Large Animal Loco-Regional Anaesthesia

Question 1

What different drugs can be used in loco-regional anaethesia ?

Answer 1

• Local anaestheticsq
• Opioids
• Alpha 2 agonists

Question 2

Wha relevance of ionisation of tissue when admin of local?

Answer 2

how quick they bind depends on pH of drug/tissue
if pKa lower than 8.9 -> long time to action

Question 3

What determinants of duration of action ?

Answer 3

• Protein Binding
• Vasomotor Activity

Question 4

Explain protein binding?

Answer 4

Inc protein binding -> slower systemic uptake -> longer duration of action

Question 5

Vasomotor Activity - explain

Answer 5

Most locals cause some vasoD (exception: cocaine, bupivacaine, ropivicaine)

Vasodilation -> faster systemic uptake -> shorter duration of action

by adding vasoconstriction drug (e.g.epinephrine) will last longer because of slower systemic uptake

Question 6

Describe toxicity with increasing dose of local?

Answer 6

Question 7

which local in what species?

Answer 7

Question 8

When would we use opioids?

Answer 8

Morphine (horses only)
- Epidural
- Intra-articular

Question 9

Use of alpha 2 as local?

Answer 9

Xylazine or detomidine

Question 10

What types of loco-regional anaesthetics ?

Answer 10

Topical
Local - around nerve or as a ring block/perinural
Regional - admin distant from surgical site creating whole anaesthetised region

Question 11

What locations to consider in equine head ?

Answer 11

Question 12

What locations in ruminants?

Answer 12

Question 13

What Local areas for dehorning?

Answer 13

Question 14

Castrate block?

Answer 14

Intra-testicular black

Question 15

What is an example of regional block?

Answer 15

Epidural

Question 16

What potential complications with epidural?

Answer 16

Inadvertent Intra-thecal Injection
Hypotension
Motor Block
Urinary Retention (morphine)
Neurological Injury
Drugs (e.g. preservatives, adrenalin)
Infection, Haematoma, Trauma

Question 17

Where do we admin epidurals in ruminants?

Answer 17

Intracoccygeal epidural
Cattle and small ruminants
Co1-Co2

Question 18

What doses for intraoccygeal epidural?

Answer 18

Procaine 4 ml
Xylazine 1 ml

Question 19

Horse epidural location?

Answer 19

Co1 - Co2

Question 20

Horse Epidural doses?

Answer 20

Question 21

What other region for epidural?

Answer 21

Lumbosacral epidural L6-S1

Question 22

Doses for lumbosacral epidural ?

Answer 22

1ml/4.5kg BW
15ml for 70kg sheep

Question 23

Forelimb infiltrative nerve blocks?

Answer 23

Question 24

Hindlimb infiltrative nerve blocks ?

Answer 24

Question 25

Describe IV regional anaesthesia / Bier Block

Answer 25

* Good restraint essential * Apply tourniquet * Inject approx. 20ml procaine 4% * Allow 10-15mins for full desensitization to occur * Allow min 20mins before removing tourniquet * Cattle and horses tourniquet can be left on for up to 2hrs * Provide good haemostasis

Question 26

Technique for retrobulbar block ?

Answer 26

* 1 or 4 point technique * Inset needle percutaneously through eyelid, through conjunctiva or 3rd eyelid * 4-6” needle * 10-15ml procaine 5% + epinephrine

Question 27

Potential Complications - Retrobulbar block?

Answer 27

* Globe Puncture * Increased IOP * Retrobulbar Haemorrhage * Subarachnoid Injection * Optic Nerve Trauma * Occulocardiac Reflex

Question 28

Anatomy landmarks for petersons block

Answer 28

Question 29

Technique for Peterson's block?

Answer 29

* Technically more difficult but less risky * Depression where caudal rim of orbit meets the zygomatic arch: rostral to the coronoid process of the mandable * 10cm needle aimed rostroventrally towards the point of the ‘cone’ made by the orbital contents

Question 30

Potential complications of Peterson's block

Answer 30

* Requires good knowledge of anatomy to reach correct site * IV injection * Blinking is prevented to eye vulnerable to dust/trauma * Keep out of bright light

Question 31

What techniques in order of increasing complexity can we do for a flank laparotomy?

Answer 31

Question 32

Line block advantages?

Answer 32

Question 33

Line Block Disadvantages?

Answer 33

Question 34

What does an inverted L block look like?

Answer 34

Question 35

Advantages of inverted L block?

Answer 35

* Limited anatomical knowledge * Local proximal to surgery site * Easy to extend if block fails * Some Muscle relaxation

Question 36

Disadvantages of inverted L block?

Answer 36

* Large volume of local * Time consuming

Question 37

What does a paravertebral block look like?;

Answer 37

Question 38

Liverpool technique for proximal paravertebral block?

Answer 38

Question 39

Cambridge technique for Proximal vertebral block?

Answer 39

Question 40

Advantages of paravertebral block?

Answer 40

Local distal to surgery site Small volume of local Good muscle relaxation Reliably anaesthetises all layers of body wall

Question 41

Disadvantages of paravertebral block?

Answer 41

Time consuming Requires significant anatomical knowledge Difficult in well muscled and fat individuals Not easy to extend if fails