Anaesthetics & critical care Flashcards
three types of anaesthesia?
- general
- regional
- local
three components of general anaesthesia (GA)?
AAA
Amnesia
- lack of response and recall to noxious stimuli (Unconsciousness)
Analgesia
Akinesis
- immobililsation / paralysis (nb don’t need this in every surgery)
What are the 5 stages to general anaesthesia (in chronological order)?
1) Monitoring
2) Intravenous access (To give anaesthetic drugs)
3) Start the process:
- analgesia
- Induction of anaesthesia (Induction agents)
- Start the muscle relaxation (if needed)
4) Maintain the process
- Maintenance agents for amnesia / analgesia / muscle
relaxation, replace fluid & blood loss
5) Reverse the process
- Reverse muscle relaxation
- Maintain post operative
analgesia
What are the MINIMUM things you should monitor during a GA?
- airway gases? 3
- only if a muscle relaxant is used? 1
- other things? 5
airway gases
- oxygen
- carbon dioxide
- vapour
nerve stimulator (if muscle relaxant used)
- airway pressure
- SpO2 (sats)
- ECG
- BP (non-invasive)
- temperature monitoring (if indicated)
Why do you monitor airway pressure during GA?
to detect if a blockage in airways occurs (eg tube kinks)
Also will detect any other problems like clots etc in thorax
How long can people be hypoxic before irreversible brain damage occurs?
3-5 minutes
Which operations should you monitor temperature in?
any op lasting >30mins
nb if low temp then will delay wound healing as get coagulopathies
Why is IV access harder to get preoperatively
people have been fasting and / or are sick
How long do induction agents take to work?
Induce loss of consciousness in one to two
arm-brain circulation times
10-20 secs
What are the 4 most commonly used induction drugs?
- propofol
- thiopentone
- ketamine
- etomidate
Propofol
- what does it look like?
- pros? 2
- unwanted effects? 3
most commonly used induction agent
white emulsion (only thing that’s white)
pros:
- excellent suppression of airway reflexes
- decreases incidence of PONV
unwanted effects
- marked drop in HR & BP
- pain on injection
- involuntary movements
nb involuntary movements are normal - don’t mean need more propofol
what is PONV?
post-operative nausea & vomiting
What effect does each of the 4 induction agents have of BP & HR?
propofol
- lowers BP
- lowers HR
thiopentone
- lowers BP
- raises HR
Ketamine
- raises BP
- raises HR
(also bronchodilation)
Etomidate
- no significant change to BP
- no significant change to HR
Thiopentone
- type of drug?
- mainly used for?
- advantages? 2
- unwanted effects? 4
Barbituate
rapid sequence induction (though propofol can also be used)
- faster-acting than propofol
- anti epileptic properties (& protects brain)
unwanted effects:
- Drops BP but rise in HR (think of it like drops BP as normal but because used for ‘‘rapid’ induction, HR increases)
- rash / bronchospasm
- if do intraarterial injection: thrombosis & gangrene
- contraindicated in porphyria
“thioPENtone - haven’t got time to WRITE before they go to sleep, also you use your BRAIN to use a PEN”
Ketamine
- what type of amnesia does it provide?
- which operations most commonly used for?
unwanted effects? 4
Dissociative anaesthesia
- anterograde amnesia & profound
use as sole analgesics for short procedures (as short, can get away with lower doses, which are much less likely to induce emergence phenomenon)
- slow onset (90secs)
- rise in BP & HR (also bronchodilation)
- nausea & vomiting
- emergence phenomenon (ie hallucinations / vivid dreams)
“ket is a stimulatant so explains rise in BP, HR & bronchodilation - also want to throw up after seeing weird hallucinations”
Etomide
- when mainly used?
