Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
34 Cards in this Set
- Front
- Back
|
what are local anesthetics?
|
Agents capable of producing a transient loss of sensation in a regionalized area of the body without producing a loss of consciousness.
|
|
|
what was the first local anesthetic ever used?
|
cocaine.
Cocaine is found in large amounts (0.6-1.8%) in the leaves of Erythroxylin Coca. 1859, Niemann isolated cocaine |
|
|
what did Von Anrep do?
|
observed that when cocaine was infiltrated SQ, skin
became insensitive to the prick of a pin |
|
|
who is Karl Koller?
|
Clinical introduction of cocaine (as a topical agent for eye
surgery) |
|
|
who is Halsted?
|
Clinical introduction of cocaine (e.g., regional anesthesia
|
|
|
what did Einhorn do?
|
started a search for a synthetic substitute for cocaine that led to the synthesis of procaine.
|
|
|
what did Loefgren do?
|
Synthesis of lidocaine
|
|
|
classification of local anesthetics?
|
Amides and Esters.
Amides: lidocaine mepivacaine prilocaine bupivacaine articaine Esters: Procaine Benzocaine tetracaine propoxycaine **tip to remembering which is which: Amide class has an -i before the -caine ending** |
|
|
local anesthetics mode of action?
|
Action potential generation requires an increase in membrane permeability to Na+ ions.
The blockade of the Na+ conductance is the basis of local anesthetic action. |
|
|
What occurs as the local anesthetic action progressively develops in a nerve?
|
a) the threshold for electrical excitability declines.
b) impulse conduction slows c) the safety factor for conduction decreases ** these lead to a decrease in the probability of propagation of the Action potential and the nerve conduction fails. |
|
|
What are the two theories that have been proposed for the mechanism of local anesthetic action?
|
A) The Membrane Expansion Theory (or physicochemical mechanism): Because of their lipophilicity, local anesthetics incorporate into the cell membrane, thus preventing the opening of pores and passage of electrolytes.
B) Receptor mechanism: explains the mechanism of action of almost all local anesthetics. Local anesthetic agents block nerve conduction by inhibiting the voltage-gated sodium channels of the neuronal membrane. |
|
|
local anesthetic agents metabolism?
|
A) Those of the ester series are metabolized by plasma cholinesterase.
B) The amide local anesthetics are metabolized by the hepatic microsomal mixed-function oxidase system. |
|
|
Local anesthetic agent excretion?
|
Renal clearance is inversely related to their protein binding capacity. Renal clearance is inversely proportional to the pH of urine
|
|
|
what are the major effects of local anesthetics?
|
Differential nerve blockade:
Loss of autonomic function followed by blockade of temperature sensation, pain, touch, pressure, and motor function (in that order). Loss of autonomic function will cause vasodilation, which in turn increases the absorption, peak systemic effect, and toxicity while decreasing effectiveness and duration of anesthesia. **this is the rational for the inclusion of a vasoconstrictor agent in anesthetic solutions. |
|
|
Indications for local anesthetics in dentistry?
|
A) To perform intraoral procedures of short duration.
B) As topical anesthetic agent on mucous membranes prior to injection. |
|
|
Contraindications for use of local anesthetics?
|
A) Do not use excessive vasoconstrictor in a patient prone to develop cardiac problems.
B) Judicious amount of vasoconstrictor should be used in hyperthyroid patients. |
|
|
What are the effects of lidocaine?
|
<5 ug/ml:
CNS- anticanvulsant activity, mild sedation and analgesia. CVS- antiarrythmic activity, mild in mean BP with similar increases in cardiac output or peripheral vascular resistance. 5-10ug/ml: CNS-lightheadedness, slurred speech, drowsiness, euphoria CVS- cardiovascular instability 15-20 ug/ml: CNS- disorientation, tremors, tonic-clonic seziures. CVS- cardiovascular instability 15-20ug/ml: CNS- coma and respiratory arrest CVS- Cardiovascular instability >20ug/ml: CVS- profound myocardial depression, vasodilation and cardiovascular collapse. |
|
|
What are the adverse effects of local anesthetics?
|
A) CNS stimulation followed by CNS depression.
B)CV depression: Very rare but has caused cardiac arrest in a few individuals. C) Allergic reaction: mostly seen with ester types and also due to metabisulfite. Manifested as dermatitis, asthmatic attacks, and serious anaphylactic reactions. D) Systemic effects due to vasoconstrictor (inadvertent injection into a blood vessel; ASPIRATE Manifested by anxiety, excitement, headache, dizziness, tachycardia, chest pain, hypertension, and GI disturbance. E) Fainting: typically not due to pharmacologic effects of the drug but may be due to psychological response to the fear or pain of injection. F) Prilocaine: Methemoglobinemia is an adverse effect G) Paresthesia: with articaine and other 4% solutions H) Malignant hyperthermia ………………..NO |
|
|
How can you prevent adverse effect of local anesthetics?
|
A) Take a careful medical history.
