Local Anesthesia PDF

Omar Karadsheh Lara Abu Abeeleh Dana Abu-Bakra Agents In Clinical Use Outline Background Selec?on of a Local Anaesthe?c agent Maximum doses of local anaesthe?c agents Most common local anaesthe?c agents used in den?stry Topical Anaesthe?c agents Selec?on of Local Anaesthe?c agents Indica'ons: 1- The dura'on of pulpal (hard 'ssue) and so6 'ssue (total) anesthesia needed i.e. We give LA based on the dura?on of our procedure and the loca?on. Most of the ?me, we anesthe?ze when we carry out any procedure ranging from restoring to extrac?ng 2- Needed for Postopera've pain management to numb any pain that might be felt aNer the procedure. 3- Needed for Haemostasis the vasoconstric?ng agents in LA work to stop any bleeding during the procedure. Contraindica'ons (C/I): 1- Absolute and rela've contraindica'ons the wide use of local anesthe?c deems it as ‘safe’, however, we mustn’t forget that it is in fact a drug that can have medical side eﬀects which is why we should always take a thorough medical history. Dura?on and Depth of Anesthesia Accuracy in deposi'on of the local anesthe'c if you want to treat the upper canine you need to inject the LA close to the canine/if endo then close to the apex. Anatomic varia'on like in the ID block technique where there are varia?ons that we have to keep in mind such as the posi?on of the foramen and thicker cor?cal bone. Tissue status in regards to vascularity, highly vascular ?ssue will have fast onset but short dura?on of ac?on. When it comes to pH, if the injec?on site has lower pH for example (Acidic) due to an abscess, the LA will not be eﬀec?ve (In this case, a buﬀered agent is used in LA prior to injec?ng an acidic area) Type of injec'on administered (inﬁltra?on or block) —> the block has longer dura?on because the nerve trunk is anesthe?zed whereas in inﬁltra?on the nerve endings are. Volume of L.A injected If ¼ of a cartridge is used when working on tooth #1 for example (lets say RCT), and ¾ is used when extrac?ng for example, both procedures used diﬀerent LA volumes, and as we use a higher LA volume, the dura?on of ac?on increases. Individual response to the drug (the “bell-shaped” curve) Normal distribu'on curve (bell-shaped curve): Varia?on in individual response to a drug is common and expected and is depicted in the so-called bell or normal distribu?on. There are two types of people: 1- Hypo-responders à Such individuals have a low response to LA and don’t get anesthe?zed quickly. 2- Hyper-responders à Such individuals respond quickly to LA and it’s dura?on of ac?on will be longer. Approximate Dura?on of Ac?on of Local Anaesthe?cs (short, intermediate and long) 1- Short Dura'on (Pulpal Anesthesia Approximately 30 Minutes) 1- Mepivacaine HCl 3% Without vasoconstrictors 2- Prilocaine HCl 4% (by inﬁltra?on) (try to avoid such prac?ce unless needed) 2- Intermediate Dura'on (Pulpal Anesthesia Approximately 60 Minutes) 1- Ar?caine HCl 4% + epinephrine 1:100,000 2- Ar?caine HCl 4% + epinephrine 1:200,000 3- Lidocaine HCl 2% + epinephrine 1:50,000 4- Lidocaine HCl 2% + epinephrine 1:100,000 5- Mepivacaine HCl 2% + levonordefrin 1:20,000 6- Prilocaine HCl 4% (via nerve block only) 7- Prilocaine HCl 4% + epinephrine 1:200,000 3- Long Dura'on (Pulpal Anesthesia Approximately 90+ Minutes) 1- Bupivacaine HCl 0.5% + epinephrine 1:200,000 (by nerve block) Note that the DOA of LA in so6 'ssues is 3x longer than pulpal anesthesia Usually toxic Maximum doses of L.A The max is unlikely to be reached. Maximum LA Dosage in North America Maximum dose is deduced from the pa?ent’s weight (mg/kg) or (mg/lb) – Which only provide us with an es?mate as it cannot be based on all responders; remember, we have normal responders, hypo-responders and hyper-responders Always minimize drug doses and use the smallest clinically eﬀec?ve dose Decreased in medically compromised, debilitated, or elderly persons Come