Anaesthetics

Question 1

What are the 2 forms of anaesthetic and what is their given route?

Answer 1

General and Local

• General is given IV or inhaled (Volatile)
• Local is injected regionally

Question 2

What is conscious sedation?

Answer 2

use of small amounts of anaesthetic for benzodiazapines to produce a sleepy like effect where you maintain verbal contact but feel comfortable

Question 3

What is anaesthesia and what do is cause?

Answer 3

-combination of analgesia, hypnosis, depression of spinal reflexes and muscle relaxation including insensibility and immobility

Question 4

What are the range of effects on the CNS produced during general anaesthesia?

Answer 4

-Guedel’s signs

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

Question 5

What is potency?

Answer 5

potency is a measure of drug activity expressed in terms of the amount required to produce an effect of given intensity

Question 6

What is MAC?

Answer 6

minimum alveolar concentration
-concentration of alveolar at which 50% of subjects fail to move to surgical stimulus

NOTE - at elm, conc of alveolar = conc in spinal cord

Question 7

What factors affect induction and recovery?

Answer 7

SOLUBILITY (partition coefficients)

• blood:gas partition (solubility in the blood)
• oil:gas partition (solubility in lipid (fat tissue))

Question 8

What does oil:gas partition determine?

Answer 8

the potency and slow accumulation due to partition in to the fat therefore HIGH POTENCY = HIGH SOLUBILITY IN FAT

Question 9

What factors affect MAC?

Answer 9

• age (high in infants, lower in elderly)
• hyperthermia (increased - opposite for hypothermia)
• pregnancy (increased)
• alcoholism (increased)
• central stimulants (increased)
• other anaesthetics and sedatives (decreased)
• opioids (decreased)

Question 10

What affect does nitrous oxide have on the delivery of inhalation anaesthetics?

Answer 10

reduces the MAC value as it has anaesthetic effect so increased delivery with reduced dosing

Question 11

What is the target for most anaesthetics?

Answer 11

GABA A receptors

Question 12

What is GABA?

Answer 12

major inhibitory transmitter

Question 13

What is GABA A receptor?

Answer 13

LGIC (cl- conductance=]

Question 14

What do anaesthetics tend to do and what are the exceptions and what do they do?

Answer 14

with the exception of Xe, N2O and ketamine, all other anaethestics potentiate GABA A mediated Cl- conductance to depress CNS activity
-anxiolysis *inhibits anxiety)
-sedation
-anaesthesia
the other ones work on NMDA receptors- antagonists

Question 15

What do anaesthetics modulate?

Answer 15

the balance between excitation (glutamate) and inhibition (GABA)

Question 16

What systems and structures in the brain do anaesthetics target?

Answer 16

• reticular formation depressed with connectivity lost between the 3 systems
• thalamus transmits and modifies sensory information
• hippocampus depressed (memory)
• brainstem depressed (resp and some CVS)
• spinal cord depresses dorsal horn (analgesia) and motor neuronal activity (MAC)

Question 17

What are the names of intravenous anaesthetics (general anaesthetic)?

Answer 17

PKB

• Propofol
• Ketamine
• Barbiturates

just note that ketamine is the slowest acting

Question 18

What is the MOA of propofol, ketamine and barbiturates?

Answer 18

P and B
-potentiate GABA receptors upsetting the balance between glutamate and GABA in the brain

K
-NMDA receptor antagonist

Question 19

What are the uses of propofol, ketamine and barbiturates?

Answer 19

given for induction phase in anaesthesia and puts patients to sleep in preparation for surgery

Question 20

What are the side effects of general anaesthesia?

Answer 20

• post-operative nausea and vomiting
• hypotension
• post operative confusion and delirium
• chest infection

Question 21

What are the names of volatile anaesthetics?

Answer 21

HIND

Halothane
Isoflurane
Nitrous Oxide
Desflurane

Question 22

What is the MOA of Halothane, Isoflurane, Nitrous Oxide, Desflurane

Answer 22

N20 - NMDA receptor antagonist

H/I/D - potentiate GABA receptors

Question 23

What are the uses of Halothane, Isoflurane, Nitrous Oxide, Desflurane?

Answer 23

can be used alongside nitrous oxide to reduce the MAC so reduced dosing is required

Question 24

What are the symptoms of Halothane, Isoflurane, Nitrous Oxide, Desflurane?

Answer 24

• post-operative nausea and vomiting
• hypotension
• post operative confusion and delirium
• chest infection

Question 25

What are the names of local anaesthetics?

Where are they injected into in upper extremities, lower extremities and in labour?

Answer 25

Please Refrain Bill’s Lips - CAINE

Procaine
Ropivacaine
Bupivacaine
Lidocaine

in upper extremity’s injected into inter scalene, supra clavicular, infraclavicular or axillary nerve

in lower extremity’s either femoral, sciatic, popliteal or saphenous

in labour can be extradural/intrathecal

Question 26

What is the MOA of Procaine, Ropivacaine, Bupivacaine, Lidocaine

Answer 26

All are lipid soluble

B - blocks small myelinated nerves (VG Na+ channels) causing a nociceptive and sympathetic block
B is the most potent and last longest

P is esterase metabolised so shorter lasting but not much in it

B?L?R - amides so last longer

Question 27

What does adrenaline do to local anaesthetics and why?

Answer 27

increases the duration because causes vasoconstriction so there is less distribution

Question 28

What are the uses of Procaine, Ropivacaine, Bupivacaine, Lidocaine ?

Answer 28

dentistry, obstetrics, regional surgery, post operative and pain management

Question 29

What are the side effects of Procaine, Ropivacaine, Bupivacaine, Lidocaine ?

Answer 29

cardiovascular toxicity