LA Anaesthesia Flashcards
What are the types of drugs used in loco-regional anaesthesia?
- LA
- Opioids
- Alpha 2 agonists
LA stands for local anaesthetics.
What is the normal tissue pH and how does it change in inflamed tissue?
Normal tissue pH is 7.4; inflamed tissue pH is <7.
Why are local anaesthetics not effective in inflamed tissue?
Due to the lower pH in inflamed tissue.
How does the rate of systemic uptake influence the duration of action of local anaesthetics?
Related to the rate of systemic uptake.
How does protein binding affect the rate of systemic uptake of local anaesthetics?
Increased protein binding -> slower systemic uptake -> longer duration of action.
What is the effect of vasomotor activity on the rate of systemic uptake of local anaesthetics?
Most local anaesthetics cause vasodilation, leading to faster systemic uptake and shorter duration of action.
What is the effect of combining local anaesthetics with a vasoconstricting drug?
Vasoconstriction -> slower systemic uptake -> longer duration of action.
What neurological toxicities can local anaesthetics cause?
- Nausea
- Muscle Twitching
- Sedation
- Seizures
- Unconsciousness
- Respiratory Arrest
What cardiovascular toxicities can local anaesthetics cause?
- Cardiac Arrhythmia
- Cardiac Arrest
What opioids are used in large animals?
- Morphine (horses only)
- Epidural
- Intra-articular
What alpha 2 agonists are used in large animals?
- Xylazine
- Detomidine
What are the common features of loco-regional anaesthetic techniques?
- Topical – Anaesthetise tissue directly
- Local – Administered around nerve or as a ring block/perinural
- Regional – Administered distant from surgical site creating a whole anaesthetised region
What are the injection site locations of the mandible?
- Mandibular foramen
- Mental foramen
What are the local anaesthetic locations in the ruminant head for dehorning?
Specific anatomical locations not provided.
What are the local anaesthetic locations for castration?
Intra testicular.
What are examples of regional anaesthesia?
- Epidural
- Nerve blocks
- Retrobulbar block
- Peterson’s block
- Flank laparotomy blocks
What are potential complications of epidural anaesthesia?
- Inadvertent Intra-thecal Injection
- Hypotension
- Motor Block
- Urinary Retention (morphine)
- Neurological Injury
- Infection
- Haematoma
- Trauma
What types of surgeries require regional anaesthesia?
- Digital surgery
- Ocular surgery
- Flank laparotomy
Describe infiltrative anaesthesia - bier block.
- Good restraint essential
- Apply tourniquet
- Inject approx. 20ml procaine 4%
- Allow 10-15mins for full desensitization
- Allow min 20mins before removing tourniquet
- Cattle and horses tourniquet can be left on for up to 2hrs
- Provide good haemostasis
What is the technique for a retrobulbar block?
- 1 or 4 point technique
- Insert needle percutaneously through eyelid, through conjunctiva or 3rd eyelid
- 4-6” needle
- 10-15ml procaine 5% + epinephrine
What are potential complications of retrobulbar blocks?
- Globe Puncture
- Increased IOP
- Retrobulbar Haemorrhage
- Subarachnoid Injection
- Optic Nerve Trauma
- Occulocardiac Reflex
What is the Peterson’s block technique?
- Technically more difficult but less risky
- Depression where caudal rim of orbit meets the zygomatic arch: rostral to the coronoid process of the mandible
- 10cm needle aimed rostroventrally towards the point of the ‘cone’ made by the orbital contents
What are the advantages of line blocks?
- Simple
- Requires little anatomical knowledge
What are the disadvantages of line blocks?
- Large volume of local
- No muscle relaxation
- Distortion of surgical site
What are the advantages of inverted L blocks?
- Limited anatomical knowledge
- Local proximal to surgery site
- Easy to extend if block fails
- Some muscle relaxation
What are the disadvantages of inverted L blocks?
- Large volume of local
- Time consuming
What are the two techniques for proximal paravertebral block?
- Liverpool
- Cambridge
What are the types of paravertebral block?
- Proximal
- Distal
What are the advantages of paravertebral blocks?
- Local distal to surgery site
- Small volume of local
- Good muscle relaxation
- Reliably anaesthetises all layers of body wall
What are the disadvantages of paravertebral blocks?
- Time consuming
- Requires significant anatomical knowledge
- Difficult in well muscled and fat individuals
- Not easy to extend if fails