back to this table once its men'oned. To calculate max dose, mul'ply the % concentra'on (4% when it comes to ar'caine = 40) Overdose (OD) Then mul'ply the 40 by 1.8 (vol of cartridge) = 72 When the MRD (max recommended dose) is exceeded, there is no guarantee that an OD will occur, only that there is a greater likelihood of its occurrence. Hyper-responders should be given dosages below the calculated MRD. Another factor in determining whether an OD will occur is the ?me over which the local anesthe?c dose was administered – slowly space the dura?on between cartridges to give the body ?me to metabolize the LA. Calcula'on of Maximum dosage and Number of Cartridges (single drug) Max. dose= Conc. X 10 x 1.8 Now go back to the previous table) Case à Pa?ent: 22 years old, Healthy, Female, 50 kg L.A: Lidocaine HCL + Epinephrine 1:100,000 MRD Lidocaine: 7 mg/kg Lidocaine 2% → 2/100 x 1000 = 20 mg/ml (or 2 x 10) Cartridge contains 1.8 ml solu?on, so→ 20 x 1.8 = 36mg/cartridge Maximum dose for this pa?ent is: 7 mg/kg (MRD) x 50kg = 350 mg this pa'ent can safely take 350mg of lidocaine. Number of cartridges that this pa?ent can take = 350mg/36mg = ~10 cartridges Other case scenarios: LA 1 What if 2 LAs are administered? LA 2 If a pa'ent is injected with 2 LAs, the max dose of both is calculated and the one with the lowest max dose is the one we have to keep in mind. In this case, the pa'ent ﬁrst took 2 cartridges of Mepivacaine – 2 cartridges = 72mg Then, ar'caine was administered. But since 2 LAs were taken, it should be kept in mind that the amount of ar'caine given should not exceed the maximum dose of mepivacaine (297mg) since it has the lower dose So, 72mg of Mepivacaine = 225mg le6 over of the dose 225mg/72mg (amt of Ar'caine per cartridge) = 3 approx car'dges of ar'caine to not exceed the 297mg mark Local Anaesthe'c Agents Used in Dental Injec'ons Ester Type We stopped using esters due to allergic reac?ons – rare sevng but it’s bewer to be safe ✓Procaine ✓Propoxycaine HCl ✓Mixture of Procaine + Propoxycaine Amide Type No allergies reported ✓Mepivacaine ✓Prilocaine ✓Lidocaine ✓Ar?caine ✓Bupivacaine Procaine HCL (used as a reference for potency and toxicity) It’s an ester, very strong vasodilator Potency: 1 (Procaine=1) Toxicity: 1 (Procaine=1) Metabolism: Blood plasma (Pseudocholinesterase present in blood) Excre?on:2% unchanged in urine: Onset of ac?on: 6-8 min (long onset) Anesthe?c half-life: 6 min Eﬀec?ve concentra?on: 2%-4% Topical anesthe?c ac?on: N.A 2% procaine (plain) provides essen?ally no pulpal anesthesia and from 15 to 30 minutes of soN ?ssue anesthesia – short DOA because it gets metabolized quickly in the blood + it’s a strong vasodilator thus it increases blood ﬂow and 'washes itself out’. the greatest vasodila?on of all clinically used local anesthe?c, even amides. Immediate management of inadvertent intra-arterial (IA) injec?on of a drug – this is basically the clinical use of Procaine due to its short DOA and long onset. Propoxycaine Potency: 7-8 (Procaine=1) – stronger than procaine Toxicity: 7-8 (Procaine=1) – more toxic than procaine and Metabolism: Plasma & liver – so longer DOA compared to procaine Excre?on: Kidneys Onset of ac?on: Rapid (2-3 min) Anesthe?c half-life: N.A Topical anesthe?c ac?on: N.A Eﬀec?ve concentra?on: 0.4% 0.4% propoxycaine/2% procaine (they mixed it with procaine to make procaine a stronger anesthe?c and to weaken the strength of propoxycaine) with 1:20,000 levonordefrin (United States) or with 1:30,000 norepinephrine (Canada) provided approximately 40 minutes of pulpal anesthesia and 2 to 3 hours of so6 'ssue anesthesia. Amide-Type Local Anesthe?cs Most common and safer Lidocaine Widely used and almost always a good op?on Potency: 2(Procaine=1) Toxicity: 2 (Procaine=1) but s?ll safe enough Metabolism: Liver into two metabolites Excre?on: Kidneys Eﬀec?ve concentra?on: 2% Topical anesthesia: Yes (5%) Onset