LA Theory Revision PDF - Dental Local Anaesthetics

LA Theory  Analgesia = Anaesthesia = Loss of pain sensation Loss of all forms of unaccompanied by loss of sensation; pain, touch, other forms of sensibility. pres...

LA Theory  Analgesia = Anaesthesia = Loss of pain sensation Loss of all forms of unaccompanied by loss of sensation; pain, touch, other forms of sensibility. pressure perception. Pain reaction The same stimulus produces different reactions in different people. Aim of dental treatment The same patient may also react differently to the same stimulus. is to contain active disease and prevent its recurrence Nerve impulse/action potential Local anaesthetic agents work by Electrical impulse is produced by a nerve cell. blocking Travels in one direction. transmission of Can only send one message at one speed. impulses in sensory Frequency or number of pulses can vary. nerves. Ion channels in the axon are voltage-gate. Depolarisation at one axon segment triggers the opening of ion channels in the next segment. This allows the action potential to spread along the axon as a ‘wave’ of depolarisation. Steps of nerve impulse/action potential: High sodium NA+ levels in 1. Resting neurone/nerve cell extracellular fluid 2. Excitatory stimulus High potassium K+ levels in intracellular fluid 3. Sodium channels open 4. Sodium ions enter the neurone from extracellular fluid (Depolarisation and triggers action potential) 5. Potassium channels open 7. Recharging phase 6. Potassium channels leave the neurone from intracellular fluid (Repolarisation - resting state) Blocking of nerve conduction No action potential is LA agents work in 2 ways: generated so no impulse conducted to brain! Bind to specific receptors in the sodium channels, blocking the inward movement of NA+ (sodium) ions during conduction of an impulse. Non-specific expansion of nerve cell membrane causing physical obstruction of the NA+ channels. EnneMinSee Diffuse through lipid membrane of nerve fibre. Lif Effective and reversible action on nerves. Not irritate or injure tissues. Produce rapid I’m Capable of onset of sterilisation. Properties of numbness. ideal LA agent Adequate shelf life TI Isotonic (same Adequate working time. Highly safe. Allow combination with pH as body) a vasoconstrictor. Contents of dental LA cartridge Analgesic agent - Blockage of nerve Reducing agent - Prevent oxidation of conduction. vasoconstrictor. (Lidocaine, Prilocaine, Articaine, Mepivacaine) (Sodium metabisulphite) Vasoconstrictor - Increase depth and Vehicle - Carry the other agents and duration of analgesia. ensure solution isotonic. (Epinephrine/adrenaline, Felypressin) (Sterile saline) Local anaesthetics Mepivacaine Lidocaine Scandonest 2% with epinephrine 1:100,000 Lignospan 2% with epinephrine 1:80,000 is gold Scandonest 3% plain (no vasoconstrictor) standard for most dental procedures. Similar properties to prilocaine. Effective Shorter analgesia if used as infiltration. Rapid onset DO NOT use on pregnant women or children Usual for pulpal and soft tissue analgesia under 4. Low toxicity. Prilocaine Articaine Citanest 3% with octapressin Septanest 4% Articaine hydrochloride with Citanest 4% plain (no vasoconstrictor) epinephrine 1:100,000. Shorter duration of action than lidocaine. Septanest 4% Articaine hydrochloride with Less or no vasoconstriction. epinephrine 1:200,000. Rapidly dispersed and cleared. Powerful Very low incidence of side effects. Rapid onset Longer soft tissue analgesia Rapidly metabolised in plasma and live Topical gel DO NOT use an inferior dental block. Xylonor gel, lidocaine 5% Cautions with pregnancy and breast feeding. Applied with cotton wool roll on mucosa prior to injection. Epinephrine/ adrenaline benefits: Increases depth and duration. Occurs naturally in the body. Haemorrhage control. Systemic effects of LA Absorption and metabolism of LA Not easily absorbed through intact skin. When applied to mucous membranes, they are absorbed into bloodstream - allows for distribution, metabolism and elimination. Systemic actions of LA Reversible blockage of conduction in nerve endings. Relaxation of smooth muscle. Myocardial depression - decreased; conduction rate, force and electrical excitability. Depression of central nervous system. Absorption of LA into circulation Causes the LA action to wear off. May lead to toxicity. Depends on: Anaesthetic agent and dose/concentration. Vascularity of the tissues. Presence/absence of vasoconstrictor. Accidental intravascular injection (blood vessel). Metabolism and elimination of LA Depends on patient. Most LA agents are metabolised in the liver - to make inactive metabolites. Excreted in the urine. Decreased liver and kidney function - may need less LA agent for safety. Signs of systems toxicity (rare in dentistry) Tingling and numbness of