Anaesthetics Flashcards
What are the normal ranges for sodium and potassium in the blood and why is there such a difference?
Sodium: 135-145mmol/L
Potassium: 3.5-5.0mmol/L
Sodium mostly exists in the extracellular compartment (ECF and blood), potassium mostly exists in the intracellular compartment
What are the daily requirements of water, sodium and potassium?
WATER: 30-40ml/kg (approx 2-3L for average adult)
SODIUM: 1-2mmol/kg (approx 70-140mmol/L for average adult)
POTASSIUM: 0.5-1/0mmol/kg (approx 35-70mmol/L for average adult)
***these are the sorts of levels we should aim for when prescribing MAINTENANCE FLUIDS
What kinds of things cause FLUID LOSS?
Poor oral intake (elderly, dysphagia, unconsciousness, fasting NBM) Increased requirements (Trauma, burns, post-operative) Increased loss (fever, sweating, bleeding, D&V, renal loss)
How do we classify fluid loss?
As mild, moderate or severe
MILD
- 4% body weight, loss of skin turgor and dry mucus membranes
MODERATE
- 5-8% body weight, oliguria, tachycardia and hypotension
SEVERE
- >8% body weight, profound oliguria and CVS collapse
What are some crystalloids and what are some examples?
They are water soluble substances dissolved in solution. They can be rapidly administered but can cause pulmonary oedema
NaCl 0.9%
Dextrose
Haartmans
What is in NaCl and what are some risks?
(0.9% mean 9g in 100ml) - contains 154mmol/L Na and 154mmol/L Cl
So about the right amount of sodium but there is a risk of hyperchloraemic acidosis
What is in dextrose and when should it be used?
5% = 50g per L water
Good if people have glucose requirements
What is in Haartman’s and what are some benefits of using it?
Na - 131 Cl - 111 K - 5 Ca 2 Lactate 29
this is much more isotonic and the patient is at less risk of becoming hypokalaemia
What are some examples of colloids? Where are they sometimes used?
Gelfusin Voluven Volulyte Albumin Sometimes used in trauma but rarely elsewhere
What is a fluid challenge?
Getting IV access with a wide bore cannula and administering 250-500mL of fluid as quickly as possible (usually 10-15mins) and monitoring for a response (BP, HR, UOP, JVP)
If an unwell patient hasn’t improved after 3 fluid challenges then need senior support
What is an example of a good maintenance fluid regimen in a 70kg man?
0.9% NaCl + 40mmol K over 8 hours
5% dextrose + 20mmol K over 8 hours
5% dextrose + 20mmol K over 8 hours
Why will people need more than just maintenance fluid after surgery?
People loose fluids during surgery (on average 600-900mL) so they will need some extra fluids before they’re placed on a maintenance regime
How do you manage fluid therapy in fever?
Add 10% extra fluids for every degree of fever
What should you ask in the history of a pre-operative assessment? Use A-E approach
AIRWAY
- any dental work? caps or crowns?
- any problems with your jaw
- any problems with your neck? arthritis etc
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?
RESPIRATORY SYSTEM
chronic conditions: - obstructive sleep apnoea - 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!
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)
DISABILITY
neuro PMHx
- epilepsy
- neuromuscular disorders
- nerve damage (mainly to protect yourself)
other ‘disability’ PMHx
- diabetes (DON’T FORGET!!)
- thyroid problems?
- stroke / TIA
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?
- current meds/allergies
What ongoing medical conditions in particular should you ask about during anaesthetic history?
IHD, diabetes, HTN, asthma, COPD, liver or kidney disease. Always ask how well controlled these are
What should you examine in a pre-operative assessment?
Neck movement, jaw opening and dental health (dentures, caps, crowns or loose teeth)
Mallampati
General examination (listen to heart and chest, feel abdomen, feel peripheries, feel calves for swelling or tenderness)
What is the mallampati score?
I - complete visualisation of soft palate
II - Complete visualise of uvula
III - Can only see base of uvula
IV - Cannot see soft palate
What is the ASA-GRADING for surgery?