of ac?on: Rapid (3-5 mins) DOA: 60 minutes pulpal & 3 to 5 hours of soN ?ssue anesthesia. Anesthe?c half-life: 90 min Vasodila?on proper?es: Procaine > Lidocaine > Prilocaine > Mepivacaine —> directly aNer procaine, so we can’t use it without a vasoconstrictor. Pregnancy classiﬁca?on: B (safe) Safety during lacta?on: S (yes) Lidocaine had replaced procaine (Novocaine) as the most widely used local anesthe?c in both medicine and den?stry. Compared with procaine, lidocaine possesses: ✓a signiﬁcantly more rapid onset of ac?on (3 to 5 minutes vs. 6 to 10 minutes), ✓ produces more profound anesthesia, ✓has a longer dura?on of ac?on, ✓and has greater potency + acceptable toxicity/ Which Lidocaine prepara'on? It is usually found in these prepara?ons: 1- 1:50,000 epinephrine. (has higher epi conc) 2- 1:100,000 epinephrine. (typically used) 3- 1:200,000 epinephrine. 4- 1:300,000 epinephrine. (elderly and hyper-responders) For most procedures in a typical dental pa?ent, 2% lidocaine with 1:100,000 epinephrine is preferred to 2% lidocaine with 1:50,000 epinephrine. The 1:50,000 solu?on provides excellent haemosta?c ac?on (but some studies found it can cause necrosis to high vascularity areas like the palate) The 1:100,000 dilu?on also may be used for hemostasis, but it is not as eﬀec?ve since the 1:50,000 has a higher dose of epinerphrine. Rebound vasodila'on: Occurs aNer administering epinephrine in LA due to the decrease of epinephrine concentra?on in the body aNer the metabolism of LA. Thus, the hemosta?c ac?on of epinephrine is to be used only intraopera?vely and not post- op The only recommended use of 2% lidocaine 1:50,000 epinephrine concentra?on is for hemostasis (small volumes into the surgical site). 2% lidocaine with 1:200,000 or 1:300,000 epinephrine provides the same dura?on of pulpal (60 mins) and soN ?ssue anesthesia (2-3hrs), although a lower level of hemostasis. Their use is recommended in elderly pa?ents or hyper-responders to epinephrine Lidocaine Overdose Signs and symptoms of lidocaine toxicity (overdose) may be the same (central nervous system [CNS] s?mula?on followed by CNS depression) as other agents. However, the s?mulatory phase may be brief or may not develop at all. Although muscle tremor and seizures commonly occur with overly high lidocaine blood levels. The ﬁrst signs and symptoms of lidocaine overdose may include drowsiness, leading to loss of consciousness and respiratory arrest. Mepivacaine HCl (can be used without a vasoconstrictor) Potency: 2(Procaine=1) Toxicity: 1.5-2 (Procaine=1) Metabolism: Liver Excre?on: Kidney Onset of ac?on: Rapid (3-5 mins) Anesthe?c half-life: 1.9 hours Eﬀec?ve concentra?on: 3% plain, 2% with vasoconstrictor. Topical anesthesia: N.A Vasodila?on proper?es: Slightly vasodilator DOA: 20-40 minutes pulpal anesthesia if used plain which can be enough for children (compared to 10-20min Lidocaine plain) Pregnancy classiﬁca?on: C – No. Safety during lacta?on: S – Almost considered safe, needs more research but Lidocaine is bewer. 3% Mepivacaine Without a Vasoconstrictor For pa?ents in whom a vasoconstrictor is not indicated For dental procedures requiring neither lengthy nor profound pulpal anesthesia. Mepivacaine plain is the most used local anesthe?c in pediatric pa?ents when the trea?ng doctor is not a pediatric den?st (e.g., is a general prac??oner) and oNen is quite appropriate in the management of geriatric pa?ents (elderly pa?ents). 