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Surgical Nursing > Local anaesthetic techniques > Flashcards

Local anaesthetic techniques Flashcards

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1
Q

What is local anaesthesia?

A

Loss of sensation due to blockade of action of potential transmission in nerve fibres
reduced sensory input to the spinal cord and brain

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2
Q

What different methods can be used to apply local anaesthesia?

A 
Epidural
Topical 
Infiltration 
Perineural injection 
Regional blocks
Epidural
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3
Q

How do local anaesthetics work?

A

Block voltage gated sodium ion channels and prevent the depolarisation of the nerve cell
Preventing an action potential from generating

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4
Q

What are the two types of anaesthetic block drugs?

A 
Ester linkage 
Amide linkage (more popular)
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5
Q

What is the main determinant of potency for local anaesthetic drugs?

A

Lipid solubility

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6
Q

What is the main determinate that effects the duration of local anaesthetic drugs?

A

Protein binding

Highly bound drug stays within the lipoprotein of the nerve membrane longer

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7
Q

How does the pKa effect an anaesthetic drug?

A

Higher the pKa the less of the unionised base is present
only the unionised drug can penetrate the never membranes
Lower the pKa more of the ionised drug is available therefore the faster the onset

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8
Q

What happens to the local anaesthetic drugs in a acidic enviroment?

A

Higher proportion of the local anaesthetic is ionised

reduces the speed of onset

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9
Q

What is the pKa of lidocaine?

A

7.7 25% unionised at Ph 7.4

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10
Q

What is the pKa of bupivicaine?

A

8.1 15% unionised at pH 7.4

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11
Q

When may tissue be more acidic?

A

Inflammed tissue

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12
Q

Which nerve fibres are effected first once local anaesthesia is injected?

A

Unmylienated sensory fibres
Less distance between sodium channels less of them need to be blocked to prevent an action potential
A gamma fibres are blocked first
Motor nerves less sensitive

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13
Q

Why are local anaesthetic techniques helpful?

A

pre-emptive anlgesia
Multi-modal analgesia (reduces dosing of other drugs)
Reduces central sensitisation
Reduced requirement for maintenance analgesia

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14
Q

What are the characteristics of an ester local anaesthetic block (Procaine)?

A

Short duration

rapidly metabolised by plasma cholinesterases

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15
Q

What are the characteristics of an amide local anaesthetic drug?

A

Lidocaine bupivicaine
Liver metabolised
Longer duration of action

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16
Q

What does the addition of adrenaline with a local anaesthetic block cause?

A

Vasconstriction of blood vessels in the area
Prolonged onset of action
Prolonged duration

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17
Q

List the onset of action, the duration of action and the toxicity of lidocain

A

5-10 minutes
1.5-2 hours
Fairly toxic
Can be given intravenously

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18
Q

List the onset of action, the duration of action and the toxicity of bupivicaine

A 
20-30 minutes 
6-8 hours 
Cannot be given intravenously 
Good motor and sensory nerve separation
Greater potential for cardiotoxicity
19
Q

List the onset of action, the duration of action and the toxicity of Mepivicaine

A

slightly less toxic than lidocaine
useful in equine lameness diagnosis (less post-injection odema)
Longer duration of action 2-3 hours

20
Q

What does systemic toxicity depend on?

A 
Site of injection 
-vascualr sites lead to rapd absorption greater peak in plasma concentration 
-reduce dose at area high vascularity 
Drug used 
-Bupivicaine causes cardiotoxicity
Speed of injection 
-only when giving iv
Addition of adrenaline
-local vascoconstriction
21
Q

What cardiovascular effects can be caused by the administration of local anaesthetics?

A 
hypertension 
tachycardia 
hypotension 
bradycardia 
cardiovascular collapse
22
Q

What are the CNS effects caused by the administration of local anaesthetic technique?

A 
Excitation followed by depression 
agitation 
shivering 
seizures 
depression
23
Q

What are the local toxicity effects caused by the administration of local anaesthetics?

A

Haematoma (if needle penetrates blood vessel)
Nerve damage
Vasodilation

24
Q

How can you reduce the risk on complications?

A 
Small needle 
Dilute preparation 0.9% saline 
Draw back before administering 
Use appropriately sized syringe 
Calculate the safe maximal dose
25
Q

What are the different characteristics of topical local anaesthetics, where can they be used and how are they applied?

