Conduct of General Anaesthesia

Question 1

when is thiopentone used?

Answer 1

pregnancy

Question 2

along with GAs what is usually also given during induction?

Answer 2

Sympathomimetics are used to increase blood pressure “upper”. Anti-emetics are usually given at this time too. Benzodiazepines may be given to decrease anxiety in the patient.

Question 3

onset time of IV induction

Answer 3

rapid - one brain arm circulation 20s

Question 4

planes of anaesthesia

Answer 4

• Analgesia/sedation – pleasantly lightheaded, giggly
• Excitation – disinhibition
• Anaesthesia – light à deep
o Can’t just arouse from anaesthesia like sleep – coma
o Depending on patients response to stimulus
• Overdose
o CV and resp depression
o In patients who are compromised
§ Frail, elderly, septic, hypovolaemic – window of safety narrower
• Or sleep/excited/anaesthetised

Question 5

how do you monitor conscious level during anesthesia

Answer 5

• Loss of verbal contact
• Movement
• Respiratory pattern
• Processed EEG
• “stages” or “planes” of anaesthesia

Question 6

what may cause airway obstruction?

Answer 6

ineffective triple airway manoeuvre

airway device malposition or kinking

Question 7

what is laryngospasm?

Answer 7

Laryngospasm is the forced reflex adduction of the vocal cords which may result in complete airway obstruction. It is caused by airway (or other) stimulation in light planes of anaesthesia. It is often unrelieved by simple manoeuvres.

Question 8

what is the only device that protects the airway?

Answer 8

endotracheal intubation

Question 9

why would you intibate someone?

Answer 9

• Protect the airway from gastric contents
o E.g. full stomach in an unfasted emergency patient
• Need for muscle relaxation therefore artificial ventilation
o E.g. laparotomy muscle relaxants are not selective
• Shared airway with risk of blood contamination
o E.g. tonsillectomy in ENT
• Need for tight control of blood gases
o Especially CO2 levels in neurosurgery
• Restricted access to airway
o E.g. maxillo-facial surgery

Question 10

risks to an unconscious patient?

Answer 10

• Airway, airway, airway
• Temperature – alcohol antiseptic, rapid airflow theatres
• Loss of other protective reflexes
o E.g. corneal, joint position
• VTE risk
• Consent and identification
• Pressure areas

Question 11

dreaming during anaesthesia

Answer 11

6 in 100

Question 12

risk of awareness (all)

Answer 12

1 in 14,000

Question 13

risk of awareness (low risk)

Answer 13

1 in 42,000

Question 14

risk factors for awareness

Answer 14

o Paralysed and ventilated
o Previous episode of awareness
o Chronic CNS depressant use
o Cardiac surgery 1 in 100
o Major trauma 1 in 20
o GA C-section 1 in 250