Week 4 Locomotor 3/6/14 Flashcards
Properties of Lidocaine
Onset, Duration, Potency
Amide type local anaesthetic
Short OOA: 10-15 minutes
Duration of action: up to 2 hours
Why is Lidocaine often combined with adrenaline>
Lidocaine causes vasodilation therefore often formulated with adrenaline.
Why is Lidocaine not used in horses
Causes sub-cutaneous/ skin swellings.
Rarely used.
Procaine (properties, onset, duration, potency)
Ester local anaesthetic.
Onset: 15-20 minutes
Duration: short 45-60 minutes
Potency: Poor
Which is the only local anaesthetic licenced for food producing animals in the EU
Procaine (ester)
Which local anaesthetic is used for diagnostic equine nerve blocks
Mepivacaine (amide) short onset (10 minutes) Duration of action (2 hours) Good potency
Side effects of Bupivacaine
Amide.
Long onset (30-40 minutes)
High incidence of cardiotoxicity
Why are local anaesthetics conjugated to hydrocloride salts
Because local anesthetics are weak bases they need to be solubilised for injection by conjugating with a hydrochloride salt
How do local anaesthetics work?
Blocking sodium channels therefore preventing propagation of axonal action potentials
Speed of onset is related to the the dose/ proportion of the drug in the
Non-ionised lipid soluble form. Determined by the dissociation constant (pKa)
Which two local anaesthetics are used in EMLA cream
Prilocaine (lipid soluble –> high potency) and Lidocaine
Which is the preferred block used for digit amputation in cows
Intravenous Regional Analgesia (IVRA) or Bier’s block
Where is a caudal epidural anaesthesia most commonly performed in large animals? Why?
Injected in the sacro-coccygeal space. Between the first two coccygeal vertebrae.
It is used to prevent straining during parturition
COX-1 pathway is important for…..
Production of prostaglandins that are important in the physiological modulation of function.
- gut mucosal barrier
- intra-renal perfusion when RBF is reduced
When is COX-2 pathway activated?
- Tissue damage
- Bacterial lipopolysaccharide
COX-2 inhibition (Suppression of inflamm, pain, fever)- what additional benefits are there?
Slow progression of Alzheimers disease.
Preventative against colon, pancreas, lung and transitional cell carcinoma, melanoma.
3 types of NSAIDs
- Non-selective
- Preferential (10-40 x)
- Selective (>100x selective for COX-2)
Therapeutic aim for COX-2 inhibition
COX-2 >80% inhibition for part of the 24 h period
COX-1 < 20% inhibition to avoid side effects
4 examples of non-selective COX inhibitors
- Asprin
- Phenylbutazone
- Ketoprofen
- Tolfenamic acid
What type of NSAID is Phenylbutzaone?
Non-selective COX inhibitor
What type of NSAID is Meloxicam?
Meloxicam is a preferential COX-2 inhibitor
Example of selective COX-2 inhibitor
Firocoxib and Robenocoxib (Coxibs)
What are Coxibs?
Coxibs are selective inhibitors of COX-2. Firocoxib and Robenocoxib
What is Tepoxalin?
Dual inhibitor of COX and LOX.
Inhibits LOX for short periods during day.
Non selective inhibitor of COX-1 and COX-2
Species differences for Carprofen
CarprofenL DOGS: COX-2 preferential CAT: COX-2 preferential (longer halflife than dog!) HORSE: Non-selective MAN: COX-1 preferential
Why do you need to be careful with the carprofen dosing regime in cats?
Carprofen is COX-2 preferential in dogs and cats but has a much longer half life in cats.
Daily dosing = GI disaster
Pharmacokinetics of NSAIDs
Weak acids so readily penetrate inflammed tissue.
Highly protein bound therefore accumulates in protein-rich inflammatory exudate
How does Prostacycline and PGE2 maintain the protective layer of the gastric mucosa
- Inhibiting gastric acid secretion
- Maintaining mucosal blood flow
- Being involved in secretion and composition of muscos
- Intracellular messages for cell turnover
How do NSAIDs affect the liver?
NSAIDS undergo extensive hepatic metabolism. Care with hepatic disease
Canine Elbow Dysplasia more reproducible discomfort for OCD, MCD components of condition
Elbow Dysplasia: Ununited anconeal process, osteochondritis dissecans, fragmented medial cornoid process, elbow incongruity.
Suprination (external rotation) of antebrachium while elbow held in moderate flexion.
Ununited anconeal process (UAP) =
failure of union bnetween anconeus and main part of ulna BEYOND 20 WEEKS OF AGE. Anconeal process develops as part of ulnar diaphysis BUT Some breeds (e.g. GSD, anconeal process forms as secondary ossification centre) NORMAL <20 WEEKS!
Options for Cranial Cruicate Ligament rupture
Conservative <15kg
Surgery: Mimic ligament using Lateral suture
OR Modify stifle mechanics (TPLO/ TTA)
Difference between TPLO and TTA mechanisms
TPLO: Anterior cruciate ligament looses its main function because
TTA: Modifies position of patellar ligament. Articular weight bearing forces are PARALLEL TO PATELLAR LIGAMENT NOT longitudinal access of tibial.
SEE IPHONE PHOTOS FOR ARTICLE.
