Anesthesia

1. Local AnestheticsLocal Anesthetics
HOSSAM M. ATEF;MDHOSSAM M. ATEF;MD
SUEZ CANAL UNIVERSIITYSUEZ CANAL UNIVERSIITY
ANESTHESIA DEPARTMENTANESTHESIA DEPARTMENT

2. What are local anesthetics?What are local anesthetics?
 Local anesthetic: produce loss ofLocal anesthetic: produce loss of
sensation to pain in a specific area of thesensation to pain in a specific area of the
body without the loss of consciousnessbody without the loss of consciousness

3. Local anesthetics -Local anesthetics -
MechanismMechanism
Limit influx of sodium, thereby limitingLimit influx of sodium, thereby limiting
propagation of the action potential.propagation of the action potential.

4. LidocaineLidocaine
 In 1940, the first modern localIn 1940, the first modern local
anesthetic agent was lidocaine, tradeanesthetic agent was lidocaine, trade
name Xylocaine®name Xylocaine®
 It developed as a derivative of xylidineIt developed as a derivative of xylidine
 Belongs to the amide class, cause littleBelongs to the amide class, cause little
allergenic reaction; it’s hypoallergenicallergenic reaction; it’s hypoallergenic
 Sets on quickly and produces aSets on quickly and produces a
desired anesthesia effect for severaldesired anesthesia effect for several
hourshours
 It’s accepted broadly as the localIt’s accepted broadly as the local
anesthetic in United States todayanesthetic in United States today

5. Differences of Esters and AmidesDifferences of Esters and Amides
 All local anesthetics areAll local anesthetics are weak basesweak bases. Chemical structure of local. Chemical structure of local
anesthetics have an amine group on one end and an aromatic ring on theanesthetics have an amine group on one end and an aromatic ring on the
other . The amine end is hydrophilic (soluble in water), and the aromaticother . The amine end is hydrophilic (soluble in water), and the aromatic
end is lipophilic (soluble in lipids)end is lipophilic (soluble in lipids)
 Two classes of local anesthetics are amino amides and amino esters.Two classes of local anesthetics are amino amides and amino esters.
Amides:Amides: Esters:Esters:
--Amide link b/t intermediate--Amide link b/t intermediate --Ester link b/t intermediate chain and chain--Ester link b/t intermediate chain and chain
and aromatic ringand aromatic ring aromatic ringaromatic ring
--Metabolized in liver and very--Metabolized in liver and very --Metabolized in plasma through soluble in--Metabolized in plasma through soluble in
the solutionthe solution pseudocholinesterases and notpseudocholinesterases and not
--stable in the solution--stable in the solution
--Cause allergic reactions--Cause allergic reactions

6. Local anesthetics - Classes (RuleLocal anesthetics - Classes (Rule
of “i’s”)of “i’s”)
EstersEsters
CocaineCocaine
ChloroprocaineChloroprocaine
ProcaineProcaine
TetracaineTetracaine
Am”i”desAm”i”des
BupBupiivacainevacaine
LLiidocainedocaine
RopRopiivacainevacaine
EtEtiidocainedocaine
MepMepiivacainevacaine

7. Structures of Amides and EstersStructures of Amides and Esters
 The amine end is hydrophilic (soluble in water), anesthetic moleculeThe amine end is hydrophilic (soluble in water), anesthetic molecule
dissolve in water in which it is delivered from the dentist’s syringe into thedissolve in water in which it is delivered from the dentist’s syringe into the
patient’s tissue. It’s also responsible for the solution to remain on eitherpatient’s tissue. It’s also responsible for the solution to remain on either
side of the nerve membrane.side of the nerve membrane.
 The aromatic end is lipophilic (soluble in lipids). Because nerve cell is madeThe aromatic end is lipophilic (soluble in lipids). Because nerve cell is made
of lipid bilayer it is possible for anesthetic molecule to penetrate through theof lipid bilayer it is possible for anesthetic molecule to penetrate through the
nerve membrane.nerve membrane.
 The trick the anesthetic molecule must play is getting from one side of theThe trick the anesthetic molecule must play is getting from one side of the
membrane to the other.membrane to the other.