lips Visual and hearing disturbances Reducing systemic toxicity Mood changes (irritability, agitation, anxiety) Avoid intravascular injection by aspirating Light headed/dizziness Injection slowly Increase in depth and rate of respiration Use safe doses Drowsiness Choose less toxic drugs Coma and convulsions Use vasoconstrictors Respiratory arrest Cardiac arrest Contraindications and cautions of LA Mepivacaine Lidocaine Contraindication; Contraindication; Hypersensitivity Hypersensitivity Pregnancy Heart palpitations Children under age of 4 Caution; Cautions; Beta-blockers (Propanolol) Breastfeeding Beta-blockers (Propanolol) Articaine Contraindication; Prilocaine Hypersensitivity Contraindication; Children under age of 4 Hypersensitivity Plasma cholinesterase deficiency Cautions; Do not use for ID block Sulphonamides (treat bacteria and fungal Caution; infections) Pregnancy (only use if benefits outweigh the risks) Beta-blockers (Propanalol) Avoid breastfeeding for 48hours after administration Beta-blockers (Propanolol) For cautions listed: Epinephrine/adrenaline Contraindication; Limit to 2 x 2.2ml cartridges per day. Cocaine use within last 24 hours For renal failure/dialysis/liver failure Cautions; limit to 1 x 2.2ml cartridge per day. Trycyclic antidepressants Mono-amine oxidase inhibitors (May need to liaise with patients consultant/GP Beta-blockers (Propanolol) to check safe dose) Calcium-channel blockers Diuretics Cardiac conditions Bevel Hypertension indicator Circulatory problems Extra short Short Long Previous strokes 30G 30G 27G 10mm 25mm 35mm Patient preparation Legal Valid prescription? Medical History Any contraindications? Has patient taken medication? Previous LA reactions? Food Have they eaten? Vaso-fagal (fainting) attack prevention Explain Why using LA - comfort and efficiency? Sensation. Procedure. Patient LA anxiety/phobia. Distraction techniques. Calm atmosphere. Appropriate language. Operator Positioning. Visibility. Equipment. Patient preparation Effects on patients pain Legal threshold? Valid prescription Anxiety Previous experience Medical history Culture Any contradictions? Taken medication? Any prev reactions? Age Emotional state Food Psychological make up Have they eaten as usual? Prevent vaso-fagal attack (fainting) Environment Explain Why using LA (comfort/efficiency), sensation, procedure Patient LA anxiety/phobia? Distraction techniques, calm atmosphere, appropriate language Operator Positioning, clear visibility, correct LA equipment Positioning Application of topical anaesthetic agent Patient supine, comfortable and well-supported. Dry mucosa. Patient at correct height for operator. Apply on cotton wool roll. Light directed into sulcus area for clear visibility. Leave in place for 2-3 minutes. Posterior molars Anterior 3-3. 6 - 8 (NotmB root 6's) pre-molars + 1st molarmBroot.  Buccal infiltration technique Estimate position of apex of the tooth. Pull mucosa taught. Insert short needle through mucosa at 25 degrees to the bone. Face bevel indicator towards bone. Aim for the apex of the tooth and keep parallel to long axis of tooth and bone. Allow needed to smoothly glide through taught mucosa. Avoid contacting bone, if contacted withdraw 1-2mm. Needle 25degrees to the bone Aspirate and check cartridge. Delivery gently and slow - very little pressure required. Cautions: Withdraw slowly and make needle safe. Maxillary incisors labial aspect: WAIT! (VERY sensitive - use LOTS of topical and inject SLOWLY) Perio work Restorations Mandibular incisors labial aspect: 0.5 - 1ml per site 2.2ml per site (Mentalis and depressor labii inferioris muscle attachments) Soft tissue Pulpal Achieved in 1 - 2mins Achieved in 2 - 5mins Palatal infiltration Topical application and pressure on area first with mirror handle. Infiltrate palatal mucosa of the appropriate tooth. Inject short needle 90 degrees to the mucosa at 1-1.5cm from gingival margin. Considerable resistance. Used for: Deposit 0.2ml of solution. Deep restorations It can hurt a lot. Sub-gingival PMPR Extractions Intrapapillary injection Direct short needle at right angles to interdental papilla. Used for: Insert at centre of papilla, at level of attachment to periosteum. Achieving palatal analgesia in Deposit 0.2ml of solution. children and nervous patients. Check palatal mucosa has blanched.  Maxillary nerve overview (Short 30G needle) Anterior superior alveolar Anterior incisors and canines. Middle superior alveolar Pre-molars and 1st molar MB root. Posterior superior alveolar Upper molars - (NOT MB root 1st molar) Palatine nerves overview (Short 30G needle) Needle always bevel Nasopalatine nerve to bone! Anterior incisors and canines gingivae. Nasopalatine foramen behind incisors. Greater palatine nerve Palatal gingiva pre-molars and molars. Greater palatine foramen usually posterior to 2nd molar. Inferior Dental Block (IDB) technique If bone is contacted, withdraw needle Patient can be supine or upright (large tongue/obese, upright may be better). 