General Anaethetics

Question 1

what is anaethesia?

Answer 1

“loss of sensation/ consciousness”

Question 2

What is included in the anaesthesia triangle?

Answer 2

anaesthetic agents (to produce unconsciousness)

neuromuscular blocking agents (muscle relaxation)

analgesics (pain relief)

Question 3

What are the 4 stages of anaethesia?

Answer 3

1) analgesia - conscious, drowsy

2) Excitement - loss of consciousness but delirium, irregular cardio respiration

3) Anaesthesia - regular respiration, loss of reflux and muscle tone

4) Medullary paralysis

Question 4

What are the types of anaesthetic agents?

Answer 4

general - loss of sensation throughout the body, often used during major surgical procedures

regional - loss of sensation to specific region of body, spinal, epidural and peripheral

local - small area of body is numbered fully conscious, used during minor procedures

Question 5

General anaesthetics -how it should work?

Answer 5

1) Loss of conscious awareness
2) Loss of response to noxious stimuli
3) Reversibility

Question 6

Goals of General Anaesthetics

Answer 6

Induction of sleep
Maintenance of sleep
Waking up from sleep

Question 7

Inhalational anaesthetics

Answer 7

gasses or vapours (administered via vaporizers)
(usually, halogenated ethers or hydrocarbons e.g. halothane, isoflurane)
Controllable, rapid blood-gas exchange

Question 8

types of inhalational anaethetics?

Answer 8

N2O

halothane

enflurance

isoflurane

Question 9

How GAs work?

Answer 9

Potency of GA: Minimum Alveolar Concentration (MAC) – The concentration required to prevent 50 % of patients moving when subjected to surgical midline incision

Question 10

what is the lipid theory?

Answer 10

critical volume hypothesis & perturbation theory

potency proportional to lipid solubility
Disruption of ion channel functions and disruption of annular lipids associations with ionic channels

Question 11

what reletionship between inhaled anaethetics potency and lipid solubility?

Answer 11

linear

Question 12

receptors that work on GAs:

Answer 12

GABA - inhibitory, glycine(enhance more)

nAch, NMDA - exictatory (inhibit less)

Question 13

All volatile anaesthetics _______ the respiration rate

Answer 13

increase

Question 14

What are the characteristics of IV anaethetics?

Answer 14

very rapid (onset, brain circulation time 30s)
short-acting
intro and maintenance of anaesthesia

Question 15

IV

Answer 15

thiopental

etomidate

propofol

ketamine

midazolam and other benzodiazepines

Question 16

Thiopental (+ive allosteric modulator of GABA)

Answer 16

anion channel (Cl-); GABAa Icl&raquo_space; hyperpolarisation&raquo_space; inhibitory

Question 17

thiopental pharmacological effect:

Answer 17

potentiates endogenous GABA responses
increase the frequency of channel opening
generalised increase in GABA inhibition
Hypnosis!!!

Question 18

thiopental adverse effects:

Answer 18

Respiratory depression, apnoea
CVS: myocardial depression, decrease cardiac output
Sneezing, coughing and bronchospasm

Question 19

thiopental problems

Answer 19

Extremely painful during intra-arterial administration
Hypersensitive reactions (1: 15000)

Question 20

Propofol (Positive allosteric modulator of GABA)

Answer 20

Pharmacological effect
potentiates endogenous GABA responses
increase the frequency of channel opening
generalised increase in GABA inhibition
Hypnosis!!!

contraindicates in children under 3

Adverse effects
CVS: myocardial depression, decreased peripheral vascular resistance, decreased CO
Respiratory depression
Hypersensitivity 1 : 100 000

Question 21

Etomidate (Positive allosteric modulator of GABA)

Answer 21

Pharmacological effect
Hypnosis

Contraindications
Phorphyria

Adverse effects
CVS: very little effect on HR, CO, PVR
Minimal respiratory depression
Hypersensitive reactions (1: 75000)

Question 22

ketamine (NMDA receptor antagonist- competitive)

Answer 22

ligand gated cation channels

depolarisation
AP
excitatroy action

Question 23

What type of action does ketamine have?

Answer 23

competitively antagonise glutamic acid-mediated NMDA activation: inhibition of AP

Question 24

what does ketamine interact with?

Answer 24

opioid receptors, monoaminergic receptors, muscarinic receptors and voltage-sensitive Ca ion channels.

Question 25

Which receptor does ketamine NOT REACT with?

Answer 25

GABA

Question 26

pharmalogical and side effects of ket?

Answer 26

Pharmacological effect
Hypnosis (used mainly in paediatrics)
Analgesic in emergency medicine

effects
– Increase HR, BP, CO, O2 consumption
– Increase RR, preserved laryngeal reflexes
dissociative anaesthesia, analgesia, amnesia

Question 27

Problems of use with ketamine:

Answer 27

Slow recovery
High extraneous muscle movement
Hallucinations, nightmares and transient psychotic drugs

Question 28

Criteria for selection induction agent

Answer 28

1) absolute contraindication - hypersensitivity porpohyria

2) patient realted fctors - CV health, resp health and CNS health (epilepsy)

3) drug related factors - drug-food, drug-drug or other interactions