- advantages? 3
- unwanted effects? 4
If heart failure or very unstable heart
(due to its haemodynamically stable properties)
- rapid onset
- haemodynamic stability (no big effect on BP or HR)
- lowest incidence of hypersensitivity reaction
unwanted effects - pain on injection - spontaneous movements - adreno-cortical suppression (can cause post-op adrenal collapse up to 72hrs after surgery) - high incidence of PONV
“ETO sounds like ISO - so keeping cardiac obs the same!”
Best induction agent for:
- pt requiring a burn dressing change?
- pt undergoing arm operation under GA with an LMA?
- pt with history of heart failure?
- pt with intestinal obstruction requires emergency laparotomy?
- pt with porphyria comes for inguinal hernia repair?
pt requiring a burn dressing change
= ketamine
pt undergoing arm operation under GA with an LMA?
= propofol
pt with history of heart failure?
= etomidate
pt with intestinal obstruction requires emergency laparotomy
= thiopentone (can do modified RSI with propofol)
pt with porphyria comes for inguinal hernia repair
= propofol (no thiopentione)
how long to induction agents work?
What two ways can you maintain amnesia after this? 2
4-10 mins
total intravenous anaesthesia
- propofol infusion
inhalational anaesthesia
- inhalational agents
Three most common inhalational agents for maintenance of amnesia?
suffix?
when are they stopped?
isoFLURANE
sevoFLURANE
desFLURANE
suffix = -flurane
“FLU keeps you wiped out”
(nb also enflurane but this rarely used)
can be continued to the end of the operation
MAC:
- what does it stand for in anaesthesia
- what is it / does it mean?
MAC = minimum alveolar concentration
CONCENTRATION of the anaesthetic vapour that PREVENTS the REACTION to a standard surgical STIMULUS (traditionally a set depth & width of skin incision) in 50% OF SUBJECTS
100% will have amnesia at this concentration though
Inhalational agents
- 3 most common and their main useful properties (and thus what they’re used for)
SevoFLURANE
- sweet smelling
- inhalational induction (especially when child or needle phobic)
- “S for Sweet Smelling”
desFLURANE
- low lipid solubility (so rapid onset & offset)
- used for long operations
- “DESmond tutu lived for a LONG time - used for LONG ops”
isoFLURANE
- least effect on organ blood flow
- used for organ retrieval from a donor
- “ISO stays in the SAME place, ie in the blood, not the organs”
Bets inhalational agent for:
- a long 8-hour finger re-implantation?
- chubby child, no IV access?
- organ retrieval from a donor?
a long 8-hour finger re-implantation
= DESflurane
chubby child, no IV access
= SEVOflurane
organ retrieval from a donor
= ISOflurane
Why do you use analgesia during GA? 3
- insertion of airway (LMA or IV) - suppress response to laryngoscopy
- intraoperative pain relief
- post-op pain relief
Two different types of STRONG opioids used in surgery:
- drug examples?
- drugs most commonly used?
- what each type used for?
SHORT-ACTING OPIOIDS
used for: - intra-op analgesia - suppress response to laryngoscopy - surgical pain RAPID onset, HIGH potency
Examples:
- remiFENTANIL
- alFENTANIL
- FENTANYL (commonest)
LONG-ACTING OPIOIDS
used for
- intra-op analgesia
- post-op analgesia
- morphine
- oxycodone (commonest)
When do you start giving analgesia in an operation?
BEFORE anaesthetic induction drug given (so analgesia has time to work before you intubate someone - which is v painful)
Other analgesia (ie not strong opioids) used in and peri-surgery?
which 2 most commonly used?
- paracetamol (common)
NSAIDS
- diclofenac
- parecoxib
- ketorolac
weaker opioids
- tramadol
- dihydrocodeine (common)
Which two NSAIDs are given IV?
parecoxib
ketorolac
most commonly used analgesic?
paracetamol
most commonly used ORAL opioid in adults?
codeine
Which surgeries do you need to give muscle relaxant for?
ones where pt is INTUBATED
***I think - check this though!!
What are the two TYPES of muscle relaxant?
what’s different about them physiologically?
