Anesthetics

Question 1

What are the major types of anesthesia?

Answer 1

General
Regional
Local

Question 2

Whats the difference between regional and local anesthetic?

Answer 2

Regional is when LA is applied to specific nerves supplying a whole area of the body

Local is when LA is applied directly to a specific tissue(s)

Question 3

What 3 parts make up the triad of anesthesia?

Answer 3

Analgesia (unpleasant stimuli)
Hypnosis (consciousness)
Relaxation (skeletal muscle)

Question 4

Any anesthetic drug can have variable effects on all 3 parts of the anesthesia triad. What drugs produce analgesia?

Answer 4

Mainly Opiates

Also local and general anesthetics

Question 5

What drugs produce hyponosis?

Answer 5

Mainly General anesthetics: halogenated hydrocarbons, propafol
Also opiates

Question 6

What drugs produce relaxation?

Answer 6

Primarily muscle relaxants but also local and general anesthetics

Question 7

Define the term “balanced Anesthesia”?

Answer 7

Using multiple drugs to do different jobs. This way the mixture and so the effects produced can be tailored to the patient & the surgery

Question 8

What are the major problems with multi-drug anesthesia?

Answer 8

• Risks of polypharmacy e.g. ADRs & Drug interactions
• Muscle relaxation can require artificial ventilation &airway maintanence
• Risk of relaxation without hypnosis- NEED TO MONITOR

Question 9

How do general anesthetics work?

Answer 9

They open neuronal ion channels –> Hyperpolarised neurons so they can’t fire

Inhalational: dissolve in membrane to change shape of channel
IV: bind to GABA receptors

Question 10

What kind of impact do GAs have on the resp system?

Answer 10

Reduce hypoxic/hypercarbic drive
Decrease tidal volume/increase RR

Paralyse Cilia

Decrease FRC

• lower lung volume
• V/Q mismatch

They impair control of breathing –> Mandates airway management

Question 11

How do GAs affect the CVS?

Answer 11

Centrally: depress the CV centres in the nuclei of the brainstem.
•reduce sympathetic outflow
•negative inotropic/chronotropic effect on heart
•reduced vasoconstrictor tone → vasodilation

Direct: on vascular smooth muscle and myocardium
•negatively inotropic
•vasodilation → decreased peripheral resistance

•Venodilation: decreased venous return, decreased cardiac output

This reduces SVR and CO –> Low MAP

Question 12

Give the major difference between IV and inhalational GAs along with an example of each?

Answer 12

IV e.g. Thiopentone or Propofol

• Rapid onset
• Rapid recovery

Inhalational, all are halogenated hydrocarbons

• Slow induction
• Easier to maintain

Question 13

How do we control IV GA infusion?

Answer 13

TCI - Target Controlled Infusion pump system

Question 14

How do we rate inhalational GAs?

Answer 14

MAC - Minimum Alveolar Conc.

Essentially a measure of potency, the lower the stronger

Potency: measure of the concentration required in the alveoli to produce anaesthesia

Question 15

When might you choose to use muscle relaxants during surgery?

Answer 15

If you will need to ventilate and/or intubate

If immobility is essential e.g. neurosurgery

If you need to access a body cavity via muscles e.g. abdo surgery

Question 16

What are the major issues with Muscle relaxants?

Answer 16

• Fear of being paralyzed but awake
• Incomplete reversal e.g. temp airway obstruction
• Apnoea (needs airway & ventilatory support)

Question 17

Whats the main reasons for using analgesia?

Answer 17

It’s not just removing pain

It’s to remove the body’s physiological responses to noxious stimuli e.g. tachycardia and hypertension

Question 18

How do we know the effect a local/regional anaesthetic will affect the CVS system?

Answer 18

Derangment of the CVS is proportional to the size of the anaesthetized area (think number of veins/arteries affected

Question 19

What effect does LA have on the resp system?

Answer 19

Alot less than GA since insp muscles are supplied by high up nerve roots. (hence might be preferred in patients with resp problems)

Expiratory are lower so in some LA blocks the cough reflex is still lost

Question 20

How do we ensure we deliver LA to the right nerve/area?

Answer 20

Can be US guided

Question 21

What is the limiting factor for LA and what does that depend on?

Answer 21

Toxicity (build up to toxic levels in a tissue)
This depends on:
- Dose
- Rate of absorption (akak site)
- Patient weight
- Drug

Question 22

Define the term “Differential blockade”?

Answer 22

Different fibres absorp drugs different due to thickness and myelination

This means we can easily block pain fibres without causing paralysis

Question 23

Describe the movement of Inhalational anaesthetics In the body

Answer 23

• Uptake and excretion via lungs
• Moves down the concentration gradient - lungs > blood > brain
• cross alveolar BM easily
• arterial concn equates closely to alveolar partial pressure

Question 24

Main features of Inhalational anaesthetics?

Answer 24

Induction: slow
Maintenance of anaesthesia : prolong duration - very flexible
Awakening:
- stop inhalational admin
- washout - reversal of concentration gradient

Question 25

what are some of the symptoms of LA toxicity?

Answer 25

• Circumoral and lingual numbness and tingling
• Light-headedness
• Tinnitus, visual disturbances
• Muscular twitching
• Drowsiness
• Cardiovascular depression
• Convulsions
• Coma
• Cardiorespiratory arrest

Question 26

How do anaesthetic spread?

Answer 26

From the head down?

More complex pathways first- Loss of consciousness and then loss of hearing

Question 27

What happens to refelxes in GA?

Answer 27

generally spared

Question 28

Which channels are most commonly targeted by inhalation GAs?

Answer 28

Chloride

Question 29

Why is there a rapid recovery in LA?

Answer 29

Redistribution MAIN

Metabolism LESS Common