1mm and aspirate. Ideally use topical analgesia. Patients mouth needs to be wide open - good visualisation of anatomical landmarks. Use thumb to locate retromolar fossa. Identify pterygomandibular raphe and palpate external oblique ridge. Look for crease between thumb and external oblique ridge. 1. Point of entry is + on the diagram. 2. External oblique Use long 27G 35mm needle. Retromolar fossa ridge : Position syringe barrel over contra-lateral pre- molars. Inject depth of 2-2.5cm - 5mm must always be visible. Insert smoothly and slowly into pterygomandibular space - aiming for mandibular foramen. Slowly deliver - only when needle is not into vascular. Withdraw quickly and smoothly. Bone struck too soon Withdraw, swing needle round to midline, advance for 7mm and swing Pterygomandibular back to original position and proceed. DO NOT GIVE raphe/space ARTICAINE FOR Point of entry is Electric shock sensation in tongue or lip IDB, INCISIVE OR between 1 and 2 - (+) Means lingual or mandibular nerve has been MENTAL BLOCKS touched by needed - MUST withdraw 1-2mm from nerve. IDB technique - positive aspiration It is important to aspirate to ensure placement of need isn’t in a vessel. If blood present, withdraw needle 1-2mm. Aspirate again. If no blood, continue with injection. If blood present again, reposition and repeat IDB makes yellow area numb aspiration. Incisive and mental block technique Ideally have patient in supine position for good lighting. Use topical anaesthetic and 30G short needle. Aim for mental foramen - between apices of 1st and 2nd pre-molars (check on radiograph). May be unreliable and require lingual infiltration. Aspirate - if not positive, inject at least 1ml of solution. Useful if bilateral anaesthesia is desired for pre-molars/ anteriors. Mental block makes yellow area numb Incisive/mental nerve block (Short 30G needle) Branches of the inferior alveolar nerve. Incisors, canines, pre-molars and buccal gingivae. Inferior dental/alveolar nerve overview If the needle goes in too deep (Long 27G needle) (IDB), analgesic solution will be Insert needle 2-2.5 cm. deposited into deep lobe of Mandibular teeth from third molar - midline. parotid gland - this blocks the Buccal soft tissue from pre-molars anteriorly. facial nerve, causing temporary Lower lip, chin, body of mandible, PDL. paralysis.  Maxillary (2) Ophthalmic (V1) Trigeminal Nerve Trigeminal Ganglion mandibular (v3) S Incisive nerve Long buccal nerve mental nerve mental foramen Lingual nerve Inferior dental/ alveolar nerve ↑  Legal framework What constitutes a prescription (Rx)? LA is a prescription Type of LA - Lidocaine, Articaine etc. only medicine Route of administration - Infiltrations, IDB. (POM). Dosage - How much? (1 x 2.2ml cartridge). Date - Check the Rx is in date for each course of treatment (within a year). Post-operative Documentation of LA Post-injection precautions Type of LA agent and vasoconstrictor. NEVER leave patient alone after injection. Amount of solution administered. Reactions may occur at anytime (faint, anaphylaxis). Site of injection. Any unusual effects. Post-operative instructions Post-operative instructions given Duration of anaesthesia - usually a few hours. verbally (POIGV). Avoid hot foods/drinks, biting lip/cheeks. (LA - 2.2ml Lidocaine 2% with epinephrine Do not poke/prode area - with finger or tongue. 1:80,000, buccal infiltrations UL7, UL4, UL2, No smoking - for duration of LA. POIGV) Complications of LA General complications Local complications Due to: Psychogenic Prolonged sensation impairment. Injecting an inappropriate Toxicity of LA Failure to go numb. solution. Overdose Serious: Injecting too much Reduced tolerance Facial paralysis. solution. Intravascular adrenaline Needle breakage. Injecting into the wrong Allergy-anaphylaxis Post-anaesthetic herpes site. Drug interactions reactivation. NEVER inject into an area of inflammation/ infection. (Inject mesial and distal to the area) Bleeding risk ID blocks and lingual infiltrations may be contraindicated or used with caution depending on bleeding risk. Risk relates to act of injection, not LA agent. Genetic bleeding disorders (Haemophilia). Patients taking anticoagulants or antiplatelet drugs (Warfarin, Clopidogrel). Alcoholics or patient with liver disease (reduced liver function). Failure of anaesthesia Too long delay before starting treatment. Too little solution administered. If LA fails, DO Intravascular injection (aspirate) NOT overdose, Inaccurate placement of needle. get advice Anatomical variations. Incorrect choice of technique. Anxiety, fear, negative experience. Poor storage of LA (too hot/sunlight).