How is anaesthesia continued following intubation?
O2 saturated with an appropriate level of inhalational agent is delivered
What is the intention of an anaesthetic machine?
Designed to mix an appropriate controlled level of inhalational agent with O2
What are the names of the modified Mapleson non-rebreathing circuits?
Parallel lack for Mapleson A
Co-axial Bain for Mapleson D
Which Mapleson circuit is deemed to have medium efficiency?
What is the role of the induction agent?
Provides vet with just about enough time to intubate patient
What is the role of a soda lime cannister?
To remove CO2 from expired gas thereby rendering it safe to be rebreathed
Which non-rebreathing circuit requires a flow rate of 2.5-3x minute volume?
What is the difference between Mapleson A and D non-rebreathing circuits?
Mapleson A has a fresh gas tube reaching the reservoir bag, then the expired gas tubing follows into the expiratory valve before the ET tube.
Mapleson D additionally has a connecting T-piece: the fresh gas tubing reaches the T-piece then branches into the ET on one side, and the expired gas tubing on the other which feeds into the expiratory valve and then the reservoir bag
What is the typical re-breathing circuit flow rate?
What component does Mapleson E/Ayre's T-piece lack?
A reservoir bag
What happens if the flow rate is too high?
Wasteful as freshly saturated gas will be escaping into the environment
What is the benefit of inhalational agents?
Animals regain consciousness as soon as delivery of inhalational agent is stopped
What is the alternative name for Mapleson A non-rebreathing circuit?
How are induction agents usually administered?
As IV injections
What additional feature does a re-breathing circuit have that a non-rebreathing circuit lacks?
Soda lime cannister
Is a slightly low flow rate considered an acceptable occurrence?
Yes to a degree as gasesous exchange is still occurring despite the presence of deadspace air within the non-rebreathing system
What 2 kinds of breathing circuits are there?
What is deadspace gas?
Air that is inspired but that doesn't partake in gaseous exchange
What would be a good approximation of the minute volume?
Why are maintenance agents safer than their IV counterparts?
IV agents require metabolism (usually by liver) to deactivate and allow animal to regain consciousness
What is the minute volume?
Volume of gas expired per minute
How many times the minute volume is needed for Mapleson D?
2-2.5x minute volume?
What are the main components of anaesthetic machines?
Fresh O2 supply
What is the alternative name for Mapleson F non-rebreathing circuit?
What are the main factors for rebreathing circuits?
Rebreathing circuits are when the patient rebreathes expired air:
-> expired gas contains higher levels of CO2 - this must be extracted before the paitient rebreathes it
-> high resistance - therefore only suitable for large patients >25kg
What feature does Mapleson E/Ayre's T-piece lack?
A reservoir bag
What are the two components to achieving general anaesthesia?
Which non-rebreathing circuits are redundant models?
Mapleson B, C and E (Ayre's T-piece)
What is the name of the modified Mapleson A?
Parallel lack non-rebreathing circuits
Which of the Mapleson non-rebreathing circuits has the highest efficiency?
What is the general flow rate administered in practice?
2-3 L/min until anaesthesia is stable
0.5-1 L/min maintenance
What must happen within a non-rebreathing circuit to prevent expired gases from being rebreathed?
Fresh gas flow rate must exceed the minute volume
What are the main features of non-breathing circuits?
Patient does not rebreathe expired gas:
-> gas must be flushed out of the circuit before the next inhalation
-> low resistance therefore suitable for patients
Breathing circuits are composed of which principle features?
Adapter connecting to ET tube
Fresh gas tubing
Expired gas tubing
What is the Co-axial Bain a modification of?
Mapleson D non-rebreathing circuit
What happens if the flow rate is slightly too low?
Deadpace gas remains within the non-rebreathing system, rather than being purely freshly satured O2
When is the flow rate considered to be unacceptable? Why?
When the flow rate is very low it is unacceptable because this results in expired alveolar air infiltrating the non-rebreathing circuit, preventing maximum gasesous exchange
What amount times the minute volume is needed for a Mapleson A non-rebreathing circuit?
1x minute volume
Which of the non-rebreathing circuits has the lowest efficiency? What is the resultant clinical significance?
Mapleson F has the lowest efficiency because it has the least resistance
Lowest efficiency is ideal for small patients