Local Anesthesia Midterm.

Endoneurium

insulates the electrical activity of nerve fibers

Flow meter

provides visual indications of the volume of gases being delivered

Perilemma

inner layer of the perineurium

An injection that deposits anesthetic solution near a major nerve trunk is called:

A nerve block injection

Epineural sheath

surrounds the epineurium and the entire nerve

The use of a scavenging system with N2O sedation equipment is desirable because it:

Removes any potentially toxic waste gas from the environment.

Local Anesthetic Delivered by dental hygienists since

1971 (Washington State)

The maximum recommended dose of topical anesthetic is:

200 mg/ml

What will the gauge on an oxygen tank read when it is full?

2200 psi

The didactic component must be _____hours to meet competence for New York State Certification:

30

Which of the following gauge numbers indicates the needle with the smallest lumen?

30

How long is oxygen administered at the completion of sedation?

5 minutes

Scavenging system

eliminates excess gas being exhaled by the patient and nitrous from leaking into the atmosphere

Pin index safety system

ensure the correct attachment of gas cylinders to delivery units.

Epinephrine Effects on Cardiovascular

β1 effects • Overall decrease in cardiac efficiency

Epinephrine effects on Respiratory system:

β2 effects • Bronchial dilator • Treat acute asthmatic attacks and anaphylactic reactions

Lidocaine -

• 2% lidocaine plain (without vasoconstrictor) • Very short duration = 5 to 10 minutes pulpal • 60 to 120 minutes soft tissue • 2% lidocaine with 1:100,000 epinephrine • Intermediate duration = 60 minutes pupal • 180 to 300 minutes soft tissue • 2% lidocaine with 1:50,000 epinephrine • Intermediate duration - 60 minutes pupal • 180 to 300 minutes soft tissue

MRD of Mepivacaine

• 3 mg/lb (6.6 mg/kg) • 400 milligram absolute MRD per appointment

The fee for a dental hygiene restricted local infiltration anesthesia/nitrous oxide analgesia certificate is $100.

False

The specific requirements for certification are contained in Title 25, Article 144, Section 6605-6 of New York's Education Law and Part 61 of the Commissioner's Regulations

False

The field of anesthesia of an ASA nerve block includes each of the following except

Lingual periodontium of central incisor through canine

0.5% Bupivacaine, 1:200,000 Epinephrine

Long duration = up to 12 hours pulpal and soft tissue -no topical form of anesthetic -Onset of Action • Approximately 6 to 10 minutes Metabolism • Bupivacaine's metabolism is complex. • The liver provides the major amidas used in metabolism. • Biotransformation is much slower compared with the other local anesthetic drugs. • Very little, up to 16%, is excreted in the urine unchanged

Prilocaine

MRD • 4 mg/lb (8 mg/kg) • 600 milligram absolute MRD per appointment Relative Toxicity: Special Considerations • Due to prilocaine's metabolite orthotoluidine (otoluidine), some individuals are at increased risk of developing a potentially life-threatening anemia known as methemoglobinemia.

Which of the following is the most important safety step following an injection?

Recapping the needle with a one-handed technique

Pharmacodynamics

Refers to the actions of a drug on the body (local anesthesia) • Pharmacodynamics drugs include actions on: • Peripheral nerves • CNS • Cardiovascular system • Other tissues • These actions interrupt the normal generation and conduction of nerve impulses.

Pharmacokenetics

Refers to the manner in which the body manages a drug, specifically the mechanisms of absorption, distribution, metabolism (biotransformation), and elimination

Pain is

a protective response. • Physiological reaction to the environment • Rapid, reflexive, and subconscious

The International Association for the Study of Pain defines pain as:

an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage.

The student must demonstrate the following clinical experiences:

b. A clinical experience, demonstrating the successful use of nitrous oxide analgesia in no fewer than 15 instances involving the treatment of a patient, of which at least five instances were induced by the candidate and the remaining instances were observed by the candidate and no individual patient was treated more than two times c. A clinical experience demonstrating the successful use of local infiltration anesthesia in no fewer than 15 instances involving the treatment of a patient and that no individual patient was treated more than three times (b&c)

Toxicity and Biotransformation Levonordefrin

biotransformed by COMT; however, it is not subject to significant MAO metabolism. • Its systemic effects and the termination of its actions are similar to epinephrine's.