1 - completely safe no ongoing disease
2 - Chronic disease but with no functional impairment (e.g. well controlled diabetes, HTN or smoker)
3 - Severe chronic disease with functional impairment e.g. angina or COPD
4- Severe angina, ESRD or liver disease
5 - Moribund patient who is unlikely to survive with or without operation
6 - Brainstem dead patient for transplant
What are the surgical grades for the operation?
1 (minor) - skin excision or toenail removal
2 (intermediate) - hernia repair or tonsillectomy
3 (major) - hysterectomy or thyroidectomy
4 (major+) - C/S, joint replacement, thoracic operational or radical dissection
What investigations does EVERYONE get in pre-operative assessment?
FBC, U&E, clotting and and group and save
What are some extra investigations for specific things in pre-operative assessment?
LFTs for liver or billiard op
Sickle cell screen for Afro-Caribbean patients
TFTs if they’re on thyroxine
CXR if ICU care might be required
Echo if they’ve got valve problem or murmur
Spirometry if lung disease
PT
What must you correct before the operation if found to be abnormal?
INR (with vit K or platelets/FPP/cryoprecipitate)
Anaemia
What is the general rule for stopping medications before an operation?
In general omit on the day of operation and resume the day after
What more specific medications must be stopped before operation?
Warfarin - stop 5 days before DOACs - stop 24h before LMWH - stop 48h before Aspirin/clopidogrel - stop 7 days before Insulin - don't have morning dose Oral hypoglycaemic - avoid on day of op Diuretics/ACE-is - avoid on day of Long-term steroids - consider switch to hydrocortisone COCP - stop 4 weeks before
What are the fasting guidelines before an operation?
Prolonged fasting 5 sx
Gastric emptying is prolonged by (8)
No food for 6 hours before (have dinner nil else)
No milk for 4 hours before
No alcohol for 24hrs
Only clear fluids until 2 hours before (allowed 30ml before surgery)
1) Headache
2) Hypotension/dehydration
3) Hypoglycaemia
4) Increased risk PONV
5) Increase anxiety
1) DM
2) pregnancy
3) fat
4) renal failure
5) reflux
6) head injury
7) alcohol
8) anxiety
How much oxygen can be given through nasal cannulas?
1-6L (most commonly 2L)
1L/min - 24%
2L/min - 28%
4L/min - 36%
How much oxygen can be given through a simple face mask (hudson)?
5-10L (CO2 can accumulate if the flow is less than 5L)
Not very reliable
What demonisations are there of venturi devices? In whom are they commonly used?
24 (2L), 28 (4L), 35 (8L), 40 (10L) and 60% (15L)
Good in CO2 retainers (COPD) to control concentration of O2
How much oxygen can be given through a non rebreathe mask?
15L and probably gives up to around 85% - this is about as good as we can get unless we artificially ventilate someone
What options do we have if the patient need assistance with ventilation?
BAG-VALVE MASK
NIV
ET tube or airway adjunct
What are some examples of NIV?
3 Indications
CPAP and BiPAP
(CPAP pressure is continuous and BiPAP has different inspiratory and expiratory pressures)
1) pH <7.35
2) PCO2 >6
3) RR >23
How do you measure a Gedell airway?
HARD to HARD
Angle of the mandible to the front incisors
What are the average sizes of NP tubes? When should they not be used
7mm for women
8mm for men
Do not use if any suspicion of basal skull fracture
What are some examples of supraglottic airways?
Laryngeal mask airway (LMA) and iGEL
When are LMAs preferably used and how do you insert an LMA?
Used in shorter surgeries when an ET tube is not required or if you cannot intubate someone (easier to put in)
NOT A DEFINITIVE AIRWAY
Reflexes should be suppressed e.g. with propofol then insert with the curve of the airway (no need to rotate)
What kind if airway is an ET tube? How are the sized
Definitive
Sized by diameter - 7-8mm for women, 8-9mm for men
What is the process of inserting an ET tube?
