17) Anaesthetics

Question 1

Why does polypharmacy occur with using Anaesthetics ?

Answer 1

Are lot of drugs are used for different situations

1) Pre-medication => Helps with nervous patients
2) Induction => To send patients to sleep (IV or Inhalation)
3) Analgesia
4) Muscle Paralysis => Aid intubation
5) Maintenance of Anaesthetics
6) Reversal of Muscle paralysis

Question 2

Outline the features of MAC
> Definition
> Factors which can affect MAC

Answer 2

Minimum Alveolar Concentration = The alveolar concentration of the Anaesthetic at which 50% of subjects fail to react to surgical stimulus
Often used for Volatile Anaesthetics

Factors 
> Age (High in infants and Low in elderly)
> Hyperthermia (Increased) / Hypothermia (Decreased)
> Pregnancy (Increased) 
> Alcoholism (Increased) 
> Central stimulants (Increased)
> Other Anaesthetic (NO) (Decreased)
> Opioids (Decreased)

Question 3

What factors can affect Induction and Recovery

Answer 3

> Blood : Gas Partition

• Solubility of volatile anaesthetic in the blow
• Low value means fast induction and recovery

> Oil : Gas Partition

• Solubility in fat and so determines potency.
• Greater ability to travel through fat = High potency
• However Anaesthetic can accumulate in fat meaning long recovery

Question 4

What is Guedel’s Sign

> Outline the different stages

Answer 4

Describes the level to which the anaesthetic is working
Stage 1 - Analgesia and Consciousness
Stage 2 - Unconscious, breathing erratic but delirium can occur leading o an excitement phase
Stage 3 - Surgical Anaesthesia with 4 levels describing increasing depth until breathing weaken
Stage 4 - Respiratory Paralysis and Death

Question 5

What is Anaesthesia a combination of ?

Answer 5

> Analgesia
Hypnosis
Depression of Spinal Reflexes
Muscle Relaxation

Question 6

Outline the features of Local Anaesthetics
> Mechanism of Action
> Give Examples of drugs
> Use

Answer 6

Targets Voltage Gated Sodium Channels
> They are not charged so passes through cell membrane and hen becomes charged.
> They charged agent then pass through a VGCC preventing Na+ from passing

Examples:
> Lidocaine
> Bupivacaine
> Ropivacaine

Use:
> Dentistry 
> Obstetrics 
> Regional Surgery 
> Pain Management

Question 7

What is the mechanism of action of General Anaesthetics
> Mechanism of Action
> Give examples

Answer 7

MOA
-GABA Receptors-
> GABA receptors are targeted, they modify Cl- Ion conductance making cells more negative
> This reduce AP transmission
> This depresses the reticular system in the brain which leads to depression of the hippocampus, brainstem and spinal cord

-NMDA Glutamate Receptors-
> Balance between Glutamate and GABA is needed to determine whether the patients awake or not
> Inhibit glutamate potentiation
> Xe; N2O and Ketamine

Examples

Volatile => Xe, Halothane N2O, Isoflurane, Sevoflurane

IV => Propfol (Rapid), Barbiturates (Rapid) , Ketamine (Slow)

IV => Propofol, Ketamine

Question 8

Why might you give Adrenaline with Bupivacaine

Answer 8

Reduces risk of Local Anaesthetic from spreading so effect is more localised

Question 9

Outline the main Anaesthetic Side Effects
> General
> Local / Regional

Answer 9

General
> Post operative NV
> Hypotension
> Post operative Cognitive Dysfunction 
> Chest infection if not intubated correctly 
> Polypharmacy 
> Allergic Reactions 
> Anaphylaxis
> Respiratory Depression 

LA / Regional 
> Agent specific
> Risk of Systemic Spread => Cardiotoxicity 
> Channel Blockers 
> Anaphylaxis