Term
| What are the Local Anesthetics that are administered by injection? |
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Definition
Amide Type:
Lidocaine
Mepivacaine
Prilocaine
Bupivacaine
Ester-Type:
Procaine
Tetracaine |
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Term
| What Local anesthetics are for Topical use only? |
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Definition
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Term
| What is used as a Reversal Agent? |
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Definition
Phentolamine (Oraverse)
A-antagonist
Vasodilation |
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Term
| What are the characteristics of an ideal Local Anesthetic? |
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Definition
Lipophilic and Hydrophilic
Low Toxicity
Short onset time
Completely reversible effects
Active by topical, injection, inflitration routes |
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Term
| What is the mechanism of Local anesthetics? |
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Definition
| Block voltage gated Na Channels -> prevents neuronal membrane from reaching threshold for activation of ALL Na channels and developing an AP |
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Term
| What is the intended binding site of local anesthetics? |
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Definition
Inner surface of Na Channel
(must pass through lipid layer to reach hydrophilic area) |
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Term
| Do Local anesthetics have an effect on resting membrane potential? |
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Definition
| No, only on depolarization |
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Term
| What is Differential Blockade? |
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Definition
| Capacity fo block individual nerve fibers |
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Term
| For non-myelinated nerves, what is the zone of anesthesia? |
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Definition
| much smaller than myelinated, has to block small linear area of nerve |
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Term
| How do myelinated nerves need to be blocked? |
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Definition
| with sufficient amount of Anesthetic to Block 3 successive Nodes of Ranvier, otherwise charge will skip over to the next Node and keep going. |
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Term
| What 4 things effect the Differential Block of a nerve? |
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Definition
Fiber Diameter
Myelination
Position in Nerve Bundle
Nerve Activity |
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Term
| What effects the nerves ability to be hyper or hypo responive to the anesthetic when it is applied? |
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Definition
Nerve Activity
(increased by hyperkalemia, decreased by hypercalcemia) |
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Term
| Which types of fibers are blocked most easily? |
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Definition
| small diameter myelinated and non-myelinated fibers |
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Term
| Which Functions are blocked most easily? |
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Definition
Pain, Temperature, Touch Vasomotor, visceromotor, sudomotor, pilomotor
(Muscle tone, motor, and proprioception are carried on larger diameter fibers thus more difficult to block) |
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Term
| What fiber classification has no Myelin? |
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Definition
| C Fibers, Sympathetic and Dorsal Root |
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Term
| What size fibers have the highest sensitvity fo anesthesia? |
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Definition
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Term
| Where do local anesthetics work? |
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Definition
| action on nerve fiber itself, prevents conduction of impulse down fiber. |
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Term
| Why is the activity of the anesthetic dependent on the activity of the Na Channel? |
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Definition
| Local anesthetic must reach the binding site to have affect. |
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Term
| How does inflammation affect anesthetic uptake? |
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Definition
| Inflammation has a decreased tissue pH, causes ion trapping in extraneural space and prevents drug from being taken up across the nerve fiber. |
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Term
| How does local anesthetic work in nerve bundle nerve block? |
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Definition
diffuses down concentration gradient
Proximal -> Distal |
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Term
| How does a nerve bundle recover from a block? |
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Definition
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Term
| What part of the structure of the local anesthetic binds to the Na channel receptor? |
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Definition
Amine
(carries a positive charge) |
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Term
| If the local anesthetic has an i in the prefix, what type of anesthetic is it? |
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Definition
Amide
(and metabolized in the liver) |
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Term
| What type of metabolism do amides have? What can affect this? |
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Definition
Hepatic
Cardiovaxcular status, liver disease, toxemia of pregnancy, cimetidine, volatile anesthetics, Beta-Blockers |
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Term
| How are the metabolites of Amide anesthetics eliminated? |
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Definition
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Term
| Where are the esteras enzymes present to break down the Ester agents? |
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Definition
| Everywhere except the CS fluid |
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Term
| What can affect the Esterases activity? |
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Definition
Liver disease, pregnancy, chemotherapeutics
Atypical Enzyme activity |
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Term
| How are agents with ester structure ultimately eliminated? |
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Definition
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Term
| What are the ways in which a local anesthetic can spread in systematization? |
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Definition
Neuronal Blockade
Non-specific tissue binding
Blood Stream - systemic tissues or hepatic metabolism |
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Term
| What are the signs of minor toxicity? |
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Definition
| Ringing in ears, metallic taste, numbness of lips and tongue |
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Term
| How are seizures cause by systemic toxicity managed? |
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Definition
Protect Airway
Administer Diazepam
Succinylcholine may be needed for severe reaction |
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Term
| How can uptake of neuronal drugs be maximized and avoid systemic toxicity? |
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Definition
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Term
| How do vasoconstrictors aid local anesthetics? |
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Definition
Duration of blockade prolonged
Intensity of the blockade improved |
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Term
| What drug is approved as an agent to reverse the effets of local anesthesia by facilitating bloodflow in the anesthetized area? |
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Definition
Phentolamine
A-antagonist
Vasoconstrictor
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Term
| What are most adverse reacions of Local Anesthetics due to? |
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Definition
injection anxiety - Vagal effects
pallor, unrest, sweating, fatigue, palpitations, N/V |
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Term
| Topical anesthetics may react with what vasoconstrictor and cause toxic reactions in small children and with large doses? |
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Definition
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Term
How can Epinephrine effect certain pre-existing conditions?