A

Lidocaine is absorbed better than bupivicaine
cornea
Larynx
nasal passages
Skin
must be applied to the skin for 30-60 minutes underneath a dressing

26
Q

How can you administer a local anaesthetic to the larynx if intubeaze is unavailable?

A

Drops of lidocaine onto the larynx

0.2-0.3ml

27
Q

What local anaesthetic is mostly used for ocular surgery?

A

Procaine
Must be kept in the fridge
quick onset short duration of action
10-10mins

28
Q

What can infiltration anaesthesia be used for?

A

close wounds
remove small growths
take biopsies

29
Q

What dose can you use for infiltration anaesthesia and what considerations must you make?

A

5-10mg/kg dogs
less than 6mg/kg in cats
dilute with 0.9% saline
reduce by 30-40% in sick animals

30
Q

How is a testicular skin block preformed?

A 
2mg/kg of lidocaine 
Divided between each testicle 
Inject until the testicle swells slightly 
or 
1mg/kg along the incision line
31
Q

What is the dose for a mid-line incision local infiltration of anaesthetic?

A

1-2mg/kg

32
Q

When can interpleural Local Anaesthetics be used?

A 
Thoractomy 
chest drains 
Rib trauma
Bupivicaine 1mg/kg, always dilute 0.9% saline 
cat- total voulme 5ml each side
dog- 20kg 10ml each side 
Give first dose whilst anaesthetised 
Systemic analgesia 
Painful to inject
Repeat every 8 hours
33
Q

What other blocks can be preformed?

A

Digital nerve block
ring block (distal limb procedures)
Local infiltration around soft tissue lumps for removal

34
Q

Why should dental blocks be used?

A

Dental procedures painful
will reduce maintenance of anaesthesia
improve pain management (up to 6 hours)
Improve speed of recovery

35
Q

How do you preform an infraorbital nerve block and what tissues does it block?

A 
Incisor, canine and premolar teeth 
nasal and buccal soft tissue
Cranial
-Don't insert needle deeply into canal 
-Elevate head slightly after injection 
Caudal
-tissues rostral to the 1st molar
-insert needle gently into the canal
-apply pressure after injection
-elevate head 
Care in cats and brachycephallic dogs canal is short
36
Q

What does a maxillary nerve block do and how is it preformed?

A

Bone of the maxilla, soft and hard palates
soft tissues of the upper nose and lip
insert needle at the v notch just medial to the fourth maxillary premolar

37
Q

What are the risks of a maxillary nerve block in cats?

A

Globe penetration due to the proximity of the ventral orbit to the tooth roots of the maxillary 4th premolar and the 1st molar
Blocking the infra-orbital nerve as it exits the infra-orbital canal is recommended

38
Q

Describe what the infraorbital nerve block within the canal does

A

ipsilateral maxillay 2nd, 3rd and 4th premolar teeth
Canine and incisor teeth
soft issues of the skin, muzzle and upper lip

39
Q

How do you preform an infraorbital block?

A

Use a 1ml syringe attached to a 27g needle
palpate the infraoritbal foramen
Retract the lip dorsally
The needle is held parallel to the hard palate
Advanced caudoventrally towards the foramen
The bevel is faced towards the bone
Aspiration is preformed to ensure no blood is drawn back
Local anaesthetic agent is slowly injected

40
Q

What does the middle metal nerve block effect?

A

Ipsilaters canine and incisor teeth

Bone and soft tissue rostral to the 2nd mandibular premolar

41
Q

How should you preform a middle mental nerve bloc?

A

Inject into the canal slowly can be painful

Apply digital pressure afterwards

42
Q

How do you preform a mandibular nerve block?

A

Cannot enter the foramen directly
aim to block the nerve before it enters the canal
(may block inguinal never care in recovery)
Sedate animal

43
Q

What drugs can you use for dental nerve blocks?

A

Lidocaine 2hours
Mepivicaine 2-3 hours
bupivicaine 6 hours

44
Q

How much of the local anaesthetic drug should you administer in a dental block?

A

0.1-0.5ml dogs
0.1-0.3 cats
Small needles (23g-27g)

Surgical Nursing (24 decks)

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