Anaesthtics

Question 1

What are types of anaesthesia

Answer 1

General:
Inhaled/volatile
IV

Local:
Regional

Can be combined

Question 2

What is conscious sedation

Answer 2

Conscious sedation: use of small amounts of anaesthetic or benzodiazepines
to produce a ‘sleepy-like’ state. (Maintain verbal contact but feel comfortable)

Question 3

What are the steps which occur during anaesthesi

Answer 3

• Premedication (Hypnotic-benzodiazepine).
• Induction (usually intravenous but may be inhalational) - reasonable dose
• Intraoperative analgesia (usually an opioid) - resp rate becomes depressed so need a tube
• Muscle paralysis-facilitate intubation/ventilation/stillness.
• Maintenance (intravenous and/or inhalational) -initial might be wearing off, switch to volatile typically
• Reversal of muscle paralysis and recovery which includes
postoperative analgesia (opioid/NSAID/paracetamol).
• Provision for PONV.
• POINT: during anaesthesia many (interacting) pharmacological
agents “on board” requiring excellent pharmacological knowledge
and skill to manage.

Question 4

Describe volatile general anaesthesia

Answer 4

Blow oxygen over top -
anaesthetic goes through a face
mask to patient

Question 5

What are some classes of volatile GE

Answer 5

N2O, Xe, Isoflurane, Halothane, Fluroxene

Question 6

What ate some examples of IV GE

Answer 6

Intravenous
• Propofol
• Barbiturates
• Etomidate
• Ketamine

Question 7

What are Guedel’s signs

Answer 7

Stage 1: analgesia and consciousness
Stage 2: unconscious, breathing erratic
but delirium could occur, leading to an
excitement phase.
Stage 3: surgical anaesthesia, with four
levels describing increasing depth until
breathing weak.
Stage 4: respiratory paralysis and
death.

Question 8

What is anaesthesia a combination of

Answer 8

Anaesthesia is a combination of;
• Analgesia
• Hypnosis (loss of consciousness)
• Depression of spinal reflexes
• Muscle relaxation
(insensibility and immobility)

Question 9

What is mac

Answer 9

Minimum alveolar concentration for
expression of different responses
varies. Memory goes first, then
consciousnesss.

Measure at alveolus the conc of
volatile anaesthetic. The conc that
prevents movement to a surgical
incision in 50% of population = mac

Question 10

How is the potency of volatile anaestheitcs defined

Answer 10

• What is potency ? (M&R year 1).
• Volatile anaesthetic potency is described by MAC or
Minimum Alveolar Concentration.
– [Alveolar] (at 1atm) at which 50% of subjects fail to move to
surgical stimulus (unpremedicated breathing O2/air)
– At equilibrium [alveolar] = [spinal cord]
– MAC, MAC-BAR (Autonomic Response), MACawake
• Anatomical substrate for MAC is spinal cord
– In animal models if section cord (i.e., remove connection to
the brain) MAC is unchanged.

Question 11

What afctros affecr induction and recovery

Answer 11

Partition coefficients (solubility)
• Blood:Gas partition (in the blood)
– Low value fast induction and recovery e.g., desflurane
• Oil:Gas partition (in fat)
– Determines potency and slow accumulation due to
partition into fat (e.g, halothane)

Nt very soluble in blood.- in an out
quickly. Exposing the brain very
quickly. Not dissolve. When you switch
it off - wake up quickly. Unless obese
bc more fat. Other thing
that .deterines solubility Higher
solubility = greather potency.

Question 12

Wat affects mac

Answer 12

• Age (High in infants lower in elderly)
• Hyperthermia (increased); hypothermia
(decreased)
• Pregnancy (increased)
• Alcoholism (increased)
• Central stimulants (increased)
• Other anaesthetics and sedatives (decreased)
• Opioids (decreased)

Question 13

What are the effects of n2o on mac

Answer 13

Nitrous Oxide is very often added to other
volatile agents (reduced dosing).

Typically use isoflurane with some
N2O and o2. Adding second gas -
reduce conc of first.
Ading n20 reduces the mac
N2O has good slide effect profile,
also good anaesthetic profile, can be
mixed with the primary one

Question 14

What is the role of gaba receptirs in anaesthesia

Answer 14

• GABAA receptors critical target
• Major inhibitory transmitter
• LGIC (Cl- conductance)
• Potentiate GABA activity
• Anxiolysis
• Sedation
• Anaesthesia
• With the exception of Xe,N2O and
ketamine all anaesthetics potentiate
GABAA mediated Cl- conductance to
depress CNS activity.
• NMDA receptors probable other site

Question 15

desctibe the areas of the brain targeted by anaesthesia

Answer 15

• Reticular formation (hindbrain, midbrain and thalamus)
depressed. Connectivity lost.
• Reticular system often called “activating system” due to
ability to increase arousal.
• Thalamus transmits and modifies sensory information.
• Hippocampus depressed (memory).
• Brainstem depressed (respiratory and some CVS).
• Spinal cord-depress dorsal horn (analgesia) and motor
neuronal activity (MAC).

