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
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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
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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
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4
Q

Which local anaesthetic is the only one lic in FPA?

A

Procaine

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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
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6
Q

Which block would be best for removing a lower canine under GA?

A

Mandibular n. block w/ lidocaine

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7
Q

Contraindications for epidural anaesthesia

A
  • infection @ injection site
  • coagulopathy
  • spinal/pelvic deformity
  • bacteraemia/sepsis
  • raised ICP
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8
Q

What are the 5 landmarks needed for performing a brachial plexus block int he dog?

A
  1. jugular v.
  2. cranial border greater tubercle
  3. acromion process
  4. first rib
  5. location of brachial plexus (ventral border of scalenus muscle, just cranial to first rib)
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