GARY J. WAYNE DMDDIPLOMATE AMERICAN BOARD OF

ORAL/MAXILLOFACIAL SURGERYB OYNTON ORAL & MAXILLOFACIAL

SURGERY AND DENTAL IMPLANT CENTERB OYNTON BEACH, FLORIDA

Local Anesthesia

HOW DO LOCAL ANESTHETICS WORK?WHAT ARE THE IMPLICATIONS IN MY

CHOICE OF ANESTHETICS?

Review of Neurophysiology

Summary

Local anesthetics dissociate into the ionic form in order to penetrate the nerve membrane. Anesthetics are available as salts clinical use.

Pka-the ability to dissociate into the ionic form in a given ph

The ph of a nerve is quite stable. The ph of the extracellular fluid is variable

The ph of a local anesthetic (and the surrounding tissue into which it is injected) greatly influences its nerve blocking action.

Ph of normal tissue is 7.4, ph of an inflamed area is 5 to 6

Summary

Local anesthetics containing epinephrine or other vasoconstrictors are acidified by manufacturers to inhibit oxidation of the vasopressor

The acidification causes more “burning” on injection

Ph of solutions without epinephrine are around 5.5, with epinephrine 3.3

Clinically this lower ph is more likely to produce a burning sensation, as well as a slightly slower onset of action

Summary

Increasing the ph (alkalinization) of a local anesthetic solution speeds the onset of its action, increases its clinical effectiveness, and makes its injection more comfortable

However, the local anesthetic base, because it is unstable, precipitates out of alkanized solutions, and this makes these solutions ill suited for clinical use

Adding sodium bicarb to the anesthetic solution immediately prior to injection provides greater comfort and a more rapid onset of anesthesia

Amides Esters

ArticaineBupivacaineDibucaineEtidocaineLidocaineMepivacainePrilocaine

ButacaineCocaineBenzocaineHexylcainePiperocaineTetracaine

Local Anesthetics

Esters Others

PABA Type Chloroprocaine Procaine Propoxycaine

Quinoline CentbucridineDiphenhydramineSaline

Local Anesthetics

Amide Local Anesthetics

Lidocaine “Xylocaine”Mepivacaine “Carbocaine”Prilocaine “Citanest”Articaine “Septocaine”Bupivacaine “Marcaine”

Lidocaine

Available since 1943, most commonAvailable with/without vasoconstrictorWith 1:100,000 Epi Max dose 7mg/kg not to exceed 500mgPulpal Anesthesia 60minSoft Tissue Anesthesia 3-5hrPka 7.9 Onset of action 2-3 minutes

Mepivacaine 3 %

Common for non-surgical proceduresUsed in pediatrics and geriatricsOnset of action 1.5-2 minutesSlight Vasodilation < LidocainePulpal Anesthesia 20-40 minutesSoft Tissue Anesthesia 2-3 hoursPka 7.6Maximum dose 6.6mg/kg not to exceed

400mg

Mepivacaine 2% with vasoconstrictor

1:20,000 Neo-Cobefrin/Levonordefrin1/5 Vasoconstrictor ActivityRapid onset 1.5-2 minutesSoft Tissue/Pulpal Anesthesia Similar to

Lidocaine with vasoconstrictorMaximum Dose 6.6mg/kg not to exceed

400mgIs available with 1:100,000 epi (documented

lidocaine allergy)

4% Prilocaine

Vasodilation >Mepivacaine,<LidocainePka 7.9Onset 2-4 minutesDuration Pulpal 10min infiltration, 60 min

blockMaximum Dose 6mg/kg not to exceed 400mg

4% Prilocaine with 1:200,000 epi

Rapid Biotransformation Safest of all amides Good for “epi sensitive” patients requiring

prolonged pulpal anesthesia >60minDuration of action pulpal 60-90min, soft

tissue 3-8hrsMaximum Dose 6mg/kg not to exceed 400mg

4% Articaine with 1:100,000 epi

Newest “wonder anesthetic” in U.S.Pka 7.8Onset of action 2-2.5 minutes block,1-2

minutes infiltrationClaim is that can diffuse more readily,

controlled comparisons failed to corroborateDuration of action pulp 60-70 min, soft tissue

3-6hrsMaximum dose 7mg/kg not to exceed 500mgAvailable 1:200,000 epi

.5% Bupivacaine

1:200,000 epiGood for lengthy procedures as an

adjunct/post operative analgesia“Weak” anestheticPka 8.1Onset of action 6-10 minutesMaximum dose 1.3mg/kg not to exceed 90mgDuration pulpal 90-180 min, soft tissue 4-9hrs

(12hr reported)

Esters

Can Use with documented allergy to AmidesProcaine+Propoxycaine“2 %” Procaine Provides 30-60 min of pulpal 2-3 hours of soft tissue each cartridge 7.2 mg of Propoxycaine 36mg of ProcaineMaximum dose 6.6mg/kg

Vasoconstrictors

EpinephrineNeo CobefrinLevonordefrinLevophed

When to use/not use

Discussion:Cardiovascular disease“allergy”PediatricsElderlyPost operative analgesiaHemostasis

Vasoconstrictors

“Vasoconstrictors should be included in local anesthetic solutions unless specifically contraindicated by the medical status of the patient or by the duration of the planned treatment”