DEPOLARISING
- Ach mimic, depolarises post-synaptic membrane at NMJ a lot, overstimulates muscle until it exhausts and stops
- get fasiculations then flaccid paralysis
NON-DEPOLARISING
- blocks Ach receptors on post-synaptic membrane, preventing any depolarisation
- just get flaccid paralysis
Depolarising muscle relaxant:
- examples?
- speed?
- what used for?
- adverse effects?
- reversal needed?
DEPOLARISING
- SUXmethonium
- “it SUCKS apart from when stomach has stuff in so could do with a SUCK”
- rapid onset, rapid offset
- used for rapid sequence induction
adverse effects
- muscle pains
- fasiculations
- hyperkalaemia
- malignant hyperthermia
- rise in ICP, intra-occular pressure & gastric pressure
“all these side effects make sense as these drugs stimulate lots of muscle action till it’s ‘worn out’”
no reversal needed
Non-depolarising muscle relaxant:
- examples?
- speed?
- what used for?
- adverse effects?
- reversal needed?
NON-DEPOLARISING
short acting
- atraCURium
- mivaCURium
intermediate acting
- veCUROnium
- roCUROnium
long-acting
- panCUROnium
“CURare is the muscle relaxant used in the amazon”
“CURE is better, these are better than depolarising”
“ROCuronium ROCKS, so is often used in preference to SUX, even in RSI”
slower onset & variable duration
INTERMEDIATE ones normally used for most surgeries then repeat dose if need to
less side effects (?any?**)
yes, reversal needed
What reversal drugs are used to reverse non-depolarising muscle relaxants? 3
which is the best, but expensive, one?
normal ones used with most ops:
- neoSTIGmine AND glycoPYRrolate TOGETHER
SUGGAmadex (expensive, but fast, use in emergencies)
“a SUCKER for the most expensive drugs”
Common drugs used to treat HYPOtension during surgery? 3
which used when?
(these are all vasopressors)
what are these drugs also known as
epipHEDrine
- raises BP AND HR
- “gets blood to the HEAD by increasing both”
phenylEPHerine
- raises BP (no effect on HR)
- “EH can only be bothered to raise BP”
^two most commonly used
“sounds like epinepherine - ie adrenaline which is also a vasopressor”
metaraminol
- raises BP (no effect on HR)
aka INOTROPES
- they increase the contractility of muscles, and so increase the contractility of the heart but also cause vasoconstriction as muscles in blood vessel walls also constrict
Vasopressor drugs used to treat SEVERE HYPOtension, and in ICU? 3
- noradrenaline
- adrenaline
- dobutamine
Best vaso-active agents to treat hypotension:
- low BP, high HR?
- low BP in severe sepsis?
- low BP, low HR?
low BP, high HR
= phenylephrine, metaraminol
low BP in severe sepsis
= noradrenaline, adrenaline
low BP, low HR
= ephedrine
post-op nausea & vomiting:
- how common after GA?
- 1st, 2nd & 3rd line anti-emetics?
- other anti-emetics can sometimes use? 2
20-30% after GA
1st line = ONDANSETRON
“lots of cancer pts need surgery, also use ondansetron with chemo”
2nd line = DEXAMETHASONE
“surgery causes swelling, want to reduce this with steroids”
3rd line = CYCLIZINE
“after you’ve cycled through the first 2, you get to cyclizine”
others:
- prochlorperazine (stemetil)
- metoclopramide
Which IV drugs do anaesthetists commonly prepare for a surgery? 8
(some they may use, others ‘just in case’)
1) anaesthetic (eg propofol)
2) analgesia (eg alfentanyl)
3) muscle relaxant (eg rocuronium)
4) 1st antiemetic (eg ondansetron)
5) 2nd antiemetic (eg dexamethasone)
6) drug that raises BP & HR (eg Ephedrine)
7) drug that raises just BP (eg phenylephrine)
8) antibiotic (eg co-amoxiclav)
What is the process of waking someone up from a GA? 5 steps
1) stop anaesthetic vapours
2) give oxygen
3) perform throat suction
4) reverse muscle relaxant
5) extubate (as they start coughing) and replace with oxygen mask
When handing over to recovery team after a GA:
- what to administer while transferring? 1
- what information to handover to recovery team? 3
- what to prescribe? 4
administer O2 during transfer
handover the pt
- brief history
- any problems anticipated
- intraoperative analgesia and PONV prophylaxis
prescribe
- rescue analgesia
- rescue antiemetics
- fluids
- other medications, as indicated
What should you always do before a surgery to prevent hypoxia?
