General Anaesthesia: Spontaneous Ventilation with an LMA

Question 1

List the preoperative checks

Answer 1

ABCDE

Anaesthetic machine and monitors
Airway equipment
Breathing equipment
Circulation equipment
Drugs (anaesthetic)
Emergency equipment and drugs

Question 2

What are the minimum monitoring standards as determined by the AAGBI, intraoperatively?

Answer 2

Pulse oximeter
NIBP monitor
Electrocardiograph
Airway gases
Airway pressure

A nerve stimulator and means of monitoring temperature must also be available.

Question 3

After IV access and Pre-oxygenation, what is the sequence of co-induction agents?

Answer 3

Midazolam (1 -3 mg)
Fentanyl (0.5 - 1 ug/kg)
Propofol (1.5 - 2.5 mg/Kg)

Question 4

Are a few breaths of O2 by FM appropriate during this non-RSI induction for insertion of an LMA

Answer 4

Yes.

Question 5

What benefit doe propofol and fentanyl have for the administration of inhalation volatile anaesthetic agent

Answer 5

Suppress airway reflexes so airway irritation from volatile agent is unlikely.

Question 6

What are the likely problems if the anaesthetist is unable to ventilate the patient with the bag and how should this be resolved?

Answer 6

1. LMA incorrectly positioned
2. Patient is too light (reactive closure of glottis).

Suction, remove LMA, bag with FM FiO2 100%. Replace.

Consider deepening anaesthesia with incremental doses of IV induction agent/opioid

Question 7

What should initial gas flows be for circle circuit or Bains?

Answer 7

High - at least 6L/minute initially for both

Question 8

How should the patient be ventilated during the initial period of apnoea after LMA is in place?

Answer 8

Manual - maintain ET CO2 5-6 kPa

CO2 is desired for stimulation of SV

Question 9

How can the start of SV be observed?

Answer 9

Capnograph and reservoir bag

Question 10

What should be done once the patient is breathing fully spontaneously?

Answer 10

Open the AV valve

Question 11

How often should core data be recorded on the contemporaneous anaesthetic record?

Answer 11

BP, HR, SaO2 - every 5 minutes or more if unstable

Question 12

When can the FGF be reduced

Answer 12

Once the breathing system is filled with anaesthetic gases and the period of rapid uptake of anaesthetic agents is complete

Question 13

What should be checked after the FGF has been reduced?

Answer 13

Inspired gas composition must be monitored as it will differ from the FGF

Question 14

What should be done if a rapid change in the concentration of inspired agent is needed?

Answer 14

Transiently increase the FGF as well as the vaporizer setting

Question 15

What should be done at the end of surgery

Answer 15

Turn off volatile and N2O –> turn on 100% O2 (preoxygenate again) at 6L/minute

Question 16

What are airway management options for transfer to recovery?

Answer 16

With or without LMA in situ

If LMA in situ – connect T-piece with reservoir bag and connect O2 cylinder with transfer trolley to T-piece. PAtient will then breath O2 in recovery with LMA in situ.

LMA removed in theater:
Suction –> remove LMA –> insert Geudel –> confirm clear and protected airway–> administer O2 via Hudson mask (use lateral position)

Question 17

What monitoring should be continued during the transfer?

Answer 17

Pulse oximetry

Question 18

During the maintenance phase of LMA anaesthesia the patient coughs and completely obstructs their airway. What actions should be taken

Answer 18

1. Stop surgeon (stimulation will worsen situation)
2. Propofol increment (patient may be light since coughing occurred)
3. Call for assistant (ETT may be required)
4. Remove LMA and ventilate by FM

Question 19

What volume of air should be used initially to fill the cuff of a size 3 LMA?

Answer 19

20 mL