1. Closed Angle Glucoma
2. Heart Failure
3. Coronary Heart Disease
4. Hypertension
5. Rhythm disturbance
6. Cerebrovascular disorders
7. Hyperthyroidism
8. Diabetes |
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Definition
1. Worsens condition
2. Acute decompensation, Cardiac Arrythmia
3. Angina, MI
4. Angina, MI, Stroke
5. Heart Failure, Ventricle Arrythmias
6. Stroke
7.Tachycardia, hypertension
8. Hyperglycemia |
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Term
| Why does Procaine have an increase chance of allergy? |
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Definition
| metabolite - para-aminobenzoic acid, well know allergen |
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Term
| If someone is allergic to an ester anesthetic, can they use an amide anesthetic? |
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Definition
| Yes, cross-sensitivity amongst but not between esters and amides |
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Term
| What type of preservatives may produce allergy? |
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Definition
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Term
| What is the short-acting Local anesthetics? |
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Definition
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Term
| What are the intermediate-acting local anesthetics? |
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Definition
Lidocaine
Prilocaine
Mepivacaine |
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Term
| What are the Long-acting Local anesthetics? |
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Definition
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Term
| Which local anesthetics have a Rapid onset? |
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Definition
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Term
| Which local anesthetics have a slow onset? |
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Definition
Procaine
Mepivacaine
Bupivacaine
Tetracaine |
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Term
| Which Local anesthetics have the greatest potency? |
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Definition
Long-Acting: (Potency of 16)
Bupivacaine
Tetracaine |
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Term
| How does lipid solubility correlate with the potency of an anesthetic? |
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Definition
| Greater lipid solubility enhances diffusion through neural coverings and membranes, allowing a lower mg dose. |
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Term
| What determines the portion of an administered dose that exists in the lipid-soluble state at a given pH? |
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Definition
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Term
| Agents that have a lower pKa allows what? |
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Definition
| treater proportion in the tertiary, diffusible state, Quicker Onset. |
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Term
| How does Chemical linkage correlate with metabolism? |
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Definition
Esters principally hydrolyzed in plasma by cholinesterases.
Amides transformed in liver |
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Term
| What prolongs the presence of the drug at the anesthetic site of action? |
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Definition
| affinity of the drug for the protein binding site at the Na channel |
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Term
| What is Methemoglobinemia? |
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Definition
Posioning of Hemoglobin so it can't carry oxygen
Life threatening in patients with cardiac or pulmonary disease.
Caused by Prilocaine and Benzocaine |
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Term
| What is the antidote for Methemoglobinemia? |
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Definition
| IV methylene blue or Ascorbic acid |
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Term
| What drug can be cardio toxic due to its very long duration? |
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Definition
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Term
| Why are the topical anesthetics only approved for topical use? |
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Definition
| poor aqueous solubility and/or undesirable toxicity |
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Term
| What are Benzocaine and Dyclonine used for? |
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Definition
Topically:
Mouth
Pharynx
Larynx
trachea
esophagus
urethra |
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Term
|
Definition
Eutectic Mixture of Local Anesthetics
Cream - 2.5% lidocaine and 2.5% prilocaine |
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Term
| What Topical Local anesthetic is widely used in pediatric emergency rooms? |
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Definition
| TAC (topical anesthesia through cut skin) |
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Term
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Definition
Topical Anesthesia through Cut skin
0.5% tetracaine, 1:2000 epinephrine, 10-11.8% cocaine
Used for Lacerations requiring stitches |
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Term
| How can Local anesthetic injection be less painful? |
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Definition
-use smaller needles
-inject into subcutaneous tissue
-Neutralize with NaHCO3, mix immediately before
-Solutions at Body Temperature |
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