LA Theory- part 1 (2 of 2) GN PDF

Systemic e*ects of LA  Absorp2on and metabolism of LA agents  Not easily absorbed through intact skin  When applied to mucous membranes or injected into 8ssues, they are absorbed into blood stream  Distribu8on (dilu8on) through the body  Metabolism and elimina8on Systemic ac2ons of a l...

Systemic e*ects of LA  Absorp2on and metabolism of LA agents  Not easily absorbed through intact skin  When applied to mucous membranes or injected into 8ssues, they are absorbed into blood stream  Distribu8on (dilu8on) through the body  Metabolism and elimina8on Systemic ac2ons of a local anaesthe2c agent  Reversible blockage of conduc8on in nerve endings and nerve trunks  Direct relaxa8on of smooth muscle  Myocardial depression (↓conduc8on rate, ↓force of contrac8on, ↓electrical excitability)  Depression of the central nervous system (ini8al signs are excitatory) Absorp2on of local anaesthe2c agents into the circula2on This causes the ac8on of the LA to wear oG May lead to toxicity Rate of systemic absorp8on depends on: 1. Anaesthe8c agent and its concentra8on (dose) 2. Vascularity of the 8ssues 3. Presence /absence of vasoconstrictor 4. Accidental intravascular injec8on Metabolism and elimina2on of LA  Dependent on pa8ent physiology  Most commonly used LA agents are metabolised in the liver to make inac8ve metabolites (N.B ar8caine also metabolised in plasma)  Then excreted in the urine  Decreased liver and kidney func8on - may need less LA agent for safety Signs of systemic toxicity – extremely rare in den2stry Perioral signs – 2ngling and numbness of lips Visual and hearing disturbances e.g. 2nnitus Mood changes (irritability, agita2on, anxiety, restlessness) Light-headedness/dizziness Increase in depth and rate of respira2on Drowsiness Coma and convulsions Respiratory arrest Cardiac arrest Reducing systema2c toxicity Aspirate = pulling back syringe to check haven’t injected into blood vessel Avoid intravascular Inject slowly Use safe doses injection (aspirate) Choose less toxic drugs Use (e.g. 3% prilocaine with vasoconstrictors felypressin) Maximum safe dose Contraindica2ons and cau2ons of LA Agent Lidocaine Contraindica2on Heart palpitations Hypersensi8vity (very rare) Cau2on  Betablockers e.g. propanolol Prilocaine Contraindica2on Hypersensi8vity (very rare) Cau2on  Sulphonamides  Betablockers Mepivacaine Contraindica2on Hypersensi8vity (very rare) Children under age of 4 years Cau2on  Pregnancy (Can possibly induce labour - better to be on the safe side)  BreasVeeding  Betablockers Ar2caine Contraindica2on Hypersensi8vity Under 4 years of age DeXciency in plasma cholinesterase Cau2on  Pregnancy (only use if beneXt outweighs risk)  Avoid breast feeding for 48 hours aZer administra8on  Betablockers  ID block (risk of post-op paraesthesia) Epinephrine/Adrenaline Contraindica2on Cocaine use within last 24 hours Cau2ons  Tricyclic an8depressants  Mono-amine oxidase inhibitors  Betablockers  Calcium-channel blockers  Diure8cs  Cardiac condi8ons  Hypertension  Circulatory problems (including previous strokes) Felypressin  Late stages of pregnancy - theore8cal risk of inducing labour  Similar to oxytocin (natural hormone) For cau2ons listed above  Limit to 2 x 2.2ml cartridges per day  If renal failure/dialysis or liver failure limit to 1 cartridge per day. May need to liaise with pa8ent’s physician as to safe dose LA Equipment Cartridges Plunger (handle) Safety plus needles 1. Extra short- 30G 10mm 2. Short- 30G 25mm 3. Long- 27G 35mm Bevel indicator Tradi2onal LA system YOUR TURN! Summary Today we have…  Explored diGerent LA agents used in den8stry and how they work  Outlined the systemic eGects of LA agents  Iden8Xed contra-indica8ons and cau8ons regarding LA delivery  Demonstrated how LA equipment is safely used Next session…  Revise oral anatomy and nerve supplies  Understand how to deliver inXltra8ons and inferior dental blocks Any ques2ons? Reference List Evers, H. (1990) Introduc)on to Dental Local Anaesthesia. 2nd Edi8on. Switzerland: Mediglobe SA. Udayangan, S (2017) Di4erence Between Depolariza)on and Repolariza)on. Available from: hdps://www.diGerencebetween.com/diGerence-between-depolariza8on-and-vs-re polariza8on/ [Accessed 12th December 2022]. Yapp, K.E., HopcraZ, M.S. and Parahos, P., (2011) Ar)caine: a review of the literature, Bri)sh Dental Journal volume, 210, pp. 323–329. Available from: hdps://www.nature.com/ar8cles/sj.bdj.2011.240 [Accessed on 5th January 2023].