Published on April 27, 2014
LOCAL ANESTHESIA ASHA REDDY
CONTENTS • DEFINATION • FUNDAMENTALS OF IMPULSE GENERATION AND TRANSMISSION • THEORIES OF MECHANISM OF ACTION OF LOCAL ANESTHESIA • Acetyl choline theory • Calcium Displacement Theory • Surface charge theory • membrane Expansion theory • Specific Receptor theory • LOCAL ANESTHESIA • Characteristics • History • Composition • TYPES OF ANESTHETICS USED • FACTORS EFFECTING LA EQUILIBRIUM • TOPICAL ANESTHETICS • PHARMACOKINETICS OF LOCAL ANESTHESIA • ARMAMENTARIUM • TECHNIQUES OF LOCAL ANESTHESIA • Maxillary • Mandibular • Supplemental Injection techniques • COMPLICATIONS OF LOCAL ANESTHESIA • Local • Systemic
Anaesthesia What is local anesthesia? • Local anesthesia: loss of sensation in a specific area of the body without the loss of consciousness DEFINATION • Local anesthesia is defined as a loss of sensation in a circumscribed area of the body caused by a depression of excitation in nerve endings or an inhibition of the conduction process in peripheral nerves. STANLEY F. MALAMED • Local anesthesia is defined as a reversible temporary cessation of painful impulses from a particular region of the body. KOCH FUNDAMENTALS OF IMPULSE GENERATION AND TRANSMISSION • The concept behind action of local anaesthetics is simple. They prevent both generation and conduction of a nerve impulse. They create a chemical roadblock between source of impulse and the brain. • The aborted impulse , prevented from reaching the brain is not interpreted as pain by the patient • Neuron or nerve cell- is the structural unit of the nervous system • Two types: sensory [afferent] & motor [efferent]. • sensory neurons : conduct impulses from periphery to CNS • Motor neurons : conduct impulses from CNS to the periphery
• Nerve membrane :is 70-80 Angstrom unit. • it is a flexible nonstretchable structure consisting of two layers of lipid molecules • The lipids are oriented with their hydrophilic ends facing the outer surface and hydrophobic ends projecting to the middle of the membrane • Some nerves are myelinated [vertebrates] while some are not. • Myelinated nerve fibres are enclosed in spirally wrapped layers of lipoprotein. • The outermostlayer of myelin consists of schwann cell cytoplasm and its nucleus • There are constictions at regular intervals along the myelinated nerve fiber [nodes of Ranvier] • At these nodes the nerve membrane is exposed directly to the extracellular medium. Electrophysiology of nerve conduction • Nerve conduction Resting stage Depolarisation Repolarisation Resting state / polarized state • Electric membrane potential is – 90 MV • Greater no. of anions (-) inside cell membrane and cations (+) outside cell membrane • k+ inside and Na+ , Cl- outside
• Due to relative permeability to k+ and impermeability to Na+ • Maintaiance by Na+ - Ka+ pump • Depolarization stage • Repolarization stage • Resting state:the nerve membrane is • Slightly permeable to sodium ions [Na+] migrates inwardly becos of the conc gradient [> ouside] favors such migration. Resting nerve membrane is relatively impermeable to sodium • Freely permeable to potassium ions[K+].- K+ ions remain within the axoplasm despite its ability to diffuse freely becos the negative charge of nerve membrane restrains the positively charged ions by electrostatic attraction. • Freely permeable to chloride ions [cl-] remains outside the nerve membrane becos the opposing , nearly equal electrostatic influence forces outward migration. • Membrane channels: Discrete aqeous pores [sodium channels] are molecular structures that mediate its its permeability presence of these channels help membrane permeability or impermeability to certain ions [ gating the ions ] Na ions [ hydrated ] are too large to pass thro the channels at rest during depolarization they pass easily due to widening of these channels
Release of the bound calcium ions from the ion channel receptor site may be the primary factor responsible for inc sodium permeability Theories of mechanism of action of Local Anesthetics • ACETYL CHOLINE THEORY : • CALCIUM DISPLACEMENT THEORY • SURFACE CHARGE THEORY • MEMBRANE EXPANSION THEORY • SPECIFIC RECEPTOR THEORY MEMBRANE EXPANSION THEORY
• LA diffuse to hydrophobic regions of excitable membranes, expanding critical regions in the membrane and preventing an inc in the permeability to sodium ions SPECIFIC RECEPTOR THEORY • Most favoured theory • They bind to the sp. Receptor site in the sodium channel • LA are classified by their ability to react with sp receptor sites in the sodium channel LOCAL ANESTHESIA Desirable characteristics of local anesthesia • Not be irritating to tissues • Not cause any permanent alterations of nerve structure • Low systemic toxicity • Effective: injected or applied on MM • Time of onset: short • Duration of action: long • Free from allergic reactions • Rapid biotransformation in body How local anesthesia work? • Produce conduction block to decrease permeability of ion channels to sodium ions • Sequence of action • Displacement of calcium ions from sodium channel receptor site • Binding of local anaesthetic to receptor site
• Blockade of sodium channel • Decrease in sodium conductance • Depress rate of depolarisation History • Coca leaves from the genus Erythroxylum • Erythroxylum contains high concentration of alkaloid up to 0.7- 1.8% • Alkaloid has natural nitrogen bases found in the coca leaves, also known as cocaine • Genus Erythroxylum discovered in South America, Venezuela, Bolivia, and Peru since pre-Columbian periods • Earliest cultivation and use of the coca leaf went back to about 700 BC in Bolivia and Andes regions • New discoveries showed humans used coca more than 5,000 years ago in Ecuador Development of general and local anesthesia • Took place in Western Europe from 1750 to 1850 • Chemists and physicians collected sample of coca leaves for experiments • Isolated active principle of coca leaf, synthesized to a drug for patients to feel more relief of pain when taking surgeries • In 1860, German chemist Albert Niemann successfully isolate the active principle of coca leaf; he named it cocaine • In 1865, Willhelm Lossen determine the correct molecular formula of cocaine (C17H21NO4) • Niemann discovered the effect of numbness of the tongues caused by alkaloid in 1860 • Based on Niemann’s discovery, Russian physician Basil Von Anrep did experiments on animals, such as rats, dogs, and cats. • He injected small quantity of 1% solution to his tongue; tongue became insensitive • He concluded cocaine is a good drug for surgical anesthetic • William Steward Halsted and Richard John Hall developed the inferior dental nerve block techniques for dentistry
• Procaine replaced cocaine in later years but it had many draw backs • Nitrous oxide gas was more commonly used than procaine Nitrous oxide COMPOSITION • LOCAL ANESTHETIC • VASOCONSTRICTOR • ANTIOXIDANT • PRESERVATIVE • FUNGICIDE • SALT • VEHICLE • Local anesthetic: may be an amide or ester [lidocaine 2%] • Vasoconstrictor: Epinephrine • It causes vasoconstriction and prevents rapid absorption of L.A into blood stream thereby reducing their toxicity • Increases duration of action of local anesthetics and also their potency • Causes hemostasis in the local area into which it is injected and helps in creating blood free field • Epinephrine conc – 1:100,000[normally used] • Antioxidant : sodium metabisulphite prevents rapid oxidation of the vc & prolongs shelf life of the soln • Preservative : Methyl paraben • Salt: Bicarbonate is added to make soln isotonic. LA & VS has a ph of 4-5 which cause burning sensation in pt. so bicarbonate is added to make soln isotonic • Ringers lactate/ distilled water – to dissolve all contents and make it injectable providing addnl vol. for injection without increasing total dose administered Local Anesthetic • A Drug that, when injected into tissue, has little or no irritating effects and when absorbed into the nerve will temporarily interrupt its conduction.
