Local Anaesthesia

Question 1

Why are Local Anasethetics considered to provide Total Analgesia?

Answer 1

Because they block the conduction of the Nociceptive impulses

Question 2

Why are LAs being increasingly used?

Answer 2

1. Because not only do they provide total analgesia
2. They can be used as part of a Multi-modal Approach

Question 3

Name the 3 Local Anaesthetic drugs!

Answer 3

1. Lignocaine
2. Bupivicaine
3. Mepivicaine

Question 4

What are the 3 forms of Lignocaine?

Answer 4

1. Injection
2. Gel
3. Spray

Question 5

Out of these Local Anaesthetics, which provides the slowest onset of action?

A) Lignocaine
B) Bupivicaine
C) Mepivicaine

Answer 5

B) Bupivicaine

Question 6

Out of these Local Anaesthetics, which is used most commonly for Equine Nerve Blocks?

A) Lignocaine
B) Bupivicaine
C) Mepivicaine

Answer 6

C) Mepivicaine

Question 7

What are 6 risks associated with the use of LA’s?

Answer 7

1. If inj into nerve fibres > temp or premanent loss of function
2. Tissue irritation (Mepivicaine is least irritant)
3. Self mutilation from tingling, pain + irritation around area
4. Allergic reactions
5. Systemic toxicity (Care high ax w/IV, excitability, inc rate + force of contractions, convulsions etc)
6. Hypotension (Esp post-epidural)

Question 8

Name 4 Topical LA routes

Answer 8

1. MMs
2. Ocular
3. Nasal
4. Layrngeal

Question 9

Is transdermal topical anaesthesia less reliable?

Answer 9

Yes

Question 10

Give 2 examples of Topical anaesthesia

Answer 10

1. Ocular drops of Corneal debridement
2. Spray/gel for intubation, to avoid layrngospasm

Question 11

Give 2 disadvantages of Topical ana

Answer 11

1. Only superficical analgesia = 1-2 mm
2. Absorption varies, so effectiveness if variable

Question 12

Why shouldn’t Local anaesthetics containing Epinephrine be used, under ANY circumstances?

Answer 12

• Because they impair tissue + healing
  AND
• Extreme care must be taken in patients with Cardiac disease

Question 13

What is Regional analgesia?

Answer 13

Use of LA into a MAJOR NERVE PLEXUS or close proximity for the spinal cord

Question 14

1x E + 6 b’s…

Name 6 regional analgesia techniques

Answer 14

1. Epidural
2. Spinal block
3. Limb block
4. Digital nerve blocks
5. Paravertebral blocks
6. Mandibular + Maxillary nerve blocks

Question 15

What can be used to assist when administering regional analgesia/nerve blocks?

Answer 15

Peripheral nerve stimulator

Question 16

What is an Epidural?

Answer 16

1. Inj LA into epidural space
2. L7 (Dogs) - S1 (Cats)
3. Allowing drug to circulate between vertebrae + dura mater

Question 17

When are Epidurals commonly performed?

Answer 17

1. Tail surgery
2. Orthopaedic surgery in Hindlimbs

Question 18

What is Spinal anaesthesia?

Answer 18

1. LA inj into dura mater or Subarachnoid space
2. Allow to mix w/CSF

Question 19

Give 3 Advantages + 4 Disadvantages for Spinal anaesthesia

Answer 19

Advantages
1. Densensitizes a wide surgical field
2. Fast onset of ana
3. Lower doses req

Disadvantages
1. Req technical skill + anatomical knowledge
2. Risk of iatrogenic damage to nerve tissue
3. Irritation to surrounding tissues from ana agents
4. Can’t be used in Hypotensive px’s

Question 20

What are Splash blocks?

Answer 20

1. Directly applying LA solution to area
2. By dripping agent from syringe onto exposed tissues
3. Such as; the body wall, during Laparotomy closure

Question 21

What are the 2 reasons for adding Epinephrine to LAs?

Answer 21

1. Desire for vasoconstriction of BVs, to decrease the rate of drug absorption»_space; prolonging the effect of LA
2. Vasconstriction reduces concentration of LA entering circulation»_space; reducing toxcity of drug

Question 22

What is the duration of LA dependent on?

Answer 22

The rate of absorption by the local blood vessels

Question 23

What ratio can Epinephrine be added to Lignocaine at?

