W13 45 general anaesthetic techniques

Question 1

What is general anaesthesia?

Answer 1

State of induced unconsciousness
Loss of protective airway reflexes

Question 2

What are the indications for GA!

Answer 2

Patient factors - unpleasant if awake; patients that can’t comply (eg children elderly dementia etc)m relaxation needed, too painful without it
Surgical factors

Question 3

What are the contraindications for GA?

Answer 3

Patient refusal
Risks outweigh benefits

Question 4

What are the risks of GA?

Answer 4

Risk of airway compromise
Risk of regurgitation of stomach contents and aspirating that
Risk of cardiovascular compromise

Question 5

What cardiovascular compromise can come about during GA?

Answer 5

Reduces systemic vascular resistance, dropping blood pressure
Elderly with ischaemic heart disease can induce cardiac ischaemia

Question 6

What are the 5 stages of anaesthesia?

Answer 6

Premedication - not used routinely anymore
Induction
Maintenance
Emergence
Recovery

Question 7

What are the most common premeds for GA?

Answer 7

Benzodiazepines

Question 8

What other premeds can be used for GA?

Answer 8

Others include antisialogogues to reduce oral secretions and antacids to stop stomach regurgitation

Question 9

When are sedatives/premeds used for GA since they’re not routinely used anymore?

Answer 9

Reserved for children, severe anxiety and developmental delay

Question 10

What techniques are there for premedication? (perhaps don’t need all details)

Answer 10

Face/nasal mask
Supraglottic device
ETT - endotracheal tube
Tracheostomy

Question 11

Details of premeds - probs don’t need but here for a read:

Answer 11

Face/nasal mask - doesn’t provide a safe airway, common in paeds
Supraglottic device - device sits over cords, often in paeds, easily dislodged, doesn’t protect airway from soiling or bleeding
ETT - endotracheal tube, usually in intensive care, generally most safe
Tracheostomy - if having significant upper airway procedures, pt can be awake and have a speaking valve in it.

Question 12

How is induction given?

Answer 12

Adult induction is normally with intravenous agents

Question 13

What drugs are added during induction?

Answer 13

Short-acting opiate eg fentanyl (dampens laryngeal reflexes)
Drug to induce unconsciousness eg propofol
A muscle relaxant may also be added

Question 14

How is induction different in paeds?

Answer 14

Gas induction in younger children with volatile agent - normally sevoflurane with oxygen and nitrous oxide
Older children often IV induction

Question 15

What methods can be used for induction? (Pg444 images)

Answer 15

Laryngeal mask - sits over laryngeal inlet, cuff to inflate for a good seal
Reinforced nasal tube - better access to oral cavity
Tracheostomy - for people who will swell up after eg from oral cancers. Cuff down let’s more air in, cuff up is protected airway. Difference sizes and speaking valves.

Question 16

How is GA maintained?

Answer 16

Often volatile agent via the anaesthetic machine - image pg 444
Closed circuit - no gas leaking out, so exhaled CO2 will keep going round the circuit, so soda lime absorbs this

Question 17

When is using TIVA (total intravenous anaesthetic) useful?

Answer 17

If ventilation may be disrupted eg vocal cord surgery
Volatile agents are contraindicated such as in malignant hyperpyrexia
In severe PONV

Question 18

What happens at the end of the procedure with GA?

Answer 18

Decide whether to keep asleep or wake up

Question 19

How do you wake up a patient after GA?

Answer 19

Stop the anaesthetic drugs!
- if inhalation, will slowly breathe out the vapour and wake up
- if intravenous, will metabolise
- if been paralysed, this will stop too

Question 20

Ideally you should not keep someone asleep as it is unhealthy - what are the problems?

Answer 20

Maintaining an airway
ETT between cords can cause granuloma formation
Prolonged intubation can cause tracheal stenosis
Cardiovascularly, keep people sedated to keep their blood pressure up via medication

Question 21

Why might you want to keep people asleep after the procedure?

Answer 21

If you have a lot of airway swelling (eg dental abscesses)
Trismus
If they have a precarious graft (eg head and neck tumour, to keep pt with straight head alignment)
If metabolically deranged, eg if been stabbed
(Basically to allow these patients to normalise!)

Question 22

Consider pain relief and antiemetics after GA. Which ones should you give?

Answer 22

Simple analgesias eg paracetamol
High dose opiot - eg IV, morphine
LA, regional blocks
Antiemetics - lots of people will be sick