Classification of local anesthetic agents • ESTERS • Esters of benzoic acid • Cocaine • Procaine • Benzocaine • Butacaine • Esters of PABA • Chlorprocaine • Propoxycaine • Tetracaine • AMIDES • Atricaine • Bupivacaine • Dibucaine • Etidocaine • Lidocaine • Mepivacaine • Prilocaine • Ropivacaine • QUINOLONE • Centbucridine CLINICAL CLASSIFICATION Short duration • lidocaine HCL 2% • Mepivacaine HCL 3% • Prilocaine HCL 4% ( By infiltration ) Intermediate duration • Articaine HCL 4% + epinephrine 1:100000 • Articaine HCL 4% + epinephrine 1:200000 • lidocaine HCL 2% + epinephrine 1:50000 • lidocaine HCL 2%+ epinephrine 1:100000 • Prilocaine HCL 4% ( By nerve block only ) • Mepivacaine HCL 2% + levonordefrin 1:200000 • Mepivacaine HCL 2% + epinephrine 1:100000 Long duration • Bupivacaine HCL 0.5% + epinephrine 1: 200000 Classification based on biological site and mode of action
• Class A : External surface of receptor BIOTOXINS • Class B : Internal surface of Receptors SCORPION VENOM QUARTERNARY AMMONIUM ANALOGUES OF LIDOCAINE • Class C : Receptor independent BENZOCAINE • Class D : Receptor and receptor independent MOST CLINICALLY USED AGENTS Structures of Amides and Esters • The amine end is hydrophilic (soluble in water), anesthetic molecule dissolve in water in which it is delivered from the dentist’s syringe into the patient’s tissue. It’s also responsible for the solution to remain on either side of the nerve membrane. • The aromatic end is lipophilic (soluble in lipids). Because nerve cell is made of lipid bilayer it is possible for anesthetic molecule to penetrate through the nerve membrane. • The trick the anesthetic molecule must play is getting from one side of the membrane to the other Differences of Esters and Amides • All local anesthetics are weak bases. Chemical structure of local anesthetics have an amine group on one end connect to an aromatic ring on the other and an amine group on the right side. The amine end is hydrophilic (soluble in water), and the aromatic end is lipophilic (soluble in lipids) • Two classes of local anesthetics are amino amides and amino esters. Amides: Esters: --Amide link b/t intermediate --Ester link b/t aromatic ring intermediate chain
and aromatic ring --Metabolized in liver and very --Metabolized in stable in the solution plasma --Cause allergic reactions • Ester type local anesthetics are no longer available in cartridge forms but benzocaine and tetracaine are still used as topical anesthetic agents LIDOCAINE • The most popular contains epinephrine 1:100,000 and provides good anesthesia for healthy patients. • Lidocaine with epinephrine 1:50,000 is used for hemostasis, but because of the rebound effect noted earlier, it should be used sparingly • In 1940, the first modern local anesthetic agent was lidocaine, trade name Xylocaine® • It developed as a derivative of xylidine • Lidocaine relieves pain during the dental surgeries • Belongs to the amide class, cause little allergenic reaction; it’s hypoallergenic • Sets on quickly and produces a desired anesthesia effect for several hours • Lidocaine Hcl • Prepared by Nils Lofgren,1943 • 1st amide to be marketed. Used as standard for comparison • Onset of action is 2-3 mins • Effective dental conc is 2% • Half life is 1.6 hrs [90 mins ] • Topical anesthetic action : in 5% conc • Maxm recommended dose [MRD] • 2% Lidocaine with epinephrine-3.2mg/lb or 7mg/kg body wt [not to exceed 500 mg][same for children] • 2% lidocaine without epinephrine- 2 mg/lb or 4.4 mg/kg [not to exceed 300mg] • Vasoconstrictor [adrenaline] – 0.2 mg or 200 ug [healthy pts] • 0.04mg or 40 ug – cv disease
ARTICAINE • Articaine is a newer anesthetic typically given in a 4% solution with 1:100,000 epinephrine. • Practitioners reported rarely missing a inferior alveolar nerve block with Articaine. • However, concern has arisen about its potential for tissue necrosis and persistent nerve parasthesia. • High penetrating MEPIVACAINE • 3% Mepivacaine without a vasoconstrictor is used as anesthetic for patients who cannot take a vasoconstrictor or for short procedures. • It is appropriate for pedodontics and for use on geriatric patients. • 2% Mepivacaine with vasoconstrictor provides pulpal anesthesia that is similar to lidocaine with epinephrine, but hemostasis is not as intense PRILOCAINE • The action of prilocaine plain varies with the area injected (longer with a nerve block). • Prilocaine with vasoconstrictor gives good anesthetic effect and uses a 1:200,000 concentration of epinephrine BUPIVACAINE • Bupivacaine is used when pulpal anesthesia is desired for longer appointments and when postoperative pain is anticipated. • Bupivacaine is not recommended for children or handicapped patients because of the increased risk of postoperative injury (chewing on a numb lip). CENTBUCRIDINE • It does not effect the CNS or CVS adversely except when administered in very large doses. • Used in 0.5% concentrations TAMED BIOTOXINS • Tetradotoxin and Saxitoxin • Block axonal depolarization by blocking transmembrane inward sodium current.
• The diffusion and penetrating abilities are very poor, can not cross the epineurium. • Systemic toxicity to brain , heart and muscle is also of concern HYALURONIDASE • An enzyme that breaks down intracellular cement. • Advocated as an additive to local anesthetics as it permits injected solutions to spread and penetrate tissues • Available as Wydase in a lyophilized powder and a stabilized solution. • Added to the cartridge just before administration by removing approximately 1/8th of solution. • Allergic reactions have been demonstrated PH ALTERATIONS • When a local anaesthetic is injected into tissue, two particles are in equilibrium: a lipophilic neutral particle and a positively charged hydrophilic particle Three factors can affect this equilibrium: • The pKa of the local anaesthetic, • The pH of the local anaesthetic • The pH of the tissue in which the anaesthetic is being deposited. pKa of local anesthetics • The pKa of a local anaesthetic is defined as the pH at which half of the local anaesthetic particles in equilibrium are neutral (RN) and half are charged (RNH+ ) • Most local anaesthetics have pKa > 7.4 RNH+ RN + H+ pH of local anesthetics • Most local anesthetics have a pH between 5.5 and 7 with out vasoconstrictor and less than 5.5 with vasoconstrictor The addition of substances to the anesthetic that alkalinizes the solution should make the drug’s administration more comfortable.