Perineurium

bundles fibers into fasiculi

Toxicity and Biotransformation of Epinephrine

is recycled in synaptic junctions. • Biotransformed by catecholamine-Omethyltransferase (COMT) • Further breakdown via monamine oxidase (MA O)

MRD of epinephrine

normal= 0.2 mg cardiac/compromised pt= 0.04 mg

Regulator

reduces pressures from cylinders before coming in from pipes and tubing

α Receptors

Excitatory actions

Fasiculi

Mantle bundles • Core bundles

Ester

"One Eye" in anesthetic name ex. procaine

Amide

"TWO EYES" in anesthetic name ex. lidocaine

The following are necessary considerations when utilizing nitrous oxide/oxygen sedation:

(A, C, and E) a. Proper infection control techniques with regard to local anesthetic and nitrous oxide analgesia. c. Description and use of inhalation sedation equipment e. Abuse potential and hallucinatory effects of nitrous oxide analgesia

Acute

A few seconds to no more than 6 months depending on causative factors Longer acute pain continues, the more likely to become chronic

Biotransformation of Esters

In the blood by pseudocholinesterase

Schwann cell sheath / membrane

Neurolemma

Norepinephrine activates

α receptors.

Prilocaine metabolism

• Prilocaine has a simpler hepatic metabolism compared with lidocaine and mepivacaine. • Much of the drug, however, is cleared before it is able to reach the liver. • The lungs and kidneys are alternate sites of breakdown when the liver is not used. • Only small percentages of prilocaine and its metabolites are found in the urine Onset of Action • Approximately 2 to 4 minutes

Generation and Conduction of Nerve Impulses /Return to Resting State

• Reattainment of a −70 milli Volt potential • Membrane has fully recovered • Entire process requires only one millisecond for nerve membrane to react and recover after a successful impulse-generating stimulation

Endogenous release of epinephrine

• Release of epinephrine from within can compound the adverse effects of exogenous administration of epinephrine via the anesthetic injection containing epinephrine.

Levonordefrin Effects on the Body

• Respiratory • Vasodilation of bronchiole smooth muscle but less that epinephrine • CNS • Less potent then epinephrine • Metabolism • Elevation in blood sugar and oxygen consumption less than epinephrine • Effect on endogenous epinephrine • Less than epinephrine

Nerve Cell Anatomy: Nerve Axons, Cell Bodies, and Membranes

• Sensory neurons - Carry incoming signals called IMPULSES from the body to the brain (CNS) • Motor neurons - Impulses leave the CNS to travel to effector cells, tissues, and organs • Neurolemmas = membranes • Act as barriers • Phospholipids • Lipophilic ("fat loving") • Hydrophilic ("water loving")

Axolemma

• Sheath or membrane covering of axon

Levonordefrin

• Synthetic vasoconstrictor • Approximately one-sixth as potent as epinephrine • Manufactured in higher concentrations • Available ONLY with 2% mepivacaine in 1:200,000 mg/mL • Contains sodium bisulfite • Compare mode of action • Levonordefrin: 75% α; 25% β activity • Epinephrine: 50% α; 50% β activity

Elimination Half-Life

• The rate at which a drug is removed from the systemic circulation • The time necessary to metabolize and excrete 50 percent of a drug

Local Anesthesia/Routes of Delivery

• There are two primary routes of delivery of dental local anesthetic drugs. • Topical • Submucosal injection

β Receptors

Inhibitory actions

The didactic component must include the following:

-Relevant New York State Education Law and Commissioner's Regulations -Medical history and evaluation procedures -Review of pediatric and adult respiratory and circulatory physiology and related anatomy -Pharmacology of agents used in inhalation sedation, local anesthesia, and vasoconstrictors, including drug interactions and incompatibilities (All of the above)

Which is the correct initial dosage and time interval to begin N2O-O2 sedation?

