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CPS > Maintenance > Flashcards

Maintenance Flashcards

1
Q

What are inhaled anaesthetic agents?

A

They are vapours not gases

Vapours = Liquids vaporised in a carrier gas

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2
Q

Name the common inhaled anaesthetic agents

A 
»	Nitrous oxide
»	Halothane – try not to use because it makes a hole in the ozone 
»	Isoflurane
»	Sevoflurane
»	Desflurane
»	Future: Xenon
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3
Q

What are the pros and cons of xenon?

A

Xenon, its great and has minimal side effects (cardiovascularly stable, non-toxic and does affect CO/BP) but it is very expensive to purify from the air

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4
Q

What is a vapour?

A

A vapour is a substance in the gas phase at a temp lower than its critical point so this means that the vapour can be condensed to a liquid or a solid by increasing its pressure without reducing the temperature.

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5
Q

Can a vapour co-exist in a tub with a solid?

A

A vapour can co-exist with a liquid (or solid). When this is true, the two phases will be in equilibrium, and the gas partial pressure will equal the equilibrium vapour pressure of the liquid (or solid)

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6
Q

How does a vaporiser work, what does it mean when the iso is on 3%?

A

The vapouriser diverts a proportion of the carrier gas (O2) into the vapouriser to pick up some iso and then returns the diverted gas to the carrier gas, All of the gas delivered will be saturated to 3% iso

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7
Q

What do modern vaporisers compensate for?

A

The modern vaporiser is both:
» Temperature compensated
» Flow compensated

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8
Q

Concentration of agent rises in plasma at a rate that depends upon….

A

– Ventilation
– Concentration of agent in carrier gas
– Cardiac output (inversely, Lower CO = higher conc)
– Solubility of agent in the body (inversely

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9
Q

What is the Blood : gas partition coefficient ?

A

= Solubility

This is the ratio of the amount of anaesthetic in blood and gas when the two phases are of equal pressure and volume

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10
Q

The LESS soluble agents (low coefficient) are …..

A

….washed away less quickly therefore the alveolar concentration rises FASTER

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11
Q

Recovery is the reverse of induction, so dependant on blood solubility, redistribution will have occurred into the fat, which then acts as a depot of anaesthetic so (depending on fat solubility) a fat animal will recover ………….. than a thin one

A

slower

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12
Q

A fit patient has a very high CO so it will be a lot harder to ………………. anaesthesia

A

induce/maintain

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13
Q

What is the MAC?

A

Minimum Alveolar Concentration (MAC) is..
The alveolar concentration (at 1 atm) producing immobility in 50% of patients in response to a noxious stimulus i.e. Potency
MAC is for healthy, un-premedicated patients

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14
Q

What factors do and do not affect the MAC?

A

MAC affected by: Age, N2O, hypotension, hypoxia, anaemia, opioids, sedatives, LAs, pregnancy
MAC not affected by: Stimulation, duration, species, sex, CO2, NSAIDs

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15
Q

What is the MAC of Iso for a dog and cat?

A

Dog: 1.28
Cat: 1.63

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16
Q

What is the MAC of sevo for a dog and cat?

A

Dog: 2.2
Cat: 2.58

17
Q

What is the MAC of NO for a dog and cat?

A

Dog: 188-297
Cat: 225

18
Q

What are negative effects of inhaled agents?

A

To the animal:
– Cardiorespiratory depression
– Formation of carbon monoxide with soda lime
– (Formation of other toxic gases)

To the anaesthetist:
Little or no evidence apart from nitrous oxide
• Bone marrow suppression
• Teratogenesis

19
Q

What does Fluosorber absorb?

A

(absorbs the inhalants, but not nitrous oxide)

20
Q

Is N2O analgesic? Does it affect the CVS?

A

Yes and no

21
Q

What are the pros of sevoflurane?

A
  • Great for cat mask induction or chamber induction
  • Anaesthetic induction, recovery, and intraoperative modulation of anaesthetic depths to be notably faster than halothane and isoflurane because it is less soluble
22
Q

What are the cons of sevoflurane?

A
  • More expensive

* Sevoflurane induces dose-dependent cardiovascular depression to a degree similar to that isoflurane

23
Q

When do most fatalities occur in GA?

A

60% of the fatalities occurred in the recovery period with half of these dying within 3 hours of disconnection

24
Q

Why do horses like to die under GA?

A

Horses are prone to hypotension when inhalants are used, prolonged hypotension is likely to cause post op myopathy. Post op myopathy may necessitate euthanasia or cause a fracture or injury in recovery.
Hypoxaemia is often encountered during equine anaesthesia

25
Q

Hypercapnia is also often encountered during equine anaesthesia, why is this and how can we avoid it?

A

Permissive hypercapnia is tolerated by many (60 mmHg)
Diagnosis: Capnography and or Blood gas analysis
Hypercapnia is most commonly caused by respiratory depression, Both the inhalants and TIVA can be profound respiratory depressants (less with TIVA)

26
Q

What are the goals of PIVA?

A
  • Reduce MAC
  • Reduce cardiopulmonary depression
  • Provide additional analgesia
  • Improve plane of anaesthesia
  • Less pollution
27
Q

What can we use to improve cardiovascular stability during isoflurane anaesthesia?

A

Lidocaine + ketamine

28
Q

What are the benefits of using lidocaine in PIVA?

A

Analgesic, MAC reduction, Anti-dysrhythmic, Reduction of post op ileus, Anti-inflammatory, Protects against endotoxaemia (TNFα reduced), Protects against ischaemic and reperfusion injury, Reduced LPS induced leucocyte-endothelial cell adhesion & macromolecular leakage from vessels

29
Q

How should ketamine be administered for PIVA?

A

Often given as boluses during anaesthesia, Do not >2mg/kg in total increments, Allow 20 mins to elapse after final dose before switching off

30
Q

What are the benefits of using ketamine in PIVA?

A

Ketamine CRI (30% MAC reduction), Can be combined with lidocaine medetomidine, xylazine, propofol etc (not licensed)

31
Q

Can A2 agonists be used in PIVA?

A

In tiny boluses

Xylazine (25% MAC reduction), Detomidine used in (equine),

CPS (16 decks)

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