Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
19 Cards in this Set
- Front
- Back
|
MOA of Local Anesthetics
|
Na+ channel has 3 subunits- alpha, B-1, B-2. alpha is req for activity and B anchor channel in membrane. ALPHA has 4 homnologous domains- form ion channel within membrane. as neuron depolarizes, each domain undergoes conformational change in sequence- causes channel to open. after opening-> channel enters INACTIVATED state-> densensitized.
LA- binds to open activvated state. (depolarized) and inactivated states rather than closed (resting) channels. Prolongs inactivated state. Decreases AP conduction. |
|
|
MOA of Local Anesthetics
|
-Cationic form has HIGHER affinity for R at intracellular side of NA channel. after passing thru neuronal membrane, non ionized, lipopohilci form will gain H+ and beome ionized form that binds to Na channel. Both ionized and non ionized forms contribute to LA effect
|
|
|
LA effects
|
threshold for excitation increases 2) impulse conduction decreases 3) rate of rise of AP decreases 4) AP amplitude decr 5) complete block of conduction- at high concentrations
|
|
|
Differential nerve block
|
small Nerve fibers are more susceptible than large nere fibers . smaller unmyelinated are more susceptible than myelinated . For myelinated- impulse conduction occurs at nodes of ranvier and 3 succssive nodes must be blocked to inhibit conduction.
|
|
|
Degree of block
|
ACTIVELY firing and repetively stimualted nerve is much more SENSITIVE to LA than resting nerve b) high frequency stimulation is blocked mroe readily than low frequency stimulation. Type C and type A-delta are blocked much more than Type A alpha
|
|
|
Cocaine exception and lidocaine exception
|
Cocaine cause intense CNS stimulation and euphorie by inhibiting NE and DA reuptake. Lidocaine may intitally cause drosiness and sedation
|
|
|
CNS side effects of all LA
|
in high conc can-> CNS stimulation- restlessness, dizziness, euphoria, tremor, convusions.-> resp depression and death. Blockade of central activity-> CNS depression and stimulation Tx: Diazepam- valum- IV for convulsions
|
|
|
CV side effects of all LA
|
can decrease electrical excitability, conduction rate, force of contraction of heart, may be used in certain cardiac arrhthmias- (e.g. lidocaine)- membrane stabilizing- quinidine like or LA effect ...arterioal dilation and hypotention (except for cocaine- sympathomimetic effects due to blockade of NE reuptake) - bradycardia, hypotension, heart block, shock , cardiac arrest- (BUPIvacaine- Cardiotoxic)
|
|
|
LA effects on exciteable tissues
|
Neuromuscular junction-> weakly blocked.
Autonomic ganglia-> blocked Smooth muscle-> relaxed |
|
|
Absorption of LA
|
Vasoconstrictor (Epi)-> decrease the rate of absoprtion by decreasing blood flow and increasing uptake by nerve. Application to mucosal surfaces-> very rapid and extensive absoprtion
|
|
|
Allergic rxns- LA
|
Estern type LA- contact dermatitis- rarely anaphylaxis- metabolized to PABA
|
|
|
Cocaine- MOA and SE
|
MOA: only LA with sympathomimetic effects- vasoconstrictiona nd tachycardia (fast HR). topically to decrease bleeding after nasal surg and inENT procedures. schedule II controlled substance- abuse potnetial
|
|
|
Procaine- MOA and Se
|
Amide-
low potency, short duration- 15-30 mins. give perenterally- metabolized to PABA. may cause allergic rxns |
|
|
Tetracaine- MOA and SE
|
potent LA, long duration of 203 hrs
used paraenterally for spinal AND, epidural anesthesia |
|
|
Benzocaine
|
Ester- OTC- topically as creammlotion, sunburn skin conditions. also in cough lozenges and spray to decreasing coughing
|
|
|
Lidocaine
|
AMIDE type LA- int duration- short duration procedures- anti-arythmic, can be in path, infiltration blocks. epidural and spinal anesethesia. antiarrythmic agent.
|
|
|
EMLA
|
mix of lidocaine and prilocaine- topically as cream- venipuncture, IV cannulation, dental procedures, in children
|
|
|
Prilocaine- SE
|
AMIDE type. 'Prilo does METH'- int duration- , can cause methemoglobinemia- metabolized to O-Toluidine that oxidizes Hb to MET-Hb, cyanosis, can cause decompoensation in pts with CV or pulmonary Ds, treated with IV Methylene blue . Topical and infiltration anesthesia.
|
|
|
Bupivacaine, Ropivacaine
|
Amides- potent, long duration of action. bupivacaine- obstretical anesthesia- cardiac depression and ventricular arrhythmia. Ropivacaine- newer drug- may cause fewer cardiac toxicity
|