Question 16

what are the main iv anaesthetivs

Answer 16

• Propofol (rapid), Barbiturates (rapid), Ketamine
(slower).
• Given intravenously for ‘induction’.
• Can be used as sole anaesthetic in TIVA (Total
IntraVenous Anaesthesia).
• Target sites as for inhalational.
• With exception of Ketamine (NMDA) all potentiate
GABAA.
• Systems target as for inhalational.

Question 17

How Do We Describe Intravenous

Anaesthetic Potency?

Answer 17

• Plasma concentration to achieve a specific end
point (loss of eyelash reflex or a BIS value or…..).
• For induction in mixed anaesthesia – Bolus to end
point then switch to volatile.
• TIVA uses a defined PK based algorithm to infuse
at a rate to maintain set point. Pre-ceeded by a
bolus. Electrodes

Question 18

In which situations are local and recional anaestehtic sued

Answer 18

Dentistry
Obstetrics
Regional surgery (patient awake)
Post-op (wound pain)
Chronic pain management (PHN)

Question 19

What are some egs of local anestehtics and what are

Answer 19

Lidocaine,

Bupivacaine, Ropivacaine and Procaine.

Question 20

Wat are the charactersistsic of local anaesthetics

Answer 20

Characteristics
• Lipid solubility – potency
(higher greater potency)
• Dissociation constant (pKa)
– time of onset. Lower pKa
faster onset
• Chemical link – metabolism
• Protein binding – duration
(higher for longer duration)

Question 21

Whats the diffreence between an ester and amide link

Answer 21

If ester - esterases will chop it up. Very short acting. Aside link - longer acting.
Can predict degree to Chico will block a response based on the chemistry o
these molecules. Lipid solubility determines potency.

Question 22

Describe bupivacqaine infiltration for wound analgesia

Answer 22

• Cocaine archetypal
• Esters-shorter acting
• Amides-longer acting
• Block is USE Dependent
• Block small myelinated
(afferent) nerves in
preferance hence
nociceptive and symp block
• Adrenaline ↑ duration
Bupivacaine an amide so more stable-longer lasting. Slow onset (pKa 8.2).

Block voltage Na Chanels. Use depended blocks. Dont want it to bock non-firing neurones. Want to switch off pain fibres and nothing
else. Pain - they fire - selective black of pain fibres. Goes into memb, loses charge, sucked into inside of Na Handel. It blocks the
channel. Ap is then stopped. The degree it goes in is proportial to the degree to which the nerve is firing . Can potentiate effects by
adding adrenaline

Question 23

Compare lidocaine, bipivaxaine, ropivacains ancd procaine

Answer 23

ss

Question 24

What is regional anesthsia

Answer 24

• As the name suggests selectively anaesthetising a part
of the body.
• Often described as a ‘block’ of a nerve and hence the
patient remains awake.
• Uses local anaesthetic and or an opioid.
• Upper extremity (e.g.,); interscalene, supraclavicular,
infraclavicular, axillary.
• Lower extremity (e.g.,) ; femoral, sciatic, popliteal,
saphenous.
• Extradural / Intrathecal / Combined (labour).

Local into nerve root thats supplying a region - booking outflow and inflow from that area.

Question 25

What are the main anaesthtic side effects

Answer 25

• Too many agent specific effects to list and remember
polypharmacology !
• General anaesthesia
– PONV (opioids)
– CVS – hypotension
– POCD (increases with increasing age)
– Chest infection
• Local and regional
– Depends on the agent used and usually result from systemic spread (Locals are Na+
channel blockers so cardiovascular toxicity)
• Increased general concern re: allergic reactions/anaphylaxis

If they vomited ast time, they will again. F they are particularly sensitive
to a particular anaesthetic or opioid, use a different one. Cvs unstable
patients - anaesthetic might be too much, think abt local instead. Post
operative cognitive dysfunction - use a different, low exposure, dont put
to sleep for example. if it ends up in vascular compartment- wills top
heart.