10 - anaesthesia

Question 1

what are components of the reticular activating system?

Answer 1

• midbrain reticular formation
• mesencephalic nucleus (in midbrain)
• thalamic intralaminar nucleus
• dorsal hypothalamus
• tegmentum

Question 2

anterior vs posterior part of reticular activating system

Answer 2

anterior — mood and behaviour
posterior — sleep awake cycle

Question 3

the RAS receives sensory information and sends the sensory information to the cerebral cortex throguh what?

Answer 3

specific relay nuclei in the thalamus, esp the intralaminar and reticular nuclei of the thalamus

Question 4

where does the ascending reticular activating system project to?

Answer 4

intralaminar nuclei of the brainstem, whcih in turn projects diffusely to the cerebral cortex

Question 5

what serves as the central pacemaker of the circadian timing sstem and regulates most circadian rhythms in the body?

Answer 5

suprachiasmatic nucleus (bilateral structure located in the anterior part of the hypothalamus)

Question 6

what is the tegmentum?

Answer 6

a region of grey matter on either side of the cerebral aqueduct in the midbrain

Question 7

what does the tegmentum consist of?

Answer 7

this anterior surface of the midbrain contains numerous structures including :

the reticular formation, the periaqueductal gray (PAG) matter, certain cranial nerve nuclei, sensory and motor nerve pathways (the corticospinal and spinothalamic tract), the red nucleus, the substantia nigra, and the ventral tegmental area (VTA)

Question 8

what part of the midbrain contains the superior and inferior colliculus?

Answer 8

tectum

Question 9

what are the phases of surgery and anaesthesia?

Answer 9

• preparation
• induction
• maintenance
• early recovery
• delayed recovery

Question 10

what is Bis?

Answer 10

bispectral analysis

• measures electrical activity of brain
• iv induction agent : Bis = 80/100
• flattens out. want it to be 60-40 — wont wake up at this level (electrical activity depressed enough)

Question 11

why is an overweight person harder to anaesthetise?

Answer 11

more lipid to absorb drug — more drug needed and takes longer to work

Question 12

what are the different types of anaesthesia?

Answer 12

• local — consciousness not impaired : topical, field, regional (spinal, epidural)
• general — hypnosis is an essential feature
• combined — general anaesthesia is combined with some regional technique

Question 13

what are key components of general anaesthesia?

Answer 13

• hypnosis
• analgesia
• muscle relaxation

Question 14

what are used for hypnosis?

Answer 14

iv agents — propofol, barbiturates (thiopentone), benzodiazepines

Question 15

what are used for analgesia?

Answer 15

opiates (synthetic or natural) and non-opiates

Question 16

what are the 2 types of muscle relaxants?

Answer 16

depolarising and non-depolarising

Question 17

more soluble inhalational anaesthetic agents have a ______

Answer 17

higher coefficient

Question 18

agents with a lower coefficient have a ___ onset and _____ emergence

Answer 18

faster

Question 19

more lipid soluble = ____ onset

Answer 19

quicker

Question 20

N2O potency?

Answer 20

low

Question 21

rank the anaesthetic inhalational agents in terms of potency

Answer 21

halothane > isoflurane > sevoflurane > desflruane > N2O

Question 22

characteristics of propofol

Answer 22

• rapidly acting
• high potency
• rapid elimination
• usually propofol and remifentanyl
• total intravenous anaesthesia (TIVA) (not as easy as inhalation, have to be careful where cannula is put)

Question 23

what are some potential advantages of TIVA?

Answer 23

reduced incidence of post-operative nausea and vomiting, reduced atmospheric pollution, more predictable and rapid recovery, greater haemodynamic stability, preservation of hypoxic pulmonary vasoconstriction, reduction in intracerebral pressure and reduced risk of organ toxicity

Question 24

where does the thalamus project to (descending inhibition) in pain pathway?

Answer 24

periaqueductal grey matter

Question 25

what part of the midbrain is involved in the supraspinal modulation of pain?

Answer 25

periaqueductal grey matter

Question 26

name 3 natural opiates

Answer 26

morphine

dihydropyridine-morphine

codeine

Question 27

name an opiate analogue

Answer 27

tramadol

Question 28

name 4 synthetic or semisynethic opiates

Answer 28

pethidine

fentanyl

alfentanyl

remifentanyl

used more byt more addictive. less SE and renal excretion

Question 29

analgesia and respiratory depression and vasodilation are mediated by what opiod receptors?

Answer 29

mu receptors

u1 = analgesia
u2 = resp depression
u3 = vasodilation

Question 30

side effects of opioids

Answer 30

dependence, miosis (excessive pupil constriction), constipation, nausea, vomiting, confusion, dysphoria

Question 31

where do muscle relaxers work?

Answer 31

motor end plate

Question 32

what is suxamethonium?

Answer 32

• 2 ACh molecules bound together
• depolarising agent — Na+ influx, K+ efflux, Ca release
• prolonging action

Question 33

adverse effects of suxamethonium

Answer 33

• muscle pain
• hyperkalaemia
• malignant hyperthermia
• anaphylaxis
• suxamethonium apnoea
• increase intra ocular and cranial pressure (due to twitches)
• muscle twitches

Question 34

what is suxamethonium apnoea?

Answer 34

genetic inability to break it down

Question 35

adverse effects of non-depolarising blockers

Answer 35

• hypotension
• histamine release
• wheeze
• tachycardia or bradycardia
• anaphylaxis
• incomplete reversal

Question 36

describe components of long term recovery

Answer 36

• early mobilisation
• physiotherapy : prevention of pulmonary complications
• prevention of thrombo-embolic disorders (LMWH)
• early enteral nutrition