Higher the pH more rapid is the onset of action and greater potency. Carbonated local anesthetics • Nerves internal pH is least affected by external pH fluctuations. • Gases diffuse readily across the nerve membranes Co2 CO2 + H2O H2CO3 H + + HCO3 RNH+ RN + H+ Block conduction SODIUM BICARBONATE Added immediately before injection alkalinizes the solution increasing the number of uncharged base molecules NaHCO3 Na+ + HCO3 RNH+ RN + H+ H2CO3 Disadvantages of alkalinization • If ph is too high local anesthetic may precipitate out as the drug base • Stability of local anesthetic decreases as ph increases hence shelf life is decreased TOPICAL ANESTHETICS • Important component for atraumatic admn of intraoral local anesthesia • Do not contain vasoconstrictors • Effective only on surface tissues • Benzocaine and Lidocaine are most commonly used • Effective only on abraded skin
INTRAORAL TOPICAL ANESTHETIC DELIVERY 1. As water soluble salts 2. Dissolved in organic solvents 3. As oil–water emulsions 4. As eutectic mixtures 5. Incorporated into patches and controlled release devices 6. Using iontophoresis and phonophoresis 7. Incorporated into liposome's EUTECTIC MIXTURE OF LOCAL ANESTHESIA [EMLA • EUTECTIC…Melts at a temperature lower than either of its crystalline constituents • 5% of la +92% of water+ inert stabilizer • Local anesthetic agent oil is emulsified with water • 2.5% lidocaine and 2.5% prilocaine • Agent is made to form a cream with ph of 9 well above the pka of either local anesthetic agents. • High ph ensures 90% or more of the local anesthetic agent is in diffusible uncharged free base for • Intact skin is barrier to diffusion • EMLA should be applied 1 hour before the procedure • Satisfactory numbing occurs 1 hour after application and reaches maximum at 2 to 3 hours and lasts for 1 to 2 hours after removal • Supplied in a 5 g or 30 g tube or as an EMLA anesthetic disc. • It is white round, cellulose disc preloaded with EMLA packaged in a protective laminate foil surrounded with adhesive tape.
LIDOCAINE PATCH • It is an adhesive containing 46.1 mg of lidocaine. • The lidocaine is absorbed by the mucosa, and they claim anesthetic onset within 2.5 minutes of application. • The patch is left in place up to 15 minutes and the anesthetic effect can last up to 30 minutes after removal • levels of lidocaine following application are less than 0.1 µg/mL. • Unlike conventional anesthetic ointments and gels ,patches produce a fair amount of periosteal anesthesia when applied to intact buccal mucosa Iontophoresis • Iontophoresis is a means of delivering local anesthetics to deeper tissue after topical application . • Positively charged drugs such as lignocaine and adrenaline can be encouraged to penetrate the tissue under the influence of electrical charge PHONOPHORESIS
• Phonophoresis is the use of high frequency radio waves to drive drugs into tissues and has been suggested as a possible method of increasing the efficacy of topical applications • . LIPOSOMES • Carrier vehicles composed of naturally occurring lipid and cholesterol , similar in composition to biological membranes. • The relatively large size of the liposome's assures that they remain at the site of administration for a prolonged period of time. • ELECTRONIC DENTAL ANESTHESIA WHAT IS THE MECHANISM OF ACTION OF EDA? • CHRONIC PAIN • ACUTE PAIN Chronic pain • At low frequency setting produces measurable changes in blood levels of L-tryptophan, Seratonin, and beta endorphins. • L tryptophan Seratonin • Seratonin Analgesic actions
Elevates the pain threshold level • Beta endorphins and enkephalins Potent analgesics ACUTE DENTAL PAIN • Melzack and walls gate control theory of pain provides adequate explanation for prevention of acute pain provided by EDA • At high frequency >120 hzs , Patient experiences sensation described as vibratory , throbbing , pulsing , twitching Involves stimulation of large diameter A delta fibers . • If minimum threshold intensity of large diameter a delta fibers is maintained pain impulses brought about by smaller a delta and c fibers will come on a closed gate to be unable to reach the brain. • The large fiber input is said to inhibit central transmission of the overall effects of small fiber input. • Blood levels of seratonin and endorphins likewise are also elevated during high frequency stimulation • Produces elevated blood levels of seratonin and endorphins. • Increased levels persist for several hours after termination of TENS. • Help to block the pain cycle which is responsible for chronicity of pain • When EDA is utilized, electrodes initially are placed in the region of the maxilla/mandible where "anesthesia" is desired. • After establishing a baseline comfort zone of electrical impulses, the patient adjusts the electronic stimulation to suit his or her comfort level. • Patients who have received both local anesthesia and EDA report mixed results with regard to the effectiveness of EDA in pain control and EDA alone does not mitigate the possibility that a dental local anesthetic may be needed. EDA is used most appropriately in routine operative procedures and simple pediatric extractions. Its usefulness may be questioned, however, when cavity preparations more closely approximate the pulp. PHARMACOKINETICS
ABSORPTION DISTRIBUTION METABOLISM (BIOTRANSFORMATION) EXCRETION Absorption: • VASOACTIVITY : All the LA are vasodilators. • ESTER LA are potent vasodilators • COCAINE is the only LA which causes persistent vasoconstriction. (bcoz it inhibits uptake of catecholamines into tissue binding sites.) • PROCAINE is probably the most potent vasodilator ABSORPTION • ORAL ROUTE : All LA are poorly absorbed. • Most LA undergo HEPATIC first pass effect following oral administration. • TOPICAL : Absorbed at different rates. -tracheal –fast as IV - pharyngeal – slower -esophageal/bladder- even slower When no intact layer of skin - it acts.(sunburn remedies ABSORPTION • Injection : The rate of uptake after injection (subcutaneous, intramuscular, IV ) depends on the vascularity of the injection site and the vasoactivity of the drug. • IV- Most rapid intake and is used for the treatment of ventricular dysrhythmias DISTRIBUTION Distribution to body organs : 1. Brain, liver spleen,head,kidney (because they are highly perfused) –initially high levels of LA. 2.SKELETAL MUSCLE : Greatest percentage because it makes largest mass of tissue in the body
• LA can readily cross the blood-brain barrier. • LA can also cross the placenta and can enter the circulating system of the developing fetus. METABOLISM Esters – Hydrolysis in the plasma by the enzyme Pseudo cholinesterase Amides – Metabolized in the liver via a Multi step pathway by Microsomal mixed function Oxidase system (cytochrome p450). EXCRETION The kidneys are the primary excretory organ for both local anesthetic groups. ESTERS appear only in very small quantities in the urine as the parent compound. Amides bcoz of complex process of biotransformation – appear in greater percentage than the esters ARMAMENTARIUM • Equipment necessary for LA administration • Syringes • Needles • topical anesthetics • Anesthetics • Mouth props Types of syringes • Nondisposable breech loading,metallic cartridge type aspirating breech loading, plastic cartridge type aspirating