1 liter for one minute

Dentists allowed to administer local anesthetics in cartridge form since

1921

Neurophysiology 2

A nerve is in the resting state when it receives little to no stimulation • Intracellular (axoplasm) [inner environment of nerve] is negatively charged • Extracellular is positively charged • Difference in the electrical charge = Electrical potential = −70 milliVolts = resting state • Result of an imbalance of electrolytes on either side of the membrane • Sodium (Na) • Potassium (K)

Epinephrine activates

ALL alpha and beta receptors

Dental Neural Plexus

An interwoven, interconnecting network of nerves supplying the teeth and their supporting structures • Maxillary • Mandibular

Onset of Action of Mepivacaine

Approximately 1.5 to 2 minutes

Epinephrine Effects on Vasculature:

Both α and β2 • Smaller doses = (β2) vasodilatation • Higher doses = (α) vasoconstriction

What is the first step a clinician should take when mild over-sedation is observed?

Discontinue the N2O

Which of the following best explains why infiltration techniques are highly successful in the maxilla?

Ease of diffusion through bone

Sensory innervation of the posterior 1/3 of the tongue is supplied by the _____ nerve.

Glossopharyngeal

The palatal gingiva of tooth #3 is supplied by which of the following?

Greater palatine nerve

Epinephrine effects on Hemostasis:

High doses stimulate α receptors, resulting in vasoconstriction.

The nerves of the dental plexus include: CHECK ALL THAT APPLY!

Interdental branches Interradicular branches Dental nerves

The buccal gingiva of #23 is supplied by which of the following?

Mental nerve

When lingual nerve is anesthetized, which of the following tissue will NOT be affected?

Palatal periodontium

Which of the following patients would NOT be a good candidate for the use of N2O?

Patient with chronic obstructive pulmonary disease

Conduction tubing

Provides the connection from the cylinders to the tubing feeding the nasal hood and to the suction

Epinephrine Effects on BP

Small doses = increase systolic pressure Higher doses = increase diastolic pressure

Pharmacodynamics 1

Specific protein receptor theory • Action of local anesthetics on nerve membranes explained by the binding of local anesthetic molecules to structural proteins known as specific protein receptor sites • Temporarily transform nerve membranes to nonexcitable states Highly perfused organs such as the lungs, brain, heart, and kidneys will receive more systemically distributed drugs than less perfused tissues. • Muscle by mass receives the highest percentage of drug

Nitrous levels vary from patient to patient. Fortunately, once the nitrous level has been established for an individual patient, that level is to be used at each appointment for that patient.

The first statement is true and the second is false

Which statement describes the correct positioning of the long window of the syringe?

Toward the clinician to permit visibility throughout the injection

Which of the following nerve branches anesthetizes the upper lip and skin of the cheek?

Trigeminal nerve, division 2

Which of the following procedures represents the correct response following a positive aspiration when a small wormlike thread enters the cartridge?

Withdraw the syringe, change the cartridge, clear the needle of blood and reinject

a & c fibers

both found in dental pulp more c-fibers then a-fibers

Nociceptors

sensory receptors that that detect injury. -Are polymodal - They will never adapt - they will always respond • Patient does not get 'used to' the pain

Epineurium

- loose connective tissue layer surrounding fasciculi

Which structures are affected by supraperiosteal infiltration injections? CHECK ALL THAT APPLY!

-Alveolus -Pulp of tooth -Periodontal ligament -Related facial or lingual areas of the gingiva

To meet the education requirements for certification, you must have completed:

-An educational program provided by a New York State dental or dental hygiene school that is registered by the New York State Education Department and includes 30 hours of didactic coursework and 15 hours of clinical training. -Equivalent educational preparation acceptable to the New York State Education Department, offered by an institution with programs leading to licensure in dentistry and/or dental hygiene that are accredited by an acceptable accrediting body. (BOTH)

Which of the following are signs of excessive nitrous sedation?

-Dilated pupils -Agitated, combative behavior -Uncontrolled laughter -Inability to follow commands

Which of the following are true of the facial nerve? CHECK ALL THAT APPLY!

-It is an afferent nerve for the body of the tongue -It provides taste sensation to the palate -Is an efferent nerve for the sublingual and submandibular glands -It innervated the muscles of facial expression

Which of the following are ADA criteria for syringe acceptance?

-Provide for effective aspiration so blood may be easily observed in the cartridge. -Durable, can withstand sterilization without damage. -Inexpensive, self-contained lightweight and easy to use with one hand -Can accept different cartridges and needles.

