Local Anesthetics Flashcards
LA MoA
- Block voltage gated Na channels
- Stop propogation of action potentials in axon fibers
- Un-ionized form can cross membrane
- LA are normally basic (pH 8-9)
- Inflammed tissue is acidic and ionizes LA
LA sensitivity to block
- More sensitive to LA
- Small diameter fibers
- Nociceptive fibers more than sensory input (touch/pressure, proprioception)
- Order of sensitivity to block most to least
- Small myelinated–> non-myelinated–> large myelinated
- So motor fibers are less affected than sensory
LA Unwanted Effects
- Block of Na in CNS
- confusion, agitation, convulsions, resp depression
- Block in heart
- Blocks AP conduction and myocardial contraction
- Most (not COCAINE) cause severe vasodilation and drop in BP
Lidocaine
Onset half life
found in 4
and even used in
Inherent
- rapid onset
- t 1/2 2 hrs
- Topical, transdermal, spray, injectable
- Used in IV for ventricular dysrhythmias
- inherent vasodilation properties
Mepvicaine
Onset
Less inherent
Similar to lidocaine
Less inherent vasodilation
Tetracaine
Onset
duration of action
less
Slower onset but longer duration of action than lido
Bupvicaine
Action
Commonly used with
Longer action
Commonly used in epidurals together with opioid
Cocaine
Dual action
- LA
- Catecholamine reuptake blocker
- epi and dopamine
- Sympathomimetic–> inc herat rate, vasoconstriction (HTN) inc body temp
- Does not cause vasodilation
GABA_A receptors and general anesthetics
- Most anesthetics potentiate GABA-A receptors
- Not ketamine, cyclopropane, xenon
- Barbituates inc the duration R stay open
- Benzodiazepines inc the number that open
- Two-pore domain K channels
- Volatile anesthetics potentiate these channels
- not activated by iv
- NMDA receptors
- N2O, ketamine block NMDA receptors
Gen Anesthesia involves 3 neurological changes
Unconciousness
Loss of response to stimuli
Loss of reflexes
Propofol
Type of anesthetic
used for
- General intravenous
- Induction anesthetic
- preferred induction agent
- rapid onset and recovery with little symptoms
Thiopental
Type
belongs to what class of drugs
solubility and metabolim
cqan cause
- Intravenous
- Induction
- Barbiturate
- High lipid solubility and slow metabolism
- can cause tissue necrosis
Etomidate
Type of anes for
can cause
IV
Induction
Adrenal steroid suppression
Midazolam
type for
belongs to what drug class
- IV
- Induction
- Benzodiazepines
Fentanyl
type
agonist of
useful as
- IV
- Highly potent opioid agonist
- Useful analgesic
Ketamine
type
onset
does not cause
- IV
- Slower onset
- Does not cause cardiovascular depression or resp supression
Inhalation Anesthetic Agents
Properties
- Small, lipophilic, can readily cross alveolar membranes
- Most are volatile liquids at room temp (except N2O)
- Used to maintain anesthesia
- Rapid induction and recovery
Nitrous Oxide
- Good analgesic properties but low potency as anesthetic
Isoflurane
Type
Currently the…
Can cause
- Inhalation
- Most widely used volatile anesthetic
- Hypotension
Halothane
Type
not used bc
Inhalation
not used bc of liver toxicity
