Pharmacology Of Anaestheisa Flashcards

1
Q

Advantages and disadvantages of IV induction

A

Pleasant for patients
Rapid loss of consciousness under control of the anaesthetists
Loss and recovery of consciousness dependent on passive pharmacokinetic processes so relatively predictable

May be adverse CVS and RS effects esp in elderly those in pain or shocked
Easy to OD if cardiac output low and there is slow arm to brain circulation time
Need to inject the agent slowly t prevent relative OD

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2
Q

What is propofol

A

2,6 di-isopropyl phenol
Commonest IV anaesthetic in the developed world
It is lipohilic and insoluble in water so is suspended in a soybean oil, egg phosphatide emulsion
Rapid recovery
Fast acting it’s offset of action is due to rapid redistribution rather than and not metabolism
Induction and maintenance - TIVA, TCI
Problems - can be pain on injection
antiemetic effect

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3
Q

Who is prop for CI in

A

Egg or soybean allergy
<17 years for sedation
Extremes of age
Compromise airway

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4
Q

What is etomidate

A
Ester 
Carboxylated imidazole 
No accumulation - rapid recovery 
Little CVS effect 
Used as a induction agent only
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5
Q

Why is etomidate used in induction only

A

Prolonged us - can lead to lethal adrenal suppression

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6
Q

Side effects etomidate

A
  • adrenal suppression
  • local thrombophlebitis at the site of injection
  • can cause involuntary muscle spasms
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7
Q

What is thiopentone sodium

A
Barbiturate powder 
Rapid onset 
Cheap
Effects last 3-8 min 
Long terminal half life Hangover effect
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8
Q

SE/CI thiopentone

A

Mycocardial depressent

CI
Airway obstruction
Barbiturate allergy
Fixed cardiac output
Hypovolamia /dec BP
Porphyria
Compromised airway
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9
Q

What is ketamine

A

Phencyclidine derivative
Acts on NMDA receptor
Can be given IM or IV
IM - useful for being an in the field agent producing analgesia without shock

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10
Q

Effects of ketamine

A

Useful in positioning patients in order to facilitate spinal anaesthesia in the setting of features esp FNOF
Used in children as anaesthesia ad sedation in adults
CO is unchanged or increased - so doesn’t produce shock
Also bronchodilators properties so an be considered in the intubation of status asthmaticus

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11
Q

Problems with ketamine

A
Hypertonus and salivation
Slow recovery 
Lirum
Hallucinations
Nighmares
All made worse if the patient is disturbed during recovery 
Avoid in hypertensive 
Inc ICP
Inc IOP
Avoid in psych patients
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12
Q

Pros and cons of inhalation induction

A

Ad
Slower and greater onset on ‘sleep’effects
More control over unwanted side effects
If problems arise the patient can be allowed to waken
Good in peads if diff to cannulate
Adults who are diff to cannulate or have difficult airways and fear of needles
Dis
Requires skill and attention to technique to do it well
Needs skilled assistant\
Needs good patient cooperation
Speed of action depends on drug solubility, resp rate and depth and CO

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13
Q

What are Guedels stages of anaesthesia

A

Stage 1 - amnesia and analgesia
Stage 2 - excitement or delirium
Stage 3 - surgical anaesthesia
Stage 4 - anaesthetic overdoses

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14
Q

What is the ideal inhalation agent (there is none that exist which have all these properties)

A

Non flamm, non exposure at room temp
Stable in light
Liquid an vaporisable at room temp - low latent heat of vaporisation
Stable at RTP with long shelf life
Stable with soda lime and plastic and metals
Environmentally friendly - no ozone depletion
Cheap an easy to manufacture
Have low solubility in blood and tissue to allow for quick induction and recovery
No injuries effects on tissues
Be administrable in reliable and known concentration
Please to inhale non irritant
Minimal effects on other systems
Excreted by lungs ideally
Non toxic to theatre personnel