The clinical component didactic information must include:

-Selection and preparation of the armamentaria for administering various local anesthetic agents and nitrous oxide analgesia including demonstrations regarding scavenging systems -Demonstration of proper infection control techniques with regard to local anesthetics agents and nitrous oxide analgesia and proper disposal of sharps -Demonstration of proper evaluation of the patient's health status, taking the patient's vital signs and monitoring the patient's physical status while under the effects of local anesthesia and/or nitrous oxide analgesia -Administration of local anesthetic in conjunction with inhalation sedation techniques (All of The Above)

The dental anesthetic cartridge contains which of the following? CHECK ALL THAT APPLY! Correct!

-Vasopressor drug plus preservative (sodium bisulfate) -Sodium chloride; bio compatible with the body -Distilled water-to provide the volume of solution -Local anesthetic drug

Local Anesthesia primary benefit

-pain sensations can be suppressed without significant central nervous system (CNS) depression. -It allows for the majority of dental procedures to be performed under local anesthesia without exposing patients to the risks of general anesthesia.

The hour requirement for local anesthesia/nitrous oxide-oxygen sedation clinical and laboratory experience component is:

15

In the absence of an MSA nerve, which of the following two nerves may innervate the premolars and the mesiobuccal root of the first molar?

Anterior superior alveolar and posterior superior alveolar

Local Anesthesia/ chemical components

Aromatic (lipophilic) end • Secondary or tertiary (hydrophilic) end • Facilitates effectiveness in tissues

Mantle and Core Bundles

Arrangement of these bundles will impact how anesthesia develops when exposed to anesthetic drugs

What color is a N2O tank in the United States?

Blue

The soft tissue of alveolar process of the mandible is innervated by

Buccal, lingual, and mental nerves.

Pharmacodynamics 6

CNS and CVS actions of LA drugs • CNS is particularly susceptible • Biphasic, temporary signs of excitation followed by CNS depression • Impact CNS well before CVS • CVS effects require higher concentrations • Vasodilation occurs, leading to depression of the myocardium

Neuropathic pain

Caused by nerve injury or dysfunction of the sensory nerves in the central or peripheral nervous system • Frequently chronic • Inflammatory, noninflammatory, &/or immune system components • Examples • Trigeminal neuralgia • Carpal tunnel syndrome • Post-herpetic neuralgia

Nitrous contraindications

Chronic obstructive pulmonary disease Gastrointestinal obstructions Psychiatric disorders Recent eye surgery

Dissociation of Anesthetic Molecules

Dental local anesthetics are commonly prepared as acid salts. • Dissolved in sterile water dissociate into two forms • A positively charged molecule (cation) • More stable • An uncharged or neutral molecule (neutral base) • Drug actions are dependent upon the actions of both the base and the cation.

Which of the following conditions does NOT contraindicate the administration of N2O?

Hypertension or cardiovascular disease

Notes About pKa

If cations are increased, the local anesthetic is more soluable. • An increase in the pH of the solution will increase the neutral base molecule concentrations • A decrease in the pH of the solution favors increase in cation concentration • The equilibrium between neutral base and cations is the pKa

Sympathetic Nervous System

In response to pain, CNS activates the sympathetic nervous system. • The sympathetic nervous system stimulates the adrenal medulla, resulting in the release of norepinephrine and epinephrine.

Stimulation of β1 receptors by adrenergic drugs causes:

Increased rate and force of heart contractions

Pharmacodynamics 4

Inflammation • Lower pH inhibits base molecule production • Results in insufficient numbers of base molecules (RN) penetrating nerve membrane • Profound anesthesia difficult to achieve or to sustain

Epinephrine Effects on Metabolic:

Inhibits insulin secretion

Pharmacodynamics 3

Ionic basis of local anesthesia • Base molecule is lipophilic and passes through membrane • Then combines with hydrogen ions to form hydrophilic cations • Only cations bind to receptor sites in sodium ion channels to block nerve impulse generation and transmission

Manifold

It joins multiple gas cylinders with one line exiting for each gas.

Lidocaine systemic effects

Maximum Recommended Dose (MRD) • 3.2 mg/lb (7mg/kg) • 500 milligram absolute MRD per appointment Metabolism • Lidocaine is metabolized by hepatic enzymes also known as oxidases and amidases. Excretion • Less than 10% of lidocaine is excreted unchanged by the kidneys. Vasoactivity • Lidocaine is a potent vasodilator with a very short duration when administered without a vasoconstrictor. Onset of Action • Approximately 2 to 3 minutes

Pharmacodynamics 2

Membrane expansion theory • A modification of the membrane structure narrows the diameters of ion channels, which limits the membrane's permeability to sodium ions.

good alternatives for patients who cannot receive a vasoconstrictor.