- preoxygenate the patient
- Wait for the neuromuscular blockage (90-120s)
- Place the patient in the sniffing the morning air position
- Hold laryngoscope in L hand
- Insert the laryngoscope in the R hand corner of the mouth and slide it down between the tongue and the epiglottis
- then lift with your whole arm up and to the left
- Aim to visualise the vocal cord
- Insert the tube to just beyond the vocal cords
- Inflate the cuff of the tube, attach to the bag valve mask and look for signs that it is in the right place
What signs are there that the ET tube is in the right place?
Rising of the chest (symmetrically, if it is not symmetrical it might have gone too far down the R main bronchus)
Misting of the tube
EtCO2 properly traced (5 clear traces)
Pulse oximetry
What are some possible complications of ET tubing?
Breaking teeth with the laryngoscope
Incorrectly positioned tube (into oesophagus) if in doubt take it out
Right lung intubation if put too far down
Laryngospasm - especially if someone has asthma or COPD
What are the three types of anaesthetic?
Local, Regional, General
When putting someone under a general anaesthesia what three things do you need to achieve?
AMNESIA - unconscious and won’t remember
AKINESIA - cannot move
ANALGESIA - won’t be in pain or have a pain response
How do we achieve amnesia in general anaesthesia?
INDUCTION AGENTS - 1-2 arm-brain circulation times (10-20secs)
Then maintained with VOLATILE AGENTS/propofol infusion
Propofol
Dose
Pros (2)
Unwanted effects (3)
- 5-2.5mg/kg
- Good suppression of airway reflexes
- Prevents PONV
Unwanted:
- Marked drop in HR and BP
- painful to inject because it is lipid based
- involuntary movements
Thiopentone
Dose
Pros (2)
Unwanted effects (4)
BARBITUATE
- 4-5mg/kg doses
- RSI
- anti-epileptic properties + neuroprotective
Unwanted effects:
- DROPS BP + INCREASES HR
- rash and bronchospasm
- needs to be injected intra-arterially = can lead to gangrene and thrombus.
- AVOID in PORPHYRIA
Ketamine
Dose
Pros (1)
Unwanted effects (4)
Used for what procedures?
It is a DISSOCIATIVE ANAESTHETIC and is also profoundly analgesic/amnesic
- 1-1.5mg/kg - it is quite slow to act (90s)
Unwanted effects:
- Increases HR + BP
- bronchodilation
- PONV
- EMERGENCE PHENOMENON (vivid dreams and hallucinations)
Used for burn dressing change
What dose is etomiidate used in? In whom is it most suitable and what are some risks (4) and benefits (2)
0.3mg/kg
1) Haemodynamic stability and so is good in people with cardiovascular conditions
2) Lowest incidence hypersensitivity
- Painful on injection
- Involuntary movements
- Adrenocorticoid suppression (don’t use in septic shock)
- PONV
What agents are used to maintain anaesthesia?
What is sevoflurane, isoflurane & desflurane used for?
Volatile agents (desflurane, isoflurane, enflurane, sevoflurane and NO)
Sevoflurane
- sweet
- where IV access NA
Isoflurane
- organ donation (least effect on organ blood flow)
Desflurane
- long operations (DESmond tutu lived for LONG time)
- low lipid solubility
What is minimum alveolar concentration?
MAC - this is the minimum concentration of gas required to eliminate a reaction to a standard stimulus
What are the MACs of sevoflurane, desflurane, NO, enflurane and isoflurane?
Sevo - 2% Isoflurane - 1.15% Desflurane - 6% Enfluane - 1.6% NO - 104% (low anaesthetic potency)
How does pain affect people under anaesthesia?
They don’t FEEL pain because this is a conscious interpretation. However, they do have nociceptors stimulated which can cause the physiological response of increased HR and BP. That’s why it’s important to give someone analgesics
What are some examples of short acting analgesics?
Fentanyl, ramifentanil, alfentanyl
What are some examples of long acting analgesics?
Morphine and oxycodone
Process of muscle contraction
AP arrives at neuromuscular junction –> influx of Ca –> Ach released –> depolarisation of nicotinic receptors –> influx of Na + efflux of K = contract
What are the two types of akinesis agents and how do their actions differ?