pre-oxygenate everyone!
What is the purposes of a pre-op assessment?
1) allay patients fears & anxieties
2) identify potential anaesthetic difficulties and medical conditions
3) improve safety by assessing & quantifying risk
4) optimise & plan of the peri-operative care
5) provide an opportunity for explanation & consent
so basically:
1) reduce pt anxiety
2) identify comorbidities & potential difficulties
3) make clear plan for peri-operative care (when to stop drugs etc)
4) consent the pt
How would you approach a history for a pre-op patient?
A-E plus DRUGS (“as anaesthetists love drugs”)
conditions / past surgeries that affect each one
eg A is any conditions that affect the airway
examine airway bits but apart from that examine relevant system but don’t need to - depends on severity of comorbidity etc
What things would you ask about assessing the ‘A’ of a pre-op assessment:
- PMHx? 3
- exam? 3
- previous anaesthetics? 4
AIRWAY
basically think mouth, jaw, neck (order the IV goes in) then ask about any previous anaesthetics and FHx
history
- any dental work? caps or crowns?
- any problems with your jaw
- any problems with your neck? arthritis etc
exam
- Mallampati score
- ask pt to move jaw side to side (also note beards but don’t ask to shave unless really serious)
- ask patient to fully extend & flex neck (& side to side & rotate?)
Previous anaesthetics?
- any previous PMHx of GA? any severe reaction? any PONV? pain relief problems? (also what did they have done)
- any FHx of any problems with GA?
How do you assess someone’s mallampati score?
which class is what?
ask pt to open mouth as WIDE AS POSSIBLE and stick tongue out
Class I - complete visualisation of the soft palate - incl the pillars (ie there is a space under the uvula)
Class II - complete visualisation of the uvula
Class III - only the top (ie base) of the uvula can be visualised
Class IV - only hard palate visible
What things would you ask about assessing the ‘B’ of a pre-op assessment history:
- chronic airway conditions? 1
- chronic lung conditions? 3
- acute lung problems? 1
- social history?
RESPIRATORY SYSTEM
chronic airway conditions:
- obstructive sleep apnoea
chronic lung conditions: - COPD - asthma - any restrictive lung disease (take a full hx of whatever you find to assess severity & risk with GA)
acute lung problems
- any cough? new breathlessness? fever? other signs of infection?
social history
- how far can you walk on the flat? (why do you stop? SOB or joint pain etc?)
- smoking (current or past) - PERSUADE THEM THAT LONGER THEY STOP BEFORE SURGERY, EVEN IF JUST A DAY, THE BTTER THEIR RECOVERY WILL BE!
What things would you ask about assessing the ‘C’ of a pre-op assessment history:
- chronic CV conditions? 5
- questions to assess severity? 4
CARDIOVASCULAR HISTORY
chronic CV conditions:
- high blood pressure (find out their normal)
- angina
- previous heart attacks
- previous heart surgery
- heart failure
Qs to assess severity
- chest pain (on exertion or random)
- paroxysmal nocturnal dyspnoea
- orthopnoea
- exercise tolerance (if not already asked)
What things would you ask about assessing the ‘D’ of a pre-op assessment history:
- neuro PMHx? 3
- other ‘disability’ PMHx? 3
DISABILITY
neuro PMHx
- epilepsy
- neuromuscular disorders
- nerve damage (mainly to protect yourself)
other ‘disability’ PMHx
- diabetes (DON’T FORGET!!)
