Lecture 25 - Anaesthetics

Question 1

What are the 2 main methods that anaesthetics act?

Answer 1

General
Local

Question 2

What are the 2 ways by which general anaesthesia can be administered?

Answer 2

Inhaled or volatile

Intravenous

Question 3

What are the ways by which local anaesthesia is given?

Answer 3

Regionally so injection

Question 4

What is conscious sedation?

Answer 4

When a small amount of anaesthetic or benzodiazepines to produce a sleepy-like state

Question 5

What type of drug is give as a premedication (to help calm a patient down before surgery) for anaesthesia?

Answer 5

Hypnotic-benzodiazepine

Question 6

How can you induce anaesthesia?

Answer 6

IV
Inhalational

Question 7

What type of drug is often given as an Intra operative analgesic?

Answer 7

Opioid like fentanyl

Question 8

What type of drug needs to be given to allow for intubation?

Answer 8

Muscle relaxant

Question 9

What drugs need to be given to a patient after surgery?

Answer 9

Reverse muscle relaxants so can breathe again
Post op analgesia
Anti-emetic

Question 10

How does inhaational volatile general anaesthesia work?

Answer 10

Liquid containing anaesthetic gets vaporised into a gas and so gets delivered to lungs via an agent specific vaporiser

Question 11

What is the most common anaesthetic delivered intravenously to induce anaesthesia?

Answer 11

Propofol
Barbiturates
Etomidate
Ketamine

Question 12

What are some gases/volatiles that can be delivered to induce anaesthetics?

Answer 12

Xenon
Fluorxene
Halothane
Nitrous oxide (N2O)
Chloroform
Desflurane

Question 13

What are the 3 main features that are observed as a patient goes under anaesthesia?

Answer 13

Muscle tone
Breathing
Eye movement

Guedels signs

Question 14

What are the 4 stages of anaesthesia? (Guedels signs)

Answer 14

1 = analgesia and consciousness (muscle normal and slight eye movement)
2 = uncosncosius, erratic breathing, delirium (moderate eye movment and increased muscle tone)
3 = surgical anaesthesia muscles become increasingly relaxed and eye movment. Becomes zero
4 = flaccid muscles, respiratory paralysis

Question 15

What is achieved in anaesthesia?

Answer 15

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

Question 16

As anaesthetic concentration increases, what repsonse are lost first to last?

Answer 16

First:
Memory
Consciousness
Movement
Cardiovascualr response
Last

Question 17

How do you measure potentcy of a volatile aneasthetic?

Answer 17

MAC
Minimum Alveolar Concentration

Question 18

What is Minimum Alveolar Concentration (MAC)?

Answer 18

The alveolar concentration of a volatile anaesthetic at which 50% of patients fail to move to a surgical stimulus

Question 19

How is the concentration of volatile anaesthetic in the alveoli at equilibrium related to the conc at the spinal cord?

Answer 19

They are equal

Question 20

What is the anatomical site/substrate for MAC (Minimum ALveolar Concentrtation)?

Answer 20

Spinal cord

Question 21

What values determine how fast induction and recovery will be?

Answer 21

BLood:Gas partition coefficient (measure of solubility/how it partitions into the blood)

Question 22

What partition coefficient determines the potentcy of an anaesthetic?

Answer 22

Oil:Gas partition
(How it partitions into fat)

Question 23

What are some factors affecting Minimum Alveolar Concentration of a volatile anaesthetic?

Answer 23

Age (high in infants, low in elderly)
Hyperthermia (inc)
Hypothermia (dec)
Pregancy (inc)
Alcoholism (inc)
Central stimulants (inc)
Other anaesthetics and sedatives (dec)
Opioids (dec)

Question 24

Why is Nitrous Oxide often added to other volatile anaesthetics?

Answer 24

To reduce the required dosing/ MAC

Question 25

What determines the potency of an anaesthetic?

Answer 25

Lipid solubility

Question 26

How are potency and lipid solubility related?

Answer 26

Higher lipid solubility = higher potency

Question 27

What receptor do most anaesthetics interact with to provide effects?

Answer 27

GABA(a)

Question 28

What is the major method of action of most anaesthetics causing anaesthesia?

Answer 28

Anaesthetics bind to and potentiate GABA(a) receptors leading to enhanced Cl- influx leading to hyperpolarisation. Of neurones

Question 29

What is the effect of most anaesthetics potentiating GABA activity?

Answer 29

Anxiolytics Sedation Anaesthesia

Question 30

Which anaesthetics dont potentiate GABA activity?

Answer 30

Xenon Argon N2O Ketamine

Question 31

What receptor do Xe, Argon, N2O and ketamine act on? What neurotransmitter is involved?

Answer 31

NMDA receptors Glutamate

Question 32

The balance of activity of what 2 receptors determines the aneasthetic status?

