19 pts?

A

No, but if present, are associated with worse outcomes

32
Q

*What’s the rate of thrombotic complications in severe COVID-19?

A

9.5%

33
Q

*Is there an association between blood group & SARS-CoV-2 infection?

A

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