breech loading metallic cartridge type self aspirating Pressure syringe for periodontal ligament injection • Jet injector • Disposable syringes • Safety syringes • Computer controlled local anesthetic delivery systems • Breech loading ,metallic,catridge-type aspirating • Pressure syringes-used for Intra ligamentary injections JET INJECTOR • Figge and Scherer 1947 needle less injection • Margetis et al 1958 in dentistry • Jet injector-based on principle that liquids forced through very small openings,called jets, at very high pressure can penetrate intact skin or mucous membrane DISADVANTAGES • Cost • Potential to frighten patients with the sudden noise
• Pressure sensation that occur on delivery of the anesthetic • Intrusive appearance of the device • possibility of small Residual hematomas • Leakage of anesthetic • Questionable efficacy for pulpal anesthesia SAFETY SYRINGES • Minimizes accidental needle stick injury. • Syringes posses a sheath that locks over the needle when it is removed from the patient tissues. • Safety syringes are designed to be for single use items. • Reloading the syringe with a second anesthetic catridge and reinjecting with the same syringe is discouraged because this obviates the important safety aspect of the device CCLAD • Wand/compudent • Comfort control syringe • Halstead performed the first anesthetic nerve block a century ago and identified an appropriate drug delivery system –the syringe and hollow bore needle. • Spinello ,later in 1997developed an innovative dental device, which was commercially available as Wand (Milestone Scientific
What does wand do? • Provides increased tactile control and ergonomics , precise needle control during the injection. • Available flow rates of local anesthetic delivery are computer controlled and remains consistent from one injection to the next. • controlled flow of anesthetic is thought to reduce pain and thus patients fear and anxiety. FEATURES OF WAND • With traditional syringe the static position of the needle relative to the beveled end causes deflection , results in missed block or delayed onset of result. • Pen like grasp has the advantage of allowing the operator to rotate the hand piece during penetration and insertion • As the needle is inserted anesthetic is delivered in a constant computer controlled manner regardless of tissue density. • The device provides a better alternative to traditional recapping • Aspiration test can be activated at any time by simply releasing the pressure on foot control rheostat starting a 4.5 second aspiration cycle. • Delivers a controlled rate of flow and controls pressure developing with in the tissue • Administers local anesthetic agent at 2 specific rates of delivery COMFORT CONTROL SYRINGE • CCS has 2 stage delivery system injection begins at an extremely slow rate to prevent pain associated with quick delivery. • After 10 seconds CCS automatically increases speed to the preprogrammed injection rate. • NEEDLES: long,medium,short BIROTATIONAL INSERTION TECHNIQUE (BRIT • Minimizing needle deflection Why needle deflects
• During insertion a force perpendicular to the forward directional movement acts on the surface of needle. • This causes the needle to bend or deflect in a direction opposite to which the bevel faces. NEEDLE FACTORS INFLUENCING DEFLECTION • Longer the needle length more is the deflection, because the needle has to travel greater distance along the deflecting path. • Smaller the diameter of needle more exaggerated is the bending or deflection. • Small gauge is less capable of resisting the deflection. BRIT AND TRADITIONAL SYRINGE • Traditional syringe is typically held with a palm and thumb grasp and does not permit such a technique effectively. • The wand compudent employs a light weight hand piece that is held with a pen like or dart grasp that is easily rotated. deflection is eliminated or neutralized from the constant changing of bevel orientation as it is rotated DISADVANTAGES • Cost • Potential to frighten patients with the sudden noise • Pressure sensation that occur on delivery of the anesthetic • Intrusive appearance of the device • possibility of small Residual hematomas • Leakage of anesthetic • Questionable efficacy for pulpal anesthesia SAFETY SYRINGES • Safety syringes are designed to be for single use items. • Reloading the syringe with a second anesthetic catridge and reinjecting with the same syringe is discouraged because this obviates the important safety aspect of the device ADDITIONAL ARMAMENTARIUM • Topical antiseptic • Topical anesthetic • Applicator sticks • Cotton gauge
• Hemostat NERVE BLOCK TECHNIQUES • For dental anaesthesia, the neuroanatomical focus is the fifth cranial nerve, also known as the trigeminal nerve. • This nerve has three divisions - the ophthalmic division (V1), the maxillary division (V2) and the mandibular division (V3). • The maxillary dentition receives innervation from V2, and the mandibular dentition receives innervation from V3. THE MAXILLARY NERVE • The maxillary nerve enters the pterygopalatine fossa and branches into three major sections: the ganglionic branches, the zygomatic nerve and the posterior superior alveolar nerve. • The ganglionic branches travel to the pterygopalatine ganglion, which in turn sends sensory, parasympathetic and sympathetic fibres back to the maxillary nerve • The zygomatic nerve enters the orbit and travels along the lateral wall. It bifurcates into two terminal branches, the zygomaticofacial nerve, which supplies sensation to the cheek, and
the zygomaticotemporal nerve, which supplies sensation to the temple area • There is also a parasympathetic component to the lacrimal gland • The posterior superior alveolar nerve travels inferiorly on the infratemporal surface of the maxilla, entering the maxillary sinus and eventually terminating in sensory branches for the maxillary molars and their surrounding buccal gingiva, with the possible exception of the mesiobuccal root of the first molar • However,the middle superior alveolar nerve is not present in all people; if the nerve is absent, these areas are innervated by the posterior and anterior superior alveolar nerves • The main areas of sensory innervation for the anterior superior alveolar nerve are the cuspid, and central and lateral incisors and the buccal gingiva in that area. • The infraorbital nerve continues and eventually passes through the infraorbital foramen onto the face, supplying the lower eyelid, the side of the nose and the upper lip • LOCAL INFILTRATION: • Small terminal nerve endings in the area of dental treatment are flooded with local anaesthetic solution.Treatment is done in the same area of in which solution has been deposited.