S.Malamed

Local Complications

Needle Breakage Pain on Injection Burning on Injection Persistent Anesthesia or Paresthesia Trismus Hematoma Infection Edema Sloughing of Tissues Soft Tissue Injury Facial Nerve Paralysis Post Anesthetic Intraoral Lesions

Systemic Complications

Overdose

Overdose

Patient Factors Age Weight Other Drugs Sex (pregnancy) Presence of Disease Genetics Mental Attitude and enviroment

Overdose

Drug Factors Vasoactivity Concentration Dose Route of Administration Rate of Injection Vascularity of the Injection Site Presence of Vasoconstrictors

Overdose

“Many local anesthetic overdose reactions occur as a result of the combination of inadvertant intravascular injection and too rapid rate of injection, both of which are virtually 100% preventable”

S. Malamed

Minima/Moderate Overdose Levels

SignsTalkativeness ApprehensionExcitability Slurred SpeechGeneralized Stutter EuphoriaDysarthria NystagmusSweating VomitingFailure to follow commands DisorientationLoss of response to pain ^Blood Pressure^Heart Rate ^Respiratory Rate

Minimal/Moderate Overdose Levels

Symptoms (progressive with increasing blood levels)

Light-Headedness and dizziness RestlessnessNervousness NumbnessSensation of twitching, before observed Metallic

TasteVisual Disturbances Auditory

DisturbancesDrowsiness and disorientation Loss of

consciousness

Moderate/High Overdose Levels

Tonic-Clonic seizure activity followed byGeneralized CNS DepressionDepressed blood pressure, heart rate, and

respiratory rate

Management of Mild Overdosage>5min

Reassure patientO2 via nasal cannula or hoodMonitor and record vital signsIV if ableSelf Limiting, discharge when recovered

Mild Overdose-Slower Onset>15min

Biotransformation trouble All of the previous methods plusAnticonvulsantSummon medical assistancePatient to be examined by physician or

hospital

Severe Overdose

BLSAnticonvulsantTerminate treatmentSummon Help

Epinephrine Overdose

More common in gingival retraction cordSymptomsFear,Anxiety Respiratory difficultyTenseness PalpitationsRestessness PallorThrobbing Headache DizzinessTremor WeaknessPerspiration

Epinephrine Overdose

Signs of epinephrine overdose Sharp elevation in blood pressure, systolic Elevated heart rate Possible cardiac dysrhythmias

(PVC,Vtach,Vfib)

Management of Epinephrine Overdose

Terminate procedurePosition patient –Semisitting or erect Minimized CNS EffectMonitor Blood PressureAdminister O2 (except hyperventilation)Recover-Most are self limiting

Allergic Reactions

Rare with amidesSeen with topical anesthetics-estersSodium metabisulfites-only with vasoconstrictorsTreatment BLS Oral Histamine Blocker Sub Q epi IM Histamine Blocker Bronchial Treatment Laryngeal Treatment

Maxillary Anesthesia

Field BlockInfiltrationNerve BlockIntraseptalIntraosseousPeriodontal Ligament

Infiltration

Area of treatment is flooded with local anesthesia

Periodontal treatment Selective restorative procedures

Field Block

Anterior SuperiorMiddle SuperiorPosterior Superior

Nerve Blocks

Maxillary (Second Division) Junction of Vertical/Horizontal Shelves Second Molar Long Needle 2cc of solutionGreater Palatine NasopalatineInfra-orbital

Infraorbital

Problems with Maxillary Anesthesia

FewRelated to inflammation/infectionPosterior teethUse Nerve Blocks Infraorbital-Extra/Intra Oral Nasopalatine Secondary Division

Mandibular Anesthesia

Mandibular Anesthesia

Inferior Alveolar Block

80-85% SuccessfulRelated to Greater Density of Bone Limited Accessibility Wide Variation of Anatomy Solution Depot within 1mmMost Important BlockVariationsAccessory Innervation

Inferior Alveolar Block

Deepest Part of Ascending RamusParallel to Occlusal PlaneLateral To RapheHit bonePull Back?Bevel aimed away, assist in needle deflection

and direction of liquid

Accessory Innervation

Determine Objective Anesthesia of IANMylohyoidAccessory ForaminaCervical Branches

Mental Nerve Block

Does not anesthetize incisive branchAngle needle anteriorSecond PremolarHigh risk of nerve injury

Buccal Nerve Block

Bevel Toward BoneDistal and buccal to most distal molar

Gow-Gates

Anesthetizes all branches IAN,lingual,mylohyoid,mental, incisive

auriculotemporal and buccalHigh Success >95%Low AspirationParallel tragus to anterior border of ramusMesiolingual cusp of maxillary second molarHit neck of condyle and back off 1mmStay open 1-2 minutes-bite block

Gow-Gates Target

Vazirani-Akinosi Closed Mouth Block

IAN, Incisive, Mental, Lingual and MylohyoidMucogingival of Maxillary Third or Second

MolarParallel Maxillary Occlusal PlaneMedial of Anterior RamusApproximate 25mm (midway)

Supplemental Aids

Ligamentary InjectionsIntraosseous InjectionsIntrapulpalElectronicHypnosisNitrous OxideIV/General Anesthesia Always reduces local anesthesia“Gizmos”