Week 1 Lecture Flashcards
What is an Axolemma?
Cell membrane of an axon.
What is an Axon?
An extension of a centrally located neuron, is the functional unit of peripheral nerves.
What is axoplasma?
Intracellular contents of the axon.
What are the MAJOR components of an axon?
Axoplasm and axolemma.
What are Schwann cells?
Surround, support, and insulate each axon.
What are nodes of Ranvier?
Small segments of nerve that do not contain myelin.
Have limited diffusion barriers for drugs to penetrate.
Therefore - may be primary site for LA’s to exert action.
What are fasciculi?
bundles of axons.
What is saltatory conduction?
This phenomenon significantly facilitates conduction speed along the axon, through large numbers of sodium channels which can generate an intense action potential to jump from node to node.
(it is the movement of an ation potential along the axon from one node of Ranvier to the next node. This increases the conduction velocity without needing to increase the diameter of an axon)
What is the endonerium?
collagenous tissue which surrounds and imbeds axons within the fasciculi (innermost layer of nerve fiber).
What is the perineurium?
Binds fascicles together (middle layer).
What is the epineurium?
Connective tissue that SURROUNDS the perineurium and holds the fascicles together. (outer-most layer) ex: if you inadvertently inject LA directly into this layer, you’ll have prolonged “block” for 3 to 6 months.
What 3 connected layers must LA’s diffuse through to exert pharmacologic action?
- Epineurium
- Perineurium
- Endoneurium
What determines the LA as an ester or amide?
The intermediate chain
What functional state of the sodium channel does an LA exert its action?
Inactive state
Lipid solubility directly correlates to what?
LA Potency
Protein binding directly correlates to what?
LA duration
What is the resting membrane potential?
The voltage difference across the neuronal membrane (-70 to -90 mV)
What is the function of Epi in administration with an LA?
Decreases total required LA dose, decreases uptake, increases duration of action, minimizes bleeding, serves as a MARKER for intravascular injection.
How can you tell difference between an ester and amides?
Two ii’s (and intermediate chain of course)
Which is more cardiotoxic, bupivacaine or ropivacaine?
Bupivacaine
Onset of action directly correlates to what?
LA Ionization
What 3 LA’s produce vasoconstriction?
Cocaine, Lidocaine, and Ropivacaine
What are the only PARENTALLY administered LA’s with vasoconstrictive properties?
Ropivacaine and Lidocaine - hence longer duration of action and lower incidence of LAST.
In Time I Can Please Everyone But Susie & Sally
I - IV T - Tracheal I - Intercostal C - Caudal P - Paracervical E - Epidural B - Brachial Plexus S - Subarachnoid, sciatic, femoral S - Subcutaneous
Give an example of tumescent LA administration.
Liposuction
Acid + Acid = ?
Base + Base = ?
more nonionized or un-ionized
Base + Acid = ?
More ionized
Will an induction with sodium thiopental be faster if the patient is acidotic or alkalotic?
Faster
Mixing a weak acid with a low pH solution may lead to what?
The formation of precipitate (phenergan and toridal).
The ____ the fetal pH, the ____ the amount of LA in the ionized form in the fetus.
Lower, greater (the greater the ion trapping)
Ester’s are derivatives of what acids?
Benzoic acid.
How does cocaine differ from other anesthetics?
Causes vasoconstriction and it is only given topically.
Is normal Hgb in Fe++ or Fe+++? Why does it matter?
Fe++. Fe+++ is methemoglobin and will not release O2, therefore hypoxia can occur
What is PABA?
Para aminobenzoic acid - preservative of the ester.
Which of the following determines the peak plasma concentration? Total dose, volume, or concentration?
Total dose
Tissue sites with an increased blood flow will do what to absorption?
Increases it.
Lidocaine plasma concentration clinical signs at 0 - 5 mcg/ml?
Lightheadedness, tinnitus, circumoral and tongue numbness.
Lidocaine plasma concentration clinical signs at 5 - 10 mcg/ml?
Visual disturbances & muscular twitching
Lidocaine plasma concentration clinical signs 10 - 15 mcg/ml?
muscular twitching, convulsions, and unconciousness
Lidocaine plasma concentration clinical signs at 15 - 20 mcg/ml?
Unconsciousness and Coma
Lidocaine plasma concentration clinical signs at 20 - 25 mcg/ml?
Coma, Respiratory depression, CVS depression
What is the preservative of Ester LAs?
PABA
What is the preservative of Amide LAs?
methyparaben
What causes methemoglobinemia?
the metabolite o-tuildine (produced what using prilocaine) which oxidizes hgb and Methgb, causing the patient to develop tissue hypoxia, acidosis, and a grayish-colored cyanosis.
What is the reversal and dose for methemoglobinemia?
Methylene blue, 1 mg/kg
What can aid in the prevention of LAST?
pre-treatment with benzodiazepines
What is used to treat LAST and what is the dosing?
Intralipid, Bolus 20% 1.5 ml/kg over 1 minute, continuous infusion of 0.25 ml/kg/min, double rate if BP returns but remains low. (must run for a minimum of 30 minutes)
Where do you NOT use Epi?
Fingers, nose, toes, hose
What group of people should we avoid using EMLA cream in?
< 12 months of age
EMLA is Lido and Prilocaine
Lidocaine (2345678)
Molecular weight: 234 g/mol, % protein bound: 56, pKa: 7.8
