Airway and ventilation Flashcards
Rapid sequence induction.
a) Indications
b) Process: the 10 Ps
c) Induction agent is used in classic vs. modified RSI
d) What relaxant is used and why?
a) - Rapidly deteriorating situation
- Non-cooperative patient
- Oxygenation/ventilation compromise
- Full stomach (risk of reflux and aspiration); including laparoscopy - abdomen full of CO2
b) - Plan,
- prep,
- protect C-spine,
- positioning,
- pre-oxygenation,
- pre-treatment (optional: e.g. fentanyl, lignocaine and atropine),
- pressure (cricoid),
- paralysis and induction,
- placement with proof,
- post-intubation management
c) Classic RSI = Thiopentone
(modified RSI - Propofol)
d) Suxamethonium (depolarising)
- quicker onset (around 30 seconds compared with 120-180s for non-depolarising;
- however, rocuronium is quick also so may be used in a modified RSI)
ETT.
a) Indications
b) Why muscle relaxant needed
c) Mallampati score
d) Cormack-Lehane classification
e) Misplaced tube - 3 locations
f) vs. tracheostomy
g) Why are ETTs and tracheostomies a ‘definitive’ airway
a) Anyone who can’t protect their airway: reduced or fluctuating GCS, head injury (to regulate ICP), aspiration risks (laparoscopy, other major abdominal ops, bowel obstruction, other)
b) To relax tracheal opening (glottis)
c) 1 - 4: 1 (complete soft palate visualisation), 2 (tonsillar pillars not visualised), 3 (only base of uvula visible), 4 (soft palate not visualised at all)
d) 1 - 4: 1 (all glottis and cords visible), 2 (most of glottis), 3 (just epiglottis), 4 (nothing visible)
e) Endobronchial, oesophageal, herniating through cords
f) Inserted in front of neck
g) Cuffed tube below the vocal cords to create a seal and prevent aspiration
LMA (i-gel).
a) Insertion
Indications
a) Lubricate and advance into hard palate to avoid tongue. Tip of the airway should sit at oesophageal inlet
OP airway (Guedel).
a) Purpose
b) Alternative - indication, contraindication
a) Keeps tongue out of the way, aids bag mask ventilation (BMV)
b) NPA - aids BMV in conscious patient; CI - basilar skull fracture
Pre-oxygenation.
a) Residual volume in normal lungs
b) Oxygen use per minute
c) Hence pre-optimisation to fill residual volume with lungs can provide patient with oxygen for how long?
d) How it’s performed
a) 1500ml (1.5 L)
b) ~ 250ml/min
c) ~ 8 minutes ( = 1500/250)
d) 3 very large breaths or breathe normal for 2 mins
Note: pre-oxygenation has traditionally not been considered mandatory in all cases but reasonable to do so (the anaesthetist for Elaine Bromiley did NOT pre-oxygenate her)
Intra-operative oxygen.
a) How much should you give?
b) Why is 100% not recommended unless indicated?
a) Enough to maintain sats around 99-100%
b) Damages lining of the lungs, causes atelectasis when ventilation removed (nitrogen required to maintain alveolar volume - when oxygen replaces this quick diffusion causes alveolar collapse)
Airway positioning.
Neck flexed (use pillow) and occiput extended, open mouth, jaw thrust to move tongue
How to tell if airway/mask is correctly placed
- Symmetrical chest rising and falling
- etCO2 trace on machine
- Misting
- No leak
Two main techniques to manage breathing in theatre
- Spontaneous breathing - bag and mask, then insert LMA
- Controlled ventilation - induction, muscle relaxation and intubation
Invasive ventilation.
a) 2 types of control - preference in ITU vs theatres
b) Indications
c) How to oxygenate?
d) How to remove CO2?
e) Risks
a) Pres- or Vol-control:
- Pressure control (prevents barotrauma) preferred in ITU
- Either used in theatre, often volume control
b) - Pulmonary - severe pneumonia, ARDS, etc.
- Extra-pulmonary - unconscious patients, neuromuscular weakness (eg. MG, GBS)
c) - Alter FiO2 or PEEP (reduces shunt)
d) - Tidal volume or RR (to affect minute ventilation)
e) - Ventilator-associated pneumonia (VAP)
- Ventilator-associated lung injury (VALI): barotrauma, volutrauma
- Cardiac failure - reduced preload - reduced CO
- Failed extubation - need good physiological reserve pre-intubation if this is going to be likely
Extubation.
a) When?
b) Adjuvant treatment - why?
a) When patient can protect their own airway - they should have effective cough and be practically pulling the tube out themselves.
b) Furosemide - sudden drop from a positive pressure to negative pressure in the alveoli would cause any fluid in lungs to be sucked into the alveoli. Furosemide helps to prevent this happening.
Pre-operative assessment.
a) Clues of possible difficult intubation
b) PMHx - what should you establish about any conditions they have?
c) Reflux - how to ask?
d) Allergies - how to ask?
e) FHx - why important?
a) Mallampati 3-4, unable to protrude jaw anteriorly, neck extension difficulty, previous neck surgery, funny faces and beards, snoring/OSA
b) Does it lead to physiological decompensation (think ASA score) and does it require medicating?
c) “Any reflux, heartburn or indigestion” - get them to describe (e.g. vomiting, frequency, severity)
d) “Allergic to any medications… and anything else?” (strawberry/kiwi allergies = 50x more likely to have latex allergy)
e) Malignant hyper-pyrexia
Functional status.
a) METS
b) ASA scores
a) Metabolic equivalent task - 1 = 70kg male at rest, 4 = climbing a flight of stairs (usually good enough for surgery if 4 or more)
b) ASA:
1 - no conditions.
1e - no conditions but some physiological derangement as a result of this current emergency
2 - medical condition but no physiological decompensation (e.g. well-controlled asthma)
3 - medical conditions with some decompensation (most patients in this category)
4 - severe decompensation (e.g. CCF, on HMV/LTOT)
5 - palliative, likely to die
6 - dead (organ retrieval).
Intubation: procedure
- Correct head and airway position
- Pre-oxygenate (ventilate with 100% O2)
- Laryngoscopy (hold with left hand, insert from the right and move tongue to the side)
- Lift epiglottis up to visualise vocal cords
- Go in from the right so as not to obscure view
- Vocal cords should be between the two black lines (tube is often at around 20cm at teeth)
- Inflate cuff
- Ventilate: should see symmetrical chest expansion, CO2 trace, misting of tube, maintenance of good oxygen sats, ventilator pressures at normal level (if very high, may be intrabronchial intubation - to deliver set tidal volume to one lung, pressures would need to be higher)
Difficult intubation.
a) Can’t intubate - what should you do?
b) Why might poking the ETT not be desirable?
c) Can’t ventilate - what should you do now?
a) Maintain SITUATIONAL awareness (don’t become task-focused) - go back to BVM ventilation and ensure saturation are okay
b) Can cause trauma, bleeding and inflammation, which may lead to a catastrophic CICV scenario
