Ans: A (Shorter,,.) DIBUCAINE"Dibucaine: Longest: acting local anesthetic, most potent & most toxic"- Ajay Yadov 2nd/110"DibucainefCin chocaine}:!t is the most potent, most toxic & longest acting LA It is used as a surface anaesthetic on less delicate mucous membrane (anal canal). Use for spinal anaesthesia of long durartion has declined after the availability ofbupivacaine"- KDT 6th/358"The dibucaine number is a measure of the qualitative activity of pseudocholinesterase and is the percentage of inhibition of the enzyme by the local anesthetic dibucaine. Normal individuals are homozygous for the wild type, and their dibucaine number is 80 because their plasma cholinesterase is 80% inhibited by dibucaine. Those who are homozygous for the atypical genes have a dibucaine number of 20 because of 20% inhibition Heterozygous individuals have a dibucaine number of 60 because of approximately 60% inhibition. The plasma cholinesterase level is a quantitative measure of this enzyme. Plasma cholinesterase should not be confused with cholinesterase activity, which is an assessment of erythrocyte or red blood cell cholinesterase. The combination of dibucaine number and plasma cholinesterase can differentiate genetic from nongenetic causes of prolonged apnea after the administration of succinylcholine"-Millter 7th/1095Atypical Pseudocholinesterase Ajay Yadav 2nd/88# Incidence :1 in 3000.This can be diagnosed by Dibucaine numberDibucaine is a local anaesthetic which can inhibit 80% of normal enzyme & 20% of abnormal enzyme. So normal dibucaine number in homozygous typical (normal person) is 70-80%Sodium floride can be used in place of dibucaine(Floride number)Usually apnoea is for 1 to 2 hrTable (Ajay Yadav):Summary of properties of local AnestheticsDrugPotencyT1/2Duration of actionWithout adrenalineDuration of action With adrenalineMaximum safe dose (mg/ kg)CommentsEsters Procaine+ 15-30 minute30-90 minutes12 mg/kg Chloroprocaine+ 15-25 minute30-90 minutes12 mg/kgShortest actingCocaine+ + 3 mg/kgUsed for topicalAnesthesiaPotentvasoconstrictorTetracaine+ + + + 2-3 hours3-5 hours3 mg/kg AmidesLignocaine(Xyocaine)+ +1.6 hrs45-60 minutes'12-3 hours3 mg/kg (without adrenaline); 7 mg/kg without adrenaline)Most commonly used local anaestheticPrilocaine+ + 45-60 minutes2-3 hours8 mg/kgCan cause methaemoglobinemiaMepivacaine+ + 45-60 minutes2-3 hours4.5 mg/kg Etidocaine+ + + + 2-3 hours3-5 hours4 mg/kg Bupiva caine (Sensoricaine, Mancaine)+ + + +3.5 hrs2-3 hours3-5 hours2 mg/kgVery commonly used local anaestheticRopivacaine+ + + 2-3 hours3-5 hours3 mg/kgLess cardiotoxic than bupivacaineDibucaine+ + +4 hrs2.5-3.5 hours3.5-5.5 hours1 mg/kgLongest acting, most potent, most toxicProperty of local anaesthesia (KDT 6th/356)DrugMax. safe dose (mg)Duration of nerve block (min)Lidocaine30060-120Bupivacaine100180-360Tetracaine80180-480Dibucaine50180-600Drug used for spinor/ anaesthesia (KDT 6th/360)DrugTotal dose(mg)Duration of action (min)Lidocaine25-10060-90Bupivacaine10-2590-150Tetracaine5-1590-150Dibucaine2.5-10120-180 Type of Butyryl- cholinesteraseIncidenceDibucaine NumberResponse to SuccinylcholineHomozygous TypicalNormal70-80NormalHeterozygous Atypical1/48050-60Lengthened 50- 100%Homozygous Atypical1/320020-30Prolonged to 4-8 hrsButyrylchofinesterase (Pseudocholinesterase) Deficiency:# Levels can be affected by liver disease, advanced age, malnutrition, pregnancy, bums, OCP, etc.Large decreases in butyrylcholinesterase causes only- moderate increase in duration of action of succinylcholineDibucaine NumberDibucaine inhibits normal enzyme to far greater extent that variant. Thus, if the dibucaine number is low (i.e. the native enzyme is not inhibited by dibucaine), one should suspect or? abnormal variant of butyrylcholinesterase.