8. MechanismMechanism
 The mechanism of local anesthetics connects withThe mechanism of local anesthetics connects with the ion channels,the ion channels,
nerve, and depolarization.nerve, and depolarization.
 Local anesthetics block the conduction in peripheral nerves that inhibitedLocal anesthetics block the conduction in peripheral nerves that inhibited
the nerve to excited and created anesthesia.the nerve to excited and created anesthesia.
 The anesthetic is a reversible reaction. It binds and activates the sodiumThe anesthetic is a reversible reaction. It binds and activates the sodium
channels.channels.
 The sodium influx through these channels and depolarizes the nerve cellThe sodium influx through these channels and depolarizes the nerve cell
membranes.membranes.
 As a result, the nerve loses depolarization and the capacity to create theAs a result, the nerve loses depolarization and the capacity to create the
impulse, the patient loses sensation in the area supplied by the nerve.impulse, the patient loses sensation in the area supplied by the nerve.

9. Local anesthetics - FormulationLocal anesthetics - Formulation
Biologically active substances are frequentlyBiologically active substances are frequently
administered as very dilute solutions whichadministered as very dilute solutions which
can be expressed ascan be expressed as parts of active drug perparts of active drug per
100 parts of solution (grams percent)100 parts of solution (grams percent)
Ex.: 2% solution =Ex.: 2% solution =
__2 grams2 grams__ = ___ = _2000 mg2000 mg_ = ___ = __20 mg20 mg____
100 cc’s 100 cc’s 1 cc100 cc’s 100 cc’s 1 cc

10. Local anesthetics - FormulationLocal anesthetics - Formulation
Biologically active substances are frequentlyBiologically active substances are frequently
administered as very dilute solutions whichadministered as very dilute solutions which
can be expressed ascan be expressed as parts of active drug perparts of active drug per
100 parts of solution (grams percent)100 parts of solution (grams percent)
Ex.: 2% solution =Ex.: 2% solution =
__2 grams2 grams__ = ___ = _2000 mg2000 mg_ = ___ = __20 mg20 mg____
100 cc’s 100 cc’s 1 cc100 cc’s 100 cc’s 1 cc

11. Factors Affect the Reaction of Local AnestheticsFactors Affect the Reaction of Local Anesthetics
Lipid solubilityLipid solubility
 All local anesthetics haveAll local anesthetics have weak basesweak bases. Increasing the. Increasing the lipid solubilitylipid solubility
leads to faster nerve penetration, block sodium channels, and speedleads to faster nerve penetration, block sodium channels, and speed
up the onset of action.up the onset of action.
 The more tightly local anesthetics bind to the protein, the longer theThe more tightly local anesthetics bind to the protein, the longer the
duration of onset action.duration of onset action.
 Local anesthetics have two forms, ionized and nonionized. TheLocal anesthetics have two forms, ionized and nonionized. The
nonionizednonionized form can cross the nerve membranes and block theform can cross the nerve membranes and block the
sodium channels.sodium channels.
 So, the more nonionized presented, the faster the onset action.So, the more nonionized presented, the faster the onset action.
pH influencepH influence
 Usually at range 7.6 – 8.9Usually at range 7.6 – 8.9
 Decrease in pH (acidosis) shifts equilibrium toward the ionized form,Decrease in pH (acidosis) shifts equilibrium toward the ionized form,
delaying the onset action.delaying the onset action.

