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rhodes 3a
local anesthetics
| Question | Answer |
|---|---|
| Definition of a local anesthetics | Drugs that block conduction in nerve tissue |
| What happens when the AP decreases? | It causes neuron to go quiet |
| What can you manipulate with drugs? | receptor action |
| What three post-synaptic receptors is research directed at? | NP (neuroreceptor peptide), NMDA, AMPA |
| What are the three noci receptors | Acid, Injury, heat |
| The nerve ending bears opioid receptors, what can they do? | Inhibit action potential generation. |
| what two channels are instumental in AP propagation | Na+ and K+ channels |
| Name a few properties of an ideal local anesthetic | non-irritating, causes no perm. damage, low syst. toxicity, works topically and injection, short latency, good doa, h2o soluble, stable in solution |
| name 2 chemical classes for local anesthetics | esters, amides |
| What's a suffix for local anethetics? | "caine" |
| name 3 esters and their doa | PROCAINE (novocaine) - short; BENZOCAINE - Medium; TETRACAINE - long |
| most local anesthetics are (chemically) what with pKa's around what number? | weak bases - pKa 8-9 |
| Although usually a pingpong match bt ionized and nonionized; what is the predominant form and what's the pH? | Ionized (7.4) |
| The ionized form is most active where? | Receptor site |
| Why's the nonionized form important? | for penetratoin fo biological membranes |
| What kind of bonds are best for binding? | Ionic bonds at receptor site |
| What can be added to the injection to decrease the onset of action time? | Bicarbonate |
| Systemic absorption is infl by 4 things: | Dose, site of inj., tissue blood flow, coadmin. of vasoconstrictors |
| Blood levels are dependent on what? | Site of injection |
| Name 5 sites of injection from highest blood levels (absorbtion site) to lowest | Intercostal>caudal>epidural>bracial>sciatic |
| Is the highest or lowest blood levels more basic? | The highest |
| Adding bicarb will do what? | Make it into more ionized form. |
| What happens when the drug's too ionized? | tissue acidosis |
| Would you want to manipulate drugs that had more or less absorbtion? | Less |
| PNEUMONIC: I.C.E.B.S | intercostal, caudal, epidural, bracial, sciatic |
| The MOA of local anesthetics: which neurons are affected first, which second? | small, unmyelinated>myelinated |
| What's the critical length? | 2-3 nodes of ranvier |
| why the critical length? | by blocking <3, the AP will continue to skip along |
| what's affected more, resting neurons or rapidly firing? | rapidly firing |
| Fiber type A has 4 subunits: 1. what are they 2. function 3. neuron diameter 4. sensitivity to block | Alpha {lrg, +}:proprioception & motor - Beta {lrg, ++}: Touch, pressure - Gamma {lrg, ++}: Mscle spindles - Delta {lrg, +++}: Pain, temp |
| Fiber type B: 1. Function, diameter, sensitivity to block? | 1. Preganglionic autonomic 2. small 3. ++++ |
| Name the two categories of fiber type C 2. diameter 3. sensitivity to block | Doral root: pain {very small, ++++}; Sympathetic: postganglionic {very small, ++++} |
| Name the 3 MOA of Local Anesthetics: | 1. Conduction blockade of nerve cells (volt sens. Na+ channels) 2. Incr. threshold for electrical stimuli 3. Decrease AP amplitude & rate |
| ADVERSE EFFECTS: CNS - name 2 early signs, name 4 other things that could happen | EARLY: circumoral and tongue numbness/metallic tast - STIMULATION then depression - restlessness, tremors, convulsions (premed w/ benzo can prevent this) |
| What's GABA have to do with it? | When things get out of control, GABA's there (it's the breaking mechanism) |
| 4 CVS adverse effects are? | depression of the myocardium - arrhythmias - arteriolor dilation {decr in sym., incr in parasym} (except cocaine causes constriction - bupivacaine - asso. w/ cardia arrest/death laboring women |
| Are there more allergic reactions in esters or amides? | esters |
| Hematological: When you give large doses of PRILOCAINE, what happens and what can you give to fix it? | Increases metabolite toluidine which converts hg to methemoglobin (oxidized) - it can't carry O2 the same way. FIX: methylene blue or Vit C |
| Name 7 types of block | surface (eye, nose, throat) - Infiltration ({wounds/burns} dir into tissue - pH driven) - block (nerve trunks {paravertebral} - spinal (subaracnoid/CSF) - epidural (epi space below L2) - caudal (epi space) - bier block (IV regional) |
Created by:
kelbj819
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