Process & Maintenance of Anaesthesia Flashcards
What are the different types of anaesthetic?
- Regional (neuroaxial, nerve block)
- General
- Local
- Sedation
Why is regional anaesthesia good?
- Less systemic derangement
- Avoids polypharmacy
- Extended analgesia
- Shortened recovery
What is regional anaesthesia not so good?
- CV changes
- Limited scope
- Failure rate
- Time constraints
- Anticoagulation
- Nerve injury
What is the triad of ‘balanced anaesthesia’?
3 factors that go together to provide a good balance of general anaesthetic:
- Hypnosis
- Analgesia
- Muscle relaxation
Mechanism is unclear - ?lipid bilayer effect, ?direct molecular effect
What are the muscle relaxants?
- For intubation and/or surgical purposes
- Depolarising (suxamethonium)
- Non-depolarising (vecuronium, rocuronium)
What needs to be prepared before the patient arrives, in the anaesthetic room?
- Consent & checklist
- Drugs prepared
- Equipment needed
- Machine check
- Monitoring
- Intravenous access
- Fluids
- Preoxygenation for GA
What are phases of general anaesthesia?
What are IV induction agents?
- Propofol → most commonly used
- Barbiturates
- Etomidate
- Ketamine → for those haemodynamically unstable due to blood loss, eg. trauma pts
- (Thiopentone used to be commonly used in obstetrics, now taken over by propofol)
Opioids are also used to dampen down the haemodynamic response to IV induction agents. Which opioids?
- Fentanyl, alfentanil, remifentanil
- Reduction in sympathetic response
- Opioid receptors (OP3/mu suprasinal analgesia, resp depression)
What is inhaled induction and when is it used instead of IV induction?
- Sevoflurane or Halothane
- Common in children
- Airway obstruction
- Difficult IV access
- Induction slower with longer excitatory phase
What is rapid sequence induction (RSI)?
- Minimise risks of regurgitation and aspiration of gastric contents
- Traditionally includes:
- preoxygenation
- rapidly acting IV induction agent (thio) + suxamethonium (quick onset and offset)
- cricoid pressure (shut oesophagus, avoid passive regurg)
- avoid manual inflation of lungs until intubation achieved
- Most now “modified”
What scores can be used to assess airway before and during anaesthesia?
- Malampatti score identifies patients at risk for difficult tracheal intubation
- Cormack & Lehane score describes laryngeal view during direct laryngoscopy
What ‘other’ intraoperative considerations need to be made for anaesthetic patients?
- DVT prophylaxis → TED
- Eyes → pad eyes as pts get corneal scratches
- Temperature → warm mattress, bear hugger, hat,
- Pressure points & Positioning
How is anaesthesia maintained?
- Inhalation → MAC, O2 requirement, N2O or air
- Target controlled infusion (TCI/TIVA) → BIS monitor (modified EEG), normal awake is 98-100, for GA should be between 40-60
Can also combine both of the above. So can induce a patient with IV and then maintain inhaled or TIVA (or both!). An unlikely method would be to induce with inhaled and then maintain with IV however.
What are CVS effects of anaesthesia?
- Reduce SVR and myocardiac depression → hypotension
- Inhibition of baroreceptor reflex
- Episodes of sympathetic sitmulation