• FIELD BLOCK: Local anaesthetic solution is deposited near the larger terminal branch, so the anaesthetized area will be circumscribed to prevent the passage of impulse from the tooth to CNS.Treatment is done in an area away from the site of injection NERVE BLOCK: LA deposited close to the main nerve trunk usually at a distance from the site of operative intervention. Eg: posterior superior alveolar nerve block. Inferior alveolar nerve block MAXILLARY INJECTION TECHNIQUES SUPRA PERIOSTEAL INJECTION: ( Local Infiltration ) INDICATIONS: • Pulpal anaesthesia of maxillary teeth when treatment is limited to one or two tooth . • Soft tissue anaesthesia for surgical procedure in a circumscribed area CONTRAINDICATION: • Infection or acute inflammation in the area of injection. DISADVANTAGES: • Need for multiple needle insertions. • Necessary to administer large volume of solution. TECHNIQUE:
AMOUNT TO BE DEPOSITED- 0.6ml over 20 sec. POSTERIOR SUPERIOR ALVEOLAR NERVE BLOCK • One of the frequently used nerve blocks in dentistry. • The anesthetic solution is deposited behind the tuberosity , near the posterior superior alveolar nerve before it enters the maxillary sinus • The posterior superior alveolar (PSA) nerve block, otherwise known as the tuberosity block or the zygomatic block, is used to achieve anesthesia of the maxillary molar teeth up to the 1st molar with the exception of its mesiobuccal root in some cases. • One of the potential complications of this technique is the risk of hematoma formation from injection of anesthetic into the pterygoid plexus of veins or accidental puncture of the maxillary artery. Aspiration prior to injection is indicated when the PSA block is given • The indications for this technique are the need to anesthetize multiple molar teeth • In individuals with coagulation disorders, care must be taken to avoid injection into the pterygoid plexus or puncture of the maxillary artery. 25- or 27-gauge short needle is preferred for this technique. Technique • Identify the height of the mucobuccal fold over the 2nd molar. This will be the injection site. • The right handed operator should stand at the nine o’clock to ten o’clock position whereas the left handed operator should stand at the two o’clock to three o’clock position. Retract the lip with a retraction instrumen • Hold the syringe with the bevel toward the bone. • Insert the needle at the height of the mucobuccal fold above the maxillary 2nd molar at a 45 degree angle directed superiorly, medially, and posteriorly (one continuous
movement). Advance the needle to a depth of three quarters of its total length • No resistance should be felt while advancing the needle through the soft tissue. • If bone is contacted, the medial angulation is too great. Slowly retract the needle (without removing it) and bring the syringe barrel toward the occlusal plane. This will allow the needle to be angulated slightly more lateral to the posterior aspect of the maxilla. • Prior to injecting, one should aspirate in two planes to avoid accidental injection into the pterygoid plexus. After the first aspiration, the needle should be rotated one quarter turn. The operator should then reaspirate. • If positive aspiration occurs, slowly retract the needle one to two millimeters and reaspirate in two planes. • Successful injection technique will result in anesthesia of the maxillary molars (with the exception of the mesiobuccal root of the first molar in some cases), and associated soft tissue on the buccal aspect. Complications HEMATOMA • This is commonly produced by inserting the needle too for posteriorly into the pterygoid plexus of veins . • In addition maxillary artery may be perforated. • Use of short needle minimises the risk of pterygoid plexus puncture Middle Superior Alveolar Nerve Block • The middle superior alveolar nerve block is useful for procedures where the maxillary premolar teeth or the mesiobuccal root of the 1st molar require anesthesia. • Although not always present, it is useful if the posterior or anterior superior alveolar nerve blocks or supraperiosteal infiltration fails to achieve adequate anesthesia • Individuals in whom the MSA nerve is absent, the PSA and ASA nerves provide innervation to the maxillary premolar teeth and the mesiobuccal root of the 1st molar • Contraindications include acute inflammation and infection in the area of injection or a procedure involving one tooth where local
infiltration will be sufficient. A 25- or 27-gauge short needle is preferred for this technique. Technique • Identify the height of the mucobuccal fold above the maxillary 2nd premolar. This will be the injection site. • The right handed operator should stand at the nine o’clock to ten o’clock position whereas the left handed operator should stand at the two o’clock to three o’clock position. • Retract the lip with a retraction instrument and insert the needle until the tip is above the apex of the 2nd premolar tooth . • Aspirate and inject anesthetic solution slowly over the course of one minute. Successful execution of this technique provides anesthesia to the pulp, surrounding soft tissue and bone of the 1st and 2nd premolar teeth and mesiobuccal root of the 1st molar.1 Contraindications • Infection or inflammation in the area of injection or needle insertion or drug deposition Anterior Superior Alveolar Nerve Block/ Infraorbital Nerve Block • The anterior superior alveolar (ASA) nerve block or infraorbital nerve block is a useful technique for achieving anesthesia of the maxillary central and lateral incisors and canine as well as the surrounding soft tissue on the buccal aspect. • In patients that do not have an MSA nerve, the ASA nerve may also innervate the premolar teeth and mesiobuccal root of the 1st molar. Indications for the use of this technique include procedures
involving multiple teeth and inadequate anesthesia from the supraperiosteal technique. A 25 gauge long needle is preferred for this technique Technique • Place the patient in the supine position. Identify the height of the mucobuccal fold above the maxillary 1st premolar. • This will be the injection site. • The right handed operator should stand at the ten o’clock position whereas the left handed operator should stand at the two o’clock position. • Identify the infraorbital notch on the inferior orbital rim. • The infraorbital foramen lies just inferior to the notch usually in line with the second premolar. • Slight discomfort is felt by the patient when digital pressure is placed on the foramen. It is helpful but not necessary to mark the position of the infraorbital foramen • Retract the lip with a retraction instrument while noting the location of the foramen • Orient the bevel of the needle toward bone and insert the needle at the height of the mucobuccal fold above the 1st premolar • The syringe should be angled toward the infraorbital foramen and kept parallel with the long axis of the 1st premolar to avoid hitting the maxillary bone prematurely. • The needle is advanced into the soft tissue until the bone over the roof of the foramen is contacted. After aspiration, anesthetic cartridge is deposited slowly over the course of one minute. • It is recommended that pressure be kept over the site of injection to facilitate the diffusion of anesthetic solution into the foramen. • Successful execution of this technique results in aesthesia of the lower eyelid, lateral aspect of the nose, and the upper lip. • Pulpal anesthesia of the maxillary central and lateral incisors, canine, buccal soft tissue, and bone is also achieved. In a certain percentage of people, the premolar teeth and the mesiobuccal root of the 1st molar is also anesthetized. • The second direction of insertion bisects the crown of the central incisor from the mesio incisal angle to the distogingival angle
• The needle is inserted about 5mm from the mucobuccal fold and guided into position by the thumb marking the location of infraorbital foramen Greater Palatine Nerve Block • The greater palatine nerve block is useful when treatment is necessary on the palatal aspect of the maxillary premolar and molar dentition • Also called as Anterior palatine nerve block. • This technique targets the area just anterior to the greater palatine canal. The greater palatine nerve exits the canal and travels forward between the bone and soft tissue of the palate. • Contraindications to this technique are acute inflammation and infection at the injection site. A 25- or 27- gauge long needle is preferred for this technique Technique • The patient should be in the supine position with the chin tilted upward for visibility of the area to be anesthetized. The right handed operator should stand at the eight o’clock position whereas the left handed operator should stand at the four o’clock position. • Using a cotton swab, locate the greater palatine foramen by placing it on the palatal tissue approximately one centimeter medial to the junction of the 2nd and 3rd molar • While this is the usual position for the foramen, it may be located slightly anterior or posterior to this location. • Gently press the swab into the tissue until the depression created by the foramen is felt. The area approximately one to two millimeters anterior to the foramen is the target injection site. • Using the cotton swab, apply pressure to the area of the foramen until the tissue blanches.
• Aim the syringe perpendicular to the injection site which is one to two millimeters anterior to the foramen. • While keeping pressure on the foramen, inject small volumes of anesthetic solution as the needle is advanced through the tissue until bone is contacted. • The tissue will blanch in the area surrounding the injection site. • Depth of penetration is usually few millimeters. • Once bone is contacted, aspirate and inject anesthetic solution. • Resistance to deposition of anesthetic solution is normally felt by the operator. • This technique provides anesthesia to the palatal mucosa and hard palate from the 1st premolar anteriorly to the posterior aspect of the hard palate and to the midline medially Nasopalatine Nerve Block • The nasopalatine nerve block, otherwise known as the incisive nerve block and sphenopalatine nerve block, anesthetizes the nasopalatine nerves bilaterally. • In this technique anesthetic solution is deposited in the area of the incisive foramen. • This technique is indicated when treatment requires anesthesia of the lingual aspect of multiple anterior teeth. A 25- or 27-gauge short needle is preferred for this technique. Technique • The patient should be in the supine position with the chin tilted upward for visibility of the area to be anesthetized. • The right handed operator should be at the nine o’clock position whereas the left handed operator should be at the three o’clock position. • Identify the incisive papillae.
