Local Anesthesia Gary J. Wayne DMD Diplomate American Board Of Oral/Maxillofacial Surgery Boynton Oral & Maxillofacial Surgery and Dental Implant Center Boynton Beach, Florida

Review of Neurophysiology How do local anesthetics work? What are the implications in my choice of anesthetics?

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

Local Anesthetics Articaine Bupivacaine Dibucaine Etidocaine Lidocaine Amides Esters Articaine Bupivacaine Dibucaine Etidocaine Lidocaine Mepivacaine Prilocaine Butacaine Cocaine Benzocaine Hexylcaine Piperocaine Tetracaine

Local Anesthetics PABA Type Chloroprocaine Procaine Propoxycaine Esters Others PABA Type Chloroprocaine Procaine Propoxycaine Quinoline Centbucridine Diphenhydramine Saline

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

Lidocaine Available since 1943, most common Available with/without vasoconstrictor With 1:100,000 Epi Max dose 7mg/kg not to exceed 500mg Pulpal Anesthesia 60min Soft Tissue Anesthesia 3-5hr Pka 7.9 Onset of action 2-3 minutes

Mepivacaine 3 % Common for non-surgical procedures Used in pediatrics and geriatrics Onset of action 1.5-2 minutes Slight Vasodilation < Lidocaine Pulpal Anesthesia 20-40 minutes Soft Tissue Anesthesia 2-3 hours Pka 7.6 Maximum dose 6.6mg/kg not to exceed 400mg

Mepivacaine 2% with vasoconstrictor 1:20,000 Neo-Cobefrin/Levonordefrin 1/5 Vasoconstrictor Activity Rapid onset 1.5-2 minutes Soft Tissue/Pulpal Anesthesia Similar to Lidocaine with vasoconstrictor Maximum Dose 6.6mg/kg not to exceed 400mg Is available with 1:100,000 epi (documented lidocaine allergy)

4% Prilocaine Vasodilation >Mepivacaine,<Lidocaine Pka 7.9 Onset 2-4 minutes Duration Pulpal 10min infiltration, 60 min block Maximum 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 >60min Duration of action pulpal 60-90min, soft tissue 3-8hrs Maximum Dose 6mg/kg not to exceed 400mg

4% Articaine with 1:100,000 epi Newest “wonder anesthetic” in U.S. Pka 7.8 Onset of action 2-2.5 minutes block,1-2 minutes infiltration Claim is that can diffuse more readily, controlled comparisons failed to corroborate Duration of action pulp 60-70 min, soft tissue 3-6hrs Maximum dose 7mg/kg not to exceed 500mg Available 1:200,000 epi

.5% Bupivacaine 1:200,000 epi Good for lengthy procedures as an adjunct/post operative analgesia “Weak” anesthetic Pka 8.1 Onset of action 6-10 minutes Maximum dose 1.3mg/kg not to exceed 90mg Duration pulpal 90-180 min, soft tissue 4-9hrs (12hr reported)

Esters Can Use with documented allergy to Amides Procaine+Propoxycaine Provides 30-60 min of pulpal 2-3 hours of soft tissue each cartridge 7.2 mg of Propoxycaine 36mg of Procaine Maximum dose 6.6mg/kg

Vasoconstrictors Epinephrine Neo Cobefrin Levonordefrin Levophed

When to use/not use Discussion: Cardiovascular disease “allergy” Pediatrics Elderly Post operative analgesia Hemostasis

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 Signs Talkativeness Apprehension Excitability Slurred Speech Generalized Stutter Euphoria Dysarthria Nystagmus Sweating Vomiting Failure to follow commands Disorientation Loss of response to pain ^Blood Pressure ^Heart Rate ^Respiratory Rate

Minimal/Moderate Overdose Levels Symptoms (progressive with increasing blood levels) Light-Headedness and dizziness Restlessness Nervousness Numbness Sensation of twitching, before observed Metallic Taste Visual Disturbances Auditory Disturbances Drowsiness and disorientation Loss of consciousness

Moderate/High Overdose Levels Tonic-Clonic seizure activity followed by Generalized CNS Depression Depressed blood pressure, heart rate, and respiratory rate

Management of Mild Overdosage>5min Reassure patient O2 via nasal cannula or hood Monitor and record vital signs IV if able Self Limiting, discharge when recovered

Mild Overdose-Slower Onset>15min Biotransformation trouble All of the previous methods plus Anticonvulsant Summon medical assistance Patient to be examined by physician or hospital

Severe Overdose BLS Anticonvulsant Terminate treatment Summon Help

Epinephrine Overdose More common in gingival retraction cord Symptoms Fear,Anxiety Respiratory difficulty Tenseness Palpitations Restessness Pallor Throbbing Headache Dizziness Tremor Weakness Perspiration

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 procedure Position patient –Semisitting or erect Minimized CNS Effect Monitor Blood Pressure Administer O2 (except hyperventilation) Recover-Most are self limiting

Allergic Reactions Rare with amides Seen with topical anesthetics-esters Sodium metabisulfites-only with vasoconstrictors Treatment BLS Oral Histamine Blocker Sub Q epi IM Histamine Blocker Bronchial Treatment Laryngeal Treatment

Maxillary Anesthesia Field Block Infiltration Nerve Block Intraseptal Intraosseous Periodontal Ligament

Infiltration Area of treatment is flooded with local anesthesia Periodontal treatment Selective restorative procedures

Field Block Anterior Superior Middle Superior Posterior Superior

Nerve Blocks Maxillary (Second Division) Junction of Vertical/Horizontal Shelves Second Molar Long Needle 2cc of solution Greater Palatine Nasopalatine Infra-orbital

Infraorbital

Problems with Maxillary Anesthesia Few Related to inflammation/infection Posterior teeth Use Nerve Blocks Infraorbital-Extra/Intra Oral Nasopalatine Secondary Division

Mandibular Anesthesia

Mandibular Anesthesia

Inferior Alveolar Block 80-85% Successful Related to Greater Density of Bone Limited Accessibility Wide Variation of Anatomy Solution Depot within 1mm Most Important Block Variations Accessory Innervation

Inferior Alveolar Block Deepest Part of Ascending Ramus Parallel to Occlusal Plane Lateral To Raphe Hit bone Pull Back? Bevel aimed away, assist in needle deflection and direction of liquid

Accessory Innervation Determine Objective Anesthesia of IAN Mylohyoid Accessory Foramina Cervical Branches

Mental Nerve Block Does not anesthetize incisive branch Angle needle anterior Second Premolar High risk of nerve injury

Buccal Nerve Block Bevel Toward Bone Distal and buccal to most distal molar

Gow-Gates Anesthetizes all branches IAN,lingual,mylohyoid,mental, incisive auriculotemporal and buccal High Success >95% Low Aspiration Parallel tragus to anterior border of ramus Mesiolingual cusp of maxillary second molar Hit neck of condyle and back off 1mm Stay open 1-2 minutes-bite block

Gow-Gates Target

Vazirani-Akinosi Closed Mouth Block IAN, Incisive, Mental, Lingual and Mylohyoid Mucogingival of Maxillary Third or Second Molar Parallel Maxillary Occlusal Plane Medial of Anterior Ramus Approximate 25mm (midway)

Supplemental Aids Ligamentary Injections Intraosseous Injections Intrapulpal Electronic Hypnosis Nitrous Oxide IV/General Anesthesia Always reduces local anesthesia “Gizmos”