What Is Anaesthesia Flashcards

1
Q

Sleep vs anaesthesia

A
Sleep
- respond to pain
- move around
- dream
-maintain airway - may be partial closure snoring or transient closure OSA
-Normal breathing
-Swallowing normal
-Sleep EEG
Anaesthesia
- no response to pain
- no movement 
- no dream
- lose airway
- depressed ventilation
 -Reduced swallowing
- anaesthesia EEG
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2
Q

Types of anaesthesia

A

Balanced - combination of different components that cause an anaesthetised state - anaesthesia to reduce consciousness, muscle relaxant that prevents movement - and analgesia that obtunds painful stimuli
Simple - just anaesthetic agent

The balanced anaesthesia approach reduces the side affects of anaesthetic agents by having multiple agents that target different needs to maintain during anaesthesia

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3
Q

Features or single agent anaesthetic

A

Simple - only one component
You need a larger amount of the drug so more likely to get cardiac or resp depression
Short procedures only

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4
Q

Features of balanced anaesthesia

A

Each component contributes to its affect
Side effects are reduced by the relatively smaller doses
Requires attention to detail
- too little anaesthetic agent = awareness
- to little analgesia = excess response to pain
- too little relaxant = unwanted movement

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5
Q

How is GA administered

A

Inhaled
IV
Induced and maintained
GA can be combined with Analgesics, relaxants, local or regional anaesthesia

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6
Q

What is sedation

A

Form of semi-hyponosis in which the patient is rousable, can talk but may have no memory of the events
Important they can maintain there airway
There is a concern that to much sedation a patient will no longer be able to do so

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7
Q

Types of anaesthesia

A

Local - topical or infiltration
RA- peripheral nerve block, ganglion/plexus block/ epidural, spinal, IV regional
GA - simple or balanced, inhalational - TIVA, TCI

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8
Q

How does the mechanism of GA work

A

GA prevents pain generated peripherally being interpreted as pain by the CNS
It does not stop the transmission of painful stimuli from the source of the pain

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9
Q

Mechanism on RA or LA

A

They prevent the transmission of a painful stimulus reaching the CNS

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10
Q

Chemistry of LA and how this affects their mechanism

A

Most have a lipid soluble hydrophobic aromatic group
And a charged hydrophilic aside group
Amide or Ester bond between groups
LA inhibit sodium influx through sodium voltage gated channels in the neuronal cell membrane
The molecule can exist in an unionised and ionised form
The pH determines which is the most predominant
PH is higher in the tissues so the molecule dissociates and the base enters the axon when inside the axon the pH is lower so re-ionisation takes place
The recognised portion enter the Na channels and blocks them preventing depolarisation

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11
Q

What happens when LA get into the plasma

A
1) they should not go into the plasma 
Increasing dose inc the severity of SE
4 - lightheaded, tinnitus
10 - convulsion 
20 - resp arrest 
26 - CV collapse
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12
Q

What is the max safe dose of bupivicaine

A

2mg/kg

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13
Q

What is the max safe dose of lignocaine

A

3mg/kg

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14
Q

What is the max safe dose of Prilocaine

A

6mg/kg

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15
Q

What topical application of LA are there

A

Eutectic mixture of LA (EMLA) lignocaine and prilocaine
Amethocaine cream/gel
Lignocaine spray
Benzocaine lozenges

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16
Q

What is local infiltration LA

A

Cannula, sutures
Field block - inguinal hernia
Wound infiltration - often with adrenaline

17
Q

Why is adrenaline given with LA

A

Slows the systemic absorption of LA thus inc duration of LA effect and is useful in areas of inc vascularity where the risk of systemic absorption is higher
Adrenaline is CI in penile, digital block and around the nose and ear due to the risk of ischaemia

18
Q

Where does spinal anaesthesia go

A

Into the subarachnoid space
L3-4
25-27G needle

19
Q

What confirms the correct placement of needle in spinal anaesthesia

A

The flow of CSF back through the needle

20
Q

What is epidural anaesthesia

A

Anaesthetic into the extradural space
Insert an indwelling catheter through a tuohy needle
Larger volumes on anaesthetic also opioids can be given this way
Thoracic lumbar and cervical can be given but need great skill

21
Q

What is the name of the technique in epidural anaesthesia

A

Loss of resistance technique

22
Q

Features of nerve blocks

A
LA injected close to the nerve
Need to avoid vessels 
Up to 30mls required 
Single nerve 
Multiple - plexus of multiple nerve that supply an area such as an ankle block
23
Q

What is IV regional anaesthesia known as in the wrist and how is it done

A

Biers block and is done in for a fractured wrist
The arm needs to be exsanguinated with a double tourniquet to prevent blood flow cuff up for >20 mins
Can be hazardous if cuff let down too soon - toxic effects of
LA in the circulation

24
Q

What are the CI absolute and relative to LA

A

Consent unable
Surg unhappy with the conditions provided under LA
Absence operating too staff
Anticog coagulopathy
Infection at site of injection
Existing or suspected neurological deficit