• The area directly lateral to the incisive papilla is the injection site. • With a cotton swab, hold pressure over the incisive papilla. • Insert the needle just lateral to the papilla with the bevel against the tissue • Advance the needle slowly toward the incisive foramen while depositing small volumes of anesthetic and maintaining pressure on the papilla. • Once bone is contacted, retract the needle approximately one millimeter, aspirate, and inject anesthetic solution over the course of thirty seconds. • Blanching of surrounding tissues and resistance to the deposition of anesthetic solution is normal. • Anesthesia will be provided to the soft and hard tissue of the lingual aspect of the anterior teeth from the distal of the canine on one side to the distal of the canine on the opposite side Anterior Middle Superior alveolar nerve block • Reported by Friedman and Hochman in 1997 with CCLAD system • Provides anesthesia of multiple maxillary teeth incisors, canines, premolars from single injection site. WHAT IS AMSA NERVE BLOCK • It is a field block of the terminal branches subneural dental plexus of the ASA nerve that innervates the incisors to premolar teeth. • Two anatomical structures the nasal aperture and maxillary sinus cause the convergence of the branches of ASA , MSA nerves and associated subneural dental plexus in the region of apices of the premolars
INJECTION SITE • Hard palate about half way along the imaginary line connecting the mid palatal suture to the free gingival margin. • The location of the line is at the contact point between first and second premolars. ADVANTAGES • As local anesthesia is deposited on the palate so muscles of facial expression and upper lip are not anesthetized. • Minimum volume of local anesthesia is needed. AREAS ANESTHETIZED • Pulpal anesthesia of maxillary incisors, canines and Premolars. • Buccal attached gingiva of the same teeth • Attached palatal tissues from midline to free gingival margin of the associated teeth. PALATAL APPROACH ANTERIOR SUPERIOR ALVEOLAR NERVE BLOCK • Defined by Friedman and • Hochman with CCLAD.
• P ASA is similar to nasopalatine nerve block in many aspects but it differs from it in its final target. • The position of the needle is within the incisive canal • Volume of anesthetic administered is 1.4 to 1.8 ml • Nerves anesthetised Nasopalatine , Anterior branches of ASA • Areas anesthetised • Pulps of maxillary central incisors, lateral incisors, and the canines(bilaterally) • Facial periodontal tissue associated with the same teeth • Palatal periodontal tissue associated with the same teeth • Area of insertion Just lateral to the incisive papilla in the papillary groove. Ensure the needle is in contact with the inner bony wall of the canal • A well defined naso-palatine canal may not be present in some patients TECHNIQUES OF MANDIBULA ANESTHESIA TECHNIQUES OF MANDIBULAR REGIONAL ANESTHESIA • Techniques used in clinical practice for the anesthesia of the hard and soft tissues of the mandible include the supraperiosteal technique, PDL injection, intrapulpal anesthesia, intraseptal injection, inferior alveolar nerve block, long buccal nerve block, Gow -Gates technique, Vazirani-Akinosi closed mouth mandibular block, mental nerve block, and incisive nerve block. • When anesthetizing the mandible the patient should be in the semisupine or reclined position. The right handed operator should stand at the nine o’clock to ten o’clock position whereas the left handed operator should stand at the three o’clock to four o’ clock position
INFERIOR ALVEOLAR NERVE BLOCK [mandibular block] • The inferior alveolar nerve block is one of the most commonly employed techniques in mandibular regional anesthesia. • It is used when multiple teeth in one quadrant require treatment. • While effective, this technique carries a high failure rate even when strict adherence to protocol is maintained. • The target for this technique is the mandibular nerve as it travels on the medial aspect of the ramus, prior to its entry into the mandibular foramen. The lingual, mental, and incisive nerves are also anesthetized. A 25 gauge long needle is preferred for this technique. Technique • The patient should be in the semisupine position. • The right handed operator should be in the eight o’clock position whereas the left handed operator should be in the four o’clock position. • With the mouth open maximally, identify the coronoid notch and the pterygomandibular raphae. • Three quarters of the anteroposterior distance between these two landmarks, and approximately six to ten millimeters above the occlusal plane is the injection site
• Bring the needle to the injection site from the contralateral premolar region. • As the needle passes through the soft tissue, deposit one or two drops of anesthetic solution. • Advance the needle until bone is contacted. • Once bone is contacted, withdraw the needle one millimeter and redirect the needle posteriorly by bringing the barrel of the syringe towards the occlusal plane • Advance the needle to three quarters of its depth, aspirate, and inject three quarters of a cartridge of anesthetic solution slowly over the course of one minute. • Successful execution of this technique results in anesthesia of the mandibular teeth on the ipsilateral side to the midline, associated buccal and lingual soft tissue, lateral aspect of the tongue on the ipsilateral side, and lower lip on the ipsilateral side
Buccal Nerve Block • The buccal nerve block, otherwise known as the long buccal or buccinator block, is a useful adjunct to the inferior alveolar nerve block when manipulation of the buccal soft tissue in the mandibular molar region is indicated. • The target for this technique is the buccal nerve as it passes over the anterior aspect of the ramus. • Contraindications to the procedure include acute inflammation and infection over the site of injection. A 25 gauge long needle is preferred for this technique. Technique • The patient should be in the semisupine position. The right handed operator should be in the eight o’clock position whereas the left handed operator should be in the four o’clock position. • Identify the most distal molar tooth on the side to be treated. The tissue just distal and buccal to the last molar tooth is the target area for injection
• The bevel of the needle should be toward bone and the syringe should be held parallel to the occlusal plane on the side of the injection. • The needle is inserted into the soft tissue and a few drops of anesthetic solution are administered. • The needle is advanced approximately one or two millimeters until bone is contacted. • Once bone is contacted and aspiration is negative, 0.2cc of local anesthetic solution is deposited. • Successful execution of this technique results in anesthesia of the buccal soft tissue of the mandibular molar region Gow -Gates Technique • The Gow -Gates technique or third division nerve block is useful alternative to the inferior alveolar nerve block and is often used when the latter fails to provide adequate anesthesia. • Advantages of this technique versus the inferior alveolar technique are its low failure rate and low incidence of positive aspiration. • The Gow-Gates technique anesthetizes the auriculotemporal, inferior alveolar, buccal, mental, incisive, mylohyoid and lingual nerves. • Contraindications to this procedure include acute inflammation and infection over the site of injection and trismatic patients. • A 25 gauge long needle is preferred for this technique Technique • The patient should be in the semisupine position. • The right handed operator should be in the eight o’clock position whereas the left handed operator should be in the four o’clock position. • The target area for this technique is the neck of the condyle below the area of insertion of the lateral pterygoid muscle. • A retraction instrument is used to retract the cheek.