DEPOLARISING - constant depolarisation = fasciculations = desensitised to effects of Ach
Used for:
1) after suxamthonium to maintain muscle relaxation
2) facilitate tracheal intubation
NON-DEPOLARISING - competitive, block the nicotinic receptor without activating them
What is an example of a depolarising akinesis agent? What dose is it used in and what are 5 adverse effects?
What is used to counteract it?
SUXAMETHONIUM: 1-1.5mg/kg OFTEN USED IN RSI SEs: 1) muscle pains 2) fasciculations 3) hyperkalameia 4) malignant hyperthermia 5) rise in ICP, IOP and gastric pressures
Dantrolene
What are 2 examples of short-acting non-depolarising agents?
Minutes
Atracurium and mivacurium
15 mins
What are 2 examples of intermediate acting akinesis agents?
Minutes
vecuronium and rocuronium
30-60 mins
What is an example of a long acting akinesis agent?
Minutes
pancuironium
>60
What is the main advantage of non-depolarising agents?
THEY ARE REVERSIBLE
How do we reverse non-depolarising agents?
2 SEs of it
Another agent - MOA & doses
2 SEs
Neostigmine - anti-cholinesterase that prevents breakdown of ACh increasing its conc so that it can outcompete akinesis agent
SEs:
1) Bradycardia
2) Bowel/bladder/bronchospasm
Sugammadex - Reduces conc of non-depolarising agents at NMJ - onset of reversal from shortest: rocuronium > vecuronium >> Pancuronium - 16mg/kg immediate - 2-4mg/kg routine SEs: 1) Hypotension 2) Airway complication
How can we prevent adverse effects of neostigmine?
Glycopyrrolate - anti-muscarinic (prevent SEs of neostigmine)
What other drugs are often prescribed peri-operatively?
Anti-emetics and vaso-active drugs
What class of drug is ondansetron?
5HT3 blocker - anti emetic
What class of drug is cyclizine?
Anti-histamine anti-emetic
What class of drug is metaclopramide?
Anti dopaminergic anti emetic
What other anti-emetics are there and what classes are they?
Dexamethasone (steroid)
Prochlorperazine
What vaso-active drug should you consider if someone’s HR and BP are low?
Ephedrine (rise in rate and contractility of heart)
What vaso-active drug should you consider if someones BP is low but their HR is high?
Phenylephrine - is more alpha selective and just causes vasoconstriction OR Metaraminol (another vasoconstrictor)
If someones hypotension is severe and non-responsive what drugs should you consider?
Adrenaline, Noradrenaline or dobutamine
What is the sequence of events when putting someone under a GA?
- Oxygenate them
- Give them opioid (need to have painkiller before being tubed) - opioids take a little while to work
- INDUCTION AGENT (e.g. propofol to send them to sleep)
- Turn on volatile agent - keep them asleep
- Bag valve mask ventilate them to maintain oxygenation
- Insert the airway and ventilate them
READY FOR SURGERY
What things should you consider prescribing for post-operative patient?
Analgesics - most patients will need some analgesic cover
Fluids - most patients will lose fluids during surgery so will need some element of replacement and then maintenance
Antibiotics - internal surgeries sometimes require prophylactic abx
How do we manage pain post-operatively?
Following guidelines from essential pain management (EPM) RAT system of pain management - Recognise - Assess - Treat
How do we recognise pain?
If the patient is conscious they will tell you - pain is what the patient says it is
Pain response might be dulled in trauma when sympathetic surges of adrenaline dull the response
How do we assess the pain?
Need to get an idea of WHERE it is
Need to get an idea of what the CHARACTER of the pain is like?
Get an idea of associated symptoms
Scale of 1-10: this gives idea of baseline
What are the three classification strategies for pain?
Is it acute or chronic?
Is it cancerous or non-cancerous?
Is it neuropathic or nociceptive?
What is nociceptive pain?
Sometimes called inflammatory or physiological pain this is pain that is in response to illness or injury
It has a protective function - is usually well localised
What is neuropathic pain?
Nerve damage e.g. sciatica or CES
Does not have a protective function
Might be burning, shocking or feel hot/cold
What is the difference between pain and nociception?
Pain is the cerebral input into nociception
What is the nociceptive pathway?