12. Factors Affect the Reaction of Local AnestheticsFactors Affect the Reaction of Local Anesthetics
(cont.)(cont.)
VasodilationVasodilation
 Vasoconstrictor is a substance used to keep the anesthetic solution inVasoconstrictor is a substance used to keep the anesthetic solution in
place atplace at a longer period and prolongs the action of the druga longer period and prolongs the action of the drug
 vasoconstrictor delays the absorptionvasoconstrictor delays the absorption
 Lower vasodilator activity of a local anesthetic leads to a slowerLower vasodilator activity of a local anesthetic leads to a slower
absorption and longer duration of actionabsorption and longer duration of action
 Vasoconstrictor used the naturally hormone called epinephrineVasoconstrictor used the naturally hormone called epinephrine
(adrenaline).(adrenaline).
Side effects of epinephrineSide effects of epinephrine
 Epinephrine HR,BP and arrythmiaEpinephrine HR,BP and arrythmia

13. ToxicityToxicity
 Toxicity is the peak circulation levels of local anestheticsToxicity is the peak circulation levels of local anesthetics
 Levels of local anesthetic concentration administered to patients areLevels of local anesthetic concentration administered to patients are
varied according to age, weight, and health.varied according to age, weight, and health.
 Maximum dose for an individual is usually between 70mg to 500mgMaximum dose for an individual is usually between 70mg to 500mg
 The amount of dose also varied based on the type of solution usedThe amount of dose also varied based on the type of solution used
and the presence of vasoconstrictorand the presence of vasoconstrictor
Example:Example:
---For adult whose weight is 100kg and up, maximum dose of lidocaine---For adult whose weight is 100kg and up, maximum dose of lidocaine
is about 500mgis about 500mg
---For children, the dosage reduced to about 1/3 to ½ depending on---For children, the dosage reduced to about 1/3 to ½ depending on
their weight.their weight.
The doses are not considered lethal.The doses are not considered lethal.
Some common toxic effects:Some common toxic effects:
--light headedness--light headedness ---shivering or twitching---shivering or twitching --seizures--seizures
--hypotension (low blood pressure)--hypotension (low blood pressure) --numbness--numbness

14. Local Anesthetics - AllergyLocal Anesthetics - Allergy
 True allergy is very rareTrue allergy is very rare
 Most reactions are from ester class - esterMost reactions are from ester class - ester
hydrolysis (normal metabolism) leads tohydrolysis (normal metabolism) leads to
formation of PABA - like compoundsformation of PABA - like compounds
 Patient reports of “allergy” are frequently due toPatient reports of “allergy” are frequently due to
previous intravascular injectionsprevious intravascular injections

15. Local Anesthetics - ToxicityLocal Anesthetics - Toxicity
Tissue toxicity - RareTissue toxicity - Rare
 Can occur ifCan occur if
administered in highadministered in high
enough concentrationsenough concentrations
 Usually related toUsually related to
preservatives added topreservatives added to
solutionsolution
Systemic toxicity - RareSystemic toxicity - Rare
 Related to blood level ofRelated to blood level of
drug secondary todrug secondary to
absorption from site ofabsorption from site of
injection.injection.
 Range fromRange from
lightheadedness, tinnituslightheadedness, tinnitus
to seizures andto seizures and
CNS/cardiovascularCNS/cardiovascular
collapsecollapse

16. Factors of circulation levelsFactors of circulation levels
 Factors of circulation levels are the rates of absorption,Factors of circulation levels are the rates of absorption,
distribution, and metabolism.distribution, and metabolism.
 Absorption depends on the speed of administration andAbsorption depends on the speed of administration and
levels of the doses.levels of the doses.
 Distribution allows absorption to occur in three phases.Distribution allows absorption to occur in three phases.
First, the drug occurs at highly vascular tissues in theFirst, the drug occurs at highly vascular tissues in the
lungs and kidneys. Then it appears less in vascularlungs and kidneys. Then it appears less in vascular
muscle and fat. Then the drug is metabolized.muscle and fat. Then the drug is metabolized.
 Metabolism involves in the chemical structure based onMetabolism involves in the chemical structure based on
two classes, amide and ester .two classes, amide and ester .
 Decreasing the potential toxicity resulted in rapidDecreasing the potential toxicity resulted in rapid
metabolism.metabolism.