- thyroid problems?
- stroke / TIA
What things would you ask about assessing the ‘E’ of a pre-op assessment history:
- GI history? 4
- other history? 3
EXPOSURE
GI history
- reflux? (could affect airway)
- any other problems with liver? gut?
- time of last meal (if operation imminent)
- alcohol consumption?
other history
- any kidney problems?
- ANY CHANCE YOU COULD BE PREGNANT?
- any other reasons you see the GP or been into hospital or surgeries?
What things would you ask about assessing the ‘DRUGS’ of a pre-op assessment history:
- general opening questions? 2
- specific drugs to ask about? 2
1) ANY ALLERGIES?
2) What medications do you currently take?
other drugs to ask about:
- blood thinning medications,warfarin, LMWH, DOACs (also ask re aspirin / clopidogrel)
- insulin or hypoglycaemic medication
What is ASA grading? how many grades are there?
physical status classification for assessing fitness for surgery
6 grades
nb add ‘E’ suffix if surgery is emergency
What are the ASA grades? 6
ASA GRADES
Grade 1
= healthy pt with no systemic disease
Grade 2
= mild systemic disease only, without substantive functional limitations (incl social drinkers, obesity & depression)
Grade 3
= severe systemic disease with substantive functional limitations
Grade 4
= Severe systemic disease which is a CONSTANT THREAT TO LIFE
Grade 5
= moribund pt who is not expected to survive with or without surgery
Grade 6
= A brainstem-dead pt whose organs are being removed for donation
nb 2 and 3 are most common - sometimes hard to differentiate between them
What are the different ‘surgical grades’? 4
give examples
SURGICAL GRADES:
GRADE 1 (minor): excisions skin lesion, abscess drainage, toenail removed etc.
GRADE 2 (intermediate): inguinal hernia, knee arthroscopy, tonsillectomy
GRADE 3 (major): hysterectomy or thyroidectomy
GRADE 4 (major+/complex): Joint replacement, C-section, thoracic operations, radical neck dissection
What should you do before a GA in a pre-menopausal woman?
a pregnancy test - with their consent!
What is the CEPOD (actually NCEPOD) classification of surgery? 4
IMMEDIATE / EMERGENCY
- immediate life, limb or organ-saving intervention
- (eg repair of ruptured AAA, post-op tonsillectomy bleed, fasciotomy)
- within MINUTES
URGENT
- Intervention for acute onset or clinical deterioration or potentially life or limb threatening conditions
- (eg appendicitis, ruptured ectopic pregnancy)
- within HOURS
EXPEDIATED / SCHEDULED
- pt requires early treatment where condition is not immediate threat to life or limb
- (eg excision of tumour with potential to bleed or obstruct, acute cholecystectomy, NOF fracture)
- within DAYS
ELECTIVE
- intervention planned in advance of routine admission to hospital. Timing to suit pt, hospital & staff
- (eg resection for non-obstructing bowel ca)
- within 18 WEEKS
How to ask about exercise tolerance in a pre-op assessment?
How much can you do physically (just dressing, walking, running - how far?) AND what stops you? (eg lungs or legs etc)
What sort of things prolong gastric emptying?
- metabolic causes? 2
- anatomical causes? 2
- mechanical causes? 2
- trauma? 2
- others? 3
metabolic causes
- diabetes (as probs have a bit of gastric autonomic neuropathy)
- end stage renal failure
anatomical causes
- pyloric stenosis
- reflux
mechanical causes
- pregnancy (also higher progesterone which dilates lower oesophageal sphincter)
- obesity
trauma (as body goes fight or flight so doesn’t digest)
- road traffic accident
- head injury
others
- high fat content
- recent consumption of alcohol
- anxiety (again fight or flight)
What fluids can patients have before surgery?
