Term
| central blocks include what three kinds |
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Definition
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Term
| definition of local anesthetics |
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Definition
| drugs used to produce reversible conduction blockade of impulses along central and peripheral nerve pathways |
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Term
| today's LA are descendents of cocain which is? |
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Definition
| poorly water soluble, weak base, benzoic acid derivative joined by an ester linkage to a tertiary amine |
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Term
| synthetic LA derivatives possess same three essential functional units... which are |
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Definition
Hydrophilic chain (tertiary amine)
Joined to
Lipophilic portion (aromatic ring)
By
An ester or amide linkage (hydrocarbon chain) |
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Term
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Definition
Esters:
Are less stable (shorter shelf life)
Metabolized in the plasma by pseudocholinesterases (not ACHE)
More prone to cause allergic reactions |
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Term
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Definition
| more stable, metabolized by liver, rare allergies |
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Term
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Definition
| commercially prepared as water soluble HCL salts-- this makes them acidic with ph range of 4-7. |
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Term
| Why is NAHCO3 added to LA |
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Definition
| to hasten (speed up) the onset |
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Term
| What is the specific receptor for LA |
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Definition
| sodium channel - alpha-subunit |
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Term
| T/F there is more affinity for LA;s in open and inactivated states then resting state |
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Definition
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Term
| What is the minimum concentration CM of LA |
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Definition
| the min amt of drug needed to produce a block |
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Term
| To successfully block myelinated fibers; LA’s must generally inhibit ___ successive nodes of ranvier |
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Definition
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Term
| frequency dependent blockade or use dependence is |
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Definition
| the more action potential that occur the more likely the local will encounter the sodium channel in the open or inactive state |
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Term
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Definition
| motor efferent conduction- A fibers are all myelinated |
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Term
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Definition
| innervate sketetal muscle motor/ proprioception |
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Term
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Definition
| sensations of touch/ pressure |
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Term
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Definition
| skeletal muscles for muscle tone |
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Term
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Definition
| sensation of pain (1st; fast), temp, touch |
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Term
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Definition
| preganglionic autonomic nerve fibers, myleinated, frequently firing |
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Term
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Definition
| pain (slow, second pain, dull, ache) reflex response, postganglionic autonomic, unmyelinated small fibers |
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Term
| are A delta and C fibers blocked by the same concentration of local |
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Definition
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Term
| which fibers are blocked first |
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Definition
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Term
| what is the order of nerve block recovery |
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Definition
A-alpha
A-beta
A-gamma
C and A-delta
Beta |
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Term
| what is the clinical sequence of blockade |
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Definition
Phenomena of differential blockade
S T P T P M V P
Sympathetic
Temperature
Pain
Touch
Pressure
Motor
Vibration
Proprioception |
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Term
| lipid solubility is related to |
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Definition
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Term
| protein binding is related to |
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Definition
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Term
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Definition
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Term
| epinephrine does what to LA |
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Definition
Epinephrine
Makes more acidic; increases shelf life- prolongs the duration of action
Decreases blood flow to area thus less taken up in blood and carried away; also increasing time fibers are exposed to increased concentrations (incr. block)
Now also thought to exert presynaptic adrenergic receptor activity that contributes to analgesia |
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Term
| sodium bicarbonate is used to |
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Definition
Sodium Bicarbonate
Used clinically to speed onset of block
Increases amount of “nonionized” form available to cross membrane
Inconsistent- more effective with acidic solution
May see more effect with epinephrine containing locals |
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Term
| alpha -2 adrenergic agonists are used with LA to |
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Definition
Alpha-2 adrenergic agonists
Most commonly clonidine
Used in central blockade
Enhances analgesia without opioid side effect profile
Binds to a-2 receptors on primary afferent fibers and several brainstem nuclei
Increases AcH and norepi in CSF and inhibits release of several neurotransmitters- that are responsible for nociception |
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Term
| order of more vascular injection sites for LA |
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Definition
Injection site:
Tissue blood flow: More vascular/ incr. absorption
IV
Intercostal
Tracheal
Caudal/paracervical
Epidural
Brachial plexus
Spinal
SubQ
****presence of epi will decrease absorption |
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Term
| what is the active metabolite of lidocaine |
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Definition
| mono ethyl glycine xylidide ( with liver disease > toxicity) |
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Term
| what is the metabolite of prilocaine |
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Definition
| ortho toluidine (converts HGB to meth hgb treatment is methylene blue 1-2mg/kg) |
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Term
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Definition
Locals readily cross the BBB
CNS toxicity can occur with direct IV injection or systemic absorption
S/S dose dependent
Vertigo/Lightheadedness
“Tinnitius” Visual/auditory disturbances
Circumoral numbness
Ominous feelings
Muscle twitching
Convulsions
unconsciousness
Coma
Resp collapse
CV collapse |
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Term
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Definition
Dependent on severity
Stop injection
Know s/s
Minor rx’s may be allowed to spont terminate
Maintain patent airway/O2
barbs/benzo’s- raise seizure threshold
Tx CV s/s
Initially excitation
Tachy, hypertension
Followed by depression
Decr CO, hypotension
Fluids, phenylephrine, ephedrine, norepi
Cardiac arrest
Amniodarone, vasopressin vs. epi and lidocaine
Increased resuscitation time |
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Term
| what is the dose for 20% intralipids for LA toxicity |
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Definition
Administer 1.5 mL/kg as an initial bolus; the bolus can be repeated 1- 2 times for persistent asystole.
Start an infusion at 0.25 mL/kg/min for 30-60 minutes; increase infusion rate up to 0.50 mL/kg/min for refractory hypotension |
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Term
| what is the local to which all others are compared |
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Definition
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Term
| where is pseudocholinesterase produced |
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Definition
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Term
| what is methemoglobinemia |
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Definition
| Methemoglobinemia: Normal hemoglobin has iron in the ferrous state (Fe++) Met-Hb has iron in the ferric state (Fe+++) O2 carrying capability is poor. Tx. Methylene blue 1-2mg/kg over 5 minutes. |
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Term
| what do perservatives in LA cause |
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Definition
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Term
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Definition
procaine max dose 12mg/kg 30-60 min
duration with epi 30-90 min |
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Term
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Definition
chloroprocaine max dose 12mg/kg 30-60 min
max dose with epi 14mg/kg 30-90 min |
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Term
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Definition
tetracaine max dose 3mg/kg 90-2.5 hrs
with epi 4-6 hrs |
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Term
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Definition
| 3mg/kg duration 30-60 min |
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Term
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Definition
xylocaine max dose 4mg/kg for 30-120 min
with epi 7mg/kg for 120-360 min |
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Term
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Definition
carbocaine max dose 4mg/kg for 45-90 min
max dose with epi 7mg/kg for 120-360 min |
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Term
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Definition
| max dose 3mg/kg for 90-240 min |
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Term
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Definition
marcaine max dose 2.5 mg/kg for 120-240 min
with epi 3.2mg/kg 180-420 min |
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Term
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Definition
duranest max dose 6mg/kg for 120-180 min
with epi- 8mg/kg for 180-420 |
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