• The patient is asked to open maximally and the mesiolingual cusp of the maxillary 2nd molar on the side of desired anesthesia is identified. • The insertion site of the needle will be just distal to the maxillary 2nd molar at the level of the mesiolingual cusp. • Bring the needle to the insertion site in a plane that is parallel to an imaginary line drawn from the intertragic notch to the corner of the mouth on the same side as the injection. • Advance the needle through soft tissue approximately 25mm until bone is contacted at the neck of the condyle. • Once bone is contacted, withdraw the needle one millimeter and aspirate. • Redirect the needle superiorly and reaspirate. • If aspiration in two planes is negative, slowly inject one cartridge of local anesthetic solution over the course of one minute. • Successful execution of this technique provides anesthesia to the ipsilateral mandibular teeth up to the midline, and associated buccal and lingual hard and soft tissue. • The anterior two thirds of the tongue, floor of the mouth, skin over the zygoma, posterior aspect of the cheek and temporal region on the ipsilateral side of injection are also anesthetized Vazirani -Akinosi Closed Mouth Mandibular Block • The Vazirani -Akinosi closed mouth mandibular block is a useful technique for patients with limited opening due trismus or ankylosis of the temporomandibular joint. • Limited mandibular opening precludes the administration of the inferior alveolar nerve block or use of the Gow-Gates technique both of which require the patient to be open maximally.
• Other advantages to this technique are the minimal risk of trauma to the inferior alveolar nerve, artery, vein, and pterygoid muscle, low complication rate and minimal discomfort upon injection. • Contraindications to this technique are acute inflammation and infection in the pterygomandibular space, deformity or tumor in the maxillary tuberosity region or an inability to visualize the medial aspect of the ramus. A 25 gauge long needle is preferred for this technique. TECHNIQUE • The patient should be in the semisupine position. • The right handed operator should be in the eight o’clock position whereas the left handed operator should be in the four o’clock position. • The gingival margin above the maxillary 2nd and 3rd molars and the pterygomandibular raphae are the landmarks for this technique. • A retraction instrument is used to stretch the cheek laterally. • The patient should occlude gently on the posterior teeth. • The needle is held parallel to the occlusal plane at the level of the gingival margin of the maxillary 2nd and 3rd molars. • The bevel is directed away from the bone facing the midline. • The needle is advanced through the mucous membrane and buccinator muscle to enter the pterygomandibular space. • The needle is inserted to approximately one half to three quarters of its length • At this point the needle will be in the midsection of the ptyerygomandibular space.
• Aspirate and if negative, anesthetic solution is deposited over the course of one minute. • Diffusion and gravitation of the local anesthetic solution will anesthetize the lingual and long buccal nerves in addition to the inferior alveolar nerve. • Successful execution of this technique provides anesthesia of the ipsilateral mandibular teeth up to the midline, and associated buccal and lingual hard and soft tissue. The anterior two thirds of the tongue and floor of the mouth are also anesthetized MENTAL NERVE BLOCK • The mental nerve block is indicated for procedures where manipulation of buccal soft tissue anterior to the mental foramen is necessary. • Contraindications to this technique are acute inflammation and infection over the injection site. A 25 or 27 gauge short needle is preferred for this technique Technique • The patient should be in the semisupine position. • The right handed operator should be in the eight o’clock position whereas the left handed operator should be in the four o’clock position. • The target area is the height of the mucobuccal fold over the mental foramen • The foramen can be manually palpated by applying gentle finger pressure to the body of the mandible in the area of the premolar apicies. • The patient will feel slight discomfort upon palpation of the foramen
• Use a retraction instrument to retract the soft tissue. • The needle is directed toward the mental foramen with the bevel facing the bone. • Penetrate the soft tissue to a depth of five millimeters, aspirate and inject approximately 0.6cc of anesthetic solution. • Successful execution of this technique results in anesthesia of the buccal soft tissue anterior to the foramen, lower lip and chin on the side of the injection. Incisive Nerve Block • The incisive nerve block is not as frequently employed in clinical practice • However it proves very useful when treatment is limited to mandibular anterior teeth and full quadrant anesthesia is not necessary. • The technique is almost identical to the mental nerve block. • Both the mental and incisive nerves are anesthetized using this technique. • Contraindications to this technique are acute inflammation and infection at the site of injection. • A 25 or 27 gauge short needle is preferred for this technique. Technique • The patient should be in the semisupine position. • The right handed operator should be in the eight o’clock position whereas the left handed operator should be in the four o’clock position • The target area is the height of the mucobuccal fold over the mental foramen • Identify the mental foramen as previously described. • Give the patient a mental nerve block as described above and apply digital pressure at the site of injection during administration of anesthetic solution. • Continue to apply digital pressure at the site of injection two to three minutes after the injection is complete to aid the anesthetic in diffusing into the foramen. • Successful implementation of this technique provides anesthesia to the premolars, canine, incisor teeth, lower lip, skin of the chin, and buccal soft tissue anterior to the mental foramen.
SUPPLEMENTAL INJECTION PERIODONTAL LIGAMENT INJECTION • Also called intraligamentary injection • Terminal nerve endings at the site of injection are anaesthetized • Technique : • 27 gauge needle is inserted at long axis of tooth to be treated at depth of gingival sulcus • Deposit 0.2ml in 20 secs • Treatment to start after 30 secs and lasts for 5-55mins PERIODONTAL LIGAMENT INJECTION [pressure syringes] INTRASEPTAL INJECTION • Similar to pdl injection • Anesthetizes terminal nerve endings • Bone, soft tissue, root structure are anesthetized • Area of insertion:centre of interdental papilla adj to the tooth to be treated • Orient the needle at 450 to the long axis of the tooth • Deposit 0.2 to 0.4ml of local anesthetic in 20secs Intraseptal injection INTRAOSSEOUS INJECTION
• Here a perforation is made into the bone into which the local anesthetic is injected • Stabident system is replaced by Intraflow IO system • A drill makes a perforation thro the bone in a pecking motion and the guide sleeve is left in place until the LA is injected • 2mm apical to the gingival margin is the injection site • Pulpal anesthesia of between 15 and 30 mins can be expected • Fistula formn is the most common complication Intra osseous anesthesia INTRAPULPAL INJECTION • Deposits LA directly into the pulp chamber • Very effective for pulp extirpation and instrumentation procedures • A small opening in the pulp chamber is sufficient for max effectiveness • There is a brief period of sensitivity followed by relief Local anesthetic dose calculation • Doses are even more critical in the paediatric patient, and it is important to note how little one should give to a child.. • High-concentration solutions, namely prilocaine and articaine, reach toxic levels with fewer cartridges. • Calculations of Doses Percent solutions represent grams per 100 mL (i.e. lidocaine 2% = 20 mg/mL) Most cartridges = 1.8 mL. Therefore, one cartridge of 2% lidocaine contains 1.8 mL x 20 mg/mL = 36 mg