Answer 32

NMDA glutamate receptor excitation GABA(a) receptor inhibition

Question 33

What is the function of the reticular system? What is the affect of depressing its connectivity to the cortex in anaesthesia?

Answer 33

The activating system which increases arousal keeping a person awake Person loses consciousness

Question 34

What is the purpose of suppressing the connections from the thalamus to the cortex in anaesthesia?

Answer 34

Thalamus transmits and modifies sensory information so if depressed loss of sensation

Question 35

What is the purpose of suppressing the connections from the hippocampus to the cortex in anaesthesia?

Answer 35

Loss of memory

Question 36

What part of the body is depressed leading to analgesia?

Answer 36

Spinal cord-depression in dorsal horn (Maybe periaqueductal grey too)

Question 37

What are the main IV anaesthetics?

Answer 37

Propofol (rapid) Barbiturates (rapid) Ketamine (slower)

Question 38

What is it called when IV anaesthetic is the sole method of anaesthesias?

Answer 38

TIVA Total IntraVenous Anaesthesia

Question 39

How do we describe IV anaesthesia potency?

Answer 39

Plasma conc to a acheive a specific end point like loss of eyelash reflex or a certain BIS value (Bispectral index) 0= brain inactivity 100 = full brain function

Question 40

What is the process of induction in mixed anaesthesia?

Answer 40

IV bolus to end point then switch to the volatile

Question 41

What are some scenarios where local and regional aneasthetic issued?

Answer 41

Dentistry Obstetrics Regional surgery (patient awake) Post-op (wound pain) Chronic pain management

Question 42

What are some local anaesthetics?

Answer 42

Lidocaine Bupivacaine Ropivacaine Procaine

Question 43

How is pKa (dissociation constant) related to the time of onset of local anaesthetic?

Answer 43

Lower pKa the faster the onset since theres more unionised drug which is present to access the site

Question 44

What leads to a local anaesthetic having a longer duration?

Answer 44

Higher protein binding

Question 45

What are the 2 types of chemical link which change how long anaesthetics last?

Answer 45

Ester link Amide link

Question 46

Which chemical link takes longer to break down leading to the aneasthetic lasting longer, ester link or amide link?

Answer 46

Amide link Most cells have esterases so ester links are gonna get broken down so dont last as long

Question 47

Are anaesthetics going to prefer blocking highly active neurones or inactive neurones?

Answer 47

Highly active

Question 48

What do local anaesthetics block to causes anaesthetic affect?

Answer 48

Voltage gated sodium channels

Question 49

What are the 2 pathways by which voltage gated sodium channels become blocked by local anaesthetics?

Answer 49

Hydrophobic pathway Hydrophilic pathway

Question 50

What is the hydrophilic pathway of local anaesthesia?

Answer 50

Charged local aneasthetic directly goes in and blocks the channel of a open sodium voltage gated ion channel

Question 51

What is the hydrophobic pathway of local anaesthesia?

Answer 51

Uncharged local anaesthetic passes through plasma membrane into the cell Becomes charged within the cell Then goes into and blocks the open voltage gated Na+ channel

Question 52

What is the benefit of administering both local anaesthetic like lidocaine with adrenaline?

Answer 52

The adrenaline helps prolong the duration which the local anaesthetic is able to act at its intended site Since adrenaline causes vasoconstriction

Question 53

What does a high value of pKa indicate?

Answer 53

Slow speed of onset of action

Question 54

How does bupivacaine differ in terms of potency and duration of action compared to procaine?

Answer 54

Bupivacaine is more potent and longer duration of action

Question 55

What is regional aneasthesia?

Answer 55

Selectively anaesthetising a part of the body causing a block of a nerve

Question 56

What types of drugs are used for regional anaesthesia?

Answer 56

Local anaesthetic Opioid

Question 57

What is the point in the neck you can inject local anaesthetic to cause nerve block in. The upper limb?

Answer 57

Interscalene triangle (Erbs point)

Question 58

Where can local anaesthetic be injected to cause nerve block in the lower limb?

Answer 58

Femoral nerve Sciatic nerve Popliteal nerve Spahenous nerve

Question 59

What side effects do opioids typically cause in anaesthesia?

Answer 59

Nausea and vomiting

Question 60

What are some side effects of general anaesthesia?

Answer 60

Post op nausea and vomiting (opioids) CVS (HYPOTENSION) Post op Congnitive dysfunction Chest infection

Question 61

What are some side effects of local and regional anaesthetic?

Answer 61

Depends on agent use and usually occurs due to systemic spread Locals that block Na+ VGC are cardiovascular toxic

Question 62

What type of hyeprsensitivty can occur due to anaesthesia?

Answer 62

Type I allergic reactions (Anaphylaxis)