Anaesthesia

Question 1

7 stages of general anaesthesia which require drugs

Answer 1

Premed e.g benzodiazepine 
Induction (most IV but some volatile)
Intraop analgesia 
Muscle paralysis
Maintenance
Recovery/reversal
Provision for post op N&V

Question 2

Types of IV GA

Answer 2

Propofol
Barbiturates
Ketamine

Question 3

Types of volatile GA

Answer 3

N20
Isoflurane
Desflurane
Xenon for neonates

Question 4

What is anaesthesia a combo of

Answer 4

Analgesia
Hypnosis (loss of consciousness)
Depression of spinal reflexes
Muscle relaxation

Question 5

What are measured in Guedel’s sign

Answer 5

Muscle tone
Breathing
Eye movements - glabellar reflex (blink when tapped between eyes)

Question 6

4 stages of Geudel’s signs

Answer 6

Analgesia
Excitement
Surgical anaesthesia (the aim)
Respiratory paralysis

Question 7

Describe analgesia in terms of Guedel’s signs

Answer 7

Analgesia
Conscious
Normal muscle tone and breathing

Question 8

Describe excitement in terms of Guedel’s signs

Answer 8

Unconscious
Erratic breathing
Increased muscle tone

Question 9

Describe surgical anaesthesia in terms of Guedel’s signs

Answer 9

Relaxed muscle tone

Subdivided into 4 stages with decreasing resp rate

Question 10

Describe respiratory paralysis in terms of Guedel’s signs

Answer 10

Resp rate too low leading to death

Question 11

Definition of MAC

Answer 11

Minimum alveolar concentration measures potency of volatile anaesthetic
Alveolar concentration at which 50% of subjects fail to move to surgical stimulus

Question 12

Factors increasing MAC

Answer 12

Hyperthermia
Pregnancy
Central stimulants
Alcoholism

Question 13

Factors decreasing MAC

Answer 13

Increasing age
Opioids
Anaesthetic drugs (N20 added to other volatile anaesthetics to decrease dosing)

Question 14

Consequence of a low blood:gas partition and a drug example

Answer 14

Fast induction and fast recovery e.g desflurane

Means low water solubility so drug wants to leave blood and go to target sites

Question 15

Consequence of a high oil:gas partition and a drug example

Answer 15

High lipid solubility so drug has a higher potency because membranes are lipid rich e.g halothane

Question 16

Possible target receptors of anaesthetics

Answer 16

GABA agonist for most drugs

NMDA antagonist for xenon, N20 and ketamine

Question 17

Target systems of anaesthetics

Answer 17

Reticular system
Hippocampus (memory)
Brainstem (cvs and resp)
Spinal cord (motor and sensory activity)

Question 18

Describe potency of IV GA

Answer 18

Plasma concentration at which 50% patients reach an end point e.g loss of glabellar reflex or a specific bispectral index number

Question 19

Chemical structure of local anaesthesia

Answer 19

Aromatic ring
Amine group
Amide or ester link

Question 20

What increases LA potency

Answer 20

Higher lipid solubility

Question 21

What increases speed of LA onset

Answer 21

Lower pKa (dissociation constant)

Question 22

What type of LA chemical structures are shorter acting

Answer 22

Drugs with an ester link e.g procaine

Broken down by esterases in cells

Question 23

What type of LA drugs are longer acting

Answer 23

Drugs that are protein bound e.g bupivacaine

Max dose is 2mg/kg

Question 24

MoA of LA

Answer 24

Unionised and lipophilic so cross plasma membrane and enter cell 
Become charged (rate related to pKa)
Enters and blocks Voltage gated Na channels in nerves

Question 25

What nerves are blocked first by LA

Answer 25

Myelinated afferent fibres because highest AP firing rate

Question 26

Describe regional anaesthesia

Answer 26

Local anaesthetic and/or opioid to block an entire nerve

Question 27

Describe anaesthesia for labour

Answer 27

Extradural - LA around spinal cord
Intrathecal - LA through meninges
Combined called an epidural

Question 28

Side effects of GA

Answer 28

Post op N&V
Hypotension
Post op cognitive decline of elderly
Aspiration pneumonia

Question 29

Side effects of LA

Answer 29

If systemic spread can cause cardiotoxicity