principles of general anaesthesia

Question 1

effects of general anaesthesia

Answer 1

MAIN EFFECTS loss of conciousness at LOW conc., and supression of reflexes at HIGH conc.- may also cause pain relief, muscle relaxation and amnesia

Question 2

types of general anaesthetics

Answer 2

either gaseous (ie inhaled, haloagents/NO) or intravenous (propofol/etomidate)

Question 3

mechanism of intravenous agents including subunits

Answer 3

they activate GABAa/glycine receptors ie at the SYNAPSE- affect B3 subunit to surpress reflexes, and alpha 5 subunit to cause amnesia

Question 4

targets of inhalation agents- neurones+ synapse

Answer 4

haloagents- activate GABAa/glycine receptors (affect alpha 1 unit to surpress reflexes), inhibit ACh receptors (analgesic effects), and activates TREK (background leaking) K+ channels, thus increased hyperpolarisation ie affect neurones, NOT JUST synapses (leads to loss of conciousness): NO- blocks NMDA-type receptors

Question 5

how they cause loss of conciousness

Answer 5

surpress thalamocortical neurons via GABA action, and supress RAS via TREK channels

Question 6

how they surpress reflex responses

Answer 6

affect GABA/glycine in spinal cord

Question 7

how they surpress amnesia

Answer 7

less synaptic transmission in hippocampus/amygdala

Question 8

inhalation vs intravenous

Answer 8

inhalation has a LOW BLOOD:GAS partition coefficient ie can get to and from alveoli and brain quickly= RAPIDLY ELIMINATED and RAPID CONTROL of how much anaesthesia you want ie can easily extend anaesthesia or remove it- intravenous has a HIGH BLOOD:GAS coeffecient, so excreted slowly from brain= FAST INDUCTION but LESS CONTROL: also LESS COUGHING (as not being inhaled)

Question 9

how anaesthetics are given

Answer 9

first intravenous given to quickly make them unconcious, and then inhaled to either extend or decrease anaesthesi

Question 10

good things+ issues with anaesthesia and solution

Answer 10

good for conciousness loss/reflex surpression, but not very good as analgesic, muscle relaxant, or amnesia- thus give opioids, NMJ blocking drugs and benzodiazepines respectively