B) Aspirate before injection. C) Inject the smallest amount of the least toxic drug possible to produce anesthesia. D) Inject slowly E) Avoid repeated injection into the same area over a prolonged time (i.e. hard palate). |
|
|
Reasons for local anesthetic failures?
|
A. Anatomic variations.
B. Inflammation & infection. C. Intravascular injection. D. Defective solutions. E. Technical errors of administration. |
|
|
what happens with combination of local anesthetics?
|
Combination with other CNS acting agents can result in permanent neurological deficits and even death, particularly when the child patient is overdosed with the local anesthetic agent(s).
|
|
|
what are some possible drug interactions for the vasoconstrictor agent?
|
Potential elevation in blood pressure in patients who are on tricyclic antidepressants.
Contrary to some suggestions, there is no interaction between exogenously administered epinephrine and monoamine oxidase inhibitors |
|
|
What is the reversal agent for the local anesthetic?
|
Phentolamine mesylate (an alpha adrenergic blocking agent)
|
|
|
what is the dosage calculation for local anesthetic?
|
Clark's rule:
Based on patient's body weight Child dose = (Weight in lbs. X Adult dose )/ 150 Young's rule: Child dose = (Age in years X Adult dose )/ (Age in years + 12) |
|
|
How are local anesthetics formulated?
|
Local anesthetic solutions range in pH from under 3.0 to over 6.0; generally, preparations with vasoconstrictors are adjusted to a lower pH than are plain formulations to enhance stability of the sympathomimetic amine constituents.
A) Local anesthetic B) Vasoconstrictor C) Metabisulfite* antioxidant D) Isotonic NaCl solvent E) HCl/ NaOH to adjust pH |
|
|
what is lidocaine?
|
Currently the most frequently used local anesthetic. Compared to procaine, it has a more rapid onset of action and results in more profound anesthesia that is of longer duration.
It can be used either alone or in combination with a vasoconstrictor. Although CNS stimulation can occur, CNS depression without stimulation also may be observed. Lidocaine is used either as an anesthetic or antiarrhythmic agent. It can be administered via infiltration, topical, or for spinal anesthesia. Minimal local irritation occurs with lidocaine. |
|
|
what is mepivacaine?
|
Although equivalent to lidocaine in potency, it may be used alone because it has less vasodilator property.
It is recommended for patients for whom a vasoconstrictor is not indicated. |
|
|
what is bupivacaine?
|
Major clinical advantage is a prolonged duration of action. It is indicated in dentistry when pulpal anesthesia is required for longer than 90 min. or when prolonged postoperative analgesia is desired.
It should minimize the need for analgesics since anesthesia is reported to last 8 hrs. in the mandible and about 5 hrs. in the maxilla. However, since bupivacaine ismore toxic than lidocaine, care is advised to avoid intravenous injection. Bupivacaine can precipitate ventricular arrhythmia. |
|
|
what is articaine?
|
Relatively rapid ester hydrolysis reduces risk of toxicity.
-4% solution with 1:100,000 epi.; higher risk Associated with greater propensity for paresthesia; paresthesia is more likely with the use of 4% local anesthetic solutions |
|
|
what are topical anesthetic agents?
|
Effective on surface tissues and may help minimize discomfort associated with needle penetration.
A variety of agents are available in gel, liquid, ointment, patch and aerosal forms. Compounded formulation used for palatal tissue anesthesia prior to injection, extraction of loose primary teeth (obviating an injection), and placement of mini-screw implants to aid tooth movement. -20% lidocaine, 4% tetracaine and 2% phenylephrine -10% lidocaine, 10% prilocaine, 4% tetracaine and 2% phenylephrine **Systemic absorption of topically applied agents should be considered in calculation of total administered dose.** |
|
|
What are EMLA (Eutectic Mixture of Local Anesthetics)?
|
2.5% of lidocaine & 2.5% of prilocaine
Cream for topical anesthesia of skin Placed under occlusive dressing for 1 hr for relief of pain of venopunture Useful for children and other patients intolerant of needle insertion Unfavorable features for oral mucosal application |
|
|
what are some characteristics of Epinephrine as a vasoconstrictor agent?
|
Effects on blood pressure include elevation of arterial pressure through:
A) vasoconstriction via a-1 receptor activation B) increased ventricular activation through b-1 receptors, C) initial increase in the heart rate, which at the height of vasopressor response will be slowed by a compensatory vagal discharge. |
|
|
what are some characteristics of Levonordefrine (Neo-Cobefrine) as a vasoconstrictor agent?
|
Relatively less cardiac effect than equal doses of epinephrine. However, about 5 times more concentrated in anesthetic solutions and at these concentrations, cardiac effects will be similar to epinephrine
|
|
|
What are the dosage calculations for local anesthetics?
|
Local anesthetic component:
- A 2% solution means: 2 grams/100 ml OR 2000mg/100 ml OR 20 mg/ml - A 3% solution means: 30 mg/ml - A 4% solution means: 40 mg/ml |