Mepivacaine 3% and prilocaine 4%

Mepivicaine effects on the body

Metabolism • Mepivacaine is metabolized in the liver. • Pathways are different compared with lidocaine • Unlike lidocaine, amidase activity is insignificant. Excretion Excretion is variable with anywhere from virtually none to up to 16% excreted unchanged. Safety during Lactation • It is not known whether mepivacaine is excreted in human milk. • Caution is recommended.

Procaine Metabolism/Onset/pregnancy risk

Metabolism • Procaine is rapidly metabolized via plasma cholinesterase. • There are no hepatic pathways for its biotransformation. • More than 2% is excreted unchanged by the kidneys. Onset of Action • Approximately 6 to 10 minutes FDA Pregnancy Category B. • Procaine is equal in safety to lidocaine and prilocaine.

Other Vasoconstrictors

Norepinephrine • Phenylephrine • Felypressin

Chronic

Persists for more than 6 months with or without an identifiable cause

Levonordefrin (Neo-Cobefrin)

Produces same systemic action as epinephrine but to a lesser extent • Terminated by reuptake by adrenergic nerves and escaped drug is inactivated by enzymes catechol-Omethyltransferase (COMT) but not monoamine oxidase (MAO) • Maximum permissible dose • Healthy patient 1 mg • Medically compromised patient 0.2 mg

Reservoir bag

Provides a source from which additional gas may be drawn should the respiratory demands of the patient exceed the gas flow delivered by the machine

Impulse Extinction

The event where impulse propagation may be interrupted by local anesthesia is known as nontransmission, or impulse extinction. • Local anesthetic drugs block Na+ ion influx • Sodium-dependent depolarization prevented Related to • Volume of anesthetic • Concentration of anesthetic • Length of nerve exposed to the anesthetic • Myelinated nerves • Anesthetic only effective at the nodes of Ranvier • Greater volume of anesthetic solution required for impulse extinction • Example - inferior alveolar nerve

• Pain threshold

The point at which a stimulus first produces a sensation of pain

Saltatory Conduction

The process whereby impulses are more rapidly conducted along myelinated nerves • Impulses 'jump over' Schwann cells from node to node • Larger, more heavily myelinated nerves transmit impulses more rapidly

All forms, along with the appropriate fee, must be submitted to the New York State Office of the Professions. It is your responsibility to follow up with anyone you have asked to send us material.

True

The fee due is the one in law when your application is received (unless fees are increased retroactively). You will be billed for the difference if fees have been increased.

True

To be certified in New York State you must be a New York State licensed dental hygienist currently registered to practice or applying concurrently for licensure and meet additional education and training requirements.

True

Pharmacodynamics 5

Vasoactivity • Dental local anesthetic drugs are peripheral vasodilators. • Limits their duration and efficacy unless vasoconstrictors are added

Stimulation of α receptors by adrenergic drugs causes:

Vasoconstriction or constriction of smooth muscle in the blood vessels

Articaine

• 3.2 mg/lb (7 mg/kg) • Absolute MRD per appointment not provided Special Toxicity Considerations • In addition to potential central nervous system and cardiovascular system toxicity,articaine may induce methemoglobinemia when used in higher than therapeutic doses. -Not available as a topical anesthetic -Caution with lactating patients, safe use has not been established.

Sodium Bisulfite Preservative

• Advantage • Increases shelf life • Disadvantages • Further acidify the pH of the anesthetic solution; range 3.8 to 5 • Allergic reactions to sodium bisulfites

Dilation of the blood vessels causes an increase in blood flow to the site of injection, which in turn causes:

• An increased rate of anesthetic absorption into the bloodstream • A decrease in the duration of the anesthetic's action • Higher plasma levels of local anesthetics, increasing the risk of toxicity • Increased bleeding in the area

Pain tolerance

• An individual's reaction to painful stimuli • Indicates amount of pain individual is willing or able to endure • Highly variable from person to person

Psychogenic Factors

• Are related to mental or emotional problems that affect the experience of pain

metabolism of articaine

• Articaine's metabolism is unique. • Five to ten percent is metabolized via hepatic p450 enzymes. • The majority of articaine's metabolism is by rapid plasma cholinesterase to articainic acid, prior to reaching the liver. • Very little articaine, about 2%, is excreted unchanged.