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15
Q

Ideal IV agent

A

Act rapidly with arm within one arm brain circulation
Recovery quick with no hangover effect
Analgesic properties
Resp and CVS effects minimal
Not interact with other anaesthetic agents
No hypersensitivity reactions
There should be no post-op phenomena N/V hallucinations

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16
Q

Ideal muscle relaxant

A
Non-depolarising mode of action
Rapid onset 
Short duration of action with high potency 
Spontaneous predictable reversal 
No CV effects 
Pharmacologically inactive metabolites
Unaffected by renal or hepatic failure
17
Q

What is MAC

A

The concentration that prevents movement in response to skin incision in 50% of unpremeditated animals

Do not move during surgery due to the anaesthetic

18
Q

Advantages of MAC

A

Alveolar concentration can be easily measured
Near equilibrium, alveolar and brain tensions are virtually equal
The high cerebral blood flow produces the rapid equilibrium
Factor which support the use of the measure are:
- MAC is invariant with a variety of noxious stimuli
- individual variability is small
- sex, height and weight and anaesthetic duration do not alter MAC
Doses of anaesthetic in MACS are additive

19
Q

N2O as a anaesthetic agent

A

Odourless odourless gas
Ineffective as a sole agent
MAC is 105% so therefore if this was a sole agent you’d die cos there would be no oxygen
It has analgesic properties

20
Q

How is N2O usually given to patients

A

As entonox
50:50 mix of N2O and O2
Used in labour, trauma, children

21
Q

What is halothane

A

It is a halogenated hydrocarbon
No longer used in the UK
It is pleasant smelling with a small analgesic affect had a MAC of 0.75%

22
Q

Problems with halothane

A
Chemically unstable in light 
Increases Vagal tone - bradycardia 
Halothane hepatitis
- rare but ha a high mortality 
Immune mechanism
23
Q

What are enflurane and isoflurane

A

They are fluorinated ethers
Optical isomers of each other
MAC enflurane - 1.68%
MAC isoflurane - 1.15%

24
Q

Problems with enflurane and isoflurane

A

Irritant - so produce coughing but this can be reduced with opioids
Although should be quick onset can take longer due to the time it takes for the agent to be inhaled
Enflurane no longer used due to renal damage

25
Q

What is sevoflurane

A
It is a fluorinated methyl-isopropyl ether 
MAC -2%
It is non-irritant
Rapid induction
Cardiovascular stable 
Decomposed by soda lime 
Agent of choice for inhalation induction
Fast onset offset
26
Q

What is desflurane

A

Is a fluorinated methyl-ethyl ether
Rapid onset and quick recovery
Low absorption into fat so it a choice for the morbidly obese as it provides the quickest recovery post surgery

27
Q

Problem with desflurane

A

Low boiling point and is pungent so is irritant
Used mainly for maintenance
May ask have a greater CV depressant effect
Needs a specialised vapouriser due to it boiling point

28
Q

Ad and disad of maintenance anaesthesia inhaled

A
Ad - easy to administer 
Predictable behaviour
Dis
Take up in Fat depot - affects recovery
Potential toxicity 
Recovery dependent upon ventilation 
Need to was out circle systems otherwise the patient wont recover
29
Q

What is TIVA

A

Total intravenous anaesthesia

So maintenance anaesthesia with IV anaesthetic agent

30
Q

Which anaesthetic agent used with TIVA

A

Realistically only propofol

31
Q

Ad and disad of TIVA

A
Easy to continue from induction 
Titratable
Smooth anaesthesia 
\flow rated for hypnosis are predictable  based on weight and age 
Disad
Can be unpredictable wake up time - depends upon elimination half-life 
Unsuitable for short cases
Dependent upon action of syringe pumps
IV cannula can become displaced/detached
32
Q

What is TCI

A

Target controlled pump

Bonus early on and then steady release of anaesthetic agent and this can be adjusted