Tissue injury - nociceptors are activated by cytokines such as PGs, histamine and leukotrienes
THEN EITHER TRAVELS in A-delta (fast response) or C pathway (later throbbing pain)
Signal carried to dorsal root ganglion in dorsal horn
Fibers decussate into contralateral spinothalamic tract
Run up into thalamus and pain is perceived
Stimulus is moderated by sending signal back down the descending pathway
How does pain impact the surgical recovery process?
Physical immobility - e.g. chest pain limits breathing leading to infections
If someone has had lots of pain from one procedure might be less willing to have another
Longer stay in hospital and more time off work
How does the body respond to pain?
Tachycardia and hypertension
GI N&V
RESP reduced VC and FRC
DVT and PE
What are the three levels of the analgesic ladder?
0 - Paracetamol 1g PRN max 4g daily
1 - Paracetamol + NSAID (400mg) OR weak opioid e.g. codeine (30-60mg)
2 - Paracetamol + NSAID (400mg) + regular weak opioid e.g. codeine + strong opioid e.g. oromorph
How does paracetamol work?
Inhibits PG production
Selective inhibitor of COX-3
Good anti-pyretic
Poor anti-inflammatory
How do NSAIDs work?
COX-inhibitors
Block production of PGs and thromboxane which potentiate the action of cytokines on nociceptors
What is the difference between COX-1 and COX-2?
COX-1 is a constitutive isoenzyme responsible for lots of homeostatic measures thus is the reason for lots of the side effects (bronchospasm, GI effects, renal, platelets)
COX-2 is a INDUCIBLE enzyme - responsible for inflammation
Which NSAIDs are most COX-2 specific?
PARECOXIB and Celocoxib
In whom are NSAIDs contraindicated?
Those prone to bleeding
Those with peptic ulcers
Caution with asthma
CI’d in renal failure - really excreted
What are some examples of weak opioids and how do they work? Common doses?
Codeine and tramadol Work by unregulated the signal from the descending pathway moderating pain (activate mu receptors) Codeine: 30-60mg Tramadol: 50-100mg Dihydrocodeine: 30-60mg
What are some examples of strong opioids, how do they work and what kind of pain are they useful in?
Morphine, oxycodone and diamorphine
Strong OP3 receptor agonists
Work well on longer term C fibre pain and less for A-delta pain
What are some examples of short acting opioids?
Fentanyl
Ramifentanil
Alfentanyl
What are some side effects of opioids?
Drowsy, constipated, N&V, tolerance and dependence, hypotension
Respiratory depression - infrequent gulping breaths
What methods of administration are there for post-operative morphine?
oromorph - works very quickly and is very effective - 20mg/hr PRN
IV morphine - common. Can given 10-20mg diluted into 1mg/mL IV dose is 1/3 oral dose
PCAS - patient gives themselves 1mg every 5mins - idea is that this stops spikes of analgesia - keeps constant level
How do you dose paracetamol and ibuprofen?
Paracetamol you can have 1g (2 tablets) every 4 hours no more than 4 times a day (max 8 tablet per day)
Ibuprofen can take 400mg every 6-8 hours up to 3 times a day.
What doses are appropriate for codeine, tramadol and morphine?
Codeine - 30-60mg every 4 hours up to 240mg every 24h
Tramadol - 50-100mg every 4 hours up to 400mg every 24h
Morphine - give them a 10mg dose titrated in over 10mins (they might not need all 10mg)
What can you give for a patient who has had an overdose of opioids?
Naloxone
Other than oral analgesics what other options do we have for managing pain post-operatively?
Local anaesthetic injections
Very often after surgery local anaesthetics are injected around the surgical site to numb it and block the pain
BUPIVACAINE IS OFTEN GIVEN
What drugs are more often given for chronic pain and why?
Amitriptyline, Pregablin and gabapentin, Clonidine, corticosteroids, capsaicin
Different types of drugs are needed because chronic pain is more likely to be neuropathic in nature
Other analgesia given during/after surgery & 2 most common?