How much?
Up to when?
exceptions? 2
Translucent fluids (eg can have orange squash, black tea but not orange juice)
however much up to 2 hours before surgery
children: up to 1 hour before surgery
if up to 30ml (to take with tablets) then up the the surgery
How long before surgery can people have:
- solids & non-clear drinks?
- breast milk?
- alcohol?
- boiled sweets / chewing gum?
solids & non-clear drinks
= 6 hours
breast milk
= 4 hours
alcohol
= 24 hours (delays gastric emptying)
boiled sweets / chewing gum
= try & avoid as leads to increased gastric volume & acidity - but carry on with surgery if someone has had
What is the indication for a rapid sequence induction?
what is the objective?
full stomach for any reason
aim is to reduce the risk of aspiration
Who always gets a RSI?
Women over 20 weeks pregnant
Rapid sequence induction:
- Which drugs do you use in a typical RSI? 2
- Which drugs are more commonly used in RSI (aka a modified RSI)? 2
- which drug is used in both?
Typical RSI
- thiopentone (fast induction agent)
- suxmethonium (muscle relaxant - but lots of side effects)
modified RSI
- propofol (induction agent, slightly slower but still fast)
- rocuronium . (muscle relaxant - fewer aside effects)
opioids - norm fentanyl or alfentanyl
Rapid sequence induction:
aside from choice of induction agent and muscle relaxant what else do you do during RSI:
- before induction? 1
- during induction? 2
- after induction? 1
- what should have at the ready throughout? 1
before induction
- preoxygenate with 100% oxygen (to increase O2 in lungs so meaning have longer time to intubate without ventilation)
during induction
- don’t ventilate! (just fills up stomach with air -> increased risk of aspiration)
- cricoid cartilage pressure (aka Sellick’s manouvere)
after induction
- ensure tube is in correct place, then remove cricoid pressure
have suction at the ready - if they vomit, release cricoid pressure, tilt head down and suction!
nb can give PPIs / H2 agonists if worried about reflux
How can you tell that you have intubated in the correct place? 5
which of these is the gold standard? 1
1) Visualisation of vocal cords (during intubation)
2) Chest rising bilaterally
3) Auscultation of breath sounds
4) Fogging of tube
5) EtCO2 trace on the monitor
Who should be preoxygenated?
tbh everyone - can get pt to look at the screen and do it themselves to reduce anxiety
but especially important in RSI
What is the RAT system for pain?
Recognise (that someone is in pain)
Assess (the type of pain & it’s cause)
Treat (the underlying cause and/or the pain)
Which groups of patients often have unrecognised pain? 6
Who should you ask about pain in?
- stoic older pts
- learning difficulties
- language barriers
- dementia
- sedation
- unconscious
EVERYONE!!
Why is it important that people have good pain control post-operatively?
because they need to be able to take deep breaths and cough to avoid getting pneumonia!
people take shallow breaths and don’t cough when in pain - as it hurts more to breath deeply and cough
ALSO pain gets worse if pts feel like their pain is getting dismissed
How do you assess pain?
SOCRATES
- trying to work out cause of pain AND the type of pain - both guide tratment
What are the two broad types of treatment for pain?
pharmalogical and non-pharmological
What is pain?
need to know this!!!
An UNPLEASANT sensory and/or emotional experience associated with actual OR potential TISSUE DAMAGE, or described in terms of such damage!
What are non-verbal signs that you can use to tell that someone is in pain?
How can you tell if a child is in pain?
- frowning
- wincing
- shallow breaths
- sweating (people sweat when in pain)
ask parents if child is acting normally!
Why is asking the severity (eg 1-10) of pain useful? 2
allows you to compare patient’s pain over time
- especially before / after analgesia
guides which analgesics you will use