17. ConclusionConclusion
AnestheticAnesthetic pKapKa OnsetOnset Duration (withDuration (with
Epinephrine)Epinephrine)
in minutesin minutes
Max DoseMax Dose
(with(with
Epinephrine)Epinephrine)
ProcaineProcaine 9.19.1 SlowSlow 45 - 9045 - 90 8mg/kg –8mg/kg –
10mg/kg10mg/kg
LidocaineLidocaine 7.97.9 RapidRapid 120 - 240120 - 240 4.5mg/kg –4.5mg/kg –
7mg/kg7mg/kg
BupivacaineBupivacaine 8.18.1 SlowSlow 4 hours – 84 hours – 8
hourshours
2.5mg/kg –2.5mg/kg –
3mg/kg3mg/kg
PrilocainePrilocaine 7.97.9 MediumMedium 90 - 36090 - 360 5mg/kg –5mg/kg –
7.5mg/kg7.5mg/kg
ArticaineArticaine 7.87.8 RapidRapid 140 - 270140 - 270 4.0mg/kg –4.0mg/kg –
7mg/kg7mg/kg

18. Local anesthetics - DurationLocal anesthetics - Duration
 Determined by rate of elimination ofDetermined by rate of elimination of
agent from site injectedagent from site injected
 Factors include lipid solubility, doseFactors include lipid solubility, dose
given, blood flow at site, addition ofgiven, blood flow at site, addition of
vasoconstrictors (does not reliablyvasoconstrictors (does not reliably
prolong all agents)prolong all agents)
 Some techniques allowSome techniques allow multiplemultiple
injections over timeinjections over time to increase duration,to increase duration,
e.g. epidural cathetere.g. epidural catheter

20. Local anesthetics - vasoconstrictorsLocal anesthetics - vasoconstrictors
Ratios
Epinephrine is added to local anesthetics in
extremely dilute concentrations, best expressed
as a ratio of grams of drug:total cc’s of solution.
Expressed numerically, a 1:1000 preparation of
epinephrine would be
1 gram epi
1000 cc’s solution
1000 mg epi
1000cc’s solution
=
1 mg epi
1 cc
=

21. Local anesthetics - vasoconstrictorsLocal anesthetics - vasoconstrictors
Therefore, a 1 : 200,000 solution of epinephrine
would be
1 gram epi
200,000 cc’s
solution
=
1000 mg epi
200,000 cc’s
solution
or
5 mcg epi
1 cc
solution

22. Local anesthetics - vasoconstrictorsLocal anesthetics - vasoconstrictors
Vasoconstrictors should not be used in theVasoconstrictors should not be used in the
following locationsfollowing locations
 FingersFingers
 ToesToes
 NoseNose
 Ear lobesEar lobes
 PenisPenis

23. REGIONAL ANESTHESIAREGIONAL ANESTHESIA

24. Regional anesthesia - DefinitionRegional anesthesia - Definition
Rendering a specific area of the body,Rendering a specific area of the body,
e.g. foot, arm, lower extremities,e.g. foot, arm, lower extremities,
insensate to stimulus of surgery orinsensate to stimulus of surgery or
other instrumentationother instrumentation

25. Regional anesthesia - UsesRegional anesthesia - Uses
 Provide anesthesia for a surgicalProvide anesthesia for a surgical
procedureprocedure
 Provide analgesia post-operatively orProvide analgesia post-operatively or
during labor and deliveryduring labor and delivery
 Diagnosis or therapy for patients withDiagnosis or therapy for patients with
chronic pain syndromeschronic pain syndromes

26. Regional anesthesia - typesRegional anesthesia - types
 TopicalTopical
 Local/FieldLocal/Field
 Intravenous block (“Bier” block)Intravenous block (“Bier” block)
 Peripheral (named) nerve, e.g. radial n.Peripheral (named) nerve, e.g. radial n.
 Plexus - brachial, lumbarPlexus - brachial, lumbar
 Central neuraxial - epidural, spinalCentral neuraxial - epidural, spinal

27. Topical AnesthesiaTopical Anesthesia
 Application of local anesthetic toApplication of local anesthetic to
mucous membrane - cornea, nasal/oralmucous membrane - cornea, nasal/oral
mucosamucosa
 Uses :Uses :
 awake oral, nasal intubation, superficialawake oral, nasal intubation, superficial
surgical proceduresurgical procedure
 Advantages :Advantages :
 technically easytechnically easy
 minimal equipmentminimal equipment
 Disadvantages :Disadvantages :
 potential for large doses leading to toxicitypotential for large doses leading to toxicity