Paracetamol (common)
NSAIDs
Diclofenac (ORAL)
Paracoxib
Ketorolac
Weaker opioids:
codeine
dihydrocodeine (common)
What is the equation for cardiac output?
CO = SV X HR
What is the equation for SBP?
SBP = CO X SVR
What effects do each of these noradrenergic receptors have? Alpha 1 = vasopressor Beta 1 = chronotrope & inotrope Beta 2 Dopamine
1st line inotrope
1st line vasopressor
Alpha 1 - vasoconstriction = increased SVR
Beta 1 - increased HR (chronotrope) & contraction (inotrope)
Beta 2 - bronchodilation
Dopamine - increased renal blood flow
1st line inotrope - dobutamine
1st line vasopressor - noradrenaline (CAN ONLY BE GIVEN THROUGH CENTRAL LINE)
What receptors does adrenaline act on & what type of vasoactive drug is?
At low rates it acts like…
At high rates it acts like…
a1, b1, b2
inotrope + chronotrope + vasopressor
At low rates - mainly inotropic (increase HR & BP
At high rates - mainly vasopressor (decrease HR & increase BP)
What receptors does dobutamine act on & what type of vasoactive drug is it?
b1, b2
inotrope + chronotrope
Increase HR
Increase BP
What receptors does noradrenaline act on & what type of vasoactive drug is it?
a1, b1
inotrope + vasopressor
What receptor does phenylephrine act on & what type of vasoactive drug is it?
a1
vasopressor
Increase BP
Decrease HR
What receptors does dopamine act on & what type of vasoactive drug is it?
a1, b1, dopamine
inotrope + chronotrope + vasopressor
What effect does Ephedrine have on HR & BP?
Increase HR
Increase BP
What effect does Metaraminol have on BP & HR?
Increase BP
LA
Mechanism of action
Block sodium channels
Active in ionised form (unionised when crossing membrane)
More sensitive to LA if increased extracellular conc of K+
Analgesia first, then paralysis
EMLA 50.50 is a topical anaesthetic made up of which 2 LAs
Prilocaine
Lignocaine
3 short duration LA Esters
2 long duration LA Esters
Esters are associated with (2)
- 5-1hr
1) Cocaine
2) Benzocaine
3) Procaine - 5-6hr
1) Amethocaine
2) Tetracaine
Allergic reactions
Less ability to store for long
3 medium duration LA amides
- max dose (with/without adrenaline) & duration
3 long duration LA amides
- max dose (with/without adrenaline) & duration
0.5-2hr Lignocaine - 3 --> 7 Prilocaine - 6 -->9 Mepivacaine - 3-->7
1.5-8hr Bupivacaine/levobupivacane - 2-->2 Ropivocaine - 3
Which LA is more toxic - lignocaine vs prilocaine?
lignocaine
Which LA has reduced cardiotoxicity?
Levobupvacaine
Which LA is used for nerve blocks, epidurals, spinals?
Bupivacaine
What is used alongside LAs & why?
BUT never use it in (5)
ADRENALINE
- LA causes vasodilation + adrenaline counteracts = vasoconstriction
- reduces blood loss
- increase LA duration
- reduces toxicity by delaying LA absorption
NEVER use in:
1) End organs = ischaemia
2) HTN
3) IHD
4) PVD
5) thryotoxicosis
LA dose calculation
0.25% bupivacaine
o Multiply % by 10 to get mg/ml
o 0.25% solution: 0.25 x 10 = 2.5mg/ml
• Multiply patients weight by max safe dose
o Eg. 60kg and 2mg/kg max dose = 120mg total dose
• Divide patients maximum safe dose by content of LA
o 120/2.5=48mL max
o For 0.5% bupivacaine = 120/5=24ml max
2 main categories of LA toxicity (& sx in each)
Neurological toxicity 1st:
1) Excitatory sx
2) Tingling
3) Slurred speech
4) Tinnitus
5) Confusion/drowsy
6) Twitch
7) Convulsion
CV toxicity:
1) Initial tachy & HTN –> brady & hypotension
2) cardiac arrest
How to treat LA toxicity?
Intralipid 20% 1.5mls/kg over 1 min
RSI process (4 steps)
Who always gets RSI?
