Long-acting local anesthetic agent :
Ans: C BupivacaineRef: Ajay Yadav, Short Textbook of Anesthesia. 1st edition, pg 105.Explanation:Both C & D appear to he equally long-acting Duration of Action of Local AnestheticsIt depends on;Dose: Increasing the dose, increases the durationPharmacokinetic profile of drug: It includes Plasma protein binding (Alpha I acid glycoprotein)o Agents with high protein binding like bupivacaine have prolonged action.Metabolismo Esters are metabolized by pseudocholinesterase and amides are metabolized in the liver by microsomal enzymes, o Esters have a small duration of action than amidesAddition of VasoconstrictorsVasoconstrictors decrease the systemic absorption of LA in blood, so increases the concentration thereby increasing the duration of action. Eg; Adrenaline, Phenylephrine (1:20000), Noradrenaline. Felypressin (a synthetic analog of vasopressin)AdrenalineIt is used in a concentration of 1: 200000 (I in 2 lakh)Duration of both sensory and motor blockade is increased in Adrenaline + LignocaineThe only sensory blockade is prolonged without any effect on motor blockade in Adrenaline + BupivacaineAddition of Adrenaline is contraindicated ino Ring block of fingers, toes, penis, pinna (Absolute contraindication)o When an inhalational agent which sensitizes myocardium to adrenaline is usedo Myocardial ischemiao Hyperthyroid patiento Severe Hypertensiono Intravenous regional anesthesia [Bier's block)Sodium BicarbonateAdding NAHC03 (1ml of 8.4% to If) ml lignocaine) increases both onset and duration of actionIt increases the onset by making pH more alkaline so more drug is available in unionized formLater C02 is released from Soda bicarb metabolism enters intracellularly making the pH more acidic making more drug to be available in ionized form, thereby increasing duration of action also.Duration of Action of Various Local AnestheticsLocalAnestheticMean Duration of Blockade without AdrenalineMean Duration of Blockade with AdrenalineChloroprocaine30 minutes90 minutesProcaine45 minutes90 minutesPrilocaine90 minutes6 hoursLidocaine2 hours4 hoursMepivacaine3 hours6 hoursTetracaine3 hours10 hoursRopivacaine3 hours6 hoursBupivacaine4 hours8 hoursEtidocaine4 hours8 hours
Procaine
Lidocaine
Bupivacaine
Etidocaine