General and Anatomy Flashcards
What do local anesthetics bind to? What does the binding do?
The bind to sodium channels in NERVES to BLOCK NERVE TRANSMISSION.
What is the difference between myelinated and non-myelinated?
with myelinated need to block ~3 nodes of Ranvier (longer with NON myelinated)
Spinal/epidural anesthesia, which is easiest to block?
sympathectomy (B)>sensory (pain)>motor (MOST challenging to block)
Electrophysiology of Nerve conduction
- AP activates voltage gated sodium channels..more depolarization
- voltage fated sodium channels: M (activated) and H (INactivated)…3 distinct states of channel
What type of voltage gated sodium channels do LA bind ti?
Preferentially to inactivated and open states…freqeuncy dependent blockade
What is the frequency dependent blockade theory
In very active nerves, lots of opening and closing will be more quickly blocked (LA is not going thru the channel)
Ester Drugs
Cocaine
Procaine
Tetracaine
Benzocaine
Amides
Lidocaine Mepivacaine Bupivicaine Levobupivacaine Ropivacaine
PK/PD of LA: Where does binding occur?
On the cytoplasmic (inside) side of the receptor
UNcharged vs. Charged
UN-cross
Charged-ACTIVE
need an equilibrium
pH and pKa
Artificially raise the pH of the solution can generate more UNCHARGED LA molecules to drive them across to the inside of the cell more quickly. SODIUM BICARB can help SPEED UP the onset of the block.
Lipid solubility
PRIMARY determinant of potency. more lipophilic=give LESS of the LA, can cross membrane easier.
Protein Binding
LOCAL TISSUE PROTEINS that LA can bind to and creat a sink of LA that can be slowly released to the nerve (NOT talking about albumin). Bind protein longer=will last longer
Clinical uses for LA
- IV; arrythmias Beir block
- Epidural
- Caudal
- Intrathecal (spinal)
- peripheral Nerve (brachial plexus, sciatic, femoral)
- SQ
- Topical
We usually dont want LA in vascular space, what is the one exception?
LIDOCAINE in lower doses can treat arrythmias, causes toxicity if given too much.