2% Mepivacaine With a Vasoconstrictor, Levonordefrin 1:20,000 Depth and dura?on of anesthesia is similar to Lidocaine combina?ons. Mepivacaine is available in combina?on with levonordefrin (vasocon) (1:20,000). Where hemostasis is desired, epinephrine is preferred to levonordefrin Signs and symptoms of mepivacaine overdose usually follow the more typical pawern of CNS s?mula?on followed by depression. Can be used in pa?ents with an epinephrine allergy. Prilocaine HCL one of the safest amides LA + can be used plain Potency: 2 (procaine = 1; lidocaine = 2). Toxicity: 1 (procaine = 1; lidocaine = 2); 40% less toxic than lidocaine. Metabolism: ✓Is signiﬁcantly diﬀerent from lidocaine and mepivacaine as it undergoes more rapid and complete biotransforma?on. ✓Orthotoluidine, a by-product, can induce methemoglobinemia which leads to observable cyanosis. Especially those who have sickle cell anemia ✓Limi?ng the total prilocaine dose to 600 mg (FDA recommenda?on) avoids symptoma?c cyanosis. Excre?on: kidneys. Renal clearance of prilocaine is faster than for other amides, Onset of Ac?on: Slightly slower than that of lidocaine (3 to 5 minutes). Eﬀec?ve Dental Concentra?on 4%. Anesthe?c Half-Life: 1.6 hours. Topical Anesthe?c Ac?on: ✓Not in clinically acceptable concentra?ons. ✓Prilocaine, in its uncharged base form, is an integral part of EMLA cream Vasodila?ng Proper?es: Procaine > Lidocaine > Prilocaine > Mepivacaine Pregnancy Classiﬁca?on B, safe. Safety During Lacta?on: Unknown. Prilocaine Prepara'ons: Inﬁltra?on with Prilocaine 4% plain provides short dura?ons of pulpal (10 to 15 minutes) and soN ?ssue (up to 2 hours) anesthesia – Can be used in pediatrics. Whereas regional nerve block provides pulpal anesthesia of 40 to 60 minutes & soN ?ssue anesthesia for 2 to 4 hours. Thus, a plain prilocaine block = Lidocaine or mepivacaine with a vasoconstrictor. Prilocaine with epinephrine provides lengthy anesthesia while oﬀering a less concentrated epinephrine dilu?on: 1:200,000 = might not be hemosta?c enough. In epinephrine-sensi?ve pa?ents requiring prolonged pulpal anesthesia (≥60 minutes), prilocaine plain or with 1:200,000 epinephrine is strongly recommended. It is rapidly bio transformed and, for this reason, is considered to be a safe local anesthe?c (e.g., lower toxicity) C/I of Prilocaine: Prilocaine is rela?vely contraindicated in pa?ents with idiopathic or congenital methemoglobinemia, hemoglobinopathies (sickle cell anemia), anemia, or cardiac or respiratory failure evidenced by hypoxia, because methemoglobin levels are increased, decreasing oxygen-carrying capacity. Prilocaine administra?on is also rela?vely contraindicated in pa?ents receiving acetaminophen or phenace?n, both of which produce eleva?ons in methemoglobin levels. Neurotoxicity and paresthesia? Ar'caine HCl Newest agent Classiﬁca?on: Hybrid molecule. Classiﬁed as an amide; however, it possesses both amide and ester characteris?cs. Metabolism: both plasma and liver (because it’s an ester x amide) Potency 1.5 ?mes that of lidocaine; 1.9 ?mes that of procaine. Toxicity Similar to lidocaine and procaine. Stronger but less toxic because it gets metabolized in the plasma alongside the liver. Excre?on: Via kidneys Vasodila?ng Proper?es: Ar?caine = lidocaine – not used plain. Onset of Ac?on: ✓Ar?caine 1:200,000, inﬁltra?on 1 to 2 minutes, mandibular block 2 to 3 minutes; ✓Ar?caine 1:100,000, inﬁltra?on 1 to 2 minutes, mandibular block 2 to 3 minutes. Eﬀec?ve Dental Concentra?on: 4% with 1:100,000 or 1:200,000 epinephrine. Anaesthe?c Half-Life: 0.5 hours [27 minutes]. Topical Anaesthe?c Ac?on: N.A Pregnancy Classiﬁca?on: C, unafe. Safety During Lacta?on: Unknown (use with cau?on in females who are breast- feeding because it is not known whether ar?caine is excreted in milk). It has been claimed that ar?caine is able to diﬀuse through so6 and hard 'ssues more reliably than other local anesthe?cs Thus, it is claimed clinically that following maxillary buccal inﬁltra?on, ar?caine on occasion may provide palatal soN ?ssue anesthesia, obvia?ng the need for palatal injec?on. The signiﬁcant success of ar?caine administered by buccal inﬁltra'on in the mandible of adult pa?ents. Reports of paranesthesia following local anesthe?c administra?on. An overwhelming majority of reported cases occurred following inferior alveolar nerve block and primarily involved