anaesethics Flashcards
into what space is a spinal anaesethic put
subarachnoid (normally below the level where the spinal cord ends at L2)
what is different about the local anaesethics used for spinal compared to normal local anaesthetics
they are made hyperbaric by adding glucose so that they are heavier than CSF and move more with gravity
how long does a single spinal injection last
2-3 hours (so can’t be used for longer operations)
does spinal injection affect the sympathetic nervous system
yes - reduces systemic vasoconstriction so can drop BP
what is different about the needle used for epidural rather than spinal
is it longer and larger
why is an epidural better for longer surgery
catheter remains in place so anaesethic can be put in continuously
how is hypotension from epidural managed
can use phenylephrine
how does local anaesethic work
block Na channels
why is adrenaline added to local anaesethic (not in fingers)
reduce blood flow so reduce systemic uptake and potentiate action
IV commonly used induction anaesethic for GA
propofol (potentiates GABAa)
inhaled / volatile commonly used anaesethic for GA
sevoflurane (can cause malignant hyperthermia)
Mx of malignant hyperthermia (caused by suxamethonium and sevoflurane) and will show raised CK on Ix
dantrolene (muscle relaxant)
stages of a GA
1) oxygen (to replace the nitrogen in the lungs)
2) induction - IV propofol
3) muscle relaxant
4) secure airway
5) phenylephrine to maintain BP as SNS impaired
6) consider if anything else is need eg IV hydrocortisone if on LT steroid or insulin
what score assesses the airway
malampati
what is an ASA VI pt
brain dead
what is an ASA V pt
unlikely to survive eg ruptured AAA
what is an ASA II patient
mild, well controlled illness eg well controlled diabetes/smoker or obese
what is an ASA III patient
not well controlled disease HTN/DM/ BMI >40
what is an ASA IV pt
severe disease which is a constant threat to life –> LTOT, MI in last 3 months
RF of post op nausea
female, young, personal hx of motion sickness
when is the WHO checklist for surgical safety done
before induction of anaesthesia, before incision of skin and before the patient leaves the operating theatre
what are checked in the surgical safety
- Patient identity and allergies checked
- Site is marked
- Pulse oximetry on patient and working
- Risk of blood loss
Anaesthesia safety check
when is a pre op done
2-4 weeks before elective and 4-7 days before urgent
when is an ECG done at preop
if >80
or if > 60 and a surgical severity score of 3+
SE of epidural
hypotension, post dural puncture headache, epidural haematoma
MX of post dural puncture headache (can get from LP, spinal or epidural)
lie flat, stay hydrated, drink caffeine
May need a blood patch
how does a post dural puncture headache present
like a bad migraine which is worse when stood up
does a spinal or epidural work faster
spinal as this is in the CSF
into what space is an epidural put
between the ligamentum flavum and the dura matter
how long do patients need to fast before surgery
at least 6 hours
how long before surgery can patients drink clear fluid
2 hours
when do type 2 DM who normally control DM with oral meds, need a VRIII in surgery
poor glycamic control, more than one meal missed
is metformin taken on surgery day
yes, just omit lunchtime dose (if there is one)
is gliclazide taken on surgery day
no
are SGLT2 inhibitors taken on surgery day
no
are the glitazones, gliptins and GLP1 mimetics taken on surgery day
yes
are long acting insulin taken on surgery day
yes just reduce dose by 20%
what needs to happen to steroid dose on surgery
-double usual steroid for 24-48 hours
-hydrocortisone 100mg IV on induction followed by IV infusion 200mg/24 hours
when does a DOAC need to be stopped
24 -72 hours before surgery
when does clopidogrel need to be stopped before surgery
7 days
when does warfarin need to be stopped before surgery
5 days and then bridging therapy with LMWH used
what do all patients need before surgery
G+S (and cross match if high risk of bleeding) and MRSA screen
when does COCP / HRT need to be stopped before surgery
4 weeks
considerations for diabetic patients
first on list, switch back to normal insulin regime at first meal but need to have SC insulin before taking down as half life of insulin is 5 minutes, optimisation of diabetes before surgery
what is an acceptable CBG in surgery and how often is it monitored
6-10 and monitored hourly
what is insulin infused through in VRIII
dextrose 5% (+added K+)
how is hyperglycaemia managed on surgery day
if CBG >12, check ketones.
risks of diabetics having surgery
higher risk son wound infections, risks of mistakes with insulin prescribing, underlying diabetes problems like higher risk of kidney insult
what are the diabetes sick day rules
increase CBG monitoring to hourly, increase fluid to 3L, continue insulin even if not eating and measure ketones
what happens in HIT
heparin induced antibodies attack platelet factor 4 and cause hypercoaguable state of blood. May present with a DVT. Need to stop UFH and start another anticoagulant.
complications of anaesthetic
1) sore throat post intubation
2) aspiration of gastric contents in non fasted individuals
3) urinary retention
4) PONV (RF - female, young, opioids used in surgery, hx of motion sickness)
5) PO cognitive dysfunction - increasing age / lower IQ
6) hypothermia
whats a sign of local anaesthetic toxicity
tingling around mouth + arrhythmias
RF for SSI
shaving with a razor (disposable clippers preferred), tissue hypoxia, delayed administration of prophylactic abx
Prevention of SSI
-don’t routinely remove body hair
-give prophylactic abx if surgery involves any sort of prosthesis, if it is clean contaminated or contaminated
-if tourniquet is use in surgery, need to give the prophylactic abx earlier
what does propofol give some protection against
PONV
what is propofol biggest SE
hypotension (in causes of haemodynaimc instability etomidate may be used instead but this causes adrenal suppression)
MOA of ketamine
blocks NMDA receptors
why is ketamine useful as a induction anaesthetic in trauma
doesn’t cause a drop in BP
muscle relaxant of choice for rapid sequence induction
suxamethonium
what kind of muscle relaxant is suxamethonium
depolarising (causes depolarisation at the motor end plate), people with MG are more resistant to this kind of muscle relaxant as they have fewer receptors for it to act on
when is suxamethonisum contraindicated
in eye trauma or glaucoma as it increase IOP
is ESRF ASA III or IV
III if undergoing regular dialysis and IV if not
how is someone fed post oesophagectomy
jejunostomy
what is an Igel also known as
laryngeal mask (this provides poor protection of aspiration if patient is not fasted)
Actually NO - LMA has an inflatable cuff but Igel does not
if nitrous oxide is given to someone with a pneumothorax, what can happen
become a tension pneumothorax
example of volatile liquid that can be used for induction and maintenance of anaesthesia
sevoflurane (can cause malignant hyperthermia)
features of propofol
provides some protection against PONV
-cause hypotension (due to myocardial depression)
-potentiates GABA
-pain on injection
SE of etomidate
adrenal suppression
what is the agent of choice for a rapid sequence induction
thiopentone due to working RAPID
what is a depolarising muscle relaxant
binds to nAChR causing persistent depolarisation of the end plate (suxamethonium)
what is a non depolarising muscle relaxant
competitive antagonism of nACHr, so can be reverse by acetylcholinesterase inhibitors
what kind of muscle relaxants exacerbate myasthenia gravis
non depolarising !!!!
when is LMWH started after a tHR
6-12 hrs
whats the time out part of the WHO checklist
the part before the incision (the other part are sign in and sign out)
what blood transfusion bloods have to be done for elective C section
G+S only
what does no trace on capnography indicate
in the wrong place (oesophageal)