Felypressin

• Available in Great Britain and other countries • Felypressin + 3% prilocaine • Few side effects with little or no direct effect on the myocardium or adrenergic nerve transmission • May be administered safely to patients who: • Have uncontrolled hyperthyroidism • Are taking tricyclic antidepressants • Are taking MAO inhibitors

Stimulation of β2 receptors by adrenergic drugs causes:

• Bronchi of the lungs to dilate

Summary/Pharmacodynamics

• Calcium ions displaced, receptor bound • Sodium channel blocked • Depolarization decreased • Firing threshold never reached • Action potential never generated • Neuron blockade (anesthesia)

Nociceptive pain

• Caused by injury or disease in body tissues • Constant or intermittent • Somatic or visceral • Somatic • On superficial structures • Caused by traumatic injuries • Sharp, aching, or throbbing pain • Visceral • On internal body cavities • Caused by compression, expansion, stretching, or infiltration • Squeezing or gnawing sensations

Vasoconstrictors enhance local anesthetic drugs in a number of important ways:

• Constrict local vessels, increasing safety by decreasing the blood flow and slowing systemic absorption • Prolong local actions of drugs (increases the duration of the anesthetic's effect) • Increase their profoundness • Provide hemostasis at the injection site • Reduces toxicity - lower dose of drug because of lasting effect

Local Anesthesia/Safety and Efficacy

• Effective in tissues and mucous membranes • Short onsets and no residual effects • Reasonable durations • Adequate potency • Sterilizable • Patients remain conscious

Generation and Conduction of Nerve Impulses /Resting Potential (Resting State)

• Electrical potential of nerve axoplasm −70 milli Volts(range −40 to −95 milliVolts) • Potential is maintained by Na+ and K+ ions • Chloride (Na+) ions participate • Ion channels are "gated" by Ca+2 ions at specific receptor sites

Two vasoconstrictors are routinely found in dental local anesthetic drugs in North America:

• Epinephrine • Levonordefrin

Nodes of Ranvier

• Gaps of unprotected nerve between adjacent Schwann cells

pKa

• In local anesthetics pKa ranges from 7.7 to 8.1 in the 5 injectable amides • This number provides onsets of anesthesia • Higher the pKa >>> longer the onset of anesthesia

Biotransformation of Amides

• In the liver by hepatic p450 isoenzyme system

Generation and Conduction of Nerve Impulses /Refractory State

• Inability to successfully restimulate the membrane after impulse generation and conduction. • Absolute refractory • Membrane cannot be restimulated no matter how great the stimulus • Relative refractory • Resting state partially attained; a larger stimulus is required to achieve a firing threshold

Consequences of Fight or Flight Response

• Increased heart rate • Increased blood pressure • Pupil dilation • Dilation of bronchial and skeletal muscle vasculature • Constriction of mesenteric vessels • Caused by the anticipation of pain and the perception of pain

onset of action articaine

• Infiltration = approximately 1 to 2 minutes • Nerve block = approximately 2 to 3 minutes

Lidocaine and Safety during Lactation

• Lidocaine enters breast milk (small amounts). • Caution is recommended.

Topical Applications/ Lidocaine

• Lidocaine is effective as a topical anesthetic. • Concentrations range from 2%-10%. • It is available in various ointments, viscous solutions, and mixtures.

Nerve Fiber Types/ A fibers

• Lightly myelinated, conduct more rapidly • Provide sensations of sharp, stabbing pain

Core and Mantle Bundles

• Mantle (outer) bundle fibers innervate structures in close proximity to them. • Core (inner) bundles innervate structures at some distance away.