30. Local/Field AnesthesiaLocal/Field Anesthesia
 Application of local subcutaneously toApplication of local subcutaneously to
anesthetizeanesthetize distal nerve endingsdistal nerve endings
 Uses:Uses:
 Suturing, minor superficial surgery, lineSuturing, minor superficial surgery, line
placement, more extensive surgery withplacement, more extensive surgery with
sedationsedation
 Advantages:Advantages:
 minimal equipment, technically easy, rapidminimal equipment, technically easy, rapid
onsetonset
 Disadvantages:Disadvantages:
 potential for toxicity if large fieldpotential for toxicity if large field

31. IV Block - “Bier” blockIV Block - “Bier” block
 Injection of local anesthetic intravenously forInjection of local anesthetic intravenously for
anesthesia of an extremityanesthesia of an extremity
 UsesUses
 any surgical procedure on an extremityany surgical procedure on an extremity
 Advantages:Advantages:
 technically simple, minimal equipment, rapid onsettechnically simple, minimal equipment, rapid onset
 Disadvantages:Disadvantages:
 duration limited by tolerance of tourniquet pain,duration limited by tolerance of tourniquet pain,
toxicitytoxicity

33. PeripheralPeripheral nerve blocknerve block
 Injecting local anestheticInjecting local anesthetic near thenear the
course of a named nervecourse of a named nerve
 Uses:Uses:
 Surgical procedures in the distribution ofSurgical procedures in the distribution of
the blocked nervethe blocked nerve
 Advantages:Advantages:
 relatively small dose of local anesthetic torelatively small dose of local anesthetic to
cover large area; rapid onsetcover large area; rapid onset
 Disadvantages:Disadvantages:
 technical complexity, neuropathytechnical complexity, neuropathy

36. Plexus BlockadePlexus Blockade
 Injection of local anesthetic adjacent to aInjection of local anesthetic adjacent to a
plexus, e.g cervical, brachial or lumbar plexusplexus, e.g cervical, brachial or lumbar plexus
 Uses :Uses :
 surgical anesthesia or post-operative analgesia insurgical anesthesia or post-operative analgesia in
the distribution of the plexusthe distribution of the plexus
 Advantages:Advantages:
 large area of anesthesia with relatively large doselarge area of anesthesia with relatively large dose
of agentof agent
 Disadvantages:Disadvantages:
 technically complex, potential for toxicity andtechnically complex, potential for toxicity and
neuropathy.neuropathy.

39. Central neuraxial blockade -Central neuraxial blockade -
“Spinal”“Spinal”
 Injection of local anesthetic into CSFInjection of local anesthetic into CSF
 Uses:Uses:
 profound anesthesia of lower abdomen andprofound anesthesia of lower abdomen and
extremitiesextremities
 Advantages:Advantages:
 technically easy (LP technique), high success rate,technically easy (LP technique), high success rate,
rapid onsetrapid onset
 Disadvantages:Disadvantages:
 ““high spinal”, hypotension due to sympathetic block,high spinal”, hypotension due to sympathetic block,
post dural puncture headache.post dural puncture headache.

42. Central Neuraxial Blockade -Central Neuraxial Blockade -
“epidural”“epidural”
 Injection of local anesthetic in to the epiduralInjection of local anesthetic in to the epidural
space at any level of the spinal columnspace at any level of the spinal column
 Uses:Uses:
 Anesthesia/analgesia of the thorax,Anesthesia/analgesia of the thorax,
abdomen, lower extremitiesabdomen, lower extremities
 Advantages:Advantages:
 Controlled onset of blockade, long duration whenControlled onset of blockade, long duration when
catheter is placed, post-operative analgesia.catheter is placed, post-operative analgesia.
 Disadvantages:Disadvantages:
 Technically complex, toxicity, “spinal headache”Technically complex, toxicity, “spinal headache”