1) Preoxygenation
2) Induction - thiopentone, propofol
3) Muscle relaxant - suxamthonium (onset <1min, DOA 6 mins), rocuronium (onset <1min, DOA >30)
4) Cricoid pressure (prevent regurg) - remove after confirmation of tube position
- bilateral expansion, auscultation, moisture in expired air, EtCO2
<20wks pregnant
What information to give patient regarding anaesthesia? (10)
1) Environmnet of surgical room
2) Need for IV access & drip
3) Invasive monitoring
4) What to expect
5) Induction (IV/inhalational)
6) Where they will wake up
7) Drains, catheters, drips
8) Possibility of blood transfusion
9) Risks
10) Questions
4 Common & 6 rarer SEs of GA
Common:
1) Sore throat
2) Confusion
3) PONV
4) Damage to lips/tongue
Rarer:
1) chest infection
2) muscle pain
3) damage to teeth
4) awareness during operation
5) nerve damage
6) allergic reaction
SPINAL BLOCK - where is it given - how do you know you are in the correct position - what is it made up of - onset duration
L2 - S2 into subarachnoid space Presence of CSF LA +/- opioid Rapid onset 5-10mins 2-3hrs
3 layers of spinal cord (inside-out)
Where is the CSF
Where does the spinal cord end
Where does the subarachnoid space end
Where does the epidural space end
Pia
Arachnoid
Dura
Subarachnoid
L1
S1
Sacrococcygeal hiatus
EPIDURAL BLOCK
- where is it given
- how do you tell if in right place
- when is it given
- with what
- onset
above L1 POP of ligamentum flavum Longer operation - up to 72hrs LA +/- opioid via catheter Slower onset - 15-30mins
What layers are crossed in an epidural (6 steps)/spinal (9 steps)?
1) Skin
2) SC fat
3) supraspinous ligament
4) infraspinous lig
5) ligamentum flavum
6) epidural space
7) dura mater
8) arachnoid
9) subarachnoid
6 advantages of spinal/epidural?
1) Less chance of chest infection
2) Less chance VTE
3) Pain relief post-op
4) Less PONV
5) Earlier return to drinking/eating
6) less confusion
7 Complications of spinal/epidural
1) Urinary retention
2) Hypotension
3) Itching
4) PONV
5) Backache
6) Post dural puncture headache - worse sitting up, CSF leaks out & causes low pressure
7) paralysis for few hours post-op
5 contraindications to spinal/epidural
1) Hypovolaemia
2) Aortic/mitral stenosis
3) Sepsis
4) Coagulopathy
5) Raised ICP
Partial airway obstruction signs vs complete obstruction
PARTIAL
1) trachea tug (down on inspiration)
2) accessory muscles
3) Reduced expansion
4) stridor/wheeze/snoring
COMPLETE
1) see saw
2) silent chest
VTE prophylaxis
- hip replacement
LMWH 10 days followed by aspirin 28 days OR LMWH 28 days + stocking OR rivaroxaban
Tidal volume is how many ml
it is made up of 2 sections
500ml - enters & leaves with each breath
anatomical dead space (150)
alveolar ventilation (350)
Volume & definition: Inspiratory reserve volume Expiratory reserve volume Residual volume Total lung capacity Vital capacity Functional residual capacity
3000ml, extra inspired volume 1500ml, extra expired volume 1000ml, remaining after max expiration 6000ml, after max inspiration 5000ml, max expiration after max inspiration 2500ml, volume after quiet expiration
Increasing resistance is seen in which resp disease?
Decreasing compliance is seen in which resp disease?
Obstructive
Restrictive
What is ventilation & where is it highest?
What is perfusion & where is it highest?
Which increases more?
What is a shunt
What is dead space
Where is there a higher V/Q ratio?
