Local Anesthesia PDF

Local anesthesia  1. Patient medical history 2. The expected duration of dental procedures 3. Possibility for self-inflicted injury; long duration of action Factors affecting can ↑ danger of tissue in...

Local anesthesia  1. Patient medical history 2. The expected duration of dental procedures 3. Possibility for self-inflicted injury; long duration of action Factors affecting can ↑ danger of tissue injury (children or hand capped selection of LA agent patients) 4. Need for hemorrhage control 5. The practitioner's knowledge of anesthetic agent  I - Absolute contraindications (Drug allergy) Medical problem Avoid Use LA agent allergy Same class Different class Bisulfite allergy (If you have an LA with vasoconstrictor Plain LA allergy to amides, it is most likely due to the Na bisulfite) Sulfur allergy Articaine Non-sulfur types Uncontrolled thyrotoxicosis LA with VC Plain LA  II - Relative contraindications It is preferable to avoid drug in question, but it may Medical problem Avoid Use be used with smallest 1) Cholinesterase deficiency Esters Amides effective dose 2) Methemoglobinemia Prilocaine and Articaine Others 3) Severe liver or congestive Amides Esters or amide in small heart failure dose 4) Severe kidney disease Amides and esters Used but in small doses 5) Severe cardiovascular Excess VC Plain LA or ↓↓ VC dose disease  Esters rarely used in our clinic because:- 1) Their PKa higher than that of normal PH of tissues so they have slow onset 2) They are absorped rapidly to blood, as they have great tendency to bind with plasma protein (have short duration) Ester group 3) PABA is the main metabolic product of them (allergen), so may produce allergic reactions 4) PABA can interfere with antibacterial effect of sulfonamide class of antibiotics. So esters cannot be used with sulfonamide antibiotics  Vasoconstrictors (VC)  They are added to LA to counteract their vasodilating effect Advantages Disadvantages 1. Maintain drug concentration at injection site by ↓ the rate of absorption from receptors into the circulation, so: 1. ↓ shelf life of LA, which depends on stability of VC a. ↑ drug onset N.B. LA molecules are relatively stable & degrade slowly b. Produce more profound anesthesia 2. Addition of sodium bisulfite, ↑ LA acidity: c. Prolongs LA duration The higher the amount of VC, the more preservative is 2. ↓ the LA level in the blood, thus reducing risk of toxicity required, resulting in more acidic PH, slowing down LA onset 3. ↓ bleeding at the surgical site (Hemostasis) Systemic effect of VC They are sympathomimetic drugs i.e. produce the same effect of sympathetic nervous system mediators (epinephrine & nor-epinephrine) on sympathetic effector organs So they have clinical actions besides vasoconstriction due to their effect on sympathetic organs which have adrenergic receptors  Adrenergic receptors Alpha receptors (a), two types: Beta receptors (b), two types: a) a1 Excitatory receptors (vasoconstrictor) b1) Present in: b) a2 Inhibitory receptors (vasodilator) (i) Heart: ↑ rate & force of contraction They are present in smooth muscles of BVs (ii) Small intestines b2) Present in: (i) Bronchi: cause bronchodilation (ii) Uterus: induces relaxation & opening VCs used in dentistry: 1. Epinephrine (Adrenaline) 2. Norepinephrine (Noradrenaline) 3. Levonordefrin (isomer to noradrenaline, but with lesser effect), usually present with mepivacaine They have direct action on adrenergic receptor: 1. Epinephrine acts on α and β but its effect on α predominates 2. Norepinephrine acts on both α and β but its effect on β predominates Felypressin VC Concentrations - It is a synthetic vasoconstrictor 1: 200,000 (means 1 gram VC is dissolved in - Used with prilocaine 200,000 mL water) - Its concentration is 0.03 IU/ml 1:100,000, - Has less side effect on the heart 1: 50,000 - Should be minimized or avoided in pregnant females 1: 8000 because its oxytocin effect Mode of action of vasoconstrictors: VCs that used in small quantities in dentistry, 1. Direct action on adrenergic receptors e.g. stimulates receptors in BVs causing Epinephrine, Norepinephrine, Levonordephrine vasoconstriction No other organs or systems will be greatly 2. Indirect action by stimulating release of affected norepinephrine from adrenergic nerve ending But if they reach toxic blood level (overdose or e.g. Amphetamine intravenous injection) they produce adverse 3. Mixed action (direct & indirect) e.g. Ephedrine systemic reaction  Contraindications to vasoconstrictors in dentistry 1. Heart diseases: According to WHO “The typical concentrations of a.Unstable angina VCs contained in LA are not contraindicated in b.Recent (