COMPLICATIONS of ANESTHESIA INTRODUCTION • An anesthetic complication may be defined as any deviation from the normally expected pattern during or after the securing of regional analgesia. • Complications may be classified as follows: 1.primary or secondary. 2.mild or severe 3.transient or permanent • They can be classified according to the site 1.Locally in the region of the injection 2. or systemically Local Complications • 1)Needle Breakage • 2)Persistent anaesthesia • 3)Facial Nerve paralysis • 4)Trismus • 5)soft tissue injury • 6)hematoma • 7)pain on injection • 8)burning on injection • 9)Infection • 10)Edema • 11)Sloughing of tissues • 12)pos anaesthetic intraoral lesions Systemic complications • 1)overdose • 2)allergy • 3)Idiosyncrasy Classification of Adverse drug reactions • 1)toxicity caused by direct extension of the usual pharmacological effects of the drug:- -Side Effects -Overdose -Local Toxic effects • 2)Toxicity caused by the alteration in recipient of the drug :-
-disease process – hepatic dysfunction, heart failure -Emotional disturbances -Genetic abberations – atypical plasma cholinessterse , malignan hyperthermia - Idiosyncrasy • 3) Toxicity caused by allergic responses to the drug • Complications may be further divided into 2 groups: 1.Those attributed to the solutions used 2. Those attributed to the insertion of the needle Those attributed to the solutions used 1.Toxicity 2.Idiosyncrasy 3.Allergy 4.Anaphylactoid reactions 5.Infections caused by contaminated solutions. 6.Local irritations or tissue reactions caused by solutions Those attributed to the insertion of the needle 1.Syncope 2.Muscle trismus 3.Pain or hyperalgesia 4.Edema 5.Infections 6.Broken needles 7.Prolonged anesthesia other than from the anesthetic solution. 8.Hematoma 9.Sloughing 10.Bizarre neurological symptoms COMPLICATIONS CAUSED BY THE ANESTHETIC SOLUTION • Toxicity • The term toxicity, or toxic overdose, refers to the symptoms manifested as the result of over dosage or excessive administration of a drug • This complication depends on a sufficient concentration of the drug in the blood stream to adversely affect the central nervous system, the respiratory system, or the circulatory system • Toxicity
• LA blood level high enough to cause the symptoms of toxic overdose may come about in one or more of the following four ways: 1. Too large a dose of local anesthetic drug 2. Unusually rapid absorption of the drug or intravascular injection 3. Unusually slow biotransformation 4. Slow elimination or redistribution • The blood level necessary to create a toxic overdose is variable and depends on a variety of factors, some of which follow: 1. Patient’s general physical condition at the time of the injection 2. Rapidity of injection 3. Route of administration (for example, inadvertent intravascular injection) 4. Amount of the drug used 5. Age of patient • SYMPTOMS. Usually early central nervous system stimulation followed by a proportionate degree of depression. (On occasion central nervous system depression may appear as the first sign of toxicity.) 1. Cerebral cortical stimulation a. Talkativeness b. Restlessness c. Apprehension d. Excitement • 2. Cerebral cortical depression a. Lethargy b. Sleepiness c. Unconsciousness • After mild cortical stimulation the may be little or no cortical depression. However, convulsions are usually followed by severe cortical depression and unconsciousness. • 3. Medullary stimulation a. increased blood pressure b. Increased pulse rate c. Increased respirations
d. Possible nausea and vomiting • 4. Medullary depression will usually occur in proportion to the amount of medullary stimulation. a. Blood pressure may remain normal in mild cases or drop to zero in severe cases. b. Pulse may range from normal to weak, thready, or absent. c. Respiratory changes may be slight, or the patient may become apneic in severe cases • Treatment should be directed toward alleviating symptoms;early recognition and early treatment are imperative. 1. Mildly stimulated patients should require no treatment other than the discontinuing of further administration of the anesthetic drug 2. Moderately stimulated patients should be given pentobarbital sodium or secobarbital intravenously very slowly until they are calmed, plus inhalations of oxygen 3. Convulsive patients should receive 20 to 40 mg of succinylcholine chloride intravenous or double the dose intramuscularly to control the convulsions. Adequate ventilation must be maintained. 4. Treatment of central nervous system depression should be directed toward supporting respiration with artificial ventilation and maintaining adequate cardiovascular system function through positional changes and vasopressors, if required PREVENTION Toxicity 1. Aspiration must be performed before injecting. 2. The smallest possible volume of drug should be used. 3. The weakest efficient percentage strength of the drug should be used. 4. The anesthetic drug should be injected slowly 5 A vasoconstrictor should be employed with the local anesthetic if not contraindicated IDIOSYNCRASY
• The term idiosyncrasy is often assigned to a bizarre type of reaction that cannot be classified as toxic or allergic ALLERGIC REACTIONS • CAUSE. The primary cause of allergic reactions is a specific antigen antibody reaction in a patient who has previously been sensitized to a particular drug or chemical derivative thereof • SYMPTOMS. Reaction affects a particular shock organ, most likely the skin, mucous membrane, or blood vessels. 1. Rashes 2. Urticaria 3.Angioneurotic edema 4.Mucous membrane congestion a. Rhinitis b. Asthmatic symptoms • TREATMENT 1. Antihistaminic agents (Benadryl, 20 to 50 mg) 2. Isoproterenol or epinephrine inhalants 3. Epinephrine (0.5 ml of 1:1,000 intramuscularly) 4. Aminophylline (0.5 gm intravenously) 5. Oxygen • PREVENTION 1. Adequate preanesthetic evaluation must be done. 2. No drug or drugs should be used if the patient previous allergic reaction to them. 3. No patient should be tested to attempt to disprove his allergic history Complications attributed to the needle insertion or technical complications • SYNCOPE
• Syncope or fainting is perhaps the most frequent complication associated with local anesthesia in the dental office.This is a form of neurogenic shock and is caused by cerebral ischemia secondary to a vasodilatation or an increase in the peripheral vascular bed, with a corresponding drop in blood pressure • In most instances it is possible to detect a change in the patient’s appearance, such as pallor. The patient may also complain of feeling different or strange. • The operator should discontinue any procedures in progress and lower the chair back while the patient’s legs are slightly elevated, thus placing the patient in a semireclining position .This position aids venous return from the lower portions of the body while preventing venous congestion in the upper body, as with the conventional Trendelenburg (head down) position Muscle Trismus • Muscle trismus is a fairly common complication of regional analgesia or anesthesia, particularly after blocks of the inferior alveolar nerve • The most common cause of trismus is trauma to a muscle during the insertion of the needle. Irritating solutions, hemorrhage, or low-grade infection within the muscle may also cause varying degrees of trismus • The treatment should depend on the cause of the trismus. If the condition arises as the result of trauma, slight exercises and drug therapy may be necessary to relieve pain, if sufficiently severe. • Centrally acting muscle relaxants such as diazepam (Valium) 2.5 to 5.0 mg four times per day or meprobamate, 1200 to 1600 mg per day in three or four doses coupled with the application of warm moist compresses for 15 to 20 minutes per hour will usually relieve the symptoms in several days • Mild analgesics may also be used for discomfort. • Physiotherapy consisting of opening and closing the mouth as well as movement from side to side for 5 to 10 minutes every 3 or 4 hours will also assist recovery
• Trismus may be prevented by the use of sharp, sterile needles so that the trauma of insertion and any subsequent low- grade infections are prevented. • The area of insertion should be cleansed and painted with a suitable antiseptic solution. • Care should be exercised also so that the needle is inserted atraumatically and no muscles are penetrated Pain or hyperesthesia • Pain during or after the admin
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