the lingual nerve. Ar'caine HCL rela've C/I: Ar?caine HCl should be used with cau?on in persons with hepa'c disease and signiﬁcant impairment in cardiovascular func'on Class C drug during pregnancy. Use with cau?on in females who are breast- feeding Administra?on to children younger than 4 years is not recommended because insuﬃcient data are available to support such usage Bupivacaine HCL most common long ac?ng LA Potency: four ?mes that of lidocaine, mepivacaine, and prilocaine Toxicity: less than four ?mes than that of lidocaine and mepivacaine (highly toxic, not rou?nely used) Metabolism: Liver by amidase Excre?on: Kidneys, 16% unchanged bupivacaine has been recovered from human urine. Onset of ac?on: slower onset ?me than other commonly used LA (6 to 10 minutes) Eﬀec?ve concentra?on: 0.5% Anesthe?c half-life: 2.7 hours Vasodila?on proper?es: rela?vely signiﬁcant, greater than those lidocaine, prilocaine, and mepivacaine, yet considerably less than those of procaine. 20-40 minutes pulpal anesthesia for plain (compared to 10-20min Lidocaine plain) Topical anesthesia: N.A Pregnancy classiﬁca?on: C, unsafe. Safety during lacta?on: S ? MRD bupivacaine is 90 mg. Bupivacaine is available as a 0.5% solu?on with 1:200,000 epinephrine (used with vasoconstrictors in long procedures) Two primary indica'ons for its u'liza'on in den'stry: 1. Lengthy dental procedures for which pulpal (deep) anesthesia in excess of 90 minutes is necessary (e.g., full mouth reconstruc?on, implant surgery, extensive periodontal procedures) 2. Management of postopera?ve pain (e.g., endodon?c, periodontal, pos?mplant, surgical) The pa?ent's requirement for postopera?ve opioid analgesics is considerably lessened. Rela've C/I: Bupivacaine is not recommended in younger pa?ents or in those for whom the risk of postopera?ve soN ?ssue injury produced by self-mu?la?on is increased, such as physically and mentally disabled persons. Bupivacaine is rarely indicated in children because pediatric dental procedures are usually of short dura?on. So, in summary: The dr read them all Amides are preferred to esters whenever possible. A minimum of two drugs is recommended for most oﬃces: 1- Short-dura?on pulpal anesthe?c (≈30 minutes) 2- Intermediate-dura?on pulpal anesthe?c (≈60 minutes) 3- Long-dura?on pulpal anesthe?c (90 or more minutes) 4- Topical anesthe?c for ?ssue prepara?on before injec?on of local anesthe?c Anesthe'cs and Topical Applica'on: Conven?onal topical anesthe?cs are unable to penetrate intact skin but do diﬀuse through abraded skin and any mucous membranes. The concentra?on of a local anesthe?c applied topically is greater than that of the same local anesthe?c administered by injec?on and in addi?on, topical anesthe?cs need longer ?me to penetrate. Higher concentra?on also increases the risk of toxicity (Do not contain vasoconstrictors) the safest two topical LAs —> lidocaine and benzocaine. Many local anesthe?cs used eﬀec?vely via injec?on prove ineﬀec?ve when applied topically. As a general rule, topical anesthe?cs are eﬀec?ve only on surface ?ssues (2 to 3 mm) – superﬁcial. The topical anesthe?cs benzocaine and lidocaine base (not the HCl form used by injec?on) are insoluble in water so it can pass lipid bilayer membrane. However, they are soluble in alcohol, propylene glycol, polyethylene glycol, and other vehicles suitable for surface applica?on. The base forms of benzocaine and lidocaine are slowly absorbed into the cardiovascular system and therefore are less likely to produce an overdose reac'on following typical dental applica?on. Topical L.A in Pressurized spray containers are diﬃcult to control the amount of anesthe?c expelled and to conﬁne it to the desired site of applica?on. They are no more eﬀec?ve than other forms. Spray devices that do not deliver measured doses should not be used intraorally. + Sprays can easily be sprayed on wrong sites and goes away