Large Animal Loco-Regional Anaesthesia Flashcards
What different drugs can be used in loco-regional anaethesia ?
- Local anaestheticsq
- Opioids
- Alpha 2 agonists
Wha relevance of ionisation of tissue when admin of local?
how quick they bind depends on pH of drug/tissue
if pKa lower than 8.9 -> long time to action
What determinants of duration of action ?
- Protein Binding
- Vasomotor Activity
Explain protein binding?
Inc protein binding -> slower systemic uptake -> longer duration of action
Vasomotor Activity - explain
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
Describe toxicity with increasing dose of local?
which local in what species?
When would we use opioids?
Morphine (horses only)
- Epidural
- Intra-articular
Use of alpha 2 as local?
Xylazine or detomidine
What types of loco-regional anaesthetics ?
Topical
Local - around nerve or as a ring block/perinural
Regional - admin distant from surgical site creating whole anaesthetised region
What locations to consider in equine head ?
What locations in ruminants?
What Local areas for dehorning?
Castrate block?
Intra-testicular black
What is an example of regional block?
Epidural
What potential complications with epidural?
Inadvertent Intra-thecal Injection
Hypotension
Motor Block
Urinary Retention (morphine)
Neurological Injury
Drugs (e.g. preservatives, adrenalin)
Infection, Haematoma, Trauma
Where do we admin epidurals in ruminants?
Intracoccygeal epidural
Cattle and small ruminants
Co1-Co2
What doses for intraoccygeal epidural?
Procaine 4 ml
Xylazine 1 ml
Horse epidural location?
Co1 - Co2
Horse Epidural doses?
What other region for epidural?
Lumbosacral epidural L6-S1
Doses for lumbosacral epidural ?
1ml/4.5kg BW
15ml for 70kg sheep
Forelimb infiltrative nerve blocks?
Hindlimb infiltrative nerve blocks ?
Describe IV regional anaesthesia / Bier Block
- 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
Technique for retrobulbar block ?
- 1 or 4 point technique
- Inset needle percutaneously through eyelid, through conjunctiva or 3rd eyelid
- 4-6” needle
- 10-15ml procaine 5% + epinephrine
Potential Complications - Retrobulbar block?
- Globe Puncture
- Increased IOP
- Retrobulbar Haemorrhage
- Subarachnoid Injection
- Optic Nerve Trauma
- Occulocardiac Reflex
Anatomy landmarks for petersons block
Technique for Peterson’s block?
- 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
Potential complications of Peterson’s block
- 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
What techniques in order of increasing complexity can we do for a flank laparotomy?
Line block advantages?
Line Block Disadvantages?
What does an inverted L block look like?
Advantages of inverted L block?
- Limited anatomical knowledge
- Local proximal to surgery site
- Easy to extend if block fails
- Some Muscle relaxation
Disadvantages of inverted L block?
- Large volume of local
- Time consuming
What does a paravertebral block look like?;
Liverpool technique for proximal paravertebral block?
Cambridge technique for Proximal vertebral block?
Advantages of paravertebral block?
Local distal to surgery site
Small volume of local
Good muscle relaxation
Reliably anaesthetises all layers of
body wall
Disadvantages of paravertebral block?
Time consuming
Requires significant
anatomical knowledge
Difficult in well muscled and
fat individuals
Not easy to extend if fails
