CAL: Local Anaesthesia Flashcards
1
Q
What is a local anaesthetic?
A
drug that reversibly blocks Na channels preventing transmission of action potentials along an exon
- unionized lipid soluble drug passes through phospholipid membrane
- in axoplasm becomes ionised and binds to internal structure of Na channel preventing it leaving the inactive state
2
Q
What is the degree of blockade proportional to clinically?
A
- rate of stimulation (“frequency dependence”)
- local anesthetic attracted to open sodium channels
= inhibition of Na influx
3
Q
What effects do local anaesthetics have on the vasculature (generally)
A
- vasodilation @ low concentration(prilocaine>lidocaine>bupivacaine>ropivicaine)
- vasoconstriction @ high concentration
> cocaine solely vasoconstrictor (inhibits neuronal uptake of catecholamines and inhibits MAO)
> procaine and lidocaine mainly -> vasodilation - so give + adrenaline to ^ doa and v systemic absorption
4
Q
Which local anaesthetic is the only one lic in FPA?
A
Procaine
5
Q
What advantage does ropivacaine have over bupivacaine?
A
- less cardiac toxicity
- bupivacaine dissociates v slowly from NA channels, so may -> persistne cardiac depression, ventricular arrrythmias and VF
- lifethreatening arrhythmias may also be d/t Ca and K channel disruption
- ropivicaine dissociates more quickly from cardiac Na channels -> less myocardial depression, but has slightly shorter doa and potency so needs ^ dose for equivalent block
6
Q
Which block would be best for removing a lower canine under GA?
A
Mandibular n. block w/ lidocaine
7
Q
Contraindications for epidural anaesthesia
A
- infection @ injection site
- coagulopathy
- spinal/pelvic deformity
- bacteraemia/sepsis
- raised ICP
8
Q
What are the 5 landmarks needed for performing a brachial plexus block int he dog?
A
- jugular v.
- cranial border greater tubercle
- acromion process
- first rib
- location of brachial plexus (ventral border of scalenus muscle, just cranial to first rib)