Answer 23

1: 200000 solution

Question 24

What are the difference between a Nerve + Line block?

Answer 24

Nerve blocks
1. Inj LA close to nerve, to desensitise target area
2. Need to know location of nerve

Line blocks
1. Inj of a continuous line of LA into SC or Subcuticular tissues, close to target area
2. Insert needles along line of infiltration + gradually withdraw needle, while injecting a small ax

Question 25

What is Local **Infiltration**?

Answer 25

1. LA **infiltrated close** to a **nerve** 2. ***Intradermally***, **SC** or ***between muscles*** 3. Used for ***superficial tissue surgery*** (***Removal** of small **tumours*** or ***repair** of minor **lacerations***)

Question 26

Provide 2 examples of when Local Infiltraiton can be used

Answer 26

1. Removal of small tumours 2. Repair of minor lacerations

Question 27

List the **6** steps to provide Local **Infiltration**

Answer 27

1. **Clip** area to be treated 2. Aseptically **prepare** area 3. Use small guage needle (**23-25G**) to ***prevent tissue damage*** 4. **Inject** small amount (**0.5-1ml** usually) 5. Onset of action usually within **3-5 mins** 6. **Test effectiveness** of block by **pricking** skin

Question 28

List the 3 methods of providing LA

Answer 28

1. Local **infiltration** (Inj) 2. **Regional** anaesthesia (block, epidural etc) 3. **Topical** admin (TMuscosal, TCutaneous)

Question 29

When is EMLA cream most commonly used?

Answer 29

To catheterise Rabbit's ears!

Question 30

Name the 5 LAs

Answer 30

1. Lignocaine (lidocaine) 2. Bupivicaine 3. Mepivicaine 4. **Benzocaine** 5. **Amethocaine**

Question 31

True or False. Local anaesthetics do not normally affect the brain so have little sedative effects.

Answer 31

True

Question 32

True or False. When used incorrectly local anaesthetics have relatively few effects on the cardiovascular and respiratory system.

Answer 32

False. When used **correctly** local anaesthetics have relatively few effects on the cardiovascular and respiratory system.

Question 33

True or False. LA should be used w/**caution IV**, as most are unsuitable for use by this route + **easy** to **overdose**, leading to **Bradycardia** + **Cardiac arrest**.

Answer 33

True

Question 34

True or False. Local anaesthetics can be delivered as **targeted nerve blocks** to **enhance** a **multi-modal analgesic** approach.

Answer 34

True

Question 35

True or False. Local anaesthesia may be **safer** as well as **more economical** + lead to **quicker recovery**.

Answer 35

True

Question 36

Is it true that **pre-emptive LA** for patient's undergoing GA, will **reduce** the **ax** of **GA req**, **minimising** the **risk** of ***Cardiopulmonary depression*** that accompanies GA?

Answer 36

True

Question 37

What are Local Anaesthetics?

Answer 37

1. Substances applied locally **around** ***nerve fibres*** 1. To ***reversibly*** **block** ***conduction*** along the fibres

Question 38

True or False. The term local anaesthetic is **misleading** as they do **not** technically **produce** ***anaesthesia***. They should be termed local **analgesics**.

Answer 38

True!

Question 39

How do LAs work?

Answer 39

1. They **block** the **Sodium channels** ***at*** **nerve endings** 2. **Interrupting conduction** of nerve **impulses** 3. They can **block all types** of **fibres** (Sensory + Motor) 4. However, **sensory** neurons are **more sensitive** to their effects

Question 40

In what order do sensations **disappear**, when using LAs?

Answer 40

1. **Pain** 2. Cold 3. **Warmth** 4. Touch 5. **Pressure**

Question 41

In what order do sensations **appear**, when using LAs?

Answer 41

1. Pressure 2. Touch 3. Warmth 4. Cold 5. Pain *(Reversal of the way they are lost)*

Question 42

True or False. Local anaesthetics are not absorbed well across intact skin and have to be infiltrated locally into the desired site of action. This is generally accompanied by injecting the agent into the tissue.

Answer 42

True

Question 43

True or False. If local anaesthetics reach the systemic circulation they penetrate well into the tissues including the PNS.

Answer 43

False. If local anaesthetics reach the **systemic circulation** they penetrate well into the tissues including the **C**NS.