The air that reaches the alveoli
The blood that reaches the alveoli via the capillaries
Bases & midzones receive both more ventilation + perfusion
Perfusion increases more towards base = V/Q mismatch
Shunt = perfusion but no ventilation
Dead space = ventilation but no perfusion
Apex (less blood & high ventilation)
6 CPAP indications
2 BiPAP indications
1) pulmonary oedema
2) fluid overload
3) atelectasis
4) chest infection
5) chest wall trauma & hypoxic
6) sleep apnoea
1) COPD
2) MSK conditions with resp failure
Before anaesthetic given must monitor 3 things
1) ECG
2) SPO2
3) NIBP
On an ultrasound what do these structures look like & why? vessels bones soft tissues nerves muscles/tendons
VESSELS black - anechoic BONES white - hyperechoic SOFT TISSUE grey - isoechoic NERVES honeycomb - hypo/hyperechoic MUSCLES/TENDONS grey/white - isoechoic with white strands
What resolution & depth is used by:
high frequency transducers
low frequency transducers
What is gain
High resolution + low depth - superficial
Low resolution + high depth - deeper structures
brightness
On a doppler blue/red means…
blue - away from probe
red - towards probe
4 artefacts on USS
1) Shadowing
2) Acoustic enhancement (flaring) - deep to blood vessels, bladder, cysts, other fluid collections
3) Reverberation (multiple reflections underneath)
4) Comet tail (region of calcification)
eFAST bedside USS can be used in 5 views
1) Peri-hepatic (right mid-posterior axillary line 11-12th rib)
2) Peri-splenic (left posterior axillary line 10-11 rib)
3) Pelvic
4) Pericardial
5) Anterior thoracic (2/4th rib)
incidence of PONV risk factors (4)
20-30% previous PONV female non-smoker post-op opioids
which is better - codeine or dihydrocodeine & why?
dihydrocodeine - purer & more predictable
non-pharmacological management for pain (acronym)
RICE rest ice compression elevation
which of oxycodone and morphine is better for:
- renal impairment?
- hepatic impairment?
renal failure = oxycodone is better
hepatic failure = morphine is better
anaesthesia and diabetes:
- how should manage diabetic meds, incl insulin, and fasting before an operation? 5 (be specific)
- how and how often should blood glucose be monitored peri-operatively?
- where should pts with diabetes be on the list?
- omit oral hypoglycaemic agents the morning of surgery
- take long-acting insulin in morning
- omit short-acting insulin day of surgery
- fast the normal amount of time
- give variable infusion of insulin if need to
BMs should be measured every hour before, during and after op, until eating and drinking again
- if BM >10 intra-op then give some insulin
patients with diabetes should be first, or at least near top, of list, to prevent hypos
anaesthesia and diabetes:
- what are the increased intra and post-op risks of surgery to consider? 5
and how to mitigate these
RISK OF ASPIRATION
- delayed gastric emptying (dt autonomic neuropathy) (also, if type 2 DM, then may also be overweight, further increasing risk)
- use an RSI if really concerned
HYPOS INTRA-OP
- monitor BMs and put first on list to prevent
- be hypervigilant as anaesthetic drugs will mask symptoms
RISK OF POST-OP MIs
- diabetes increases CV risk and most operation-related MIs occur post-op - also MIs in diabetes are often silent, so easier to miss
RISK OF POST-OP INFECTION
- optimise diabetes control pre-op
- ensure good wound care follow up
RISKS ASSOCIATED WITH RENAL FUNCTION
- test UandEs pre-op
- eg can retain more morphine than normal person, which abx use etc
nb they may also be tricky to intubate dt a large neck
diabetes and anaesthesia:
- pre-op questions to ask? 1
- pre-op blood tests to do? 4
- other pre-op tests to do/consider? 2
- current blood sugar control (HbA1c and normal BM range)
- UandEs
- HbA1C
- fasting blood glucose
- BMs
- urineanalysis (looking for proteinuria and microalbuminuria)
- ECG (any ischaemic signs)
nb these are all to establish baseline and understand level of end-organ damage
Considerations for anaesthesia for laproscopic surgery:
- airway management? 2
- affects on vitals? 2
try to avoid bag and mask, or do lots of little breaths (as don’t want to inflate stomach)
always intubate (ie not LMA) as increased risk of aspiration
- drops BP (as pressure triggers parasympathetic response)
- increases CO2 (absorbed in through capillaries)