Nerve Fiber Types/ C fiber

• Most numerous of peripheral nervous system • Nonmyelinated, conduct more slowly • Provide sensations of dull and aching pain

Norepinephrine (Levartenerol)

• NOT recommended for use in dentistry • Side effects are nine times more potent than those of epinephrine. • Compare mode of action: • Levonordefrin: 75% α; 25% β activity • Epinephrine: 50% α; 50% β activity • Norepinephrine: 90% α; 10% β activity

Phenylephrine (Neo-Synephrine)

• NOT used in dentistry • Used in conjunction with local anesthetics for: • Hypotension • Nasal decongestants • Ophthalmic solutions • Compare mode of action: • Levonordefrin: 75% α; 25% β activity • Epinephrine: 50% α; 50% β activity • Norepinephrine: 90% α; 10% β activity • Phenylephrine: 95% α; very little β activity on the heart with 5% vasoconstrictor

Neurophysiology 1

• Nerve impulses are electrical in nature • Nerve impulses depend entirely upon changes in ionic activity along nerve membranes for their generation and conduction. Action potentials • In sensory nerves, energy from an impulse is duplicated and transferred to succeeding impulses along the axon in the direction of the CNS. Impulse propagation • Sequential impulse generation

Local Anesthesia/Biocompatibility

• Nonirritable • Nontoxic • Nonallergenic • Biotransformable • Completely reversible

Epinephrine effects on Central nervous system

• Normal dose: Does NOT stimulate CNS • Overdose: CNS stimulation - anxiety, nausea, restlessness, weakness, tremor, headache, hyperventilation

2% Procaine, Epinephrine 1:100,000, by Prescription Only

• Not currently available in dental cartridges • 2% procaine plain (without vasoconstrictor) • 2% procaine with 1:100,000 epinephrine • Intermediate duration = 60 minutes pulpal • 4% procaine plain (without vasoconstrictor) • Very short duration = no pulpal, 15 to 30 minutes soft tissue • Procaine can be obtained in medical vials

Generation and Conduction of Nerve Impulses /Repolarization

• Once a nerve has attained a potential of approximately +40 milli Volts, the process begins to reverse. • Recovery phase • Sodium pump moves Na+ ions out of axoplasm • Potential returns to −70 milliVolts • The reversal of ion concentrations in the recovery phase is called repolarization. • Once a nerve has attained a potential of approximately +40 mV, Na+ ions exit the nerve by passive diffusion through ion channels and through active transport of Na+ ion pumps. • Repolarization is complete when the potential is -60 mV to -90 mV

Generation and Conduction of Nerve Impulses /Rapid Depolarization

• Once the firing threshold has been achieved, the nerve quickly depolarizes due to the flood of positively charged Na+ ions • The impulse propagates • Potential is +40 mV • Na+ ion is now prevented • Sodium pump moves Na+ ions out of axoplasm

Generation and Conduction of Nerve Impulses /Slow Depolarization Firing Thresholds

• Once the nerve is stimulated, the ion channels open their gates • Ca+2 is released from receptors sites • Gates open and Na+ enters the axoplasm • Depolarizes by 15 to 20 milliVolts to −55 to −50 milliVolts • -55 mV to -50 mV = firing threshold • Nerve impulse generated If influx of Na+ is insufficient, nerve does NOT depolarize, NO nerve impulse generated.

Prilocaine/ topical

• Only in combination with other drugs, typically lidocaine • 2.5% lidocaine with 2.5% prilocaine • Oraqix (Dentsply Pharmaceutical) • EMLA (AstraZeneca)

Those who should NOT receive an anesthetic with a vasoconstrictor include:

• Patients with recent myocardial infarction, coronary bypass surgery, or cerebrovascular accident within the past 6 months • Patients with uncontrolled hypertension, angina, arrhythmias, diabetes, and hyperthyroidism

Most Significant Barriers to Diffusion of Anesthetic Solution

• Perilemma • Perineurium

PREP to Minimize Patient Anxiety and Fear

• Prepare-by utilizing relaxation techniques such as deep breathing, distraction such as music or visualization, and muscle relaxation. • Rehearse-procedures allowing patients to practice control and self-calming techniques. • Empower-patients with strategies that give them control during procedures such as raising a hand to ask the clinician to stop. • Praise-patients for using specific coping techniques that are helpful to them.

Mepivacaine

• Use for patients for whom vasoconstrictors are contraindicated (such as sulfite allergy) • Use for patients for whom the use of vasoconstrictors is against medical advice (such as severe cardiovascular disease) • Less efficiently metabolized than other LA agents so there is greater risk of toxicity in overdose