W13 45 general anaesthetic techniques Flashcards
What is general anaesthesia?
State of induced unconsciousness
Loss of protective airway reflexes
What are the indications for GA!
Patient factors - unpleasant if awake; patients that can’t comply (eg children elderly dementia etc)m relaxation needed, too painful without it
Surgical factors
What are the contraindications for GA?
Patient refusal
Risks outweigh benefits
What are the risks of GA?
Risk of airway compromise
Risk of regurgitation of stomach contents and aspirating that
Risk of cardiovascular compromise
What cardiovascular compromise can come about during GA?
Reduces systemic vascular resistance, dropping blood pressure
Elderly with ischaemic heart disease can induce cardiac ischaemia
What are the 5 stages of anaesthesia?
Premedication - not used routinely anymore
Induction
Maintenance
Emergence
Recovery
What are the most common premeds for GA?
Benzodiazepines
What other premeds can be used for GA?
Others include antisialogogues to reduce oral secretions and antacids to stop stomach regurgitation
When are sedatives/premeds used for GA since they’re not routinely used anymore?
Reserved for children, severe anxiety and developmental delay
What techniques are there for premedication? (perhaps don’t need all details)
Face/nasal mask
Supraglottic device
ETT - endotracheal tube
Tracheostomy
Details of premeds - probs don’t need but here for a read:
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.
How is induction given?
Adult induction is normally with intravenous agents
What drugs are added during induction?
Short-acting opiate eg fentanyl (dampens laryngeal reflexes)
Drug to induce unconsciousness eg propofol
A muscle relaxant may also be added
How is induction different in paeds?
Gas induction in younger children with volatile agent - normally sevoflurane with oxygen and nitrous oxide
Older children often IV induction
What methods can be used for induction? (Pg444 images)
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.
How is GA maintained?
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
When is using TIVA (total intravenous anaesthetic) useful?
If ventilation may be disrupted eg vocal cord surgery
Volatile agents are contraindicated such as in malignant hyperpyrexia
In severe PONV
What happens at the end of the procedure with GA?
Decide whether to keep asleep or wake up
How do you wake up a patient after GA?
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
Ideally you should not keep someone asleep as it is unhealthy - what are the problems?
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
Why might you want to keep people asleep after the procedure?
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!)
Consider pain relief and antiemetics after GA. Which ones should you give?
Simple analgesias eg paracetamol
High dose opiot - eg IV, morphine
LA, regional blocks
Antiemetics - lots of people will be sick
