10 - anaesthesia Flashcards
what are components of the reticular activating system?
- midbrain reticular formation
- mesencephalic nucleus (in midbrain)
- thalamic intralaminar nucleus
- dorsal hypothalamus
- tegmentum
anterior vs posterior part of reticular activating system
anterior — mood and behaviour
posterior — sleep awake cycle
the RAS receives sensory information and sends the sensory information to the cerebral cortex throguh what?
specific relay nuclei in the thalamus, esp the intralaminar and reticular nuclei of the thalamus
where does the ascending reticular activating system project to?
intralaminar nuclei of the brainstem, whcih in turn projects diffusely to the cerebral cortex
what serves as the central pacemaker of the circadian timing sstem and regulates most circadian rhythms in the body?
suprachiasmatic nucleus (bilateral structure located in the anterior part of the hypothalamus)
what is the tegmentum?
a region of grey matter on either side of the cerebral aqueduct in the midbrain
what does the tegmentum consist of?
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)
what part of the midbrain contains the superior and inferior colliculus?
tectum
what are the phases of surgery and anaesthesia?
- preparation
- induction
- maintenance
- early recovery
- delayed recovery
what is Bis?
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)
why is an overweight person harder to anaesthetise?
more lipid to absorb drug — more drug needed and takes longer to work
what are the different types of anaesthesia?
- local — consciousness not impaired : topical, field, regional (spinal, epidural)
- general — hypnosis is an essential feature
- combined — general anaesthesia is combined with some regional technique
what are key components of general anaesthesia?
- hypnosis
- analgesia
- muscle relaxation
what are used for hypnosis?
iv agents — propofol, barbiturates (thiopentone), benzodiazepines
what are used for analgesia?
opiates (synthetic or natural) and non-opiates
what are the 2 types of muscle relaxants?
depolarising and non-depolarising
more soluble inhalational anaesthetic agents have a ______
higher coefficient
agents with a lower coefficient have a ___ onset and _____ emergence
faster
more lipid soluble = ____ onset
quicker
N2O potency?
low
rank the anaesthetic inhalational agents in terms of potency
halothane > isoflurane > sevoflurane > desflruane > N2O
characteristics of propofol
- 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)
what are some potential advantages of TIVA?
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
where does the thalamus project to (descending inhibition) in pain pathway?
periaqueductal grey matter
what part of the midbrain is involved in the supraspinal modulation of pain?
periaqueductal grey matter
name 3 natural opiates
morphine
dihydropyridine-morphine
codeine
name an opiate analogue
tramadol
name 4 synthetic or semisynethic opiates
pethidine
fentanyl
alfentanyl
remifentanyl
used more byt more addictive. less SE and renal excretion
analgesia and respiratory depression and vasodilation are mediated by what opiod receptors?
mu receptors
u1 = analgesia
u2 = resp depression
u3 = vasodilation
side effects of opioids
dependence, miosis (excessive pupil constriction), constipation, nausea, vomiting, confusion, dysphoria
where do muscle relaxers work?
motor end plate
what is suxamethonium?
- 2 ACh molecules bound together
- depolarising agent — Na+ influx, K+ efflux, Ca release
- prolonging action
adverse effects of suxamethonium
- muscle pain
- hyperkalaemia
- malignant hyperthermia
- anaphylaxis
- suxamethonium apnoea
- increase intra ocular and cranial pressure (due to twitches)
- muscle twitches
what is suxamethonium apnoea?
genetic inability to break it down
adverse effects of non-depolarising blockers
- hypotension
- histamine release
- wheeze
- tachycardia or bradycardia
- anaphylaxis
- incomplete reversal
describe components of long term recovery
- early mobilisation
- physiotherapy : prevention of pulmonary complications
- prevention of thrombo-embolic disorders (LMWH)
- early enteral nutrition