quickly. When applying a topical anesthe?c that’s in the form of a gel, you need to make sure that the ?ssue/gauze/cowon is dry. You also need to be pa?ent as it can take up to 2-3 minutes to start working. Mepivacaine and procaine are not used topically. Benzocaine Most commonly used topical anesthesia Benzocaine (ethyl p-aminobenzoate) is an ester Poor solubility in water Poor absorp?on into the cardiovascular system thus its safe. Systemic toxic (overdose) reac?ons virtually unknown Remains at the site of applica?on longer, providing a prolonged dura?on of ac?on Not suitable for injec?on Inhibits the an?bacterial ac?on of sulfonamides Availability (aerosol, gel, gel patch, ointment, and solu?on) Cocaine Considered a topical anesthe?c as well Ester that occurs naturally as a white crystalline solid that is highly soluble in water Used exclusively via topical applica?on (injec?on is C/I) Onset of topical anesthesia ac?on is rapid (1 min). Dura?on up to 2 hours. It is absorbed rapidly but eliminated slowly, dosage is not carefully monitored. Cocaine is the only local anesthe?c consistently produce vasoconstric?on Poten?ate the ac?ons of endogenous epinephrine and norepinephrine. Psychological dependence and tolerance Clinical manifesta?ons: CNS excita?on, then depression ad death It is recommended that the concentra?on of cocaine not exceed 4% for topical applica?on to oral mucous membranes. Solu?ons of cocaine are unstable and deteriorate on standing. Because of the extreme abuse poten?al of cocaine, its use as a topical anesthe?c in den?stry is not recommended. Topically applied cocaine is used occasionally before nasal-endotracheal intuba?on is performed in the opera?ng theatre to minimize bleeding from this highly vascular region and pain as the endotracheal tube is passed. EMLA (Eutec'c Mixture of Local Anesthe'cs) EMLA cream (composed of lidocaine 2.5% and prilocaine 2.5% - prilocaine alone cannot be used topically so it was mixed with lidocaine) Provide surface anesthesia for intact skin Used primarily before painful procedures such as venipuncture EMLA must be applied 1 hour before the procedure., and lasts for 1 to 2 hours aNer removal. “EMLA is not recommended for use on mucous membranes,” some studies suggest otherwise. Tetracaine Hydrochloride Rela?vely new agent, more potent than cocaine Long-dura?on ester local anesthe?c that can be injected or applied topically Highly soluble in water Five to eight ?mes more potent than cocaine Onset of ac?on aNer topical applica?on is slow. Dura?on of ac?on is approximately 45 minutes aNer topical applica?on. Rapidly absorbed through mucous membranes thus it has a high toxicity poten?al. Use should be limited to small areas to avoid rapid absorp?on. Cau?on is urged because of great poten?al for systemic toxicity. Tetracaine in a 3% concentra?on, with the vasoconstrictor oxymetazocine, has been shown to provide pulpal anesthesia of maxillary teeth when administered by aerosol spray into a pa?ent's nares as it can reach the ?p of root apex of molars. Lidocaine Lidocaine is available in two forms for topical applica?on: 1- Lidocaine base, which is poorly soluble in water, used as a 5% concentra?on, indicated for use on ulcerated or abraded ?ssue; 2- Lidocaine hydrochloride, its water-soluble prepara?on, used as a 2% concentra?on and penetrates ?ssue more eﬃciently than the base form. However, greater risk of toxicity than the base form. MRD following topical applica?on is 200 mg. Availability: Lidocaine base is available as an aerosol spray, ointment, patch, and solu?on in various dosage forms Lidocaine HCl is available as an oral topical solu?on in 20 mg/mL (viscous) and 40 mg/mL (solu?on). Benzocaine and lidocaine are the most common, EMLA is used for skin and mucous membrane, tetracaine is highly absorbable can be toxic. END OF SHEET, GOOD LUCK

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